The SRE-Filter Web Server
version 1.2i
Introduction
SRE-Filter
is a full featured, and (hopefully) easy to configure,
HTTP (Web) Server for OS/2. Written in
REXX,
SRE-Filter is designed to run under the
IBM EWS GoServe program.
SRE-Filter provides a
number of useful features including:
This document describes how to use SRE-Filter.
While not necessary,
the reader should first examine
the documentation that comes with GoServe (GOSERVE.DOC). Knowledge of the
REXX
programming language would also help. However, you can still do a lot of nice stuff with only a
rudimentary understanding of GoServe, or of REXX. Lastly, if you don't know
HTML, the
"markup language" of
the world-wide web (WWW), then it's going to be hard to do anything interesting!
Before reading this manual,
we strongly recommend that you peruse the
SRE-Filter users guide --
it's a much easier read!
Other useful documentation files include:
Other GoServe filters.....
A popular alternative to this
filter is Don Meyer's
GoHTTP HTTP filter system.
GOHTTP offers
CGI-BIN, HTACCESS compatability, common-log auditing, and
rudimentary support for server side includes.
Another alternative is
the InterFilt filter of Derek Sims. It has good support for multiple realms and
multiple hosts, but lacks server side includes and other features.
A Note to upgraders
CHANGES.DOC lists the recent changes.
Table of Contents
Installation Notes
SRE-Filter consists of several filter
program files
(SREFILTR.80, SREFMON.CMD, and others), as well as
a set of files containing external routines and
samples of initialization databases.
As noted above, you'll need the
GoServe
package (ver 2.50 is recommended).
- For convenience, let us assume that the GoServe package has been installed in the
\GOSERVE directory (your working directory),
and the data directory is set to \WWW.
- Copy SREFV12I.ZIP (or the several smaller files) to a
temporary directory and then unzip it (them) in the usual manner
(i.e.;
UNZIP SREFV12I)
.
From an OS/2 prompt, run INSTALL (a REXX program
bundled with SRE-Filter),
and follow the on-line instructions. You will be asked to provide the
names of several directories.
If you select the defaults, INSTALL will create
the following directories (you select which drive):
- \GOSERVE\DATA : Contains various dynamic GoServe data files: such as
the USER_FILE,
COUNTER_FILE,
RECORD_ALL_FILE,
ACCESS_FILE,
and the common-log audit file.
- \GOSERVE\MESSAGE :contains the message boxes
- \GOSERVE\CONFIGS :contains the simple-mode
configurator support files
- \GOSERVE\TEMP : Storage for temporary data files (such as the
"recent hits" cache). The $xx.80 temporary response files are also
stored here.
- \GOSERVE\MAIL: the in-box for an SMTP server
- \GOSERVE\CGI-BIN : Location for CGI-BIN programs
- \GOSERVE\UPLOAD : Used to store uploaded files.
- \WWW\SAMPLES : Location of sample files, and SRE-Filter documentation.
- \WWW\TEMP : Work area, used for temporary file creation by server side programs.
- \WWW\IMGS : Location of icons (.GIF files) used by SRE-Filter
You will also be given the opportunity to set several SRE-Filter parameters,
and to setup a SUPERUSER. We strongly recommend that you
take this opportunity. In particular, setting up a SUPERUSER
can help avoid later configuration headaches (though if you are
very security conscious, you can skip this without terrible consequence).
After running INSTALL, you can delete the contents of this temporary directory.
- Set up GoServe to run SRE-Filter:
- Set the
filter
to be SREFILTR.80. To do this,
you can insert http filter srefiltr.80 in the
optional parameters line in GoServe's settings window
(right-mouse click on the GoServe icon ...)
- In certain cases, throughput can be markedly
improved by using the
SREFQUIK.80
variant of GoServe.
- You can start GoServe now ...
- If you intend to run "server-side" programs, you might want to
increase the following
Limits
:
-
End client after inactive
-
End client after total
- Double check that the
DataDir
option points to the directory containing your
HTML files (for example, \WWW).
- It is HIGHLY recommended that the
Data Directory and the
Working Directory be
different!
- You might want to turn on GoServe's caching; if you want to
record requests, you should also select the
call
filter anyways
option.
- To view a running log of SRE-Filter's actions, run the
PMPRINTF
program.
- At this point, the default version of SRE-Filter is running!
You'll probably
want to change the values of a number of SRE-Filter's parameters. Although you can do this by
editing the various parameter files (such asINITFILT.80)
with a text editor, for the new user
it is probably easier to run CONFIGUR.HTM -- a HTML front-end to
SRE-Filter's built-in configurator.
The most straightforward way of doing this is:
- Make sure that GoServe is running on your server, with SREFILTR.80 as it's filter.
- Fire up your favorite web browser
(say, Web Explorer 1.1 or NetScape 2.02).
- Point it at http://your.server/CONFIGUR.HTM (where your.server is the
address of your http server).
- You will be given the choice of a simple, intermediate, and expert mode
configurator. The simple mode is best suited for new users; it's a bit cumbersome
when making large changes, but is very well documented.
- Hint: If the configurator won't let you in (due to insufficient
privileges), you might want to check the OWNERS variable (in INITFILT.80)
to be sure it points to your IP address. Alternatively, you can use the
SUPERUSER username/password you created during the installation
process.
- If you need to use a port other then 80, you should:
- Change the names of all SRE-Filter files that end with
.80 to be the .nnn, where nnn is the
desired port (nnn
can be > 3 digits if HPFS is being used).
In particular, change
SREFILTR.80 and INITFILT.80
- Enter http PORT nnn FILTER SREFILTR.nnn in the
optional parameters
setting of GoServe.
- Note that it is possible to run multiple instances of the GoServe and
SRE-Filter;
using different ports, different working directories (and
possibly different data directories), and different copies of the
user-configurable files (the .IN, .CTL, .CNT, and INITFILT.nnn files).
- Remember, when using a port other then 80, clients will
need to include
:nnn
in the IP address of your server.
Now, all you have to do is create some informative, efficiently organized, and eye-catching HTML
documents, paste them together, and add links to the rest of the
net. But that's the fun part.
Description of the files that comprise SRE-Filter
The SRE-Filter package consists of a number of files. These include
the SRE-Filter REXX programs, the macrospace
procedure library, several user-configurable parameter files, samples of
"counter and control" files, and some sample HTML files. A complete
description of these files is contained in the
file list.
Many of the directories, and files, mentioned above can have their names changed
by modifying variables that are located in INITFILT.80 (the INITFILT_FILE); either by editing
the file with a text editor, or by using CONFIG2.HTM. In this documentation
we usually refer to files and directories by their "titles" (such as working directory), but occasionally the "default name" is used
(such as \GOSERVE).
If you change the names of your directories, keep the following in mind:
- If you intend to make temporary files available to clients,
the TEMPFILE_DIR directory should
be a subdirectory of the GoServe data directory.
- For SRE-Filter's documentation and examples to work properly,
the IMGS and SAMPLES sub-directories should be directly under the
GoServe data directory
To speed up processing, and to facilitate modularization, SRE-Filter makes
extensive use of REXX macrospace.
Of greater import, SRE-Filter uses several "helper" threads to handle
username lookup, alias matching, SSI-document caching,
SEL-specific access control, virtual
directory matches, and post-filter processing. These threads are
generated upon the first request to SRE-Filter. In addition,
SRE-Filter stores a number of variables in the local (GoServe) environment.
For most users, these implementation
details are unimportant. However, these
threads do use system resources (queues) which remain alive even after
GoServe has been turned off. To free these resources, it is recommended
that the FREEUP.CMD program be run after GoServe has been killed.
Citation:
SRE-Filter uses the REXXLIB library to access macrospace and to
generate/communicate between threads. A distribution copy of REXXLIB
is supplied with SRE-Filter, and may be used freely with SRE-Filter. If you wish
to use REXXLIB in other REXX programs, contact
Quercus Systems for licensing information.
Lastly, SRE-Filter monitors the parameter files, including INITFILT.80.
Changes to these files will be incorporated into SRE-Filter's parameters
about every 10 seconds.
Variables and Parameters
Throughout this documentation reference is made to variables
(aka "parameters")
used to change SRE-Filter's options and features.
In the interest of thoroughness, this manual discusses the
multitude of SRE-Filter options
in terms of directly modifying these parameters. However, most
individuals
will probably never need to actually edit a file. Instead,
almost all of the parameters mentioned herein can be
modified using the intermediate-mode
configurator (CONFIG2.HTM). In fact, in most cases the
simple-mode configurator (CONFIG0.HTM) will do the
job -- where appropriate, links to the appropriate section of the
simple-mode configurator will be made available for your browsing pleasure
.
If you are a hands-on kind of administrator, feel free to
directly modify these parameters. If so, you might also
want to read the detailed
descripton of INITFILT.80.
The SRE-Filter documentation uses some
not-necessarily-intuitively-obvious terms. The following lists a
few of the more important ones. For a more complete list, see the
terminology appendix.
- URL
-
Universal Resource Locator (URL) is a scheme for specifying Internet
resources using a single line of printable ASCII characters. A URL should
contain
a protocol, domain name, port number (optional), the location of the resource, and
an (optional) option list (following a ?).
Examples: - http://your.server.net/dir1/sample.htm
- http://pet.store.com/prices?type=mammals&class=retail
- Request string
- When a client asks for a URL (say, by clicking on a link), a
request string (along with request headers and
a request body) is sent to the server (at the domain name and port listed in
the URL). The request string
consists of three tokens: the http method, the location of the
resource on the server, and the http protocol.
Examples (assuming the above URLs):
- GET /dir1/sample.htm HTTP/1.0
- GET /prices?type=mammal&class=retail HTTP/1.0
- Selector (also referred to as the
request selector )
- The selector is the location of the resource on the
server. Specifically, it's the (slightly modified) second term
in the request string.
Examples (assuming the above request strings):
- dir1/sample.htm
- prices?type=mammal&class=retail
Note that the "slight modifications" consist of:
- dropping the leading /
- decoding URL-encoded characters
(note that the above examples do not include any URL-encoded characters).
In many cases, the connection between the selector and server resource
it refers to is simple (such as when the selector is a filename relative to
the GoServe data directory). In other cases, it's completely virtual
(as when the resource consists of the output of a program that's run using
information provided by the client).
- Selector-specific (usually written as SEL-specific )
- SEL-specific refers to SRE-Filter configuration
information that is specific to a selector -- such
as resource privileges, or a virtual directory.
The selector is a pointer to a web-server
resource. Typically, this would be a file; but it might refer to
the output of some program run just for this request.
In either case, SRE-Filter has to match the selector
to the actual resource (an activity that can become rather convoluted!).
In much the same way that OS/2 extended attributes contain
additional information about a file, SRE-Filter's SEL-specific
information contain additional information about a selector
(needless to say, this information is only used by SRE-Filter).
Return to table of contents
A summary of this section:
- SRE-Filter supports a limited form of multi-hosting. Multiple hosting can occur in
two different manners:
- When multiple numeric IP addresses are handled by a
single computer
- When multiple aliases exist for a single numeric IP address; and
the HOST: request header is provided by the client's browser.
-
SRE-Filter offers a number of logon controls.
These are used to control basic access to any of the resources
on your server.
- A set of PUBLIC_URLS
can be made available to the general public.
- User specific privileges are used to permit
(or deny) access to your server's resources.
- SEL-specific and directory-specific access controls can be used
to institute more refined access controls.
To use SRE-Filter in a multi-host environment, you must
specify host-specific entries that assign a
data-directory and a host-nickname to a specific IP
address. You should also include a host-nickname
when defining a number of SRE-Filter parameters.
You can use the
simple-mode configurator to create
these host-specific entries.
The HOSTS. stem variable (set in INITFILT.80) defines the hosts (either IP addresses
or aliases) that your server will work with. Each HOST. variable should contain
the following information (in a comma delimited list):
HOSTS.n ='ip_address, host_nickname,default_dir'
Where:
ip_address
is a IP address (integer or numeric)
host_nickname
is the "nickname" you will use when
referring to this host. The host_nickname
must
not
be a number, it must contain at least one non-digit character. Thus, a
host nickname of 1234
is invalid,
but 1234X
is okay.
default_dir
is the default directory for this host (it
is used instead of the GoServe default data directory).
If your server recieves request from a host which does not have a matching
HOSTS. entry, it will be treated as "generic" request; that is, the standard
(single host style) default directory, etc. will be used with such requests.
Thus, if all requests (regardless of intended host)
have identical access to your server's resources (it's files and programs)
you can ignore this entire section!
Given that you do want to have different resources available to
different hosts, almost all of the SRE-Filter variables and parameters can be specified
on a "host specific" basis
- To specify "host specific" parameters in the .IN, .CTL, and .CNT files the
host nickname, followed by //, is used.
For example, for a virtual directory entry that maps TIGERS/ to
D:\ANIMALS\TIGERS, but only for requests to ZOO.OURISP.NET; you might specify:
ZOOSITE// TIGERS/ D:\ANIMALS\TIGERS
where ZOOSITE is the host nickname for ZOO.OURISP.NET, and a space separates the
ZOOSITE// from TIGERS/.
- For parameter names (defined in INITFILT.80), host-specific results are
defined by appending a .HOST_NICKNAME to the variable name. For
example,
CHECKLOG.ZOOSITE='NO'
refers to this "ZOOSITE" host.
- A few of SRE-Filter's parameters are not host specific; such
as the DISPLAY_ENV parameter.
Notes
- The host specific default directories are defined in the
HOSTS. stem variables.
- Requests to IP addresses not represented by a HOSTS. entry are treated as "generic" requests;
that is, the standard (single host) variables apply.
- In general, if a SRE-Filter variable/parameter does not contain
host nickname information, then it applies to ALL hosts. In other words, if
a host specific value of a parameter does not exist, the "generic" value is used.
- INITFILT.DOC discusses in greater detail which SRE-Filter parameters
may be host specific.
- Be careful when using shorthand IP names (say, in a mixed
Internet/Intranet environment).
PUBLIC_URLS
There may be cases where you generally do not want to allow
public access to your
site, except for a set of clearly delimited public areas. For example,
you may have a private site, except for a set of
"who we are" documents. Although one could use
selective access controls
to accomplish this, the use of
PUBLIC_URLS provides a simple and direct
alternative.
You can use the
simple-mode configurator to create
these PUBLIC_URLSs.
The PUBLIC_URLS. stem variable is used to identify server resources
that are "open to the public" -- that can be accessed by clients
who have no logon rights and no access privileges.
Basically, SRE-Filter compares the request (using
wildcard matching with substitution) against
the entries in the PUBLIC_URLS. stem variable.
All requests that match a PUBLIC_URLS stem variable:
- will be examined for ALIASES and for virtual directory matches
- will be checked for an extension, and
will be examined for AUTO_NAME match (if needed).
- server side includes, and server side processing, will be performed
(provided the NO_INCLUDE and NO_PROCESSING variables are not in force).
- Caching will not be suppressed.
- The PUT and DELETE methods will not be permitted
/permi
- The clients privileges are set to:
-
PUBLICFILES PUBLIC
,
- plus the privileges in the PUBLIC_PRIVS SRE-Filter parameter,
- plus possible In-house privileges,
- plus privileges that might
be associated with a username/password sent with this request
...
even though this username/password is not required,
the browser might have
used it to gain access to a different resource on your server.
PUBLIC_URLS can also specify literal public_urls. When a
request selector
matches one of these literal public_urls; file transfer
is expedited by:
- Not performing aliasing
- Not using virtual directories and AUTO_NAME
- Not attempting server side includes
- Not attempting AUTO-HEADER.
More importantly, the SREFQUIK
variant of SRE-Filter is written to
quickly transfer these literal public_urls-- cutting
response time by as much as 50% under moderate to heavy load
Notes:
- To speed up processing, you can disable the ALWAYS_CHECK_PRIVS
parameter (in-house and username privileges will not be available).
- In a multi-host environment, the PUBLIC_URLS must be host specific (that
is, "non-host specific" values of PUBLIC_URLS are not
not used as defaults).
- For a more detailed description of how to use PUBLIC_URLS, and
details on how to specify literal public_urls-- see
INITFILT.DOC
Logon Controls
The simple-mode configurator
can be used to enable LOGON, to add users to the USER_FILE,
to add/remove IN-HOUSE clients, and to enable the
LOGON_FAIL_FILE.
Setting LOGON requirements with the CHECKLOG variable
CHECKLOG should have one of the following values:
- NO
- No logon required; unencumbered entry for all clients.
- YES
- Logon upon invocation of the default page (i.e.; an empty request).
- ALWAYS
- Logon required for all requests.
- INHOUSE
- Entry allowed only to clients with INHOUSE or SUPERUSER
privileges.
Allowing unencumbered access to IN-HOUSE users
The INHOUSEIPS. stem variable can be used to specify the numeric IP
addresses of clients who are to be given "IN-HOUSE" status. IN-HOUSE client
do not have to enter logon information, and they are automatically granted
the privileges stored in the INHOUSE_PRIVS variable.
Notes
- INHOUESIPS must be host-specific;
INHOUSEIPS.1.ZOO='151.121.65.143' (see INITFILT.DOC for details).
-
The * character can be used as a "wildcard" in the INHOUSEIPS. stem variables.
- Each INHOUSEIPS. value can include a client specific list of privileges (place
it after the IP address).
Owners have SUPERUSER status
You can give SUPERUSER
privileges to a set of numeric IP addresses by changing
the value of the OWNERS variable.
Notes:
Wildcards are not allowed in the OWNERS variable
OWNERS are given INHOUSE_PRIVS privileges, as well as SUPERUSER privileges.
The OWNERS variable must be host-specific (see INITFILT.DOC
for details).
Logon for non IN-HOUSE users.
If a logon is required, an authorization string (containing
a name and password) is obtained from the
client. SRE-Filter then examines the USER_FILE
for a match. If a match is found, the request is honored (abstracting
from SEL-specific or directory-specific access controls). Otherwise
the client is asked to re-enter her name and password. Note that entries
in the USER_FILE may be "host specific".
Be aware that ...
- The HTTP "basic access authentication scheme" is used to
encode the username and password. This is a fairly low security method.
Furthermore, the INHOUSE setting of CHECKLOG can be circumvented by
clever "spoofers". In other words, SRE-Filter is not designed for high-security
environments!
- Once asked for an authorization, most browsers will include
an "authorization field" in subsequent requests to the same site. Thus,
even if
CHECKLOG=ALWAYS
, the client will only need to enter his
username and password once (that is, she won't need to reenter it each
time a different document is requested).
Keeping out known pests
There may be cases where one needs to deny access to
particular client(s). This can be accomplished by
recording the numeric IP addresses of these "unwanted clients" in the
UNALLOWEDIPS.n stem variables (wildcards are permitted).
Note that the OWNERS and INHOUSEIPS.n
stem variables are checked first. If the
client's numeric IP address appears in either of these lists,
UNALLOWEDIPS.n is not checked. Thus, by setting
UNALLOWEDIPS.1="*.*.*.*"
, you can deny entry to everyone
except OWNERS and IN-HOUSE users.
Also note that UNALLOWEDIPS. entries must
be "host-specific" (see INITFILT.DOC for details).
Detecting fake IP addresses
For additional security, you can set the DNS_CHECK variable (to YES).
When set to YES, SRE-Filter will lookup the client's IP name; and if
it does not exist (there is no DNS entry), logon will be denied. This
provdes some security against "spoofers", but it also slows down
response time, and may keep out legitimate users using dynamic (and
possibly unnamed) numeric IP addresses.
The LOGON_FAIL_FILE
If the client does not have "logon rights", SRE-Filter will use the value
of the LOGON_LIMITand the LOGON_FAIL_FILE to determine
the response.
- LOGON_LIMIT is used to limit the number of attempts-per-minute.
- If LOGON_LIMIT is exceeded, or the username/password is incorrect,
you can then send the
LOGON_FAIL_FILE as a "response" (rather then continuing to re-request
the username and password).
For further details, see
the description of LOGON_LIMIT and LOGON_FAIL_FILE in INITFILT.DOC.
Assigning client privileges
In several circumstances, SRE-Filter will check the "client privileges"
before transferring information. In particular,
file transfer when SEL-specific access controls
are in place (i.e.; when ALLOW_ACCESS='NO'
) requires that the
client have appropriate privileges.
In a sense, privileges offer a
convenient shorthand for identifying sets of users.
Privileges are set automatically for:
IN-HOUSE clients are granted privileges stored in their INHOUSEIPS. variable,
OWNERS are granted SUPERUSER privileges.
In addition, IN-HOUSE clients and OWNERS will be granted the
privileges that are listed in the INHOUSE_PRIVS "space delimited
list" variable. It is recommended
that INHOUSE_PRIVS always include the INHOUSE privilege.
For everyone else:
If a logon is required, the privileges are read from the
USER_FILE.
Last of all ..
Privileges listed in the the PUBLIC_PRIVS "spaced
delimited list" variable are given
to everyone.
In addition to the above "static" privileges, clients can be assigned
"dynamic" privileges. These dynamic privileges are typically
set by prior actions (say, filling out a registration form, or
requesting an introductory file), and have a short life expectancy (measured
in minutes). For further discussion of these "dynamic" privileges,
see ADDPRIVS.DOC, and the discussion of the CHECK_ADD_PRIVS
and ADD_PRIVS_PREFIX variables in INITFILT.DOC.
Accesss control on a selector-specific basis.
The simple-mode configurator
can be used to enable selector-specific access controls, and to add/remove
selector-specific access control entries
There may be cases where you want clients to have unencumbered
access to some, but not to all, the resources of your server.
One way to do this is to identify which request selectors
a client has access to.
The ACCESS_FILE,
and the ALLOW_ACCESS variable, are used to construct these
selector-specific (SEL-specific)
access controls.
ALLOW_ACCESS can take the following values:
- YES
- No limits -- all clients (with logon rights)
are automatically given access rights to the server resource.
- INHOUSE
- IN-HOUSE users (and SUPERUSERs) are given automatic access rights,
all others must have appropriate privileges.
- NO
- No one (except SUPERUSERs) is given automatic access rights,
all others must have appropriate privileges.
When ALLOW_ACCESS is enabled,
SRE-Filter will examine the ACCESS_FILE
for an entry that
matches the request selector .
- If a matching entry is found, SRE-Filter
will then extract a SEL-specific resource privileges list. This
is used (along with the client privileges)
to determine if the client is authorized to access the resource.
- If a matching entry is not found, the request will
not be honored.
Additional Features of the Access Control File
In addition to general access rights (do you have any rights to the server
resource), the ACCESS_FILE contains several additional pieces of
SEL-specific information:
Permissions
The permissions list includes
information on:
- suppression of server side
includes and server side processing
- PUT and DELETE permissions
- CACHE enabling
- suppression of aliasing, directory-specific access controls, virtual directory lookup, and post-filtering
The Realm
When ALLOW_ACCESS is enabled, and the client does not have
appropriate privileges, SRE-Filter will query the client for a new
username/password. When querying, the SEL-specific realm
is displayed if available. If there is no SEL-specific realm, the
THE_REALM realm is displayed.
ACCESS_FAIL_FILE
If the client does not have access to the server resources represented
by the selector, SRE-Filter will use
the value of ACCESS_FAIL_FILE to dictate the response. If
ACCESS_FAIL_FILE=0, a username/password will be re-requested. Otherwise,
the ACCESS_FAIL_FILE, or a SEL-specific access failure file, will be
returned. For details, see the discusion of ACCESS_FAIL_FILE in
INITFILT.DOC.
Advanced Options
The SEL-specific advanced options file
allows you to specify several SEL-specific advanced options, including:
- Execution of external REXX procedures prior to returning a requested
document
- Customizing the response headers
- Suppressing specific server-side-includes (such as the header and footer).
Notes: Two types of resource privileges
There are two types of resource privileges :
- ONE_OF (the default type).
- The client must have "one of" the ONE_OF privileges.
- MUST_HAVE (start with the & character)
- The client "must have" all the MUST_HAVE privileges.
Note: if only one privilege is specified, these two types are equivalent.
Notes: Matching client privileges to resource privileges
SRE-Filter's privilege matching algorithim is quite simple:
- If a MUST_HAVE privilege appears in the
SEL-specific resource privileges list, then it must
also appear in the client privileges list. If not,
access is denied.
- After checking all of the MUST_HAVE privileges, SRE-Filter then
compares each ONE_OF privilege to the client privilege list.
If any of these ONE_OF privileges appear, then access is permitted.
Otherwise, access is denied.
- Reiterating: access is denied if there is
no overlap between the client's privileges and the
ONE_OF resource privileges
Notes: SEL-specific permissions
SEL-specific permissions are used to provide SEL-specific
control of the features of SRE-Filter. That is:
SEL-specific privileges are used to control access to a
resource
SEL-specific permissions are used to control SRE-Filter features,
assuming that the SEL-specific privileges have been satisfied!
Currently, the following permissions are available:
Suppressing server-side actions
You can suppress server-side-includes, and server-side-processing on a "SEL-specific"
basis by including NO_SSI and NO_SSP permissions (respectively). You can also
suppress "in-document" server-side processing (the SELECT and INTERPRET CODE
keyphrases) by including a NO_CODE permission (note that NO_SSP implies NO_CODE).
Permitting the PUT and DELETE methods
SRE-Filter understands the PUT and DELETE
HTTP methods. The PUT method
is used to upload a file to your server, and save it using the location
specified in the request. The DELETE method is used to delete
a file, as specified by the location specified in the request.
For security reasons, PUT and DELETE requests will only be honored if
the appropriate permssion (PUT or DELETE
respectively) appears in the permissions list .
Furthermore, when using the PUT_FILE or
GET_URL facilities to upload to a non-upload_directory subdirectory (that is,
to a virtual directory), the PUT permission must apply (to the "relative file
name" that matched this virtual directory).
Suppressing examination of HTACCESS files
To suppress the use of HTACCESS files for selected server resources, include a
NO_HTACCESS permssion. Note that this will not effect the SHOWDIR
dynamic directory list processor.
Suppressing virtual directory, post-filter, and aliasing
The NO_VIRTUAL, NO_POSTFILTER, and NO_ALIAS permissions will suppress
virtual directory lookup, post-filtering and file recording, and alias lookup
(respectively) on a SEL-specific basis.
Allowing a file to be cached
Whenever there is a possiblity that access to a resource will be
denied to a client, SRE-Filter will disable caching of the file invoked
by the request selector .
In particular, if CHECKLOG is not equal to "NO", or
if ALLOW_ACCESS is not equal to "YES", then caching
will be suppressed.
While an important security feature, there may be cases where
you are willing to sacrifice some access control in order to speed up
request processing. To achieve this, you can enable caching (on a
URL specific basis) by including CACHE in the
permission list.
Note that for caching to occur, the GoServe caching option must
be turned on!
Notes: Miscellaneous
- You can also specify REALM-specific resource privileges
which will be added to the explicit SEL-specific resource
privileges list (every selector identified
as belonging to a given realm will have the same
list of REALM-specific resource privileges).
- Entries in the ACCESS_FILE can be "host specific".
- The default ACCESS_FILE is ALL_FILE.CTL.
- Permissions are examined even when ALLOW_ACCESS=YES
- Files requested by server side includes are not subject to
access controls.
- If the ACCESS_FILE does not exist,
then access is disallowed to clients for whom ALLOW_ACCESS is enabled.
The idea is that if there is no matching entry (in the ACCESS_FILE)
for a selector, then the server resources
associated with the selector should not be accessible.
(... and if the ACCESS_FILE is unavailable, then there can't be a match).
- Wildcard matching is supported.
Note that global values of NO_INCLUDE=YES and NO_PROCESSING=YES take precedence
over the SEL-specific SSI and SSP permissions!
- Warning: use of the CACHE permission
can inadvertently subvert access control!
- You might want to include a global wildcard match.
For example:
* NO
-- if not explicitily mentioned, do NOT allow access
* *
-- if not explicitily mentioned, allow access
Return to table of contents
Directory-specific access control, using HTACCESS files.
To provide compatability with HTTPD style servers (such as Don Meyer's
GOHTTP), SRE-Filter supports the
HTACCESS method of access control.
This support uses code graciously loaned
to us by Don Meyer, suitably modifed for SRE-Filter.
Briefly, the HTACCESS method utilizes special HTACCESS
files that are placed
in your various directories (usually with the name HTACCESS.
,
or .HTACCESS
). These files (there may one in each of several
directories) contain entries pointing to password files, user-group files,
and other parameters that
are used to ascertain who shall be given access to the
files in the directory (and it's child directories).
HTACCESS control will be checked for all requests.
Note that the presumed location of
the HTACCESS file depends on the type of request:
- Request for documents (including PUT and DELETE method requests) == In the directory of the document
- File uploads == In the target directory of the upload (typically the UPLOAD_DIR directory)
- CGI-BIN requests == In the CGI-BIN directory (or appropriate subdirectory)
- SRE-Filter's built-in and included facilties == In the GoServe directory
- Other server side processing requests == In the directory containing the requested program.
In all these cases, the "parent" directories are also checked for HTACCESS files.
Notes on the use of the HTACCESS method
- Both methods of access control CAN be active: the
"native" SRE-Filter "SEL-specific" access is checked first, and then the
"HTACCESS" method of "directory specific" access is checked.
- Since just about all the options provided by the "HTACCESS" method can
be provided by the "native" SRE-Filter methods:
on speed of throughput grounds
we recommend using the "native" SRE-Filter
methods (that is, the SEL-specific method) whenever possible.
- For details on enabling SRE-Filter's support of HTACCESS controls,
see the description of the DO_HTACCESS and
HTACCESS_FILE variables in INITFILT.DOC.
- HTACCESS lookups are suppresed when the request matches a PUBLIC_URLS
(that is, HTACCESS controls, redirection, etc. will not be attempted).
- The HTACCESS files may also contain:
- URL "redirection" information,
- directory-specific default index information,
- dynamic directory list processor parameters
Modifying the request
Specifying the home page (the default)
When the client sends an empty request, a /
, or
"/?some+options"
,
SRE-Filter assumes that the client desires the "home page" (the default document).
By tradition (but not necessarily) the default document is a file named
INDEX.HTM located
in the root of the data directory.
The default can be set using the DEFAULT or DEFAULT.HOST_NICKNAME
variable
(that is, DEFAULT may be host specific).
You can use the simple-mode
configurator to set the home page and the directory-specific default
document(s)
Return to table of contents
Specifying default documents for directories
Often, a request may arrive that specifies a directory, but does not specify a
file. For example, a request for COOLJUNK/JOKES/
does not specify a particular
file, but instead implies "give me the default document for the
COOLJUNK/JOKES subdirectory of the data directory". In these cases,
the AUTO_NAME variable is examined.
AUTO_NAME
should contain a space delimited list of filenames to use when
a request for a "directory" is recieved.
SRE-Filter will attempt to find these files in this
"requested" directory --
starting with the first name in the AUTO_NAME list.
To assist in this search, a special name,
consisting of *.HTM (or *.HTML) means use the directory_name.htm file.
Lastly, an entry of !CREATE instructs SRE-Filter to generate a directory
listing of files and subdirectories in the requested directory.
This listing is generated with SRE-Filter's !DIR
special action. By default, a <PRE> formatted table is
generated, containing (for each file):
- a descriptive icon
- a link to the file
- the file creation date
- the size of the file
If you are interested, it is fairly easy to
modify these display options -- you can even
tell SRE-Filter to automatically generate a description for each file.
Example
AUTO_NAME=" *.HTM INDEX.HTM "
If the request is for /INFO/MAINE/
,
and your data directory is D:\WWW
, then ...
*.HTM
is interpreted as: D:\WWW\INFO\MAINE\MAINE.HTM
INDEX.HTM
is interpreted as: D:\WWW\INFO\MAINE\INDEX.HTM
Notes
- AUTO_NAME has no effect on calls that do not
specify a directory name --that is,
the document specified in the DEFAULT
variable is used in response to an empty (or /) request.
- AUTO_NAME, and other forms of "local redirection" can cause problems when the client's browser resolves
"partial URLS" -- see INITFILT.DOC for further discussion!
-
If you start a filename (in the AUTO_NAME list) with a /, is is
assumed to
be relative to the data directory (or to a virtual directory).
Otherwise, the file is assumed to be relative to the current
URL (you can include additional path information).
- If you are using .HTML as the default extension for HTML documents, use
*.HTML (instead of *.HTM)
For example: auto_name=" *.HTML INDEX.HTML PUBLIC_HTML/INDEX.HTML "
(note that PUBLIC_HTML/INDEX.HTM will look in the PUBLIC_HTML directory relative
to the current URL).
- If you want your default document to be a "SHTML" file, use *.SHTML
(or *.SHT, or *.HTML-SSI, etc.) instead of *.HTM.
- !CREATE should always be
the last item in AUTO_NAME (anything following it will never be reached).
- !SHOWDIR can be used as an alternative to !CREATE -- see
SHOWDIR.DOC
for details.
- For a full featured directory lister, you might want to examine the
GETAFILE add-on for SRE-Filter!
-
Requests that do not end in a /, but have no ? and have no "." extension,
can be interpreted in several manners. The NOEXT_TYPE variable is
used to select how these request are interpreted.
NOEXT_TYPE
can take values of:
DIR
: Interpret as a directory; / is added and
AUTO_NAME is used.
For example, CHARITIES/HEALTH
is interpreted as a sloppy form of
CHARITIES/HEALTH/
(the "CHARITIES/HEALTH subdirectory of the data directory, or a
"local or remote" virtual directory).
REDIR
: Similar to DIR
, but the client is
redirected back to the modified URL (that is, a remote redirection
is used).
HTM or HTML
: Interpret as an abbreviation for an
HTML file (with extensions of .HTM or .HTML respectively).
NONE
: Interpret as is.
-
other_string
: The other_string is added.
For example, if NOEXT_TYPE=.GIF
,
then .GIF
will be added to these "no extension" requests.
Return to table of contents
Using ~ to specify the home directory
You can use the simple-mode
configurator to set the home-directory
As a convenience, SRE-Filter will replace occurences of ~ characters
in request selector with a string. Since the ~ is often used to
point to a set of individual "home directories", this replacement string
is stored in the HOME_DIR variable.
To select the home directory , change the value of the
HOME_DIR (or HOME_DIR.HOST_NICKNAME) variable.
Example
If ...
HOME_DIR="BRANCH/STAFF/PERSONAL/"
and
The request
is ~JOES/PAGE.HTM
,
.. then
SRE-Filter will look for: BRANCH/STAFF/PERSONAL/JOES/PAGE.HTM
(under your data directory, or in a virtual directory).
Notes
- This HOME_DIR "string replacement" does minimal syntax checking
(// are replaced with /). Thus,
one should be careful that the definition of HOME_DIR, and it's use in the
the links included in your HTML documents, is consistent.
Advanced Option: Specifying User Subdirectories
In many cases, you may wish clients to limit access to particular
subdirectories of your HOME_DIR
directory. For example,
suppose all "students" have space on the HOME_DIR
directory
of your web server; or HOME_DIR
may be on a LAN drive
accessible as a virtual directory from the web server. These
"student" directories may contain several subdirectories; one of which
is intended for WWW use, while the others are for personal
use.
The goal is to
give clients direct access to the "web" related directories
but not to the "personal" directories.
This goal can be achieved by including a $ in the HOME_DIR
parameter.
Specifically, the $ is replaced by the portion of the
request between the ~ and the first / following this ~
For example: If:
-
HOME_DIR=USERS/$/WWW
- the request is
/~GERALD/RESUME.HTM
Then SRE-Filter will use: /USERS/GERALD/WWW/RESUME.HTM
For futher details, see the discusssion of the HOME_DIR
parameter in INITFILT.DOC.
Using virtual directories
You can use the simple-mode
configurator to add/remove virtual directories.
By default, SRE-Filter will match the
request selector
to a file in the
data directory
;
or if the request is for server side processing (such as an SRE-Filter
add-on, or a CGI-BIN script), to a file in the
working directory
or CGI-BIN directory
.
While a good security feature (files not in these directories are inaccessible),
this can be an inconvenience. To remedy this inconvenience, one can
define "virtual directories" using the VIRTUAL_FILE.
Basically, SRE-Filter will compare the
starting portion of a URL to see if
it matches an entry in VIRTUAL_FILE. If it does, the
directory listed
in the entry is used (instead of the data directory or working directory).
Thus, you can make available a wide, but controllable, set of "local"
directories (on or LAN accessible from) your server.
In addition,
"virtual directories" can point to "remote" directories on other http servers --
SRE-Filter will
attempt to retrieve the file from the remote server;
without using a redirection.
To clarify: to the client, remote virtual directories are indistinguishable
from "local" virtual directories.
In particular, HTML files with server
side includes can be remotely located -- and if the remote server makes
no attempt to process these server side includes, SRE-Filter will!
For details on the use of the virtual directories, see the description of the
VIRTUAL_FILE .
Note that entries in the VIRTUAL_FILE may be "host specific"
Return to table of contents
Using "aliases" when responding to requests
ALIASES are used in SRE-Filter to redefine and redirect
requests
Along with the ALIAS_FILE,
the CHECK_ALIAS parameter controls
whether and when ALIAS checking occurs.
CHECK_ALIAS should have one of the following values:
NO = Suppress ALIAS checking
YES = Enable ALIAS checking
- Local redirection:
To modify simple URLs's. For example:
- You may want to convert a request for
GETINFO
into: INFODIR/GETINFO.HTM
.
- Processing searchable indices.
The
DOSEARCH SRE-Filter add-on, when combined with
an ALIAS, provides a simple means of implementing
text-based searchable indices.
To use SRE-Filter's searchable index facility,
one should create an alias of the form:
INDXFILE.HTM?* DOSEARCH?FILE=FILE.NAM&TARGET=*
Where
INDXFILE.HTM
is the name of a
searchable index
(that is, an HTML document containing an <ISINDEX> element).
DOSEARCH
instructs SRE-Filter to
"execute the DOSEARCH add-on."
FILE.NAM
is the name (relative to the data directory,
or in a "local" virtual directory) of the ASCII text file to be searched.
Note that the alias will not be activated on the first
request for INDXFILE.HTM -- only upon return (when a ? is appended to
the request selector by the browser) will this alias match occur.
If you want to use some other text search program, you could set up
an alias of the form:
SEARCHIT.HTM?* SRCHREXX?*
- SEARCHIT.HTM is invoked at first (since the request does not contain a ?).
- The SRCHREXX procedure is called
after the client enters the search string (and the client appends a ? to
SEARCHIT.HTM). SRCHREXX should be a REXX procedure located in the
SRCHREXX.CMD (or SRCHREXX.80) file on your working directory; and it
might call a powerful search engine.
- Remote redirection: Redirecting requests for moved documents
There are 4 ways of using an alias to indicate that a document has been moved to
a new server
(or you can use the simple-mode
configurator to add/remove remote redirections).
target http://new.site.org/newname
- If the request selector
matches target, a "temporary" (HTTP status code 302)
redirection to the new URL (i.e.; http://new.site.org/newname) will be returned
to the client. A full URL must be specified (starting with http://).
-
target !TEMP http://new.site.org/newname
- Same as above, but you can use short-hand's URLS (i.e.; without the http://).
If you do not include an ip address, redirection will be back to the server.
-
target !MOVED http://new.site.org/newname
- Same as above, but the redirection is permanent (HTTP status code 301).
-
target !NOTIFY http://new.site.org/newname
- A "message has been moved" document will be returned to the
client, which will contain a link to it's new location. Techincally
speaking, this is not "redirection". Rather, it's a "notification of redirection",
with the intention that the client will change the appropriate links (or bookmarks).
Citation: The code for this is courtesy of Don Meyer!
Examples:
PROJ/P48.HTM http://www.prez.edu/truman.htm
PROJ/LINCOLN/* !MOVED civ.war.org/p1/alinc.htm
Notes:If you do not use !TEMP or !MOVED,
you must specify a full URL-- do not forget the http://.
- Redirecting requests for CGI-BIN scripts (somewhat obsolete,
use of CGI-BIN virtual directories is now recommended).
If you want to run a CGI-BIN script that is not in your CGI_BIN_DIR
directory, you can use the ALIAS file to provide path information. In this
case, the alias should consist of the CGI-BIN script name (without any
slashes or other path information), followed by the drive and directory
where it can be found.
For example:
- If ..
- a selector of
CGI-BIN/MAKEMAP/?NEB+IOWA
is recieved
- The ALIAS file contains a
MAKEMAP D:\EXES\GIS
entry
- MAKEMAP.EXE is a CGI-BIN script located in D:\EXES\GIS
- then...
- D:\EXES\GIS\MAKEMAP.EXE will be invoked, with NEB+IOWA placed
into standard input (along with all the other CGI-BIN variables stored in
the environment).
Note that if this MAKEMAP D:\EXES\GIS
entry did not exist,
SRE-Filter would look for a MAKEMAP program (such as MAKEMAP.CMD) in your CGI_BIN_DIR
directory.
Notes
- Entries in the ALIAS_FILE may be "host specific"
- The use of aliases as a means of identifying the location of a
CGI-Bin script is "not spec", so should be used with caution.
- "Local redirection" using aliases can cause problems when the client's browser resolves
"partial URLS" -- see INITFILT.DOC for further discussion!
- You can use wildcard matches and wildcard
matches with substitution
in your aliases (note the LINCOLN example above). This
is useful if you want to redirect all request for files that used to be in a subdirectory
to some new location.
-
ALIASES are processed before the AUTO-NAME replacement is attempted. Keep
this in mind when considering how to handle requests that arrive with
no extension, no ?, and that do not end with a /.
Return to table of contents
What to do if no document can be found
Sometimes, despite the use of "aliases" and "AUTO_NAME", the requested
"action" (such as an HTML document, or a CGI-BIN script) can not be
found. In those cases, a 404 Not found
response
is returned to the client, along with a short description. You can put
a customized message in this short description. In particular, you
can put a link to your "home page".
The NOT_FOUND_URL variable
contains this customized message. By default, it's value is:
<a href="/"> Visit the HOME_NAME home page? </a>
Note that HOME_NAME
will be replaced by the current (possibly host
specific) value of the HOME_NAME variable.
Thus, the befuddled client merely needs to click on this link to get some kind
of access.
Notes:
- For greater customizaton, you can set NOT_FOUND_URL to point
to a could not find document response file (or you can
use the simple-mode configurator).
This should be a fully qualified file name; this file will be
returned whenever the requested resource
can not be found. Typically, this would be an HTML document (say,
D:\WWW\NOTFOUND.HTM).
- HOME_NAME
should contain a
short description of your domain; say:
BIG/SERVICE: Your Friendly Government Agency!
.
Or, you can set HOME_NAME
=" "
to send a generic message!
- Note that HOME_NAME and NOT_FOUND_URL can be HOST specific.
- For further discussion of HOME_NAME and NOT_FOUND_URL, see
INITFILT.DOC.
Return to table of contents
Dynamic document creation (server side includes)
The simple-mode configurator
can be used to ..
Perhaps the greatest advantage of SRE-Filter is the extensive support for
dynamic document creation. In particular,
server side includes of files, text
strings,
and transient variables (such as the time, date, and number of requests)
are easy to accomplish, requiring modifications to your HTML documents, and
not to the server software.
The basic idea is that when writing an HTML document,
special keyphrases are inserted. When the document is
requested, SRE-Filter will detect these keyphrases,
and perform the desired action.
The basic structure of a keyphrase is:
<!-- KEYWORD
argument
-->
where:
- KEYWORD can be one of several phrases:
- SELECT -- used to selectively include blocks of HTML code
- REPLACE -- used to "replace strings"
- INCLUDE -- used to "include files"
- OPTION -- used to "include
options sent by the
client"
- INTERPRET -- used to "include
the results of a custom-designed REXX routine"
- CACHE -- controls SRE-Filter's
server side include CACHE
- #cmd -- NCSA HTTPD style server side includes
Note: If desired, you can add a "preface" (such as the !
character) to the definitions of the first six keywords (i.e.; !REPLACE
is used instead of REPLACE). See the description of the KEY_PREFACE
variable in INITFILT.DOC for details.
- argument is a string containing "arguments" that are used, in
conjunction with the keyphrase, to dictate how SRE-Filter should modify
this document.
Examples:
<-- REPLACE CREATION_DATE --> :
<-- INCLUDE ADDLIST.HTM -- >
<-- #FLASTMOD VIRTUAL="SAMPLES/SREFILTR.HTM" -->
Notes
- When SRE-Filter finds a keyphrase, it will ALWAYS remove the keyphrase, and
replace it with the file or string dictated by the KEYWORD
argument . This replacement occurs at the position in the document that was
occupied by the keyphrase. If a faulty keyphrase is encountered
(i.e.; a non-supported argument is used),
SRE-Filter will remove it.
-
The SELECT keyphrase is a little different: it dictates whether the "block of
HTML code" that follows the SELECT keyphrase is to be retained. Thus, it is
best thought of as a "server side exclude" -- the keyphrase is always removed, but
sometimes so is a lot of other stuff!
- The CACHE keyphrase is used to control SRE-Filter's caching of documents
that contain server side includes.
- The NSCA HTTPD style server side includes are provided for completeness
sake; some of them are redundant with REPLACE and INCLUDE.
- You can instruct SRE-Filter to perform server side includes only
on files that have a .SHT or .SHTML extension. See the description
of the SSI_SHTML_ONLY and SSI_EXTENSIONS parameter (in
INITFILT.DOC) for details. Or,
you can use the simple-mode configurator.
Headers and Footers
In addition to server side includes using keyphrases, a multi-line header and
footer can be automatically added to all HTML
documents. The header is added just after the (first) <BODY >
tag in the document (see the notes for an exception to this rule); and the footer is added just before the (last)
</BODY > tag.
To set these, just change the values of the HEADERS.
(for headers) and the FOOTERS. (for footers)
stem variables located in INITFILT.80.
Or, you can use the simple-mode configurator.
Notes:
- Headers and Footers can contain keyphrases.
- To suppress addition of a header and/or a footer,
set HEADERS.1=0 and/or FOOTERS.1=0.
- If the HEADER starts with
<BODY>, then the HEADER will replace the first <BODY> element.
-
The various server-side includes are only attempted for HTML files.
-
If you will NEVER have server-side includes, you can set the
NO_INCLUDE variable to equal "YES". This will speed up request
processing a bit.
- HEADERS., FOOTERS., and NO_INCLUDE can be host specific (see INITFILT.DOC for details).
- Instead of using <!-- and --> as keyphrase delimiters,
you can specify your own set(s). See the description of DELIM_1 and DELIM_2 in
INITFILT.DOC for details.
Description of Keyphrases
The REPLACE keyphrase
Syntax: <!-- REPLACE Varname -->
, where Varname
is
the name of a static or dynamic variable.
The REPLACE keyword is used to insert dynamically determined information
and short (static) strings into a document.
SRE-Filter recognizes the following "built-in" Varnames
:
- DATE : todays date (i.e.; 27 Aug 1988)
- TIME : current time (local) (i.e.; 4:54pm)
- DATEGMT : current date (at GMT)
- TIMEGMT : current time (GMT) -- a GMT is appended
- CREATION : Short message stating (local) creation time and date of the document
- CREATION_DATE : Creation date of document
- CREATION_TIME : Creation time of document
- SERVERNAME : The IP name of the server (i.e.;
WWW.MYORG.NET). If multiple hosts, this will
be the IP name of the server to whom the request was directed.
- SERVER : the server software (i.e.
GOSERVE ver. 2.45 )
- WEBMASTER : The Webmaster's address **
- USERNAME : The client's name, i.e. johndoe.somewear.net
(or his numeric ip address if a name is unavailable)
- HOME_NAME : The host specific colloquial (not necessarily IP) name of this
domain **
- URL : The current URL (includes the servername and serverport)
- BROWSER: The name of the web browser the client is using
(sometimes referred to as the 'User-Agent')
- FILTER_NAME : The name of the filter (i.e.; SRE-Filter ver 1.2).
- REFERER : The address of the server that refered the client to your site
(often unavailable).
- INHOUSE.n : n = an integer. If the user has INHOUSE
privileges (but does not have SUPERUSER
privileges)
then replace with the INHOUSE.n variable **
- SUPERUSER.n : n = an integer. If the user has SUPERUSER
privileges
then replace with the SUPERUSER.n variable **
- HITS and HITS_FILE: A string stating the number of hits
for the "URL" or the file (respectively),
being requested (the number of hits is stored in the
COUNTER_FILE ).
Note that
a given document may be reached via several different selectors (say,
due to several aliases pointing to the same file), each of which
will have a seperate counter. In contrast, each FILE has a
unique counter. Also note that on multiple host servers,
otherwise similar selectors (that may even point to the same file)
will have seperate URL counter entries -- but (if they do point
to the same file) will have only one FILE entry.
- COUNTS and COUNTS_FILE: Same as HITS, but just the number is displayed.
- OPTION_COUNTS.n and OPTION_HITS.n :
Normally, the same as COUNT and HITS. But, if an option
has been recieved, use the value of the nth
option (rather then number of
hits).
- READ_HEAD : Displays (using a <PRE>> format) the "request
header". This can be a handy debugging tool.
- PREFILTER_RESULT : Displays "status" message returned by the
PREFILTR routine. If the PRE_FILTER variable
equals NO, PREFILTER_RESULT will be an empty string.
A special argument can
be used to extract
variables from the GoServe environment, which
contains many variables created by SRE-Filter.
- VARIABLE.varname will extract the varname
variable, where varname is either in the GoServe/SRE-Filter environment,
or a value hard coded in SREFILTR.80.
For example,
VARIABLE.HOST_NICKNAME refers to "host nickname" (if available) to whom
this request was directed.
Last of all, if none of the above matches argument , the
REPSTRGS_FILE is searched for a
match (which might be host specific). If a match is found, the
information from this entry in REPSTRGS_FILE is used.
See REPSTRGS.IN for the details,
(or you can use the simple-mode configurator).
Notes
- The **'ed variables are user-configurable "static" variables that
can be modified by editing INITFILT.80.
All of them may be host specific.
- To create a host-specific "static" variable,
you should include
a .HOST_NICKNAME. For example, for a host with a nickname of
ZOO, the WEBMASTER should be specified (in INITFILT.80) using:
WEBMASTER.ZOO='MANAGER@ZOO.YOURSTATE.ORG'
.
If a matching
host-specific entry does not exist, the "generic" entry (in this case,
WEBMASTER) would be used.
- Both "built-in" and "user-defined in the REPSTRGS.IN file" variables
can be host specific (using the above syntax in both cases).
- When including static variables in your HTML documents,
the .HOST_NICKNAME should not be appended!
For example, if the ZOO host is asked for INDEX.HTM, and INDEX.HTM
containsthe tag:
<!-- REPLACE WEBMASTER -->; SRE-Filter would look up the value of the
WEBMASTER.ZOO variable.
In contrast, if the tag were: <!-- REPLACE WEBMASTER.ZOO -->
SRE-Filter would look for WEBMASTER.ZOO.ZOO.
-
Dynamically determined information consists of variables that are
determined at the moment the request is recieved. For example:
<!-- REPLACE TIME
-->
will cause the current (local) time to be placed in the document.
- Static information is the same for all requests (to a given host). Inclusion of
static variables can be a great convenience when writing sets of HTML
documents, especially if phrases that occur in all these documents are subject to
frequent change (say, a daily message).
- The HIT_CACHE_LEN and HIT_OWNER_SUPPRESS variables can be used to reduce the
number of false hits.
Return to table of contents
The INCLUDE keyphrase
Syntax: <!-- INCLUDE FileName -->
, where FileName is
the name of the File to be included.
The INCLUDE keyphrase instructs
SRE-Filter to include the contents of a file
into the requested document
(where argument is the file-to-be-included).
For example, INCLUDE PHONE.LST
would cause the contents of the file PHONE.LST
(in your data directory) to be inserted into the
document.
Notes
- It is recommended that
INCLUDE keyphrases appear on seperate lines of a file (with no other HTML
statements or text).
The file is treated as a long string (that contains linefeeds)
and replaces the keyphrase -- anything before or after the keyphrase
(on the same line) will be placed just before and after the contents of
the file.
- FileName is interpreted relative to the Data Directory, or
to a "local" virtual directory .
- The INCLUDE keyphrase will check for potentially fatal, recursive
file INCLUDES, and disallow them. Since this check is very primitive, it
will also disallow multiple INCLUDEs of the same file. If you need to
include a file multiple times
(say, to position a button bar at the top and bottom of your
document), you can use the #INCLUDE keyphrase.
- INCLUDE, in combination with the INTERPRET keyphrase, facilitates
customization of your documents , based on client specific informaton
(such as the
user agent
)!
Return to table of contents
The OPTION keyphrase
Syntax: <!-- OPTION n -->
, where n is an integer.
The OPTION keyphrase instructs SRE-Filter to insert the contents of
the n'th OPTION into the document.
OPTIONs are contained in the portion of the request following the ? character.
How to pass OPTIONs to a document
To pass OPTIONs to a document, the selector portion of the request
should have the form:
HTMLFILE.HTM?Your+OPTION+1&OPTION2
- In this example ....
OPTION 1
keyphrases in HTMLFILE.HTM
would be replaced with the string Your OPTION 1
-
OPTION 2
keyphrases in HTMLFILE.HTM
would be replaced with OPTION2
.
-
OPTION 3
keyphrases in
HTMLFILE.HTM will be removed (since only two options appear in
the request).
- URL character decoding
is done on the string following the ? character.
- You can have as many OPTIONs as you like, each seperated by a &.
OPTIONs and searchable indices.
When a browser responds to document containing the <ISINDEX >
element, the request will have the same
HTMLFILE.HTM?word1+word2
format. In order
to properly respond to such "searchable index generated" responses, you should set up an
ALIAS
Notes
- The OPTION keyphrase is somewhat obsolete -- the use of
cookies may be more appropriate
(see SAMPCOOK.HTM for an example).
- OPTIONs can be useful as a simple means of keeping track of where
the client came from. For example, you can use the OPTIONs keyphrase
to include message about "where you came" from in linked
documents.
The SAMPOPT1.SHT and SAMPOPT2.SHT files bundled with
SRE-Filter demonstrates this use of OPTION (careful, it causes
problems if disable SSI).
Another example (albeit trickier), is to use
OPTION keyphrases to customize URLS, with the goal of helping
the client return to one of several potential "invoking"
documents.
- The OPTIONs are stored in the OPTLIST. "stem" variable,
with OPTLIST.0 containing the number of OPTIONs recieved.
This information can be used in INTERPRET keyphrases to help customize
documents.
Return to table of contents
The INTERPRET keyphrase
Typical syntax: <!-- INTERPRET FILE xxx.RXX -->
INTERPRET provides a means of including and executing
a REXX-code-block
There are two major variants of the INTERPRET keyphrase:
-
INTERPRET CODE statment 1 ; statement 2 ; ...
;
where each statement n
is a valid REXX statements (and
each statement is seperated by a semi-colon).
For example:
INTERPRET CODE tmp1=server() ; interpret.result=tmp1
-
INTERPRET FILE Filename arg_list
,
where: -
Filename
is a file containing REXX code
(filename
is assumed to be relative to the working directory,
or to a "local" virtual directory).
-
arg_list
is an optional comma delimited list of
"arguments"
Example
- If your document contains the keyphrase:
- <!-- INTERPRET FILE GOBED.RXX-->
- and GOBED.RXX contains:
- tmp1=time('h') ; if tmp1<6 | tmp1>23 then
interpret.results=" <em> It is late, GO TO BED! </em> " ;
then the phrase It is late, GO TO BED! will appear in your
document whenever your local time is between 11:00 P.M and 6 A.M.
In general, the INTERPRETed REXX-code-block
should include one or more of the following:
- A SAY or AUDIT command (for writing status messages)
- Assignment of a (possibly multi-line) string to
the INTERPRET.RESULTS variable. The contents of
INTERPRET.RESULTS is
written into the document (at the location the keyphrase occupies).
- A QUEUE (or PUSH) command -- with each QUEUEd (or PUSHed) string
automatically appended to INTERPRET.RESULTS (see the discussion of
the USE_STDOUT variable in INITFILT.DOC for more details on this #EXEC-like
feature)
- RETURN 'stuff to include'
Notes:
- When processing a REXX code-block, syntax checking is turned on -- coding
errors will cause the code-block to fail, but will not crash GoServe.
INTERPRET FILE
blocks are "interpreted"
by SRE-Filter -- they are not called as external procedures.
Therefore: an INTERPRET FILE code-block
can not contain
procedures or subroutines
This inconvenience can be partially ameliorated by calling "external" procedures from
within the INTERPRET FILE code block.
- If a
RETURN
is encountered in an INTERPRET file, the "returned"
string is used as the server side include (the value stored
in INTERPRET.RESULTS, and output from PUSH and QUEUE statements, are
ignored).
- The comma delimited
arg_list
can be accessed using
the usual REXX
syntax (i.e.; parse arg aval1,aval2
). You can
include up to 10 arguments.
- The following functions and variables can be accessed by a REXX code block:
host_nickname
: The host nickname (useful on multi-host servers)
servername
: IP name of the server (useful on multi-host servers)
host_nickname
: SRE-Filter's host nickname (for this servername
)
-
optlist.
: The option list stem variable (the "options"
following a ?
in the request).
-
privset
: A list of the client's privileges
-
verbose
: The VERBOSE variable (higher values for more PMPRINTF output)
-
docname
: The "action" portion of the request
-
usedfile
: The fully qualified name of the requested file
-
Get_value(env_var)
: The GET_VALUE
function will return the value of
an SRE-Filter "environment" variable.
- You can access the GoServe functions (such as the REQFIELD function).
There are several SRE-Filter procedures, including string manipulation routines,
that you may find useful.
-
INTERPRET
will be ignored if NO_PROCESSING='YES', or if a NO_SSP permission applies to this selector.
-
INTERPRET CODE
keyphrases will be ignored if
NO_INTERPRET_CODE='YES', or if a NO_CODE permission applies to this selector.
Note that INTERPRET FILE keyphrases are not effected
by NO_INTERPRET_CODE
- When using
INTERPRET CODE
:
each statement must end with a semi-colon.
- If you wish to have INTERPRET CODE conditionally include a ssi keyphrase
(say, an <!-- INCLUDE FILE --> keyphrase), you'll have to use
'<!'||'--'
and '--'||'>'
as delimiters.
- If your needs are complicated, you might want to
write your own SRE-Filter add-on; typically this would be a
REXX routine that would generate an HTML document that SRE-Filter
would then return to the client
However, when combined with the other keyphrases, the INTERPRET
keyphrase can accomplish quite a bit of customization!
- DIRINFO.RXX, USETABL2.RXX, and ADDPRIVS.RXX are samples of
INTERPRET FILE
files (ADDPRIVS.RXX uses the arg_list
).
- Obsolete: An INTERPRET_FILE can be used to store
small rexx-code-blocks using a "label" system. However, we no longer
recommend this method.
Return to table of contents
The SELECT keyphrase is qualitatively different from the other keyphrases -- it
acts as a "conditional server side exclude" of HTML code that is already
in your document.
The power of SELECT is the ability to check dynamic variables (such as the
client's IP address, or his user agent), and retain or exclude a portion of the HTML document
accordingly.
A SELECT keyphrase expects an argument containing a block of REXX code, just
like the code blocks used in the INTERPRET keyphrase. This
block of code will be interpreted
. The code block
should "exit" with either a RETURN 1
or
RETURN 0
, where:
RETURN 1
: the subsequent HTML text block
is retained
RETURN 0
:the subsequent HTML text block is
deleted.
The "subsequent HTML text block" is delimited by a
SELECT END
keyphrase, and
can be of any length (if no SELECT END
keyphrase is encountered, the remainder of the file is dropped).
Lastly, if there is no RETURN, the code block is retained (i.e.;
the default is RETURN 1).
Example:
<!--SELECT tmp.1=extract('clientaddr') ;
if wordpos(tmp.1,owners)=0 then return 0; -->
<em> Hello! You have SuperUser Privileges !! </em>
<!-- SELECT END -->
Note that RETURN 1
is assumed by default,
hence when the clients IP address is listed in the
an OWNER variable (and the code block ends without a return)
the Hello! ...
message will not be deleted.
Notes
- If you've played around with the DELIM_1 and DELIM_2 parameters: when
entering the beginning and end SELECT keyphrases, you
must use the same set of delimiters.
- SELECT will not be done if:
NO_PROCESSING='YES', NO_INTERPRET_CODE='YES', or if
either a NO_CODE or a NO_SSP permission applies to this selector.
- SELECT blocks can not be nested. They may
contain other keyphrases.
- Older versions of SRE-Filter used
SELECT.RESULT=1 and
SELECT.RESULTS=0
instead of RETURN 1
and RETURN 0
(respectively).
This is still supported, but it is not recommended.
- SELECT keyphrases are processed somewhat more slowly then other keyphrases -- for
small replacements, you might want to use INTERPRET keyphrases instead.
Return to table of contents
You can use the simple-mode
configurator to enable caching of server side includes
To improve performance, SRE-Filter will "cache" HTML documents that
have server side includes (SSI). This caching is of the document
after the SSIs have been performed.
In simple cases SRE-Filter can send this cached file, without having to repeat the actual
process of SSI lookups, etc. Needless to say, this can greatly
improve server performance.
For a complete description of SRE-Filter's SSI-caching algorithim,
and of the various options available for the CACHE keyphrase,
please read SSICACHE.HTM .
What follows is a very brief description of the options available
for the CACHE keyphrase.
- <!-- cache no -->
- Do not cache this document
- <!-- cache asis -->
- Use a cached version "as is"
- <!-- cache notrigger -->
- Do not check the trigger files; but do check the own
file.
- <!-- cache duration nnn -->
- Set the lifespan for this file's cache entry, where nnn is the number
of (possibly fractional) days.
- <!-- cache trigger file1 file2 .. -->
- Check the file-stamps of these fully
qualified files.
- <!-- cache trigger_type stamp -->
- Selects which field(s) of the trigger file-stamps
to check.
Return to table of contents
With only minor exceptions, the server side include syntax of the NCSA HTTPD server is
fully supported by SRE-Filter.
These are invoked with a keyphrase of:
<!-- #cmd option="value" -->
Where cmd
can be: INCLUDE CONFIG FLASTMOD FSIZE ECHO EXEC
Details on NCSA HTTPD server side includes
Need more information on NCSA HTTPD server side includes?
Return to table of contents
Order of execution of KEYPHRASES
Server-side includes are processed in the following order:
- The requested document is read into memory.
- Headers and Footers, if specified, are included.
- The document,
(that now includes headers and footers),
is scanned for keyphrases.
- When a keyphrase
is encountered, the appropriate server side include is performed; or if
a SELECT keyphrase is encountered, a server side "exclude" may be conducted.
- After each keyphrase is processed, step 4 is repeated
(from the beginning of the file).
- This process continues until there are no more
keyphrases.
- If you've specified more then one set of keyphrase delimiters,
step 3 will be repeated for each set.
Note that the keyphrases in the latter part of a
document are processed after
freshly included keyphrases.
While not the most efficient algorithim (long documents with many
server side includes will cause a lot of string comparisons),
it does enable recursive processing of all keyphrases
This recursive feature allows for some powerful document manipulation strictly through
the use of keyphrases. In particular, the INTERPRET keyphrase can examine variables
such as the "referer", the "client name", or the "OPTION list", and generate
inclusions that incorporate other keyphrases (which will be
processed on the next
cycle of keyphrase interpretation).
There are several caveats:
- SRE-Filter will check for potentially fatal recursive
includes,
and disallow them. If this should occur, a simple error comment is
added to the document that is sent to the client. See the description
of the INCLUDE and #INCLUDE keyphrases for some important provisos.
- If you use the AUTO_HEADER feature, you should not
place server side include keyphrases in the <HEAD> portion of your
HTML documents.
- In general, we do not recommend use of the
DO_SEND_PIECE (the
send pieces as they become available) SRE-Filter option.
If you do use it, note that:
- SSI-caching will be suppressed ,
- You will not be able to dynamically add cookies (say,
with an INTERPRET keyphrase)
- DO_SEND_PIECE is suppressed if:
- there is more then 1 set of
keyphrase delimiters, or
- the FIX_EXPIRE option is being used.
Imagemaps, CGI-Bin Scripts, and SRE-Filter add-ons
Using imagemaps
SRE-Filter provides a simple means of responding to
image maps, using
NCSA or CERN style "MAP" descriptor files. The key is to include a
map-image indicator substring in the the "resource location" of a
URL that points to a .MAP file.
More specifically, when a MAPIMAGE/ substring is encountered in
the action portion of the request, SRE-Filter will remove MAPIMAGE/, and assume the
remaining portion of the action refers to a NSCA MAP file (similarly, a
MAPCERN/ substring refers to a CERN MAP file).
For example, if the request selector is:
MAPIMAGE/PROJECTS/BRANCH1.MAP?55,123
then the "mappable image" handler would look for
PROJECTS\BRANCH1.MAP
(under the data directory,
or a "local" virtual directory), and use
the instructions therein (in conjunction with the pixel location 55,123)
to "redirect" the client.
Type of regions recognized.
There are four types of regions recognized by SRE-Filter:
-
Circles
-
Rectangles
-
Polygons
-
Points
- and you should always specify a default URL
The selected pixel will be assigned to the URL associated
with the first Circle
, Rectangle
,
Polygon
, or 'exactly-hit' Point
it matches.
If there is no such match, and
there are Points
specified in the MAP file, then the
URL associated with the closest Point
is used.
However, if the distance to this closest Point
is greater
then the value of the MAX_POINTDIST variable,
or if there are no Points
specified in
the MAP file, the default URL is used.
Notes:
- To modify the map-image indicator substrings used to indicate
a CERN and NCSA imagemap, see the description of the NCSA_ISMAP and CERN_ISMAP variables
in INITFILT.DOC
- The MAP file must be in your data directory,
or a "local" virtual directory
(i.e.; if your data directory is
E:\WWW, then the above example refers to E:\WWW\PROJECTS\BRANCH1.MAP)
- There are several handy "map" making tools available, such as MAPEDIT.
- HTACCESS is never checked for image map requests (but
HTML documents that contain clickable images are subject to HTACCESS controls).
- The SAMPMAP.HTM file that comes with SRE-Filter (which uses SAMPMAP.MAP and SAMPMAP.GIF) provides a simple example.
- Your MAP file should, but need not, contain fullly specified URLS. The http:// will be added
if missing; and if there is no IP address, your server's address (and port) are added.
- If the selected URL (the URL corresponding to the selected point) is a
"virtual URL" (contains no IP address, and does not start with a /), then
the invoking URL (minus the MAPIMAGE/) is used.
Thus,
- if the selected point is associated with
ANIMALS/TIGER.HTM,
- the .MAP file was /ZOO/GUIDE/CAGES.MAP,
- THEN ...
- the selected URL will be /ZOO/GUIDE/ANIMALS/TIGER.HTM.
- SRE-Filter's MAPIMAGE procedures are borrowed from Don Meyer's GoHTTP
package!
Please remember that the MAPIMAGE/ "indicator string"
does not refer to the MAPIMAGE/ directory!
Return to table of contents
Creating SRE-Filter add-ons
SRE-Filter provides a simple means of creating your own,
custom written, SRE-Filter add-ons.
The basic idea
is to write an "external" REXX procedure which will do the processing, or which calls
some other executable program (such as a database manager) -- and then tell
SRE-Filter to call this procedure.
The following steps outline how to do this:
- Create an HTML document that returns an
action
that invokes a Server
Side Processing request. For example, you might include a FORM
element with an ACTION attribute of "/XXX".
- Create a file (that contains your REXX procedure), with the name
xxx.CMD (or xxx.80) , where
xxx is the action name. Note that the
xxx file is relative to the working directory (or a
"local" virtual directory).
For example, if the action name is /PROGS/FAST2, and \GOSERVE is your working directory,
SRE-Filter will look for \GOSERVE\PROGS\FAST2.CMD.
- This REXX procedure should process the request (using information
passed to it by SRE-Filter), and it
may call other programs (not necessarily REXX programs).
- xxx should issue GoServe completion
codes (such as VAR, FILE, and STRING).
Calling Syntax
SRE-Filter will call xxx with the
following arguments:
- ddir
- The data directory (typically, x:\WWW)
- TEMPFILE
- A temporary, "transaction specific" file (i.e.; D:\GOSERVE\TEMP\$341.80)
- Action
- The Action portion of the request
Example (assuming the GET HTTP method
was used by the client)
- If the request selector is:
/sports/getscore?city=boston&date=July+5+1994
-
then the Action is
sports/getscore
- list
-
- If verb=GET: the partially cleaned up portion of the request selector
after the ?
( + signs, tabs and linefeeds are converted to spaces, and
URL decoding is performed).
In the above example, list would be city=boston&date=July 5 1995
- If verb=POST: the body of the request -- without + conversions
or URL decoding.
- verb
- Either GET or POST
- Request String
- The original request string, as sent by the client to the server
(includes the verb, selector, and http protocol) --without cleanup or encoding.
This can be useful if & (and other special characters) may
be text returned by GET method client requests
- user
- The numeric IP address of the client
- servdir
- The "base directory", where GoServe and SRE-Filter are located.
- workdir
- The fully qualified name of a "temporary, working" directory
that the external procedure may wish to use
(set in the TEMPFILE_DIR variable).
- privset
- The list of privileges granted to this client.
- env_id
- A substring used when specifying semaphores and queues
- transaction
- The transaction number
- verbose
- The verbose instruction (1 signifies "say intermediate results").
- servername
- The IP name of the "host" this request is addressed to. This is derived
from a HOST: request header, or from the numeric ip address.
- Host_nickname
- The SRE-Filter nickname for the "host".
- Home_directory
- The "home directory" (used in ~ replacment)
Return Arguments
The xxx.CMD procedure should return a
simple status message of the form:
response_code bytes_returned Description Message , file_used
Where:
response_code
: the http response code (typically, 200 for
GET requests and 201 for POST requests)
bytes_returned
: the number of bytes transfered (not
including response headers)
Description message
(optional) : a descriptive
message (it's transferred to the post-filter)
file_used
(optional) : The program that was run
(must follow a comma)
Examples:
200 12515 Message Succesfully Recieved, D:\GOSERVE\MESSAGES
401 302 Unauthorized access of PRIVATE DATABASE
Notes
- How does SRE-Filter recognize a Server Side Processing Request?
- STATUS.CMD, and STATUS.HTM, contain an example of how to
request Server Side Processing using a REXX
procedure.
- If a syntax error occurs, SRE-Filter will trap it and return
a simple error message to the client.
- To call an external, non-REXX program from within an
external REXX procedure, use the
address cmd
REXX command.
- If you write HTML code to TEMPFILE (for return to the client), you
should return from your external REXX procedure using:
'FILE ERASE TYPE text/html NAME ' TEMPFILE
return response_code #_bytes a message here
- When using an HTML FORM to invoke an SRE-Filter add-on,
we recomment that the "action"
contain a leading / character
(this avoids incorrect path assignment by the browser).
- If the NO_PROCESSING variable equals YES,
or the NO_SSP permission is enabled,
then server side processing will not be permitted.
Return to table of contents
Support for CGI-BIN scripts.
SRE-Filter supports CGI-BIN scripts (using procedures adapted from
Don Meyer's GoHTTP package). To run CGI-BIN scripts, you'll need to:
- Make sure that the CGI_BIN_DIR points to an existing
directory (i.e.; \GOSERVE\CGI_BIN).
- Copy the CGI-BIN script (such as a REXX file, a binary .EXE file, etc.)
to the
CGI_BIN_DIR directory.
- Invoke it using a standard CGI-BIN request selector . For example:
href=http://foo.bar.net/cgi-bin/test-cgi/morepath/?a+message
.
SRE-Filter's implementation of CGI-BIN includes a few minor modifications:
- A few additional environment variables are created. The most
important one is SREF_PRIVSET -- it contains a list of the client
privileges.
- Requests for CGI-BIN imagemaps (such as
/CGI-BIN/IMAGEMAP/MAPFILE.MAP
) are converted
into SRE-Filter IMAGEMAP calls.
- SRE-Filter comes with a few sample CGI-BIN scripts (written in REXX).
The TEST-CGI.CMD
file (which is copied to your CGI_BIN_DIR) will display the values of the
CGI-BIN variables (invoke it using /CGI-BIN/TEST-CGI?).
Need more information on CGI-BIN ?
By default, CGI-BIN scripts are assumed to be in the CGI_BIN_DIRECTORY
(say, \GOSERVE\CGI-BIN). Obviously, this can become inconvenient
once you acquire a greater-than-small set of scripts. The obvious
solution is to place the script files in subdirectories.
Unfortunately, there does not seem to be a clearly specified method
of doing this. With this in mind, SRE-Filter offers two means
of specifying subdirectories containing your CGI-BIN scripts:
- Using "aliases".
This does not require changes to the standard syntax of
CGI-BIN request selectors; i.e.; CGI-BIN/ASCRIPT/PATHINFO/?args ).
The disadvantage is that a seperate alias is need for each script --
even for scripts in the same subdirectory.
- Using the portion of the request selector before the
CGI-BIN/
The notion is to include subdirectory information before
the CGI-BIN/
(the "this is a CGI-BIN script" indicator). SRE-Filter
will interpret this starting portion as a subdirectory of the CGI_BIN_DIR,
or as a virtual directory (in both cases,the usual HTACCESS controls may apply).
This permits a powerful division of scripts into directories. The disadvantage
is that it doesn't seem to be "spec" (hence may be cumbersome to port).
Requests for CGI-BIN scripts are often followed by /PATHINFO/.
This is typically used by the script (it does
not point to the script).
Example: KIDSTORE/INVENTORY/CGI-BIN/TOYCT?toddler
This invokes the TOYCT program (with an argument of toddler
),
which is located
in (perhaps) \GOSERVE\CGI-BIN\KIDSTORE\INVENTORY\.
Notes on creating CGI-BIN scripts
- When writing CGI-BIN scripts, keep in mind that a number of
variables are available in the enviroment.
- You can output results with SAY statments.
- Your first SAY statements should declare the MIME type. For example:
Say "Content-type: text/html"
Say
Using PERL scripts with SRE-Filter
In order to take advantage of a broad spectrum of CGI-BIN scripts,
SRE-Filter can use "non-REXX" processors to interpert CGI-BIN scripts.
As long as you have the appropriate interepreter installed on your
server, it's quite easy to do this. All that you need to do is
tell SRE-Filter (using the INTERPRET_TYPES parameter) which
interpeter to associate with different file extensions -- see
INITFILT.DOC for a details on how to change the INTERPRET_TYPES
parameter.
Of particular interest is the use of one of the OS/2 PERL interpreters;
since there are a slew of PERL scripts out there. In fact, it's not that
hard to obtain a PERL interpreter --
see PERL.DOC for details
on one we've had some success with.
Return to table of contents
Special commands, and directives, recognized by SRE-Filter
SRE-Filter offers a set of special commands,
and special directives for performing
TCP/IP actions, computing statistics on the status of GoServe, and
requesting special server actions. These command all start with
an exclamation point (!), followed by a word or a phrase.
The special commands are basically built-in "server side
programs". In contrast, the special directives are used to
modify SRE-Filter's logic.
Currently available special directives
- !force/selector
- The
!FORCE
special directive instructs SRE-Filter to
suppress the LOGON_FAIL_FILE feature when considering the selector
.
This guarantees that unauthorized clients will be presented
with a username/password screen.
!FORCE
is meant to be used in the LOGON_FAIL_FILE and
ACCESS_FAIL_FILE, where it
provides a means by which a client can try again with a different
username/password. It is also used to force re-compilation
of an HTML document with server side includes (in other words, it
suppresses use of the SSI-Cache).
Examples:
- !FORCE?DIR1/INDEX.HTM
- !FORCE?DIR2/INCS/INDEX.SHT
- !norecord?selector
- Instructs SRE-Filter to NOT record this request. It has the same
effect as a NO_POSTFILTER permission.
You can disable this option by setting the NO_NO_RECORD parameter.
- !sendas_mimetype_mimesubtype/dir/filename.ext
- The
!sendas
special action is used to force
the server to send the requested file as mimetype/mimesubtype.
This can be useful if you wish to create links to unusually named
text, or html, files. For example, if you have a series of
html documents named CHAP.1, CHAP.2, etc.; you could use links of
the form:
<a href="/!sendas_text_html/mybook/chap.3">Get chapter 3 </a>
Technical note: !sendas
suppresses SRE-Filter's
extension mapping method of determining the mime type (and subtype);
and uses the explicitly coded mimetype
and mimesubtype
instead.
For information on customizing SRE-Filter's extension mapping,
see the description of MEDIATYP.RXX.
- !delsend/filename.ext
- !delsend is used to send a file from the SRE-Filter TEMPFILE_DIR
"temporary file" directory. More precisely, !delsend will look for
filename.ext
in the TEMPFILE_DIR, send it (if it exists), and then delete it.
!delsend is provided to facilitate writing server side programs that
generate several output files -- the client would be sent back
a response containing !delsend links to these several files.
Notes
-
When a
!force
, !norecord
,
!sendas
or !delsend
request is recieved,
the !cmd portion (i.e.; the !sendas_xxx_yyy/,
or the !delsend/)
are immediately stripped off.
Thus, SRE-Filter's various "SEL-specific" operations (such as access control,
or aliasing) are performed on this "stripped" request selector .
- You can end the !cmd portion with either a ? or
a /. For example, the following two request selectors are equivalent:
-
!sendas_text_plain/hello.lst
-
!sendas_text_plain?hello.lst
Currently available special commands
- !authorize
- SRE-Filter will send back an "authorization" request. The primary users
of this will be server administrators -- since a !AUTHORIZE link will
repetitively ask for the client's username/password.
- !ping
- 'PINGS' the client.
- !statistics
- View current GoServe statistics.
- !HOST?xxx.yyy.zzz.aaa
- Get information on IP address xxx.yyy.zzz.aaa
- !reset
- Resets various GoServe statistics, and instructs SRE-Filter to re-read
parameter files immediately (only available to OWNERS, or clients with SUPERUSER
privileges).
- If !reset?params, then statistics will
not be reset.
- !save
- Saves various GoServe statistics to the GOAUDIT.80 audit file.
This is only available to SUPERUSERs, or to users with a CONTROL privilege.
- !ssi
- Used to access information on the SSI-cache. The following
sub-options are recognized:
- !ssi?status : writes a (fairly technical) status report to the PMPRINTF window.
- !ssi?status=short : writes a brief status report to the PMPRINTF window
- !ssi?status=fully_qualified_file_name : writes a report on the SSI-Cache entry
(if it exists) for the
fully_qualified_file_name
- !ssi?reset = Resest (clear) the SSI-cache
- !ssi?remove=fully_qualified_file_name : remove the SSI-Cache entry
(if it exists) for the
fully_qualified_file_name
- !ssi?cleanup = Cleans up the SSI-Cache
Notes:
- The client must have SUPERUSER privileges to invoke these
!SSI options.
- After completion of the !SSI request, a
short status report (in plain-text format) will be returned to the client.
- For an illustration of the use of !SSI, see SSICACHE.HTM
- !variable?var1&var2..
- Returns the value of environment variable var1, etc.
(client must have SUPERUSER privileges to use this).
- !write_cache
- saves the
record_all_file
cache to the record_all_file
- !dir?
dirname
- Invokes SRE-Filter's built in directory lister; which will create
a list of all files (and subdirectories) of
dirname
.
To modify the various display parameters used by !dir, see the
DIR.DOC
file, or see the description of the DIR_EXCLUSION and DIR_OPTIONS
parameters in INITFILT.DOC.
Notes:
- The !CREATE option of the AUTO_NAME parameter
also uses
!dir
to generate a directory listing.
- For a more richly featured directory lister, try the
GETAFILE add-on for SRE-Filter.
Return to table of contents
In keeping with http server standards, SRE-Filter will maintain a
common-log format audit file. Entries in common-log format
audit files have the following structure:
aclient.somehere.org - username [18/Mar/1996:16:24:08 -0500] "GET /SAMPLES/HELLO.HTM HTTP/1.0" 200 1251
Besides offering a compact synopsis, a number of tools exist to help you
analyze common-log files.
Furthermore, as an adjunct to the common-log audit file SRE-Filter can also
record
the browser used by each request (as well as the referer)
in seperate log files.
Notes
- The WRITE_LOGS parameter is used to enable SRE-Filter's common-log,
browser, and referer audit files (see INITFILT.DOC for details).
- If post-filter processing has been suppressed (with the NO_POSTFILTER
permission), the request will not be recorded to these audit files.
- The SREFLOGS.INI
file contains log-file control parameters.
For example, you can select seperate log-files for each of several hosts, you
can suppress any of these log-files, and you can suppress auditing of
400 (failure) or 300 (moved) requests.
Return to table of contents
You can use the simple-mode configurator
to enable the common-log audit file and the RECORD_ALL_FILE
running count.
As an alternative to the common-log audit file, SRE-Filter maintains
a running count of requests in the
RECORD_ALL_FILE . This file contains
a count of requests, broken down by selector or by filename.
Record refers to updating a count of the number
of times a resource has been requested.
It does not mean keeping a record of each hit! If you need
such detailed accounting, you should use the
common-log file (or you can use GoServe's GOAUDIT.80 file).
For customized auditing needs, you can add your own
procedure using the post-filter option
(POSTRCRD.80 is an example of such a procedure).
To enable the RECORD_ALL_FILE, you need to
set the RECORD_OPTION parameter.
RECORD_OPTION can take the following values:
- NO
- Do not maintain a running count
- YES
- Record requests, but remove the the argument list from the selector
(for example; remove
?hi+there
in
ANIMALS/MONKEY.HTM?hi+there
selector
- YES_ALL
- Record requests, do not remove an argument list.
Caution: Use of YES_ALL can lead to a very large
RECORD_ALL_FILE
- FILE
- Record requests by fully qualified file name. In contrast, when YES or YES_ALL
are specified, requests are recorded by selector
Caution: Use of FILE can lead to a very large
RECORD_ALL_FILE -- careful use of wildcard entries is recommended.
RECORD_ALL_FILE: Implementation details
To speed throughput, SRE-Filter caches the RECORD_ALL_FILE in memory,
with a single thread responsible for updating it (the POSTFCHK thread).
This raises several issues:
- The cache is written to disk on a regular basis (about
once every five minutes). Thus, it is possible for the file
version to be somewhat out of date; and it is possible to loose
entries (say, if the server crashes).
- If you "hand edit" the RECORD_ALL_FILE (say, to add
wildcard entries), SRE-Filter will
read it into the cache, overwriting any changes that have been recently
made. That is, any requests recieved while you were editing the
file will not be recorded.
- If the cache grows large (over 1000 entries), SRE-Filter will
start over -- and save the old RECORD_ALL_FILE (you won't loose
information, but it will be spread over at a few files).
There is one exception: SRE-Filter will retain "wild card" entries
(but will reset their count to 0).
Given the above: the RECORD_ALL_FILE should be treated as
an approximate (albeit probably very accurate) count of requests.
To avoid loosing a few minutes of entries that will occur
when you shut down GoServe, you can issue a !WRITE_CACHE request
just beforehand
Notes
- Wildcard matching of entries is supported,
both by "selector " and by "FILE".
- By default, results are written to RECRDALL.CNT -- this can
be modified by changing the RECORD_ALL_FILE
variable.
- Entries in the RECORD_ALL_FILE may be "host specific". However,
when FILE is specified, host information is not used.
- For YES and YES_ALL, each entry in the RECORD_ALL_FILE contains
the request selector (minus the
argument list if RECORD_OPTION=YES), the number of
"honored" requests, and the date of the most recent request.
- For FILE, each entry contains the fully qualified file name, the number of times
the file was requested, and the date of the most recent request. Note
that when FILE is used, information after the ? is ignored (there is
no FILE_ALL option!).
- Only "honored" requests are recorded
-- requests for actions that are not honored (when
ALLOW_ACCESS is enabled) are not recorded.
- If an entry matching the request selector is not found
in RECORD_ALL_FILE, a new entry will be created!
- ... however, a wildcard match is always attempted.
The use of "wildcard matching" is recommended if many
temporary files are likely to be requested. For example,
one should include a "wildcard" for
the "temporary" directory in your RECORD_ALL_FILE
- The size of the RECORD_ALL_FILE cache can be increased or
decreased by changing the RECORD_CACHE_LINES variable.
Or, you can suppress this caching by setting RECORD_CACHE_LINES=0.
See INITFILT.DOC for details.
-
The differences between the RECORD_ALL_FILE method, and placing a
REPLACE HITS (or REPLACE HITS_FILE) keyphrase in all documents, are:
- Nothing is written to the requested file
(the client is not given info on # of hits)
- The RECORD_ALL_FILE is updated,
not the COUNTER_FILE.
- All requests are tracked: including transfer of HTML documents and.GIF files,
and Server Side Processing requests.
Thus, if a REPLACE HITS
keyphrase is included in a document,
and RECORD_OPTION is enabled ,
a "count of requests" will be updated in the
COUNTER_FILE and in
the RECORD_ALL_FILE
- For viewing the RECORD_ALL_FILE, we recommend the
VURECORD SRE-Filter add-on.
Return to table of contents
To reduce the number of false hits from clients re-requesting
a URL after a short absence (often caused by the
use of a browser's "back" key), a list of current hits
can be maintained. If a request selector matches a request in this list of
current hits
(where the request selector and the client's IP address are both used),
the "count of hits" will not be augmented. Specifically,
the COUNTER_FILE and the RECORD_ALL_FILE will not be augmented.
In addition to "re-requests", you may also wish to not record
requests from OWNERS (such as the webmaster) -- since these are likely
to be due to site maintenance activity, and not due to interest in the content
of the requested files.
INITFILT.DOC contains details on both of these options: see the
descriptions of the
HIT_CACHE_LEN, HIT_CACHE_DURATION,
and HIT_OWNER_SUPPRESS variables (or you can
use the simple-mode configurator).
Notes
- You can control the size and duration of the
list of current hits by modifying the HIT_CACHE_LEN
and HIT_CACHE_DURATION variables
- You can not record requests from OWNERS by
enabling the HIT_OWNER_SUPPRESS variable.
- Similar request suppression options exists
for the COUNTER.RXX hit-recorder.
Return to table of contents
SRE-Filter supports a simple form of "load balancing". When load balancing
is active, the server will first check the number of active clients.
If this exceeds the number specified in the LOADTHRESHOLD variable, then the
client is redirected to one of the servers listed in the BackupServerList
variable.
For details on how to invoke load balancing, see the description of LOADTHRESHOLD
in INITFILT.DOC
Return to table of contents
In certain cases, you may wish to have a set of
custom written REXX routines
examine the request before yielding control to SRE-Filter. For example,
you may wish to shunt some special requests to a variety of different
filters.
To do this, set the PRE_FILTER variable:
- PRE_FILTER=NO: no pre-filtering will be attempted.
- PRE_FILTER=YES: a pre-filter (a REXX procedure) will
be called. The pre-filter will be called after
logon privileges have been determined; when individuals do not
have logon privileges, the pre-filter will not be called.
- PRE_FILTER=FIRST: same as PRE_FILTER=YES, except the pre-filter is
called as the very first action (before logon privileges are ascertained).
You can specify the name(s) of the pre-filter procedure file(s)
by setting the
PREFILTER_NAME variable. By default, PREFILTER_NAME="PREFILTR"
(which refers to PREFILTR.80).
When a pre-filter is called, several arguments will be passed. The first
three are generated by GoServe, the second to last is generated by SRE-Filter and
is not passed when PRE_FILTER=FIRST, and the last offers a means
of transfering results from earlier to later pre-filters.
parse arg source,request,sel,privs,servername,otherargs
source:
myaddr port transaction who whoport
request:
verb selector protocol
sel:
action '?' awords
privset
: list of privileges
servername
-- ip name of server (useful in multi-host
environments).
Other_args
-- results from prior pre-filter.
The pre-filter should return a comma delimited list:
status , status message
Where status is either 0 or 1:
0= No response to client, SRE-Filter should continue processing.
1=Response to client, SRE-Filter should exit (perhaps with response recording)
The Status message will be stored as
PREFILTER_RESULT. Note that the
REPLACE PREFILTER_RESULT
keyphrase
can be used to display this status message.
Notes
- If more then 1 pre-filter is called, the PREFILTER_RESULTS
will be from the last pre-filter specifed in PREFILTER_NAME
- If an earlier pre-filter issues responds to the client (and
issues a GoServe "completion code"), the remaining pre-filters
are skipped.
Return to table of contents
The PREFILTR.80 file that comes with SRE-Filter contains a
pre-filter that enables support for the GoRemote package.
GoRemote (the "server remote control" package bundled with GoServe)
is typically called as a special filter. By using this pre-filter, GoRemote
will automatically be called (instead of SRE-Filter) when a GoRemote
specific action is requested.
To do this, you'll need to:
- Make sure you have the GOREMOTE package (GOREMOTE.ZIP), and unarchive it to either the root of
your data directory, or to the GOREMOTE/ subdirectory of your data
directory. You'll need GOS32.GIF, GORM*.HTM and GOREMOTE.* files.
Since there are about a dozen GORM* files, placing them in
a subdirectory is asthetically preferable.
- Copy GOREMOTE.80 to your working directory. If GOREMOTE was
installed in a GOREMOTE/ directory, copy GOREMOTE.HTM, GOS32.GIF and GORMOK.HTM to the
root of your data directory
- Make sure that PREFILTR.80 (the one that comes with SRE-Filter) is
also in your working directory.
- Using CONFIG2.HTM (or by direct modification of the INITFILT.80 file),
set the PRE_FILTER variable to:
- YES = If you want to limit access to GoRemote:
- Clients with SUPERUSER or INHOUSE privileges will be able to
view filter settings and statistics.
- Clients with SUPERUSER privileges will be able to change settings.
- FIRST = If you want all clients to have access to GoRemote
You should also set PREFILTER_NAME='PREFILTR.80'
- Set up a link to GOREMOTE (or GOREMOTE/GOREMOTE if
you installed GOREMOTE in a GOREMOTE subdirectory).
- You do not need to make any other modifications, either
to SRE-Filter, or to the GoRemote files!
Notes:
- This pre-filter works by capturing all calls to GOREMOTE.*, GOS*.*, and
GOR*.* (or to these files in the GOREMOTE/ directory).
So, if you use this pre-filter, don't create files with these names (though
you can create files with these names in different subdirectories).
- When requesting GOREMOTE, do not use
GOREMOTE.HTM (the GoRemote filter is not expecting to see an extension).
Return to table of contents
In certain cases, you may wish to execute some additional actions
after responding to a client's request. For example, you may
wish to record client specific information in a custom designed audit
file. Or, you may wish to e-mail responsible parties
when certain events occur (such as a file upload). Or you may wish
to do both!
To accomodate such needs, SRE-Filter can be told to call a
series of "post-filters". As with
the "pre-filter", these post-filters are custom designed REXX procedures.
To enable post-filter calling, set the POST_FILTER variable:
- POST_FILTER=NO: post-filter(s) are not be called.
- POST_FILTER=YES: post-filter(s) are called.
Note: The post-filter(s) are called after a response
has been sent to the client.
Therefore, you can not
use a post-filter to modify the response
sent to the client!
You can specify the names of the (possibly several)
post-filter procedure files by setting the
POSTFILTER_NAME variable. By default, POSTFILTER_NAME="POSTFILT".
To specify several post-filters, just enter a space delimted list.
For example POSTFILTER_NAME="POSTMAIL.80 POSTRECRD.80 "
--
they will be executed in the order of appearance.
Note that if there is no extension, and no ending period, an extension of
.80 is assumed (or .nnn if you are using a non-80 serverport).
When a post-filter is called, several arguments will be passed:
- amessage : a short SRE-Filter status message
- source : The server address and client address
- request: The request string; the verb, the selector , and the http protocol
- sel: The selector
- tempfile: The temporary file used by this transaction
- servername: The host to whom the request was directed (the
servername)
- host_nickname: The "host nickname" corresponding to
the servername (or blank, if there is no HOSTS. variable for servername)
- USED_FILE: The fully qualified file used by the request:
such as the HTML file requested by the client,
or the CGI script executed by the server.
- TheReferer:
The value of the 'referer' request header -- if set, it contains
the fully qualified URL which contained the link which invoked this request.
- Thread_cache: A pointer to a set of request specific information.
This can be used by the SREF_READ_STATE macrospace procedure (note that
post-filter actions can not issue GoServe commands).
For details, see the description of the SAVE_STATE variable in INITFILT.DOC.
- RESPONSE_STATUS: The response code and the number
of bytes returned. For example: 200 19218.
For a simple example of a post-filter, see the POSTFILT.80 file that comes
with SRE-Filter. For more useful examples, see POSTMAIL.80 (an
e-mail alert routine) and POSTRCRD.80 (a client info recorder).
The POSTMAIL.80 that comes with SRE-Filter uses the SREF_MAILIT procedure (contained in
the SREFPRC1 macrospace procedure library) to
e-mail "event specific" alerts through an SMTP Gateway.
A different (set) of individuals can be notified
for each of a set of events, where events are identified by the
request selector (with wildcard matching supported),
or by the requesting client's IP address.
POSTMAIL.80 contains detailed instructions on how
to generate these e-mail alerts.
Notes:
- To use this facility, you must set the SMTP_GATEWAY variable to be the address
of your SMTP server. If you do not have access to an SMTP server, you might be able to use OS/2's SENDMAIL
program to set up your server machine as a SMTP server
(see the OS/2 TCP/IP Command Reference for more information on SENDMAIL).
- Ambitious programmers can use SREF_MAILIT for more advanced e-mail purposes.
Return to table of contents
SRE-Filter provides two built-in "actions" for uploading files,
one HTTP method
for uploading files, and one HTTP method for deleting files.
Each of these has it's own advantages
and disadvantages:
- GET_URL: A built-in action for uploading files from another HTTP server
- Requires that the client has ready access to an HTTP server.
- Given this access, uploading is quick and easy.
- PUT_FILE: A built-in action for uploading files from the client's own machine
- Requires that the client be using a browser that supports the
type=file
FORM attribute (such as NetScape 2.01 and above).
- The PUT method.
- Requires that the browser (or other software) know how
to issue a PUT method HTTP request. The DOPUT.CMD program illustrates
the use of the PUT method.
- The DELETE method. This can be used to delete files from
your server. As with the PUT method, it requires a browser that
knows how to issue DELETE method HTTP requests.
General Usage notes:
- GET_URL.
Set up a URL with the GET_URL action,
followed by the
URL of the file you want to get, and the "local name". The request selector
should look like: GET_URL?url=http://a_url&file=relative_file_name
For example:
-
GET_URL?url=http://www.pc.com/price.lst&file=pcprice.1
will copy price.lst
(on the server at www.pc.com
) to a file named PCPRICE.1 (in
the upload directory
).
- PUT_FILE.
Create an HTML FORM with a type=file
attribute. For example:
<FORM enctype="multipart/form-data" ACTION="/put_file" METHOD="post">
Send this file <INPUT TYPE="file" name="relative_filename">
<INPUT TYPE="submit" VALUE="send file">
</FORM>
- The PUT and DELETE HTTP methods are, by default, not permitted.
To allow PUT or DELETE methods, you must include a PUT or a
DELETE permission in the permission list of the
appropriate entry (for the requested selector ) in the ACCESS_FILE.
- PUT and DELETE refer are relative to the data directory, or to a
local virtual directory.
PUT_FILE and GET_URL usage Notes
- PUT_FILE and GET_URL store
results in files relative to the UPLOAD_DIR directory, or to a "local"
virtual directory. Note that if the target is a virtual directory,
a PUT permission must exist for the specified file.
For example, if the relative file name is TODAY/OUTPUT.1, and
TODAY has a virtual directory match, then access controls for TODAY/OUTPUT.1
will be examined for a PUT permission. In contrast, if TODAY has no virtual
directory match, then output is assumed to be to the TODAY subdirectory of
the UPLOAD_DIRECTORY -- and the PUT permission is not needed.
- Files must be less then UPLOAD_MAXSIZE in kbytes size;
and there must be UPLOAD_MINFREE kbytes free (in the UPLOAD_DIR
directory)
after the file is uploaded. If either condition can not be met, the file will
not be uploaded.
- If the filename (after resolving for is directory) exists,
an error message will be returned.
- If you do not specify a local file name, SRE-Filter will create a
"unique" file name in your UPLOAD_DIR directory.
You can specify "partially random" filenames by including ? characters in the filename.
SRE-Filter will attempt to create
a unique file name by appropriate substitutions of the ? character. For example:
- if filename=ABC??.TXT,
- and ABC01.TXT exists,
- then SRE-Filter will use ABC02.TXT.
- For GET_URL: You must completely specify the URL (including the http:// portion).
- A short status report on success of the upload operation is written to the
UPLOAD_LOG file.
- For PUT_FILE: Browsers that do not support the
type=file
FORM attribute will send back garbage (that will be ignored).
- UPLOAD.HTM contains an example of the use of GET_URL and PUT_FILE.
Return to table of contents
Automatic generation of response headers
If desired, SRE-Filter will parse a requested document, extract all LINK and
META HTTP-EQUIV elements found in the <HEAD>, and create the
appropriate response headers. This is especially useful
in response to HEAD requests.
To do this, set the value of the AUTO_HEADER variable:
- NO : Do not create response headers
- HEAD: Create response headers when a HEAD HTTP method request is recieved for
an HTML document.
- ALWAYS: Create response headers whenever a GET or HEAD request is recieved
for an HTML document.
Notes
- GoServe automatically generates several response headers (such
as content-length and file-creation-date).
- Server side includes (that might be in the <HEAD>) are not processed when a HEAD
request is recieved. Furthermore, server side includes are not processed
when response headers are created, but are processed when
the <HEAD> is returned as part of the document.
Thus, if you intend to use AUTO_HEADER,
we recommend not using server side
includes in the <HEAD> portion of your HTML documents!
- From an HTTP purist basis, the use of AUTO_HEADER="HEAD" would be
discouraged, since the response headers returned by a GET and a HEAD request
would be different. However, since many browsers understand that
LINK and META EQUIV elements (in the <HEAD> section of an
HTML document) are equivalent to response headers, this is probably
not
a serious drawback.
Return to table of contents
SRE-Filter recognizes a list of the most frequent MIME media types (using the
extension of the requested file). If you want to add to this list, you
can do so by editing the MEDIATYP.RXX
file located in your
GoServe directory.
Additions to MEDIATYP.RXX may be new media types
(say, an experimental MIME type),
or they may be assignations of a non-standard extension to a common MIME type
(say, .DOCUMENT to text/plain).
Notes
- MEDIATYP.RXX
is checked only when the requested
file has an extension that does not match one of SRE-Filter's pre-defined
mime types. Therefore, it can not be used to redefine
a built in mime type.
- Instructions on how to modify MEDIATYP.RXX are contained in
the copy of MEDIATYP.RXX that ships with SRE-Filter.
- If you add new text/html entries, and you want these to be equivalent to
SHTML entries (that is, html entries with server side includes permitted), you
should edit the SSI_EXTENSIONS variable in SREFILTR.80 (see INITFILT.DOC for
details).
Return to table of contents
Some useful facilites provided with SRE-Filter
Searching files using DOSEARCH
The DOSEARCH add-on for SRE-Filter is a generic search utility written in REXX. It searches
one (or several) ASCII text files for "paragraphs" that satisfy a set of conditions that are
specified in a "search string", and returns an HTML document containing
these paragraphs.
Using DOSEARCH.HTM
DOSEARCH.HTM is an HTML document that directly calls DOSEARCH -- it does
not require using an ALIAS or an <ISINDEX> element. It also provides
an easy means for setting a number of DOSEARCH options. If you are familiar with
HTML FORMS, you can customize (and rename) DOSEARCH.HTM. In particular,
to facilitate searches (say, of a specific document)
many of the TYPE fields can be set to be HIDDEN.
DOSEARCH details
DOSEARCH looks for "search strings" within "paragraphs", and uses "meta
commands" and "target specific" instructions to structure the search.
By default, a paragraph is defined as being
all text between blank lines. Alternatively, one can define paragraphs as single lines,
or as delimited by any arbitrary character sequence.
A search string is comprised of "targets" There are two kinds of targets:
subwords
and phrases.
Each space delimited entry in the search string is treated
as a seperate subword
, except..
for phrases
, which are delimited by parenthesis; for example: (xx yy zz)
.... and phrases must be matched precisely.
Search algorithims.
DOSEARCH has two modes: SIMPLE and LOGICAL.
Simple mode with highlighting.
Two meta-commands and 4 "target specific" instructions are recognized.
Meta-commands are signified by *& or *\ at the beginning
of the search string.
*& means "find paragraphs that match ALL targets in
the search string"
*\ means "find paragraphs that match NONE of the targets in
the search string"
If there are no meta-commands, the following target specific
commands are recognized.
& means "paragraphs MUST have this target"
| means "accept paragraph if it has this target"
Note that | is the default (assumed if no target specific
command entered).
\ means "paragraph must NOT have this target"
% means "accept paragraph if it does NOT have this target"
Summarizing: to be a "found" paragraph:
Test 1a) Any (of several) | targets must be present, or
1b) All of the % targets must be missing
If pass test 1a and 1b, then
2a) None of the \ can be present, and
2b) All of the & must be present
If present, all & and | targets will be highlighted.
Note that if there are no % targets specified, test 1b is ignored.
Logical expression mode without highlighting
The user enters REXX-like logical expression using the following operators:
& : AND operator
| : OR operator
\ : NOT operator
@ : XOR operator
( ) : to group expressions.
A sequence of words without any operators is treated as a phrase -- to
treat each word as a seperate subword, put ( ) around each one.
Basically, when using this mode, be liberal in your use of ( ).
DOSEARCH Options
DOSEARCH supports a number of options.
These options are easily set in
DOSEARH.HTM, or by modifying the ALIASE(es) that invoke DOSEARCH.
Technically speaking, the options appear in an option list,
with each option seperated by an & character.....
- if the GET method was used, the option list is placed
after a ? character in the request selector .
- If the POST methed was used, the option list is placed in the body of the request.
The option list should have the structure:
option_name=option_value&option_Nam2=option_value2&...
The DOSEARCH options are:
DELIM : The paragraph delimiter.
" " or 0 = blank lines (the default)
"$" = Each line is a paragraph
other = User specified delimiter
LINE : Maximum number of lines to display of each "found" paragraph.
If 0, no lines displayed (a summary will be displayed)
Default is to display all lines.
NUM : YES=Display the line or paragraph number,
NO=Don't (default=YES)
BAR : YES= Seperate each paragraph/line by a horizontal bar,
NO=Don't (default=YES)
EXPERT: YES= Use "logical expression mode",
NO=Use simple mode (Default=NO)
FILE : FILE=filename
A file to search (either relative to the data directory,
or in a "local" virtual directory). You can include as many
FILE options as desired (each entry will be searched in turn).
Furthermore, * and ? wildcards can be used.
SEARCH: The search string
CASE : If YES, then search is case sensitive (default is NO)
Examples
Simple mode examples
-
( The best car)
- Finds paragraphs containing the phrase
the best car
-
car truck motorcycle
- Finds paragraphs that contain one (or more) of
car, truck
or motorcycle
-
dog cat & store (pet pig)
- Finds paragraphs that contain one (or more) of
dog, cat
or the phrase pet pig
;
and that also contain store
-
*& computer price memory
- Finds paragraphs that contain
computer, price
, and memory
(must have all of them, but can be in any order)
Logical mode examples
-
The best car
- Finds paragraphs containing the phrase
the best car
-
car | truck | motorcycle
- Finds paragraphs that contain one (or more) of
car, truck
or motorcycle
-
( (dog & cat) | (pet pig) ) & stores
- Finds paragraphs that contain
stores
, and that contain either both dog
and cat
, or the phrase pet pig
Return to table of contents
The SENDFILE facility
SENDFILE is an SRE-Filter facility that transfers files to a client.
It can record the number of times this file has been completely sent.
SENDFILE is invoked with a request selector of:
SENDFILE?selector&forcetext=1&COUNTER=option_list
(the &forcetext=1 and &COUNTER=option_list are optional)
SENDFILE will ...
- Check for the existence of a file corresponding to the
selector
(the file that the selector maps to is assumed to be
relative to the data directory or relative to a "local" virtual directory).
- Look in the SENDFILE_FILE
for an occurence of the
selector
. If none exists, create an entry.
- If the
selector
exists (and the entire file was sent), the
"count of requests" for this selector
is augmented. That is, if the client
killed the connection half way through, the count will not
be augmented.
- If a COUNTER=... options is present, COUNTER.RXX will be used (with
the option_list).
- If SAVE_STATE=1 the
number of bytes sent
and the size of the file
are stored in a SENDFILE_STATUS variable in the "thread
specific" cache.
- A successful transfer will have the "number of bytes sent"
equal to the "size of the file".
- SAVE_STATE is set in SREFILTR.80 -- see INITFILT.DOC for details.
Notes
- If the client breaks the connection before the a file
is completely sent, the SENDFILE_FILE is not modified (the request
is not recorded). However, if SAVE_STATE=1, the SENDFILE_STATUS variable will be written.
- By default, SENDFILE_FILE
is SENDFILE.CNT.
- When ACCESS_ALLOW is enabled, the
ACCESS_FILE should contain an entry of the form
SENDFILE?*
- The SENDFILE_FILE supports wildcard matching.
- For details on the COUNTER= option_list, see COUNTER.DOC .
-
If
FORCETEXT=YES
, SENDFILE will
assume that all files are of "mime-type text/plain". This
can be a useful trick (it tricks the client into displaying everything
as a text file), but if .GIF (or other non-text files) are chosen,
garbage will be displayed ( use this option with discretion)!
- Entries in the SENDFILE_FILE may be "host specific".
Return to table of contents
Using Message Boxes
SRE Filter's built-in message box facility provides a mechanism for storing messages
from clients. SRE-Filter provides a few simple built-in tools for manipulating
these messages boxes. These include:
- A message writer. The message writer is invoked with
a request selector of:
MESSAGE?messbox=messagebox&field1=value&..&fieldn=value
- Two simple facilities (VIEWMESS and ASKMESSBOX) are provided for
viewing an entire message box.
- Message box access can be controlled through the use of
message box privileges.
Of perhaps greater interest, the FORUM, READMAIL,
and MAILIST
SRE-Filter add-ons make extensive use of these
SRE-Filter messages boxes.
The Message Writer
The message writer is usually invoked with an HTML FORM with ACTION="/MESSAGE" (see
SAMPMBOX.HTM for an example). In addition to an INPUT element identifying
the "message box", you can specify a number of fields (the field name, and it's
value, are written to the message box using an e-mail type format). Several
of these fields are treated specially, as explained below:
- MESSBOX (recommended)
- The particular message-box to put the note into.
If a MESSBOX field is not included, the note will be put into the ANYONE message-box.
If MESSBOX names a non-existent message-box,
a new message-box will be create.
- NAME and SUBJECT (recommended)
- These are expected, if not included a dummy value will be created.
Note that each message is automatically given a TIME and DATE stamp.
- FAX, E-MAIL, ADDRESS, and PHONE (optional).
- The name, and value of these fields are written to the message box.
Note that the E-MAIL field is explicitly used by SRE-Filter's FORUM add-on.
- PASSWORD and DURATION
- The PASSWORD and DURATION fields are used by the FORUM add-on to control "delete privileges"
for a given message. PASSWORD will be encrypted before being written to the
message box file. Note that messages boxes are not designed for security (the encryption is weak),
so don't use them when confidentiality and integrity are important.
- INDEX
- Including an
INDEX=YES
field will cause MESSAGE to
update an index file (with an .IDX extension). These .IDX files are
used by the FORUM add-on to speed up response. Note that this
.IDX file creation will occur after responding to the client (it's
a post-filter type of action) -- the client will not notice any
adverse impact from inclusion of an INDEX=YES
field
(but other clients may be impacted by the extra workload!)
- BROADCAST_LIST
- If included, SRE-Filter will simultaneously e-mail (through the SMTP gateway
you set with the SMTP_GATEWAY variable) copies of your message to
a list of e-mail addresses. This list, a file with name given by BROADCAST_LIST,
must be in (or under)the MESSBOX_DIR. Furthermore, the client must
have SUPERUSER or BROADCAST privileges, or a privilege equal to the
value of BROADCAST_LIST. If not, SRE-Filter will send authorization request
back to the client.
- Example: if BROADCAST_LIST=CLASS10.LST, then the client
must have a CLASS10.LST client privilege.
Note that the BROADCAST_LIST file (i.e.; CLASS10.LST) should contain
valid e-mail addresses, one per line.
- BROADCAST_ONLY=YES
- Do not write to message box, just BROADCAST
- BROADCAST_NAME=My_name
- Used in the "from" field of the e-mail message.
- WRITE_TO_FILE=YES
- If included, SRE-Filter will write an "E-mail" like file (containing
From, To, Date, and Subject fields; followed by the Contents) to your
MAILBOX_DIR directory. These files are designed to be read, and
processed as an "e-mail message to a list-server", by the MAILLIST (and READMAIL)
SRE-Filter add-ons.
If you are broadcasting to many recipients, the use of WRITE_TO_FILE
in conjunction with the MAILLIST add-on, rather then the BROADCAST_LIST, is recommended.
.
- Other names (optional).
- The name, and value, of these fields will be written to the message box.
The difference between "other names" and the PHONE, ADDRESS, and FAX "optional"
fields is merely in the order of appearance.
- RESPONSE_FILE
- The RESPONSE_FILE field is used to indicate a file contaning a "response"
to a posted message. If no RESPONSE_FILE is included, a very simple generic
response will be
returned.
- MESSAGE (recommended)..
- The (multi-line) message. It's written last of all.
The direct means of reading a message box is to simply view it using the OS/2 TYPE
command (message boxes are ASCII files, with a .LOG extension, located
in the MESSBOX_DIR directory).
SRE-Filter also provides a simple mechanism for remotely viewing these
message boxes.
A request selector of VIEWMESS?messbox=message_box
will
cause SRE-Filter to transfer the message-box-file to the client.
SRE-Filter also provides a simple routine that generates an HTML document
that displays a list of all available message-boxes,
and let's the client choose which one to view.
This routine can be invoked with a request selector of
askmessbox?An+optional+header
The "optional header" is displayed as an <H2> at the top of the document.
To access a message box with MESSAGE (or with the FORUM
add-on),
the client must have
"message box specific" privileges. These are specifed by including
(in the client's privilege list), entries of the form:
MESSBOX=a_message_box.
For example: MESSBOX=FORUM1
would give (read/write) access
to the FORUM1
message box. Note that this is in addition
to any "selector and FILE specific" access controls you may have imposed.
The a_message_box
portion of the privilege can
contain the * "wildcard" character. For example, MESSBOX=FORUM*
would provide access to FORUM1, FORUM2, etc.
On installation, SRE-Filter includes MESSBOX=*
in the
PUBLIC_PRIVS parameter (the effect of which is to allow
open access all message boxes). You'll need to remove this from
PUBLIC_PRIVS if you want to limit access to message boxes!
Notes
- You can also limit access to message boxes by creating an entry in the
ACCESS_FILE of the form:
MESSAGE* resource_privilege_list
(you may also want to create similar entries for
VIEWMESS and ASKMESSBOX)
Return to table of contents
The SRE-Filter procedure library
SRE-Filter uses a procedure library (that is loaded into
macrospace) to provide many functions.
Several of these routines may be quite useful to the ambitious REXX programmer.
These procedures include:
- SREF_MEDIATYPE: Return the MIME type of a file (based on it's extension)
- SREF_REPLACESTRG : Replace substrings
- SREF_MULTI_SEND: Expedites the creation of multi-part documents
- SREF_GRAB_FILE : Wait for file to become unlocked, and then
read it into a variable.
- SREF_FIX_URL : Given a local selector , and servername, and a serverport, return
a legitimate URL (including the http://).
- SREF_WILDCARD : Perform a wildcard substitution.
- SREF_JULDATE: Return the Julian date and time (days since 0/0/0, time in fraction)
- SREF_MAILIT : Send an E-mail message.
- SREF_CGIVARS : Determines one of the "CGI-BIN" variables.
- SREF_BROWSER_INFO: Check on the capabilities of the client's browser.
A complete description of these routines can be found by
downloading SREFPRC1.DOC..
For serious programmers, the
source code
is also available.
Return to table of contents
SRE-Filter Add-ons
SRE-Filter has a number of add-ons avaiable. You can download them
from the
http://rpbbcam.econ.ag.gov/srefilter site.
Currently, the add-ons include:
-
FORUM: A news-group and list-server discussion-group package.
The FORUM add-on consists of three components:
- FORUM:
The FORUM component provides a simple, but
fairly complete, multi-threaded "news group" like capability. The basic
output of FORUM is a list of "links" to messages in the message box.
The list is organized hierarchically, with indentation used to indicate
discussion threads.
Clinking on a link causes
just that message (and it's various "fields") to be displayed. The client then
has a number of options: including sending a response to the message poster (given that an
e-mail address is available), posting a new message to the message box (either
as a response to the message, or a as new entry in the discussion thread), or
viewing the next message or the next thread.
- READMAIL:
The READMAIL component that will transfer
mail to SRE-Filter message boxes. This mail is read from the
incoming mail directory of an SMTP-gateway running
on your server; for example, the SMTP-gateway provided by OS/2's
SENDMAIL daemon. By combining READMAIL, and the BROADCAST_LIST
option of MESSAGE, a simple "list server with automatic archiving" can
be implemented.
- MAILIST:
MAILIST is nearly identical to READMAIL, but is designed to run independently
of SRE-Filter. MAILLIST requires somewhat more configuration, but once
running does not suffer from "timing out" problems due to GoServe limitations
on connect time. It also automatically checks for new mail on a timed basis; in
comparision, you have to explicitily invoke READMAIL (say, by
using READMAIL.HTM).
-
BBS: A full featured "web based bulletin board system"
BBS is a WWW bulletin board system. BBS features include:
- Individual file descriptions can be displayed, along with
file size and creation date.
- Directory specific inclusion files (i.e.; FILES.BBS) and exclusion
files can be used to control file and sub-directory display.
- Optional "automatic descriptions" can be generated for
HTML, .ZIP, and text files.
- .ZIP files can be "opened and displayed", with subsequent retrieval
of a specific file from within the .ZIP archive
- Netscape 2.01, and other HTML 3.0 compliant browsers, can upload
files by using a FORM containing a file="type" element.
- Uploads and downloads can be recorded on a per user basis.
- A flexible access control mechanism allows customizaton of which
file areas a user can peruse.
- Downloads can be disallowed if a user's "download to upload" ratio grows
too large.
- Directory specific headers, footers, and "exclusion lists" can
be specified.
- Optional caching of directory-listings can greatly speed up throughput.
- SRCHINDX: A front-end (+ more) to the
freeware SWISH
search engine. SWISH is used to index
the many directories comprising your web-site. It creates
a compact index that it can search quickly for matching words.
SRCHINDX, the SRE-Filter front-end, enables you to search this from
an HTML form. In addition, SRCHINDX will automatically create
a description. You can also use SRCHINDX to create
a "description index", which you can then search for matches.
- GETAFILE: A directory displayer, with user-settable display features
GETAFILE is a similar to SRE-Filter's !DIR dynamic directory display facility.
It is somewhat easier to configure, and has a few extra bells and whistles.
- CALC: A character-mode scientific calculator with a web interface
CALC is a WWW-accessible scientific calculator.
It uses a keyboard interface, and
is based on an aging DOS program. On the other hand, it's quite feature
rich: multiple equations and temporary variables can be specified, trigonometric functions
are fully supported, analytic derivatives can be taken, and more...
Return to table of contents
User-configurable SRE-Filter files.
SRE-Filter uses several user-configurable files. These files
contain logon information, access and accounting information, and instructions to
assist in conducting server side includes.
In most cases, SRE-Filter's simple mode configurator (CONFIG0.HTM) or intermediate mode
configurator (CONFIG2.HTM) can be used to modify
these files.
In some cases, modification of these
files requires the user to edit them with a text editor. This section describes these
files; you will also find additional description in the "default" files that are
bundled with SRE-Filter.
x
Initialization Parameters File (INITFILT.80)
SRE-Filter contains a number of parameters that can, and should, be changed
to fit the needs of the user. To do this, you'll need to change the
the INITFILT.80 (or INITFILT.nnn, if you are using a port nnn).
Changes to the INITFILT.80 can be accomplished in several ways:
- You can edit it with your favorite text editor. You might want to examine
INITFILT.DOC for a detailed discussion of the meaning, and possible values, of
each variable included in INITFILT.80.
- You can use SRE-Filter's simple or intermediate mode
configurator. To run either of these configurators, point your browser
at http://your.server/configur.htm and follow the instructions.
The simple mode configurator
allows you to change the most important parameters, while the
intermediate mode let's you change almost all the parameters.
If you need to modify
the few parameters that the intermediate mode (purposefully) ignores, you'll
have to hand edit the INITFILT_FILE (and read INITFILT.DOC first!).
You must be an OWNER, or have SUPERUSER privileges, to
access these configurators. Extremely cautious administrators may wish
remove CONFIG2.CMD and SREFCONF.CMD, as well as all the *CFG.CMD files, from their
GoServe working directory.
-
A few of the parameters in the INITFILT.80 file are:
- List of supported hosts (IP addresses and IP aliases)
- Name of the default realm
- Numeric IP addresses of "owners"
- Numeric IP addresses of "in-house" clients
- Names of various SRE-Filter user-configurable parameter files
(such as the USER_FILE and the COUNTER_FILE).
- Name of default (home) page.
- Messages to include as "header" or "footer" for all requested HTML documents.
Return to table of contents
Replacement strings file (REPSTRGS_FILE)
The replacement strings file contains "custom"
replacement strings that can be used by the
REPLACE keyphrase.
Each line of this file (except lines beginning with a semi-colon, which
are treated as comments) has two fields:
- A variable_name . The variable_name
can be any length, but must have NO embedded spaces.
- A
replacement string
. The
replacement string
is the string to be used when a REPLACE keyphrase
with an argument of variable_name is found.
Example
CONTACT Contact me soon!
CONTACT is the variable_name , it may contain a
.HOST_IDENTIFIER.
Contact me soon!
is the replacement string
When a <!-- REPLACE
CONTACT -- > keyphrase is found,
it is replaced by Contact me soon!
Note on multi-line replacements
The REPLACE keyphrase can be used for
multi-line replacements (note that for
replacements of more then a few lines it is probably wiser
to use the INCLUDE
keyphrase).
To specify a multi line replacement, just enter multiple
occurences of the same label -- the values will be appended.
Example:
MYADDRESS <address> My address is:</address>
MYADDRESS 1301 New York Ave.<br>
MYADDRESS Washington, DC <br>
would generate 3 lines (when a
REPLACE MYADDRESS keyphrase is encountered).
Notes
-
The replacement strings file is REPSTRGS.IN. You can
change this by modifying the REPSTRGS_FILE variable in INITFILT.80.
- REPSTRGS_FILE is only checked if the variable_name does not match
one of the "built in" variables.
- Replacement strings can contain HTML elements.
- The variable_name can contain any printable character (including
periods and commas).
- To specify a host specific entry, include a .Host_nickname (i.e.;
VAR1.HOST1).
Return to table of contents
The HITS and COUNTS counter file (COUNTER_FILE)
The counter file
is used to record the number of requests (also known as the
number of hits) for this document. It is used whenever a REPLACE HITS or
a REPLACE COUNTS keyphrase is processed.
The counter file has syntax:
HOST_NICKNAME//AURL CTS MESSAGE_1 , MESSAGE_2
HOST_NICKNAME is optional.
AURL
is a selector corresponding to an HTML document
CTS
is the current count of the number of requests.
Message1
and message2
are used
by HITS to display the # of requests.
When a REPLACE HITS
keyphrase is encountered, SRE-Filter looks
in the counter file
for an aurl
that matches the request selector
If it finds a match,
the CTS
, MESSAGE_1
and MESSAGE_2
values are extracted. CTS
is then augmented by one
and written back to counter file.
Lastly, a "count of hits" string is included in the the requested
document. This string will have the form:
Message_1 cts+1 Message_2
a generic message_1 is used if message_1 and message_2 are missing
For REPLACE COUNTS
, the same procedure is followed,
except message_1
and message_2
are ignored.
If the request selector does not match any of the aurl
's,
a new entry will be created (with
CTS
=1 and message_1
and
message_2
left blank).
Examples
INDEX.HTM 66 You are visitor # , since <!--replace creation_date -->}
PROJECTS/PROJ1.HTM 19
CALC/CALC.HTM 9
OVERVIEW.HTM 13
BRIDGES//VERMONT/COVERED.HTM 15
Note the use of the message_1 and message_2 blocks in the entry for
INDEX.HTM. Also note the use of a REPLACE keyphrase in
the message_2 block.
Notes
- Only the portion of the request selector before a ? is used.
- The default name of the counter file is COUNTER.CNT. You
can modify this by changing the COUNTER_FILE.
- Wildcard matching is not attempted.
- An alternative means of recording "number of requests" is provided by setting
the
RECORD_OPTION variable.
-
Another alternative is the SENDFILE
facility, which keeps track of explicitily requested files.
- Or, you can use COUNTER.RXX -- invoked using an INTERPRET keyphrase (see
COUNTER.DOC
for details).
- Yet another alternative is to use external programs to generate a
"counter GIF". Many of these programs will also keep track of the
number of hits. For example, XCOUNT.CMD (a CGI-BIN script) will generate
a simple "odometer" style counter, and also keep track of the number of
hits (note that this doesn't work if the client has her browser set to
not load graphics).
-
In the COUNTER_FILE (and in the ACCESS_FILE, the SENDFILE_FILE, and
the RECORD_ALL_FILE) ...
- The request selector is used to record entries --
before ALIAS and other replacements.
- / characters are converted to \ characters; and leading \ (or /) characters
are dropped.
- lines beginning with a ; are comments.
- The "host nickname", if present, is appended to the beginning of
the selector . For example, the BRIDGES//VERMONT/COVERED.HTM example signifies
a selector of VERMONT/COVERED.HTM to a host with a host nickname of BRIDGES.
Return to table of contents
The RECORD_ALL_FILE counter file
The RECORD_ALL_FILE (with default name RECRDALL.CNT) is used
to record all actions, such as transfers of files and requests for
server side processing. It is used when RECORD_OPTION
is enabled.
The structure of the RECORD_ALL_FILE is similar to the COUNTER_FILE, with
a few exceptions:
All requests are tracked (including requests for HTML documents, requests
for .GIF files, and Server Side Processing requests).
Instead of a message_1 , message_2
following the aurl cts
, the date of the last
successful request for this selector written.
RECORD_ALL_FILE may contain "wildcard matches" --
typically subdirectory entries.
Example
PROJECT/PROJ1.HTM 9 03/01/96
TEMP/ZFVL5615.LST 1 02/28/96
DOSEARCH 4 2/29/96
OVERVIEW.HTM 7 03/01/96
TEMP/* 3 03/01/96
ZOO// SCHEDULE.HTM 120 05/03/96
Note the TEMP/* entry is used as an wildcard match;
if RECORD_OPTION="YES" or "YES_ALL", then all requests for files in the "temporary directory"
will be recorded in the TEMP/* entry (the assumption is that one is typically
not interested in specific information on temporary files).
Also note TEMP/ZFVL5615.LST -- it was
written when a file in the "temporary" directory was requested, and
before the TEMP/* entry was added to the RECORD_ALL_FILE (the server administator must have
added the TEMP/* entry on 2/29/96!).
Also, note that the date is the
date of the most recent "allowed" request.
Notes
- The RECORD_ALL_FILE is meant strictly for recording information --
it does not contain message strings, nor does it contain "access control"
information.
- Entries in the RECORD_ALL_FILE may be host specific
- If more then one "wildcard" entry matches the requested selector , the
"best match" is used.
Return to table of contents
The SENDFILE_FILE counter file
The SENDFILE_FILE counter file (with default name SENDFILE.CNT)
is used by the
SENDFILE facility to record transferals.
The structure of the SENDFILE_FILE is:
URL_NAME #_of_times_sent date_of_last_transfer
Example
CTEMP/FOO.HTM 4 07/06/96
GOS/GO1.HTM 6 07/06/96
EAA.HTM 20 07/06/96
/SAMPLES/SRCHINDX.DOC 2 07/07/96
/SAMPLES/TESTTABL.HTM 1 07/06/96
ZOO// TIGERS.DOC 5 06/07/96
Notes:
- If a SENDFILE_FILE does not exist, it will be created.
- Entries in the SENDFILE_FILE may be host specific.
- If more then one "wildcard" entry matches the request selector , the
"best match" is used.
The ACCESS_FILE access control file
The ACCESS_FILE
(with default name ALL_FILE.CTL) contains access information
on a SEL-specific basis.
Each entry in the ACCESS_FILE can contain 5 types of information:
- A selector . This may contain the wildcard (*) character (required)
It also may be preceded by the host nickname.
- A space delimited
resource privileges
list (optional).
- A space delimited
permissions list
(optional)
- A
SEL-speciflc realm name
(optional)
- and a
SEL-specific access failure file
(optional)
The structure of each entry in the ACCESS_FILE is:
host_nickname// SEL resource_privilege_list , permissions_list , realm_name , failure_file
Note that, if present,
the permissions_list
must follow a comma,
the realm_name
should follow a (second) comma,
and the failure file
should follow a (third) comma.
Special Entries: REALM-specific, additional resource privileges
Each realm can have associated with it a list of
realm-specific, additional resource privileges.
If available, this (space delimited) list
is added to the resource_privilege_list
.
The syntax of these special entries is:
!REALM realm_name realm_privilege_list
Note that if there is no !REALM entry for a given SEL-specific realm,
then just the resource_privileges list is used.
Also note that an empty resource_privileges list implies "all clients are
allowed access", but only if there is no
realm-specific, additional resource privileges for this SEL.
Examples
CLIENT1/PROJ1.DOC VENUS , NO_SSI , PLANET_2
BATMAN// CLIENT1/* ROBIN GOHTAM , NO_CODE , REALM_BAT , D:\GOSERVE\NOBATS.HTM
WORKAREA/MAPLE.IN INHOUSE MERCURY
WORKAREA/SYCAMORE.IN MERCURY VENUS MARS &EARTH
USAGE.TXT NO
WEATHER* INHOUSE , , CLIMATE_GROUP
READ.ME *
VIEWMESS?messbox=SECRET2* INHOUSE
PUBLIC/* *
GUEST/* * , NO_SSI NO_SSP
UPLOADS/* * , PUT DELETE
OREGON/* , , REALM1
imgs/*.gif * , cache no_virtual no_alias no_postfilter no_htaccess
!REALM REALM1 BIGFOOT SASQUATCH
ZOO// EMPLOYEES.HTM MANAGER
- CLIENT1/PROJ1.DOC (the file that this SEL maps to)
will only be sent to clients having VENUS privileges. Furthermore,
server side includes will not be done on this file. Lastly, should
a client not have a VENUS privilege, the query for a new
username/password will display the PLANET_2 realm name.
- BATMAN// CLIENT/ is valid only for requests to a host identified
with a host nickname of BATMAN. If the client
does not have a ROBIN or GOTHAM client privilege,
SRE-Filter will return the D:\GOSERVE\NOBATS.HTM access-failure file.
Also note that
SELECT
and INTERPRET CODE
server-side-include keyphrases are not permitted in CLIENT1/ documents.
- WORKAREA\MAPLE.IN will only be sent to clients having either an
INHOUSE or MERCURY privilege. Note there is no SEL specific realm,
so queries for a new username/password will always display the default
realm (as specified in the THE_REALM variable.
- WORKAREA\SYCAMORE.IN will only be sent clients having "one of" the
MERCURY,VENUS, or MARS privileges; and who also "must have" an
EARTH privilege.
- USAGE.TXT is never sent (except to SUPERUSERs)
- All selectors that start with
WEATHER
are available to users with INHOUSE privileges.
If necessary, authorization requests will display the
CLIMATE_GROUP realm name.
- READ.ME is always sent
- The SECRET2 (or SECRET2x) message box can only be examined by clients with
an INHOUSE privilege.
- All files in the PUBLIC directory are always sent.
- All files in the GUEST directory are sent, but no server side includes (or server side
processing) is attempted for these files.
- Selectors pointing to the UPLOADS directory can use the PUT and DELETE
HTTP methods (to upload and delete files).
- All files in IMGS\ that end with .GIF will be sent to everyone, will be
cached, aliasing won't be done, virtual directory lookup won't be done,
directory-specific (HTACCESS-file) access controls will not be attempted,
and recording and "post-filtering" (including common-log audit file recording)
will not occur.
- All files in OREGON/ will be sent to individuals
with
one of the privileges in the REALM1 list of "additional resource privileges".
The !REALM entry defines these to be BIGFOOT and SASQUATCH.
- For the ZOO host, access to EMPLOYEES.HTM is limited to clients with
MANAGER privileges.
ACCESS_FILE summary
- Assuming that ALLOW_ACCESS is enabled...
- if a matching entry (in the ACCESS_FILE) contains no resource_privileges
list, and there
is no SEL-specific realm (or no !REALM entry for a SEL-specific realm), the
selector is
honored (the appropriate file is sent to the client)
- if there is no matching entry,
either explicitily or as a wildcard, the selector is not honored.
-
If the ACCESS_FILE does not exist, the selector is not honored.
- If the resource_privileges list contains
NO
,the selector is not honored
- If the resource_privileges list contains
*
,the selector is honored
- If the client has been assigned any of the ONE_OF resource privileges,
and all of the MUST_HAVE privileges, in both the
SEL-specific
resource_privileges list
and the
realm-specific, additional resource_privileges list;
the request will be honored.
- Currently, ten permissions are recognized: NO_SSI, NO_CODE, NO_SSP, CACHE, PUT, DELETE,
NO_HTACCESS, NO_VIRTUAL, NO_ALIAS, and NO_POSTFILTER.
- If the permissions_list is missing, server side includes and server side processing
will be permitted, caching may be suppressed (if ALLOW_ACCESS or CHECKLOG is
enabled), requests using the DELETE and PUT methods will not be
honored,
directory-specific (HTACCESS-file) access controls will not be suppressed,
aliasing may occur, virtual directory lookup may occur, and post-filtering
and file recording may occur.
- The suppression of server side processing on a per-selector basis is tricky:
consider that requests for a document with an HTML
FORM
is not the same selector invoked by this FORM's "action".
Use it with care!
- Caching can greatly speed up response time (especially of in-line image
rich documents), but it also can completely subvert all access controls (including
logon requirements). Use it with care!
- ACCESS_FILE entires may be host specific.
- If there are multiple wildcard matches, the "best" match is used.
The virtual directory file
The VIRTUAL_FILE (with default name VIRTUAL.IN) is used
to specify local or remote virtual directories.
Each line of the VIRTUAL_FILE contains:
HOST_NICKNAME SEL_fragment TARGET limitation_list
.
- The optional
host_nickname
dicates which host the entry
applies to.
- If the
limitation_list
is not enabled, or
if the request is one of the types listed in the limitation_list
, then the
SEL_fragment
is compared to the beginning of the request
selector.
If it matches, the TARGET
directory,
along with the portion of the request selector that follows
this SEL_fragment
is used as the root directory
for this request.
Note that there are two kinds of virtual directories: local and remote.
- LOCAL
-
Local directories are located on, or are LAN accessible from, the server.
Local directories should be specified using a fully qualified directory
name.
- REMOTE
-
Remote directories are "web" accessible from the server. That is, requests
to other http servers can be used to obtain files in these directories (assuming
the other http server allows unrestricted access to the desired URLS).
Remote directories should be specified using a complete URL, that
must start with http://.
Remote directories are only used for document requests.
Examples:
LOCAL/DISK1/PROJECTS d:\work\PROJECTS*
- A selector of
/LOCAL/DISK1/PROJECTS/BOB/PLANE.HTM
is
"mapped" to D:\WORK\PROJECTS\BOB\PLANE.HTM
-
REMOTE1/ http://www.their.org/
- If a selector of
REMOTE1/TURNIPS.HTM
is recived, then
SRE-Filter will attempt to obtain REMOTE1/TURNIPS.HTM
from the
http server at www.their.org
. This retrieval does not
require a "redirection" by the client -- all the work is done by SRE-Filter!
-
PHYSICS// STRINGS/ d:\theory\basic\strings !HTML
- Request to a host with a host nickname of PHYSICS,
that begin with STRINGS/, are mapped to files in
d:\theory\basic\strings
.
However, only document requests will use this entry -- cgi-bin, SRE-Filter add-on, and
file upload requests will not use this entry.
-
ALASKA/ r:\states\alaska
- A request for
ALASKA/BEARS.HTM
"maps" to R:\STATES\ALASKA\BEARS.HTM
.
If R: is a LAN drive, and the server is not logged on, this could cause trouble!
Notes
The usernames and passwords file (USER_FILE)
Each entry in the the USER_FILE (with default name USERS.IN) contains
an optional host nickname, a username, password, and privilege information.
It is used in two cases:
- When logon is required of a client.
- When information on privileges is needed.
The structure of the USER_FILE is:
host_nickname NAME PASSWORD PRIV1 PRIV2 ...
Note that the PRIV1 is required, while other
privileges (PRIV2, etc.) are optional. Also note that the host_nickname is
optional
Examples
DANIEL A11S34WZ SUPERUSER
MIKE IOWAMAN CONSULTANT
JILL GOBOTS INHOUSE
JOHN KIOWA INHOUSE VENUS
FLOWERS// CHARLES BROWN PRICELIST
ANONYMOUS * PUBLIC
In the above example:
Return to table of contents
The list of ALIASES is contained in the
ALIAS_FILE (with default name ALIASES.IN)
The ALIAS_FILE contains lines having the structure:
host_nickname alias_target replace_string
where host_nickname and alias_target
should have no embedded spaces.
Note that the host_nickname is optional.
To support several special features, several special character strings
may be placed in either the alias_target
or replace_string
:
- The * character in the
alias_target
signals that
this alias_target
can be used in "wildcard matching"
- If a * appears in both the
replace_string
and the
alias_target
, then an "wildcard match with substitution" may
be performed.
- If the
replace_string
starts with !TRANSFER
,
then the (rest of) the replace_string
is assumed to be
an fully qualified file name (that is "not necessarily in the data directory").
Note that this !TRANFER syntax provides a limited alternative to
"local" virtual directories
- If the
replace_string
starts with http://
, then
the remainder of the replace_string
is assumed to be
the URL for a redirection response to the client.
Similarly, if replace_string
starts with !TEMP, !NOTIFY, or
!MOVED, a "temporary redirection", "notification of moved URL", or
"permanent" redirection response will occur.
Examples
; This first example replaces a "bad request selector " with
;a correct HTML file names
HOME INDEX.HTM
; The next example would be used if CHECKCAT.HTM was a gateway to a
; "searchable index" (CAT.DAT being the file that is actually searched).
CHECKCAT.HTM?* DOSEARCH?FILE=CAT.DAT&SEARCH=*
; This redirects all request selectors that begin with YAH to yahoo
YAH* http://www.yahoo.com/
; This converts request selectors only to a host with a host_nickname of ANIMALS,
ANIMALS// CATS/* FELINES/DOMESTIC/*
; This sends some "not in data directory" documentation to the client.
WHATGOT !TRANSFER=E:\PRODUCTS\DESCRIBE.DOC
; This performs a "wildcard match with substitution, in combination with
; a redirection. Typically, this would be called as WEBSEARCH?find_this
WEBSEARCH?* http://www.webcrawler.com/cgi-bin/WebQuery/?*
CAUTION
Unless you explicitly want to "alias" selectors that otherwise would map to
actual files,
we recommend that all "wildcard match aliases"
have "targets" that do NOT map to pre-existing files.
The point is that a "wildcard matching" alias match could
convert a legitimate selector (that points to a real file in the data directory
or a virtual directory) into something else --
rendering it impossible to obtain this "real file".
Return to table of contents
The currently known limitations of the SRE-Filter package include:
- SRE-Filter has not been tested with proxy servers
- "Byte range retrieval" is tested, but
should be viewed as experimental (GoServe can be a bit flakey when processing
multi-part sends).
- SRE-Filter does not provide a high level of security -- there
is no provision (currently) for data encryption.
- GoServe's caching is supported for most, but not all, file transfers.
Caching is disallowed whenever a byte-range is retrieved, and when there is a
possibility that a server side include will occur. Caching is also
disallowed whenever logon or access control are active, unless a CACHE
permission is enabled for this request selector .
SRE-Filter does provide two useful caches that in
certain cases can be used
instead of the GoServe cache:
the server side include cache
and the directory listing cache
When caching is on, and a cached file is requested, GoServe may call the
filter anyways (see the Options-General tab of GoServe). If this should
occur, SRE-Filter will detect that the file has already been transfered, and
SRE-Filter will appropriately record the request
(if RECORD_OPTION, WRITE_LOGS, or POST_FILTER is enabled).
Note that the COUNTER_FILE
file will not be augmented (COUNTER_FILE is augmented via a server side include, and
files with server side includes are never cached).
- SRE-Filter 1.2i does not currently run under Object Rexx.
In other words, SRE-Filter is designed as relatively full-featured package
for non-cutting edge small-to-medium
load sites being maintained by non-professionals
Summary of SRE-Filter
The following is a brief summary of SRE-Filter's features:
- Multiple hosts (either unique IP addresses, or multiple aliases
per IP address) are supported.
- Seperate data directories, aliases, etc. can be specified for
each supported host
- Logon requirements may be required of no one, everyone, or the general public.
- A set of public resources can be specifed, which will
be available to all clients.
- OWNERS (with SUPERUSER privileges) and IN-HOUSE users can
be automatically detected (using their numeric IP address), with logon
requirments waived.
- A set of "unallowed" numeric IP addresses can be specified.
- Wildcards can be used in the list of IN-HOUSE and "unallowed"
numeric IP addresses
- Several tools for resolving and redirecting requests are provided
- A "directory specific" document can be sent when a request selector
specifying a directory (with no file is name) is recieved
- Instead of a default document; a "directory listing" can be
produced, with file descriptions generated for all
plain, html, and .ZIP files. These
directory listings can be cached, and used for subsequent
requests.
- ALIASes can be used to redirect requests for moved documents,
to resolve commonly occuring "misspelled requests", and to transfer
specific files from anywhere on your server.
- A customized "not found" document (complete with suggested link) can
be sent when the requested document is missing.
- The ~ shorthand for the "home directory" is supported. In addition, ~
can point to www-specific subdirectories of the "home directory"
- Transfer of files from outside the "default data directory" is easily supported
through the use of "virtual directories".
- Transfer, with optional processing, of files from remote servers
(without using redirection) is supported through the
use of "remote" virtual directories.
- A variety of server-side includes are easily achieved
- A special caching algorithim selectively caches documents
that contain server side includes
- Headers and Footers can be included in all documents
- Recursively processed keyphrases, that dictate
server side includes, can be placed in your documents
- Dynamic and Static String REPLACEments
- Inclusion of files (from anywhere on your system)
- Inclusion of OPTIONs that appear in the request selector (after a ?)
- Execution of REXX-code blocks, and insertion of the results
- SELECTive excludes of HTML code blocks
- The NSCA HTTPD server side include syntax is fully implemented
- Standard server features include:
- NCSA and CERN style IMAGEMAPS are supported, and easily requested.
- searchable indices on text files are easy to setup
- a flexible mechanism for controlling access to selected SEL-selectors (and the
files they correspond to);
including assignation of realms on a SEL-selector-specific basis.
- support for the HTACCESS method of access control
- several mechanisms for keeping track of file requests
- several forms of redirection can be specified
- a simple form of load balancing is supported
- support for "common-log" format audit files (as well as
browser and referer log files)
- Special SRE-Filter built-in features include:
- a file display and transfer facility with easy
directory traversal
- a simple but powerful "text file" search facility
- dynamic assignation of "short-term" privileges to clients
- tracking of recent hits to prevent recording of repetitive requests
- optional limits on frequency of unsuccesful "logon" attempts, with
options for custom response files in the event of "logon" or "access"
denial.
- A simple message-box facility is built into SRE-Filter (it
can be used to support much more complex messaging packages).
- implementation of "byte range retrieval" (which is used
by Adobe Acrobat to access subsections of documents)
- reponse headers can be automatially generated, using LINK and META
HTTP-EQUIV elements in the <HEAD> portion of the document.
- Several file upload methods are supported
- Client directed retrieval of files from other HTTP servers
- Browsers that support the
type=file
FORM attribute (such as
NetScape 2.01), can upload files from their own machines.
- The PUT verb, with byte ranges, can be permitted on a per selector (or
per "set of selectors ) basis
- The DELETE method can be permitted on a per selector (or
per "set of selectors") basis
- User written server side processing (gateway programs) options include:
- Support for SRE-Filter add-ons (REXX routines that return results
directly to the client).
- CGI-BIN scripts (both REXX and binary executables, and PERL scripts
if you have a PERL interpreter installed) are
supported (using procedures adapted from the GoHTTP package).
- A "pre-filter" can be called prior to invoking SRE-Filter
- SRE-Filter comes with a special pre-filter that
implements the the GoRemote package.
- A "post-filter" can be called after SRE-Filter has responded to the
request.
- SRE-Filter comes with a special post-filter that uses socket
calls, to an SMTP server, to e-mail "event specific" alerts.
Return to table of contents
The following terms are used in this documentation. Please forgive any non-standard uses
you may encounter (better yet, let me know).
You might also want to review the
basic terminology for extended descriptions of a few key concepts.
- The \ and / characters
- The / character is used in URLs to
"indicate hierarchical structures, such as directories". It is equivalent to
the \ OS/2 (and DOS) character. Thus, / that appear in a request selector are
converted into \ when SRE-Filter needs to find a file.
- Action
- The action is the "location" portion of a request
selector.
- If the GET method was used -- it's the part
after the first / (that ends the domain name) and before the first ? (or the
end of the request selector , if no ? is present).
Examples:
-
In
http://rpbcam.econ.ag.gov/calc/calc.htm
,
the action woud be calc/calc.htm
.
- In:
http://foo.bar.net/workdir/myfile.htm?not+readyl
,
the action would be is workdir/myfile.htm
.
- In:
http://young.kids.com/toys/demo?dogs+cats
,
the action would be toys/demo
- If the POST method was used, the request selector (not including a
leading / character) is the action (there should never be a ? in a POST
method request string). All other information is
contained in the "body" of the request. SRE-Filter assumes that all POST method
requests are for Server Side Processing.
- Alias -- converting selectors
- SRE-Filter uses "aliases" to perform textual substitution. Typically, an alias is
used to replace a simple request selector with a more complicated one. In addition, aliases are
used for several special purposes: implementing "searchable indices", document redirections,
and specification of the location of CGI-BIN scripts.
- Alias -- virtual hosts
- A given IP address can be used by several hosts: including the
host associated
with the "canonical" name, and hosts associated with one of several aliases.
Unfortunately, TCP/IP requests
arrive with only the numeric IP address, making it difficult for the server
to determine to which host the request is directed to. However, HTTP 1.1 compliant
browsers (such as NetScape 2.01) will include a
HOST:
request header containing the host to whom this request is directed; and
SRE-Filter can use this request header (if present) to determine the
proper host.
- Client
- The Client (sometimes referred to as the requester)
is the individual requesting a URL -- where the URL may point to a file,
or may invoke Server Side Processing.
Typically, the request was generated by someone running a Web Browser, and
clicking on a link or submitting a FORM.
- CGI-BIN
- CGI (Common Gateway Interfact) - BIN is a standard by which server side ("gateway")
programs can be invoked. It uses environment variables to pass data, as well as
standard input and output. SRE-Filter supports CGI-BIN, using procedures adapted
from the GoHTTP package. One nice feature of SRE-Filter
is an ability to call alternate
(non-REXX) interpreters for specific scripts (such as PERL when a script has
a .PL extension).
Although this support should permit use of many CGI-BIN
scripts, the use of the "native" SRE-Filter interface (using
REXX procesures that are passed information in the argument list) offers
advantages to ambitous programmers
- The Default Data Directory
- The Default Data Directory is the root directory of your
web site -- it (and it's subdirectories) are the usual locations
for the HTML documents, images. In simple cases, the GoServe
data directory is used as the the Default Data
Directory. On multiple-hosts server, each host can
be granted it's own Default Data Directory.
A simple example might help:
- a request selector of MYFILES/PROJECT1/BIGTASK.HTM is recieved
- your default data directory is E:\WWW
then, SRE-Filter will look in E:\WWW\MYFILES\PROJECT1 for the BIGTASK.HTM file.
A Note On Data Security in SRE-Filter
In general, the only files available for clients
are those in (or under) the Data Directory. Exceptions to this rule include:
- Files explicitly transferred by user-supplied executable code
(i.e; REXX procedures). Note that
user-written Rexx code
may be invoked by a CGI-BIN script or a SRE-Filter add-on, or by INTERPRET, #EXEC
and SELECT keyphrases.
- A !TRANSFER "alias" can be used to access files from anywhere on the server.
- Files specified by literal PUBLIC_URLS.
- Virtual directories can point to anywhere.
- ELEMENT
- ELEMENT's are the constituent parts of an HTML document. They
dictate the structure, layout, and display characteristics of an
HTML document. ELEMENTS are identified using HTML tags,
where an HTML tag consists of text within
< and > characters. Often, a start
and stop tag are used.
For example:
<H1> Welcome </H1>
: defines a "level 1 Header"
<A href="/morejunk/stuff.htm"> More info? </A>
:
defines a link to a local document.
- File Names: Fully qualified and Relatve
- SRE-Filter can treat File Names as "fully qualified" names or
as "relative" names. Fully qualified names should be fully
pathed -- containing the
complete path to the file (sometimes the drive letter will be missing, in which
case the GoServe drive is usually assumed). Relative names are assumed to be in
subdirectories of some assumed default. For example, when a client asks for a file name,
it is assumed to be relative to the data directory (or to a matching
virtual directory).
- FORMS
- The HTML FORM element is used to create a fill-in form.
A FORM element
typically contains an ACTION attribute, as well as a number of elements
that provide editable fields (for the client to fill in or to otherwise
select). Typically a form is designed in tandem with a server-side program.
Although not the only
way to generate a Server Side Processing Request
(one can use sets of detailed URLS),
FORMS are probably the easiest for the average client to deal with.
- Hosts
- It is possible for one server machine to handle requests to
multiple IP addresses. This "multiple hosting" (also refered to as
multi-homing) can occur either by
having the server handle several numeric IP addresses, or by
the existence of multiple aliases for a single numeric IP address.
- Host nickname
- SRE-Filter uses host nicknames when identifying
which host a parameter applies to. Besides being a convenience,
it allows several hosts to point to identical resources (given that each
host has the same host nickname).
- HTTP : Hyper Text Transfer Protocol
- The rules by which web-aware clients and servers communicate.
- HTTP method (also known as the VERB)
- SRE-Filter recognizes five HTTP methods: GET, POST, HEAD, DELETE, and PUT.
- GET requests contain all information (action name and optional parameter list) in the
request string (with the parameter list placed after a ? character)
- POST requests
contain only the action name in the request string (the "body" of the request contains
the parameter list). Currently, SRE-Filter assumes that all POST requests
are requests for Server Side Processing.
- HEAD method requests are sent "meta information" on the requested file, the
file itself is not sent.
- PUT method requests are used to upload information to the file pointed to by
a request selector . SRE-Filter will only honor PUT method requests if specific
permissions are granted for that selector (as set in the ACCESS_FILE).
- DELETE method requests are used to delete (the file pointed) a requested
selector . SRE-Filter will only honor DELETE method requests if specific
permissions are granted for that selector (as set in the ACCESS_FILE).
- HTML
-
Hyper Text Markup Language (HTML)
is the protocol used to create
documents designed for display by WWW browsers (such as Netscape, Mosaic, MS Internet
Explorer,and IBM Web Explorer). Basically, HTML consists of a set of formatting commands,
which are included in a file containing the text to be displayed.
Note that to be recognized by SRE-Filter as an HTML file, a file
must have an .HTML, .HTM, .SHT, or a .SHTML extension
(though it's easy to add extensions to this list).
Although there is a formal HTML standard (currently 2.0, with
3.2 under discussion),
it is not rigidly adhered to. In particular,
NetScape
has it's own extensions; many of which are not recognized
by other browsers. For example, IBM's Web Explorer ver 1.03 recognizes
the CENTER element, and the SIZE attribute of the HR element, but not
the FRAMES element.
- Imagemap
- An image map (sometimes called a mappable image) is an inline image which, when
clicked with the mouse, returns a pixel location to the server. Typically, the
server then translates the pixel location into a URL, and redirects the client
to that URL (which might be on an all together different server). SRE-Filter supports
image maps using the MAPIMAGE/ "indicator string", along with NCSA and CERN style "MAP"
files to use in translating pixel locations to URL's.
Note that some browsers (such as
NETSCAPE 2.0) support "client side mappable images",
which require no action by the server (but
which require an HTML element not understood by many other browsers).
- IN-HOUSE
- IN-HOUSE refers to clients that are "in-house"; specifically, they
have had INHOUSE privileges assigned to them. The idea is that one often
wants to differentiate members of your "organization" from the rest of the
world, and place fewer
limits on what they can obtain from the server.
- Macrospace
- Marospace is best thought of as a global procedure cache used by OS/2.
When REXX programs are asked to load external procedures, they first look
in macrospace. For efficiency reasons,
SRE-Filter makes extensive use of macrospace.
- Privileges
- SRE-Filter uses "privileges" to control access to selected resources.
There are two classes of privileges:
- "resource" privileges which are
assigned to server resources (such as files, or directories), using
entries in the ACCESS_FILE.
- client privileges which are granted to clients (based on their IP address,
or their explicit username/password).
Resource privileges can be ONE_OF privileges ("or" privileges") or
MUST_HAVE privileges ("and" privileges). Client privileges may be
static (assigned using INITFILT.80 or the USER_FILE), or may be
dynamic (set on the fly as a function of the client's earlier requests).
- Request selector
- When a client sends a request to a server, it contains three components:
the http method, the selector, and the http protocol.
For example: GET /FOO1/BAR.HTM HTTP/1.0
In this documentation, the term request selector refers to
this middle component, with leading / stripped, and character decoding performed.
In the above example, the request selector would be FOO1/BAR.HTM.
Note that if a GET HTTP method was used, the request selector may contain
information following a ? (for example, SHOWINFO?database=Prices&item=apples).
- Response Header
- The response header contains "meta-information" about the requested document.
GoServe automatically sends a few response headers
(such as content length and file creation date).
In addition, using the
LINK
and HTTP-EQUIV
tags in the <HEAD> portion of your document,
you can instruct SRE-Filter to automatically add other response headers.
- Searchable Index
- A searchable index is a document that points to a file that is to be searched.
One can think of a searchable index as:
.. the front end to a gateway program,
and the file you search as the database
represented by the document.
Typically, a searchable index contains the <ISINDEX> element.
- SEL-specific
- SEL-specific means "a piece of information
specific to a request selector .
Clarifying, this means that SRE-Filter will use the value of the request selector
to find information (such as resource privilege information).
Thus, SEL-specific resource privileges
really means "privileges associated with a particular request selector
(coming up with terminology isn't easy ....)
Note: the SRE-Filter documentation sometimes uses the term
URL-specific
to mean SEL-specific
(it's a holdover from an earlier revision of the documentation).
- Server Side Includes
- Server side includes refer to on-the-fly modifications of requested HTML
documents.
Inclusions can be static, in which case the use of server side includes is mostly
to benefit the creation and maintenance of these documents. Dynamic
includes refer to information that changes, such as the current time and date --
obviously, these can not be specified in the document a priori,
but must be determined at
the time of request.
- Server Side Processing
- Often, the server provides computational services to clients. An example of
this is a client specified search of a
database, with the results displayed using an 'attractive" HTML document
(generated just for this search). Or, the client might request a map of
some portion of the U.S, displaying a choice of geographic features. Such
actions require the server to execute some kind of program (perhaps a REXX program,
or perhaps some other executable).
SRE-Filter add-ons, and
CGI-BIN scripts, are typical means by which Server Side Processing is provided
to clients.
- Server Side Processing Request
- A Server Side Processing request is, generically speaking,
"a set of parameters, sent by a client, and an action name,
that dictate
Server Side Processing". Often these are generated by a client responding
to a FORM element in an HTML document (alternatively, they may be "hand coded"
into a URL included in a HTML document). Server Side Processing requests are
recognized by:
- If the GET method was used:
the presence of a ?options string after a "non-HTML"
action name; where options contains
the "set of parameters".
Notes:
-
SRE-Filter assumes that, regardless of the presence of a ? in the request
selector ,
all action
names that end with a .HTM, .HTML, .SHT, or .SHTML are requests for HTML documents (that is,
are not requests for server side processing),
-
Actions which require no parameters must have
a ? trailing the action name.
- Server side programs are sometimes referred to as gateway programs.
- If the request selector starts with CGI-BIN/ , then it's
assumed to be a request for a CGI-BIN script.
- If the POST method was used, SRE-Filter assumes a Server Side Processing Request,
with the request selector treated as the action (which identifies the
program to run), and the "set of parameters" contained
in the "body" of the request.
- STEM variables.
- STEM variables are REXX's way of implementing arrays. A STEM variable consists
of a NAME.INDEX1.INDEX2 syntax (that is, with a . used to indicate "array indices"). SRE-Filter
uses STEM variables for several of it's configuration parameters.
- SUPERUSER status
- Clients with SUPERUSER status are granted full privileges. Currently, this
includes:
- Never having to logon (SUPERUSERs are INHOUSE users)
- Automatically granted CONTROL
privileges (can perform remote server resets)
- File uploads are never blocked.
- URL: Uniform Resource Locator.
- URL's are a scheme for specifying Internet
resources using a single line of printable ASCII characters. A URL should
contain
a protocol, domain name, port number (optional), the location of the resource, and
an (optional) option list (following a ?).
In this documentation, the URL term connotes "a link coded into an HTML document".
Upon selecting such a link, the client sends back a request string that
contains the verb (the HTTP method), the request selector , and
the http protocol (typically, HTTP/1.0)
Example:given a URL of
http://www.econ.ag.gov/calc/calc.htm
the resulting request selector would be calc/calc.htm
- URL character encoding
- Since several characters have very specific meanings in the HTTP protocol (such
as the & and the > characters), and since spaces are not allowed in request
strings, a set of
character encoding rules are needed to transmit such characters.
Caution: When handcoding URL's with an option list following a ? and
seperated by &
characters, you must encode the & character.
For example:
- INCORRECT:
<A HREF="/GETAFILE?dir=PUBLIC/&showdate=YES">
- CORRECT:
<A HREF="/GETAFILE?dir=PUBLIC/&showdate=YES">
- Web Browser
- A Web Browser is a program that can communicate over the
Internet, and that is capable of displaying HTML documents.
NetScape, Mosaic. and IBM Web Explorer are examples of Web Browsers.
- Wildcard matching
- Wildcard matching use the * as a wildcard character in a natural
fashion.
Examples:
/JOE/* will match /JOE/FOO.HTM
/JOAN/SRCH.HTM?* will match /JOAN/SRCH.HTM?search+me
/JOAN/SRCH.HTM?* will NOT match /JOAN/SRCH.HTM
(/JOAN/SRCH.HTM* will match BOTH these examples)
/PETS/*INDEX.HTM will match
/PETS/INDEX.HTM, /PETS/CAT/INDEX.HTM and /PETS/PUPPY/LAB/INDEX.HTM
but will NOT match
/PETS/CAT/PUREBRED.HTM
SRE-Filter files that support wildcard matching are:
ALIAS_FILE, RECORD_ALL_FILE,
SENDFILE_FILE, ACCESS_FILE, and the PUBLIC_URL stem variables.
The COUNTER_FILE does not support wildcard matching.
- Wildcard matching with substitution
- Wildcard matching with substitution is similar to wildcard matching.
However, rather then being a "many to one" match, it is a "many to many" match.
The basic rule is that both a "target" and a "replacement" should contain
* characters. When a wildcard match between the target and a candidate occurs,
the "covered portion of the candidate" is inserted into
the "replacement". In other words, the * character in the
replacement is deleted, and the "covered portion" is inserted.
Example:
- If the request selector is:
project/jillwork.htm
- and there is an alias of:
project/* /research/ongoing/*
- SRE-Filter will convert the request selector to
/research/ongoing/jillwork.htm
- Working Directory
- The Working Directory in the directory containing GOSERVE.EXE (typically,
\GOSERV). You
should copy the various SRE-Filter files to it (see the
installation section
for details).
Return to table of contents
For questions, contact
Daniel Hellerstein.