Logo address

httpd.rewrite

Contents

2015/06/29 Update
2003/02/11 Update

Location

/sys/lib/httpd.rewrite

Function

This file has two roles:

Case study

In the explanation below, we assume our domain name is:
pegasus.goodwill.com
And we assume five persons:
alice
bob
carol
david
emily
frank

URI

First of all I would like to explain URI(URL) briefly.
According to RFC2068, URI of HTTP is defined as follows:
scheme://host[:port][/path][;params][?query]
where
The RFC was made obsolete by RFC2616. The new URI is
scheme://host[:port][/path][?query]
That is "[;params]" is disappeared, but ';' is remained as a special character. The semantic is unclear.

Old format works in regular situation, but might make a problem if the URI is in a directory that must be authenticated. For example Mac/Safari fails to be authenticated. Therefore it is wise not to use ';'.

User's document is conventionally expressed using the path that begin with "~user" in URI, where "user" is a user name of the system. That is, "~user" is expressed as a directory under document root of real host. However implementation need not keep "~user" under the document root. Rather it would be convenient to have user's document in the directory of the user.

/sys/lib/httpd.rewrite

The following is an example of "/sys/lib/httpd.rewrite" for our case study.
# pattern        replacement
http://car       */usr/carol/www
https://car      */usr/carol/https
/~frank          http://www.eecs.harvard.edu/~frank
/~emily         */usr/david/www_removed
/private         https://pegasus.goodwill.com/private
/                */usr/bob/www
The lines in this file consist of two fields except comment line. Fields are separated by spaces.

The first field is a pattern of request. The request is limited only to http and https.
host is the name of real host or virtual host. Note that the host is not full name of the domain.

Note that we are assuming that the domain name of carol's page is

car.goodwill.com
and the server's domain is
pegasus.goodwill.com
which means both pages are running on the same domain, "goodwill.com".
Then the trailing ".goodwill.com" must be remove from the first field.
If carol's page has another domain name, say
car.bar.com
then we need to add a line
http://car.bar.com	*/usr/carol/www
to httpd.rewrite.

If the first field begin with / then the request is regarded as the request to real host or user. That is, we regard scheme://host[:port] is omitted, where host is the name of real host.

In second field:

Note that the second field that begin with '/' is not described here. I would like to examine the real needs before I specify such a field.

If the requested URI matches the first field, then we have two cases:

Understand the followings:
Comparison is executed using the following rules:
Therefore a line with "/" as the first field must be placed at the end

If there is no field in "/sys/lib/httpd.rewrite" that matches with URI, then Pegasus examines the possibility that the request is to the user.

Httpd root for real and virtual hosts

Every documents owner is permitted to have access control files and CGI files. All the system users who publish web contents have a httpd root(we refer "$web"), and can have "doc", "etc" and "bin" under the directory; "doc" is the place where document is located, "etc" is the place where access control files such as "rewrite", "allow", "passwd" and "handler" are located, and "bin" is the place where CGI files are located.
Pegasus set httpd root in "/sys/lib/httpd.rewrite". For example, assume bob administrate the the document of real host and carol administrate the the document of virtual host car. Then httpd root is specified in the second field using '*' followed by the directory path like this:
http://car      */usr/carol/www
https://car     */usr/carol/https
/               */usr/bob/www
In this case, carol are given two httpd root "/usr/carol/www" and "usr/carol/https" for her virtual host "car".
A system user alice can have their personal home page of URI:
http://pegasus.goodwill.com/~alice
without setting in "/sys/lib/httpd.rewrite" if she has "$home/web/doc". Then "$home/web" is her httpd root.

Note: name of virtual host must be registered to DNS

/usr/bob/www/etc/rewrite

File "/usr/bob/www/etc/rewrite" is read after "/sys/lib/httpd.rewrite". Expression
/private		https://pegasus.goodwill.com/private
will be considered in "$web/etc/rewrite".

Format of /sys/lib/httpd.rewrite

General rule

Meta symbols

Format of the first field

First field is one of the followings:
1.  scheme://host[:port]
2.  /path
where
Please follow the rule:

Format of second field

Second field is one of the followings:
1.  scheme://hostdom[:port][/path][;params][?query]
2.  */path
where