HTTP SERVER FOR JNOS

The http server in Jnos was written by Selcuk Ozturk, N3YCO and Brian Lantz, KO4KS.

Table of Contents

• HTTP SERVER FOR JNOS
  • HTTP:
  • HOW TO MAKE:
  • COMMENTS:

HTTP:

This http server is almost completely rewritten from it's first appearance in Jnos 1.10. Selcuk Ozturk took a lot of code and ideas from Brian Lantz' adaptation of this http server in TNOS. An unfortunate effect of this is backwards incompatibility. So, please read this document thoroughly.

• Setup

  Multiple http servers each listening on a different port number, and using a different root path can be run. The maximum number of servers is compile time configurable and is 5 by default. This document will explain the setup of only one. But, it applies to each instance of the server.

  • First decide about which drive and path you will use as the root location for this server. Only files in this directory or its sub directories will be available to the server. Well, there is a way to override this, but that's later. Default drive is C and the default path is /wwwroot.
  • Create the directory you chose above. Create a file called access.www in your spool directory. The contents of the access file will be explained later. Access file must exist even if empty.
  • Detailed logging for HTTP requests are possible. If you want this feature, you should #define HTTP_EXTLOG in config.h file. The http log files will be kept in the "/wwwlogs" directory which will be in the Jnos root directory by default. The placement of this directory can be changed via the nos.cfg file with a line like this: HLogsDir = /dir1/dir2. Every day, a new log file will be started in this directory. Warning: log files on busy http servers can grow very large! The naming convention for the log file is exactly like the general log files. So, you can use Karl-Heinz Weiss' cleanlog utility on these files.
  • Now, write your first HTML document, name it root.html, and put it into your chosen root directory. (I will assume that it is 'c:/wwwroot' from this point on.)
  • You can start the server, now. The JNOS console command for this is:

    start http [port#] [d] [rootdir]

    If you omit the bracketed options, the defaults are [port#] == 80; [d] == 'C'; [rootdir] == '/wwwroot'.

    • Example: start http 80 c /wwwroot (defaults)

• Configuration commands

  http absinclude [on|OFF]

  Allow absolute paths to be included

  http always [ON|off]

  If on, html files will always be sent regardless of their modification time. (If you use SSIs in your html files, then the file modification time of the html file is not indicative of the content change.)

  http dontlog [str1[|str2[|..]]]

  If you compiled in detailed logging option, this command lets you define strings which if contained in the URL, will suppress detailed logging for these connections.
  Example: http dontlog junkdir/|.gif|.jpg

  http maxcli [n]

  Max. number of connections allowed at one time. Default is 10. See also http simult.

  http multihomed [on|OFF]

  If your server has more than one IP addressses, sets this to on. Defaults to off.

  http simult [n]

  Max. number of connections serviced at once; the rest will wait. The default is 5. See also http maxcli.

  http status

  Shows information about started servers

  http tdisc [secs]

  Set the inactivity disconnect timer. Default is 180 seconds.

• URLs and Access to the Server

  • The documents on your server can be accessed with URLs of the form:

    http://your.internet.address/c:/dir1/dir2/file.ext

    The drive designation in the URL can be dropped, in which case, the drive you have set in the start command will be used. And dir1 is a sub directory of the [rootdir]

  • If the path points to a sub directory then the file welcome.htm in that directory will be served. If it doesn't exist, a directory listing will be prepared on the fly.
    • Note: The wwwpre.cat and wwwpost.cat files are NOT supported anymore. But, you can get the same functionality (and much more) via SSI.
  • welcome.nhd can be used instead of the welcome.htm. In which case, welcome.nhd will be sent w/o HTTP/1.0 headers. This feature can be utilized to do unusual things like automatic redirection. (Probably, not necessary anymore with today's intelligent browsers.)

• Basic Authorization Scheme

  • It is possible to require user-password authorization for some paths under the [rootdir]. Jnos uses the Basic Authorization Scheme. Which requires the client to send the username:password string in BASE64 encoded form.
  • To restrict access to, say, /wwwroot/secret directory with user guest and password hello, put a line like:

    /secret TopSecretArea Z3Vlc3Q6aGVsbG8=

    into the access.www file created above.

    • The first entry on the line is the restricted path relative to [rootdir], must begin with a '/' character, and no drive letter.
    • Second is the realm name. You should use the same realm name for all paths that require the same user - password pair, but different ones must be used otherwise.
    • The last entry on the line is BASE64 encoded form of user:password string. There is a small utility called base64.exe (created by 'make base64' in your Jnos sources directory) which you can use to generate this string. To generate the above example execute the command

      base64 guest:hello

      at the DOS prompt. Be careful to exactly copy the output to the access.www file.

  • If you want a directory not to be accessible even with a password, just put its relative path without a realm and passkey.
  • I tried to plug in all the holes in this system. But, if you discover any loopholes in the security of this server, please report to seost2+@pitt.edu.

• Server Side Includes

  • The current version is completely incompatible with the previous versions in SSI syntax. It is much more powerful and flexible. And also, is compatible with NCSA httpd server. (With some omissions and additions.)
  • The general syntax for an SSI command is:

    <!--# cmdname tag="value" -->

    where tag depends on cmdname, and value depends on tag. Here is a list of commands and their associated tags:

    • echo var="s"
      Prints the values of some variable 's'.
      • s string for the echo var="s" command can take one of these values:
        • DATE_LOCAL Current local time
        • DATE_GMT Current GMT time
        • HOSTNAME Hostname of the server
        • DOCUMENT_URI Resource Identifier of the current document on this server
        • DOCUMENT_NAME File name of the current document
        • LAST_MODIFIED Current document modification time
        • TOTAL_HITS Total number of hits to this server
        • REQ_FROM The From: header value of request (if given by browser)
        • REQ_REFERER The referring URL (if given by browser)
        • REQ_AGENT The accessing browser program name (if given by browser)
      • echo dcount="filename" Display the named counter
      • echo icount="filename" Increment and display the named counter
      • echo scount="filename" Increment the named counter
        Each of these three count tags takes a filename as value which is created in "/wwwstats" directory, and used to keep a counter in. "/wwwstats" directory will be created in the Jnos' root directory by default. Its placement can be changed from nos.cfg file with a line like this: HttpStatsDir = /dir1/dir2.

    • include
      Inserts other files and directories into the current document.
      • include file="/absolute/path" takes the absolute path of a file or directory to be included. You have to issue the http absinclude on command for this to work. Look at the setup section for this command.
      • include virtual="path" takes a path like /dir/file.ext which is interpreted relative to [rootdir].
      • Both file and virtual can also take a directory path as a value. If that is the case, the path must end with a '/' character. Otherwise, it wouldn't work.

    • exec
      • cgi takes a cgi function URI as value and executes it.

  • Each SSI command must begin and end on a single line. There can be text and/or other SSI commands on the same line, but the total length of the line must not exceed 255 characters.

  • Examples:
    • <!--# echo var="DATE_LOCAL" -->
    • <!--# echo icount="page1.cnt" -->
    • <!--# include virtual="file2.htm" -->
    • <!--# exec cgi="/cgi_function?arguments" -->

• CGI Functionality

  This version of the HTTP server has a sort of cgi support. Actually, it is just an interface for further extension of the server code. I thought a lot about how we can support some form and query processing in this server. Any general form processing function I could think of would be too limited. Some kind of scripting language seemed as a possibility, but anything useful and flexible enough would require a lot of memory and would exceed my programming abilities. So, at last, I decided to define a uniform interface and provide a hook for the extension of the server source code. That means, if you know C and the basics of the Jnos code, and a little of the HTTP 1.0 specification, you can write functions for form processing and hook it up with the server source code easily. And since the interface is uniform, these functions can be exchanged between people.

  What you have to do is just write a C function which has a certain prototype, and register it in the Cgis[] array in http.c, and that function will be called with all the necessary information passed to it. Then you just have to process the info whichever way you want, and produce an output for the client.

  I won't talk about the programming details of this here. I tried to explain how it works in http.c to which you will append your functions. I also included two such functions to demonstrate the way they work: One is a simple x-bitmap graphic hit counter which I have been using for quite a while to supply hit counting service to my friends who have their pages on a server which doesn't allow SSI. The other is a simple form entry logging function which is solely for demonstration purposes. Neither of them are compiled in by default. If you want to see their functioning, you have to turn two '#undef's in http.c to '#define's.

• Important Comments (A must read section)

  • SSI commands can be quite dangerous. Be very careful in using them. They are recursive; ie. an included file can include further files. I think this is a nice feature. But, don't abuse it, as each recursion would use up some memory. More importantly, beware of the inclusion loops; they will certainly crash your system.
  • A more important problem is in the security area. If you are like me, and sharing the same sub directory structure between the HTTP and FTP servers, and if you have anonymously writable directories, somebody can just upload an HTML file there with the absolute includes for sensitive files on your system and: all your secrets are no secrets anymore. Therefore, this version has two ways to deal with this problem:
    • http absinclude [on|off] command, with off as default.
    • Access authorization feature. I strongly recommend making all ftp incoming directories http inaccessible.
    • This server is to be seen as extremely experimental. No responsibilities accepted for any possible damages.

HOW TO MAKE:

• Get a copy of the standard JNOS distribution. Check also if a later version is availble at this site.
• First unzip jn111x5.zip, then modify the config.h as desired (be sure to #define http 1). Also edit the makefile, and then run make.

COMMENTS:

• The best information and support for general JNOS questions can be found at the NOS-BBS@hydra.carleton.ca mailing-list. Please, click here to find out more about the NOS-BBS mailing-list.

• Disclaimer: This package carries no warranties whatsoever, explicit or implied. I cannot be held responsible for any damages, physical or otherwise, it might do to you and your data and computer and cat, and wife, ... You got the idea I guess ;) Other than that, I hope you will enjoy it.

Bug reports, fixes, comments and requests to:
seost2+@pitt.edu Selcuk Ozturk

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