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61932ed91732417e05c8c6fd335acf1be896c778Mark Andrews<title>suEXEC Support - Apache HTTP Server</title>
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71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<p class="apache">Apache HTTP Server Version 2.1</p>
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71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="/images/left.gif" /></a></div>
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8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs-project/">Documentation</a> &gt; <a href="./">Version 2.1</a></div><div id="page-content"><div id="preamble"><h1>suEXEC Support</h1>
8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt<div class="toplang">
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<p><span>Available Languages: </span><a href="/en/suexec.html" title="English">&nbsp;en&nbsp;</a> |
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71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<a href="/ko/suexec.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
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71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt <p>The <strong>suEXEC</strong> feature provides
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt Apache users the ability
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt to run <strong>CGI</strong> and <strong>SSI</strong> programs
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt under user IDs different from the user ID of the calling
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt web-server. Normally, when a CGI or SSI program executes, it
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt runs as the same user who is running the web server.</p>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt <p>Used properly, this feature can reduce
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews considerably the security risks involved with allowing users to
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt develop and run private CGI or SSI programs. However, if suEXEC
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews is improperly configured, it can cause any number of problems
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt and possibly create new holes in your computer's security. If
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt you aren't familiar with managing <em>setuid root</em> programs
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt and the security issues they present, we highly recommend that
8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt you not consider using suEXEC.</p>
8fda09fc85d395d2dc955d23c5eb476cf4d2dffbEvan Hunt </div>
8fda09fc85d395d2dc955d23c5eb476cf4d2dffbEvan Hunt<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#before">Before we begin</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#model">suEXEC Security Model</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#install">Configuring &amp; Installing
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt suEXEC</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#enable">Enabling &amp; Disabling
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt suEXEC</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#usage">Using suEXEC</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#debug">Debugging suEXEC</a></li>
8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt<li><img alt="" src="/images/down.gif" /> <a href="#jabberwock">Beware the Jabberwock:
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt Warnings &amp; Examples</a></li>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt</ul></div>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<div class="section">
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews<h2><a name="before" id="before">Before we begin</a></h2>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt <p>Before jumping head-first into this document,
8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt you should be aware of the assumptions made on the part of the
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt Apache Group and this document.</p>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews <p>First, it is assumed that you are using a UNIX
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt derivative operating system that is capable of
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt <strong>setuid</strong> and <strong>setgid</strong> operations.
3916872f379457fe344afb02398a009701c5016aEvan Hunt All command examples are given in this regard. Other platforms,
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews if they are capable of supporting suEXEC, may differ in their
1c95f672323b7ac176af4225a36d33daa442542cMark Andrews configuration.</p>
3916872f379457fe344afb02398a009701c5016aEvan Hunt
3916872f379457fe344afb02398a009701c5016aEvan Hunt <p>Second, it is assumed you are familiar with
eca15167ac923ec2c16add3e7e3dd6c596aa6f8cMark Andrews some basic concepts of your computer's security and its
3916872f379457fe344afb02398a009701c5016aEvan Hunt administration. This involves an understanding of
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt <strong>setuid/setgid</strong> operations and the various
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt effects they may have on your system and its level of
d58e33bfabfee19a035031dac633d36659738d56Evan Hunt security.</p>
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt <p>Third, it is assumed that you are using an
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt <strong>unmodified</strong> version of suEXEC code. All code
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt for suEXEC has been carefully scrutinized and tested by the
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt developers as well as numerous beta testers. Every precaution
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt has been taken to ensure a simple yet solidly safe base of
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt code. Altering this code can cause unexpected problems and new
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt security risks. It is <strong>highly</strong> recommended you
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt not alter the suEXEC code unless you are well versed in the
0994d3a21baeedf28cbf7e461b3bd8de5f9a6654Evan Hunt particulars of security programming and are willing to share
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień your work with the Apache Group for consideration.</p>
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień <p>Fourth, and last, it has been the decision of
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień the Apache Group to <strong>NOT</strong> make suEXEC part of
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień the default installation of Apache. To this end, suEXEC
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień configuration requires of the administrator careful attention
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień to details. After due consideration has been given to the
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień various settings for suEXEC, the administrator may install
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień suEXEC through normal installation methods. The values for
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień these settings need to be carefully determined and specified by
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień the administrator to properly maintain system security during
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień the use of suEXEC functionality. It is through this detailed
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień process that the Apache Group hopes to limit suEXEC
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień installation only to those who are careful and determined
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień enough to use it.</p>
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień
e02fa56849131911e9554133b17a5325b37d0828Michał Kępień <p>Still with us? Yes? Good. Let's move on!</p>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
71bd858d8ed62672e7c23999dc7c02fd16a55089Evan Hunt<div class="section">
8a743600ddfcd97adbbd83f8e9f546ce7d365acbEvan Hunt<h2><a name="model" id="model">suEXEC Security Model</a></h2>
3635d8f9104e70e141a8f191a0e6c1502ceed2f3Mark Andrews
3635d8f9104e70e141a8f191a0e6c1502ceed2f3Mark Andrews <p>Before we begin configuring and installing
3635d8f9104e70e141a8f191a0e6c1502ceed2f3Mark Andrews suEXEC, we will first discuss the security model you are about
to implement. By doing so, you may better understand what
exactly is going on inside suEXEC and what precautions are
taken to ensure your system's security.</p>
<p><strong>suEXEC</strong> is based on a setuid
"wrapper" program that is called by the main Apache web server.
This wrapper is called when an HTTP request is made for a CGI
or SSI program that the administrator has designated to run as
a userid other than that of the main server. When such a
request is made, Apache provides the suEXEC wrapper with the
program's name and the user and group IDs under which the
program is to execute.</p>
<p>The wrapper then employs the following process
to determine success or failure -- if any one of these
conditions fail, the program logs the failure and exits with an
error, otherwise it will continue:</p>
<ol>
<li>
<strong>Is the user executing this wrapper a valid user of
this system?</strong>
<p class="indent">
This is to ensure that the user executing the wrapper is
truly a user of the system.
</p>
</li>
<li>
<strong>Was the wrapper called with the proper number of
arguments?</strong>
<p class="indent">
The wrapper will only execute if it is given the proper
number of arguments. The proper argument format is known
to the Apache web server. If the wrapper is not receiving
the proper number of arguments, it is either being
hacked, or there is something wrong with the suEXEC
portion of your Apache binary.
</p>
</li>
<li>
<strong>Is this valid user allowed to run the
wrapper?</strong>
<p class="indent">
Is this user the user allowed to run this wrapper? Only
one user (the Apache user) is allowed to execute this
program.
</p>
</li>
<li>
<strong>Does the target CGI or SSI program have an unsafe
hierarchical reference?</strong>
<p class="indent">
Does the target CGI or SSI program's path contain a leading
'/' or have a '..' backreference? These are not allowed; the
target CGI/SSI program must reside within suEXEC's document
root (see <code>--with-suexec-docroot=<em>DIR</em></code>
below).
</p>
</li>
<li>
<strong>Is the target user name valid?</strong>
<p class="indent">
Does the target user exist?
</p>
</li>
<li>
<strong>Is the target group name valid?</strong>
<p class="indent">
Does the target group exist?
</p>
</li>
<li>
<strong>Is the target user <em>NOT</em> superuser?</strong>
<p class="indent">
Presently, suEXEC does not allow <code><em>root</em></code>
to execute CGI/SSI programs.
</p>
</li>
<li>
<strong>Is the target userid <em>ABOVE</em> the minimum ID
number?</strong>
<p class="indent">
The minimum user ID number is specified during
configuration. This allows you to set the lowest possible
userid that will be allowed to execute CGI/SSI programs.
This is useful to block out "system" accounts.
</p>
</li>
<li>
<strong>Is the target group <em>NOT</em> the superuser
group?</strong>
<p class="indent">
Presently, suEXEC does not allow the <code><em>root</em></code>
group to execute CGI/SSI programs.
</p>
</li>
<li>
<strong>Is the target groupid <em>ABOVE</em> the minimum ID
number?</strong>
<p class="indent">
The minimum group ID number is specified during
configuration. This allows you to set the lowest possible
groupid that will be allowed to execute CGI/SSI programs.
This is useful to block out "system" groups.
</p>
</li>
<li>
<strong>Can the wrapper successfully become the target user
and group?</strong>
<p class="indent">
Here is where the program becomes the target user and
group via setuid and setgid calls. The group access list
is also initialized with all of the groups of which the
user is a member.
</p>
</li>
<li>
<strong>Can we change directory to the one in which the target
CGI/SSI program resides?</strong>
<p class="indent">
If it doesn't exist, it can't very well contain files. If we
can't change directory to it, it might aswell not exist.
</p>
</li>
<li>
<strong>Is the directory within the Apache
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
within the directory configured as suEXEC's userdir (see
<a href="#install">suEXEC's configuration options</a>)?
</p>
</li>
<li>
<strong>Is the directory <em>NOT</em> writable by anyone
else?</strong>
<p class="indent">
We don't want to open up the directory to others; only
the owner user may be able to alter this directories
contents.
</p>
</li>
<li>
<strong>Does the target CGI/SSI program exist?</strong>
<p class="indent">
If it doesn't exists, it can't very well be executed.
</p>
</li>
<li>
<strong>Is the target CGI/SSI program <em>NOT</em> writable
by anyone else?</strong>
<p class="indent">
We don't want to give anyone other than the owner the
ability to change the CGI/SSI program.
</p>
</li>
<li>
<strong>Is the target CGI/SSI program <em>NOT</em> setuid or
setgid?</strong>
<p class="indent">
We do not want to execute programs that will then change
our UID/GID again.
</p>
</li>
<li>
<strong>Is the target user/group the same as the program's
user/group?</strong>
<p class="indent">
Is the user the owner of the file?
</p>
</li>
<li>
<strong>Can we successfully clean the process environment
to ensure safe operations?</strong>
<p class="indent">
suEXEC cleans the process' environment by establishing a
safe execution PATH (defined during configuration), as
well as only passing through those variables whose names
are listed in the safe environment list (also created
during configuration).
</p>
</li>
<li>
<strong>Can we successfully become the target CGI/SSI program
and execute?</strong>
<p class="indent">
Here is where suEXEC ends and the target CGI/SSI program begins.
</p>
</li>
</ol>
<p>This is the standard operation of the
suEXEC wrapper's security model. It is somewhat stringent and
can impose new limitations and guidelines for CGI/SSI design,
but it was developed carefully step-by-step with security in
mind.</p>
<p>For more information as to how this security
model can limit your possibilities in regards to server
configuration, as well as what security risks can be avoided
with a proper suEXEC setup, see the <a href="#jabberwock">"Beware the Jabberwock"</a> section of this
document.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="install" id="install">Configuring &amp; Installing
suEXEC</a></h2>
<p>Here's where we begin the fun.</p>
<p><strong>suEXEC configuration
options</strong><br />
</p>
<dl>
<dt><code>--enable-suexec</code></dt>
<dd>This option enables the suEXEC feature which is never
installed or activated by default. At least one
<code>--with-suexec-xxxxx</code> option has to be provided
together with the <code>--enable-suexec</code> option to let
APACI accept your request for using the suEXEC feature.</dd>
<dt><code>--with-suexec-bin=<em>PATH</em></code></dt>
<dd>The path to the <code>suexec</code> binary must be hard-coded
in the server for security reasons. Use this option to override
the default path. <em>e.g.</em>
<code>--with-suexec-bin=/usr/sbin/suexec</code></dd>
<dt><code>--with-suexec-caller=<em>UID</em></code></dt>
<dd>The <a href="mod/mpm_common.html#user">username</a> under which
Apache normally runs. This is the only user allowed to
execute this program.</dd>
<dt><code>--with-suexec-userdir=<em>DIR</em></code></dt>
<dd>Define to be the subdirectory under users' home
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
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,
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
not work!</strong></dd>
<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>
<dt><code>--with-suexec-uidmin=<em>UID</em></code></dt>
<dd>Define this as the lowest UID allowed to be a target user
for suEXEC. For most systems, 500 or 100 is common. Default
value is 100.</dd>
<dt><code>--with-suexec-gidmin=<em>GID</em></code></dt>
<dd>Define this as the lowest GID allowed to be a target
group for suEXEC. For most systems, 100 is common and
therefore used as default value.</dd>
<dt><code>--with-suexec-logfile=<em>FILE</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>
<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>
</dl>
<p><strong>Checking your suEXEC
setup</strong><br />
Before you compile and install the suEXEC wrapper you can
check the configuration with the <code>--layout</code> option.<br />
Example output:</p>
<div class="example"><p><code>
suEXEC setup:<br />
suexec binary: /usr/local/apache2/sbin/suexec<br />
document root: /usr/local/apache2/share/htdocs<br />
userdir suffix: public_html<br />
logfile: /usr/local/apache2/var/log/suexec_log<br />
safe path: /usr/local/bin:/usr/bin:/bin<br />
caller ID: www<br />
minimum user ID: 100<br />
minimum group ID: 100<br />
</code></p></div>
<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/sbin/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> configure 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>
<div class="example"><p><code>
User www<br />
Group webgroup<br />
</code></p></div>
<p>and <code>suexec</code> is installed at
"/usr/local/apache2/sbin/suexec", you should run:</p>
<div class="example"><p><code>
chgrp webgroup /usr/local/apache2/bin/suexec<br />
chmod 4750 /usr/local/apache2/bin/suexec<br />
</code></p></div>
<p>This will ensure that only the group Apache runs as can even
execute the suEXEC wrapper.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="enable" id="enable">Enabling &amp; Disabling
suEXEC</a></h2>
<p>Upon startup of Apache, it looks for the file
<code>suexec</code> in the directory defined by the
<code>--sbindir</code> option (default is
"/usr/local/apache/sbin/suexec"). If Apache finds a properly
configured suEXEC wrapper, it will print the following message
to the error log:</p>
<div class="example"><p><code>
[notice] suEXEC mechanism enabled (wrapper: <em>/path/to/suexec</em>)
</code></p></div>
<p>If you don't see this message at server startup, the server is
most likely not finding the wrapper program where it expects
it, or the executable is not installed <em>setuid root</em>.</p>
<p>If you want to enable the suEXEC mechanism for the first time
and an Apache server is already running you must kill and
restart Apache. Restarting it with a simple HUP or USR1 signal
will not be enough. </p>
<p>If you want to disable suEXEC you should kill and restart
Apache after you have removed the <code>suexec</code> file. </p>
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="usage" id="usage">Using suEXEC</a></h2>
<p><strong>Virtual Hosts:</strong><br /> One way to use the suEXEC
wrapper is through the <code class="directive"><a href="/mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code> directive in
<code class="directive"><a href="/mod/core.html#virtualhost">VirtualHost</a></code> definitions. By
setting this directive to values different from the main server
user ID, all requests for CGI resources will be executed as the
<em>User</em> and <em>Group</em> defined for that <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code>. If this
directive is not specified for a <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> then the main server userid
is assumed.</p>
<p><strong>User directories:</strong><br />
The suEXEC wrapper can also be used to execute CGI programs as
the user to which the request is being directed. This is
accomplished by using the "<strong><code>~</code></strong>"
character prefixing the user ID for whom execution is desired.
The only requirement needed for this feature to work is for CGI
execution to be enabled for the user and that the script must
meet the scrutiny of the <a href="#model">security checks</a>
above.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="debug" id="debug">Debugging suEXEC</a></h2>
<p>The suEXEC wrapper will write log information
to the file defined with the <code>--with-suexec-logfile</code>
option as indicated above. If you feel you have configured and
installed the wrapper properly, have a look at this log and the
error_log for the server to see where you may have gone astray.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="jabberwock" id="jabberwock">Beware the Jabberwock:
Warnings &amp; Examples</a></h2>
<p><strong>NOTE!</strong> This section may not be
complete. For the latest revision of this section of the
documentation, see the Apache Group's <a href="http://httpd.apache.org/docs-2.1/suexec.html">Online
Documentation</a> version.</p>
<p>There are a few points of interest regarding
the wrapper that can cause limitations on server setup. Please
review these before submitting any "bugs" regarding suEXEC.</p>
<ul>
<li><strong>suEXEC Points Of Interest</strong></li>
<li>
Hierarchy limitations
<p class="indent">
For security and efficiency reasons, all suEXEC requests
must remain within either a top-level document root for
virtual host requests, or one top-level personal document
root for userdir requests. For example, if you have four
VirtualHosts configured, you would need to structure all
of your VHosts' document roots off of one main Apache
document hierarchy to take advantage of suEXEC for
VirtualHosts. (Example forthcoming.)
</p>
</li>
<li>
suEXEC's PATH environment variable
<p class="indent">
This can be a dangerous thing to change. Make certain
every path you include in this define is a
<strong>trusted</strong> directory. You don't want to
open people up to having someone from across the world
running a trojan horse on them.
</p>
</li>
<li>
Altering the suEXEC code
<p class="indent">
Again, this can cause <strong>Big Trouble</strong> if you
try this without knowing what you are doing. Stay away
from it if at all possible.
</p>
</li>
</ul>
</div></div>
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