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POWhy am I getting a SegFault when I call pdftk from PHP/Apache but not PHP/CLI or directly
 

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  1. POWhy am I getting a SegFault when I call pdftk from PHP/Apache but not PHP/CLI or directly
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    <p>When I call <code>/usr/local/bin/pdftk</code> from PHP in Apache (via <code>shell_exec()</code>, <code>exec()</code>, <code>system()</code>, <em>etc.</em>), it returns the SYNOPSIS message as expected.</p> <p>When I call <code>/usr/local/bin/pdftk input.pdf fill_form input.fdf output output.pdf flatten</code> via <code>shell_exec()</code>, nothing returns.</p> <p>When I copy and paste the exact same string to the same path in the shell (as the apache user), the output.pdf file is generated as expected.</p> <p>Moving the <code>pdftk</code> command into a PHP shell script (shebang is <code>#!/usr/bin/php</code>) and executing it with <code>php script.php</code> works perfectly.</p> <p>Calling that shell script (with its stderr redirected to stdout) from PHP in Apache (via <code>shell_exec(script.php);</code>) results in this line:</p> <pre><code>sh: line 1: 32547 Segmentation fault /usr/local/bin/pdftk input.pdf fill_form input.fdf output output.pdf flatten 2&gt;&amp;1 </code></pre> <p>Whenever I run the script from the command line (via PHP or directly), it works fine. Whenever I run the script through PHP via Apache, it either fails without any notification or gives the SegFault listed above.</p> <p>It's PHP 4.3.9 on RHEL4. Please don't shoot me. I've set memory to 512M with ini_set() and made sure that the apache user had read/write to all paths (with fopen()) and by logging in as apache ...</p> <p>Just went and checked /var/log/messages to find this:</p> <pre><code>Oct 4 21:17:58 discovery kernel: audit(1286241478.692:1764638): avc: denied { read } for pid=32627 comm="pdftk" name="zero" dev=tmpfs ino=2161 scontext=root:system_r:httpd_sys_script_t tcontext=system_u:object_r:zero_device_t tclass=chr_file </code></pre> <p><strong>NOTE:</strong> Disabling SELinux "fixed" the problem. Has this moved into a ServerFault question? Can anybody give me the 30 second SELinux access controls primer here?</p>
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