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I'm trying to track down a php issue with a tool that I'm trying to install, and have tracked it down, I believe, to a permissions issue with the filesystem, I believe...

I now have the following simple .php file:

<?php
system("/bin/ls");
?>

When I run this, I see the following error in /var/log/httpd/error_log:

sh: /bin/ls: Permission denied

If I change the php to run:

<?php
system("/bin/env");
?>

Then I see the output that I was expecting.

So it's not the execution that doesn't have permissions, it's what the executable is trying to read that is having problems.

(The tool I am trying to get working here is phplicensewatcher - a tool for keeping an eye on what is going on with various license management daemons)

Thanks

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The first two thing I would check:

  • What user is PHP running under? If it's spawned by Apache, it is likely running as "nobody", "www" or "apache" depending on the version and configuration.

  • What directory are you trying to list? Check the permissions on that directory. Does the user PHP is running as have permission to access that directory?

3
  • I checked which user it was running as by calling 'sleep 30' through php and checking the process list. It's running as 'apache'. I successfully ran "sudo -u apache /bin/ls /". And I'm just trying to list any directory. I've been trying it with /
    – Hugh
    Dec 19 '10 at 1:57
  • Do you have SELinux enabled? It will block things like this as security measures. Run the getenforce command to check.
    – John T
    Dec 19 '10 at 2:12
  • Aha! That was it! It works if I disable SELinux. Many thanks
    – Hugh
    Dec 19 '10 at 11:48

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