<ol>
<li>
<strong>Is the user executing this wrapper a valid user of
- this system?</strong>
+ this system?</strong>
<p class="indent">
This is to ensure that the user executing the wrapper is
<li>
<strong>Was the wrapper called with the proper number of
- arguments?</strong>
+ arguments?</strong>
<p class="indent">
The wrapper will only execute if it is given the proper
<li>
<strong>Is this valid user allowed to run the
- wrapper?</strong>
+ wrapper?</strong>
<p class="indent">
Is this user the user allowed to run this wrapper? Only
<li>
<strong>Does the target CGI or SSI program have an unsafe
- hierarchical reference?</strong>
+ hierarchical reference?</strong>
<p class="indent">
Does the target CGI or SSI program's path contain a leading
</li>
<li>
- <strong>Is the target user name valid?</strong>
+ <strong>Is the target user name valid?</strong>
<p class="indent">
Does the target user exist?
</li>
<li>
- <strong>Is the target group name valid?</strong>
+ <strong>Is the target group name valid?</strong>
<p class="indent">
Does the target group exist?
<li>
<strong>Is the target userid <em>ABOVE</em> the minimum ID
- number?</strong>
+ number?</strong>
<p class="indent">
The minimum user ID number is specified during
<li>
<strong>Is the target group <em>NOT</em> the superuser
- group?</strong>
+ group?</strong>
<p class="indent">
Presently, suEXEC does not allow the <code><em>root</em></code>
<li>
<strong>Is the target groupid <em>ABOVE</em> the minimum ID
- number?</strong>
+ number?</strong>
<p class="indent">
The minimum group ID number is specified during
<li>
<strong>Can the wrapper successfully become the target user
- and group?</strong>
+ and group?</strong>
<p class="indent">
Here is where the program becomes the target user and
<li>
<strong>Is the directory within the Apache
- webspace?</strong>
+ webspace?</strong>
<p class="indent">
If the request is for a regular portion of the server, is
the requested directory within suEXEC's document root? If
- the request is for a UserDir, is the requested directory
+ the request is for a <directive module="mod_userdir"
+ >UserDir</directive>, is the requested directory
within the directory configured as suEXEC's userdir (see
<a href="#install">suEXEC's configuration options</a>)?
</p>
<li>
<strong>Is the directory <em>NOT</em> writable by anyone
- else?</strong>
+ else?</strong>
<p class="indent">
We don't want to open up the directory to others; only
</li>
<li>
- <strong>Does the target CGI/SSI program exist?</strong>
+ <strong>Does the target CGI/SSI program exist?</strong>
<p class="indent">
If it doesn't exists, it can't very well be executed.
<li>
<strong>Is the target CGI/SSI program <em>NOT</em> writable
- by anyone else?</strong>
+ by anyone else?</strong>
<p class="indent">
We don't want to give anyone other than the owner the
<li>
<strong>Is the target CGI/SSI program <em>NOT</em> setuid or
- setgid?</strong>
+ setgid?</strong>
<p class="indent">
We do not want to execute programs that will then change
<li>
<strong>Is the target user/group the same as the program's
- user/group?</strong>
+ user/group?</strong>
<p class="indent">
Is the user the owner of the file?
<li>
<strong>Can we successfully clean the process environment
- to ensure safe operations?</strong>
+ to ensure safe operations?</strong>
<p class="indent">
suEXEC cleans the process' environment by establishing a
<li>
<strong>Can we successfully become the target CGI/SSI program
- and execute?</strong>
+ and execute?</strong>
<p class="indent">
Here is where suEXEC ends and the target CGI/SSI program begins.
directories where suEXEC access should be allowed. All
executables under this directory will be executable by suEXEC
as the user so they should be "safe" programs. If you are
- using a "simple" UserDir directive (ie. one without a "*" in
- it) this should be set to the same value. suEXEC will not
- work properly in cases where the UserDir directive points to
+ using a "simple" <directive module="mod_userdir">UserDir</directive>
+ directive (ie. one without a "*" in it) this should be set to the same
+ value. suEXEC will not work properly in cases where the <directive
+ module="mod_userdir">UserDir</directive> directive points to
a location that is not the same as the user's home directory
- as referenced in the passwd file. Default value is
- "public_html".<br />
- If you have virtual hosts with a different UserDir for each,
+ as referenced in the <code>passwd</code> file. Default value is
+ "<code>public_html</code>".<br />
+ If you have virtual hosts with a different <directive
+ module="mod_userdir">UserDir</directive> for each,
you will need to define them to all reside in one parent
directory; then name that parent directory here. <strong>If
this is not defined properly, "~userdir" cgi requests will
<dt><code>--with-suexec-docroot=<em>DIR</em></code></dt>
<dd>Define as the DocumentRoot set for Apache. This will be
- the only hierarchy (aside from UserDirs) that can be used for
- suEXEC behavior. The default directory is the <code>--datadir</code>
- value with the suffix "/htdocs", <em>e.g.</em> if you configure
- with "<code>--datadir=/home/apache</code>" the directory
- "/home/apache/htdocs" is used as document root for the suEXEC
- wrapper.</dd>
+ the only hierarchy (aside from <directive module="mod_userdir"
+ >UserDir</directive>s) that can be used for suEXEC behavior. The
+ default directory is the <code>--datadir</code> value with the suffix
+ "<code>/htdocs</code>", <em>e.g.</em> if you configure with
+ "<code>--datadir=/home/apache</code>" the directory
+ "<code>/home/apache/htdocs</code>" is used as document root for the
+ suEXEC wrapper.</dd>
<dt><code>--with-suexec-uidmin=<em>UID</em></code></dt>
<dd>This defines the filename to which all suEXEC
transactions and errors are logged (useful for auditing and
debugging purposes). By default the logfile is named
- "suexec_log" and located in your standard logfile directory
- (<code>--logfiledir</code>).</dd>
+ "<code>suexec_log</code>" and located in your standard logfile
+ directory (<code>--logfiledir</code>).</dd>
<dt><code>--with-suexec-safepath=<em>PATH</em></code></dt>
<dd>Define a safe PATH environment to pass to CGI
executables. Default value is
- "/usr/local/bin:/usr/bin:/bin".</dd>
+ "<code>/usr/local/bin:/usr/bin:/bin</code>".</dd>
</dl>
- <p><strong>Compiling and installing the suEXEC
- wrapper</strong><br />
- If you have enabled the suEXEC feature with the
- <code>--enable-suexec</code> option the <code>suexec</code> binary
- (together with Apache itself) is automatically built if you execute
- the <code>make</code> command.<br />
- After all components have been built you can execute the
- command <code>make install</code> to install them. The binary image
- <code>suexec</code> is installed in the directory defined by the
- <code>--sbindir</code> option. The default location is
- "/usr/local/apache2/bin/suexec".<br />
- Please note that you need <strong><em>root
- privileges</em></strong> for the installation step. In order
- for the wrapper to set the user ID, it must be installed as
- owner <code><em>root</em></code> and must have the setuserid
- execution bit set for file modes.</p>
-
- <p><strong>Setting paranoid permissions</strong><br />
- Although the suEXEC wrapper will check to ensure that its
- caller is the correct user as specified with the
- <code>--with-suexec-caller</code> <program>configure</program>
- option, there is
- always the possibility that a system or library call suEXEC uses
- before this check may be exploitable on your system. To counter
- this, and because it is best-practise in general, you should use
- filesystem permissions to ensure that only the group Apache
- runs as may execute suEXEC.</p>
-
- <p>If for example, your web server is configured to run as:</p>
-
-<example>
- User www<br />
- Group webgroup<br />
-</example>
-
- <p>and <program>suexec</program> is installed at
- "/usr/local/apache2/bin/suexec", you should run:</p>
-
-<example>
- chgrp webgroup /usr/local/apache2/bin/suexec<br />
- chmod 4750 /usr/local/apache2/bin/suexec<br />
-</example>
-
- <p>This will ensure that only the group Apache runs as can even
- execute the suEXEC wrapper.</p>
+ <section>
+ <title>Compiling and installing the suEXEC wrapper</title>
+
+ <p>If you have enabled the suEXEC feature with the
+ <code>--enable-suexec</code> option the <code>suexec</code> binary
+ (together with Apache itself) is automatically built if you execute
+ the <code>make</code> command.</p>
+
+ <p>After all components have been built you can execute the
+ command <code>make install</code> to install them. The binary image
+ <code>suexec</code> is installed in the directory defined by the
+ <code>--sbindir</code> option. The default location is
+ "/usr/local/apache2/bin/suexec".</p>
+
+ <p>Please note that you need <strong><em>root
+ privileges</em></strong> for the installation step. In order
+ for the wrapper to set the user ID, it must be installed as
+ owner <code><em>root</em></code> and must have the setuserid
+ execution bit set for file modes.</p>
+ </section>
+
+ <section>
+ <title>Setting paranoid permissions</title>
+
+ <p>Although the suEXEC wrapper will check to ensure that its
+ caller is the correct user as specified with the
+ <code>--with-suexec-caller</code> <program>configure</program>
+ option, there is
+ always the possibility that a system or library call suEXEC uses
+ before this check may be exploitable on your system. To counter
+ this, and because it is best-practise in general, you should use
+ filesystem permissions to ensure that only the group Apache
+ runs as may execute suEXEC.</p>
+
+ <p>If for example, your web server is configured to run as:</p>
+
+ <example>
+ User www<br />
+ Group webgroup<br />
+ </example>
+
+ <p>and <program>suexec</program> is installed at
+ "/usr/local/apache2/bin/suexec", you should run:</p>
+
+ <example>
+ chgrp webgroup /usr/local/apache2/bin/suexec<br />
+ chmod 4750 /usr/local/apache2/bin/suexec<br />
+ </example>
+
+ <p>This will ensure that only the group Apache runs as can even
+ execute the suEXEC wrapper.</p>
+ </section>
</section>
+
<section id="enable"><title>Enabling & Disabling
suEXEC</title>
<li><strong>suEXEC Points Of Interest</strong></li>
<li>
- Hierarchy limitations
+ Hierarchy limitations
<p class="indent">
For security and efficiency reasons, all suEXEC requests
</li>
<li>
- suEXEC's PATH environment variable
+ suEXEC's PATH environment variable
<p class="indent">
This can be a dangerous thing to change. Make certain
</li>
<li>
- Altering the suEXEC code
+ Altering the suEXEC code
<p class="indent">
Again, this can cause <strong>Big Trouble</strong> if you
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