Output issue with sudo and php system/shell_exec functions

5ury4 · 05-25-2008, 04:28 PM

Hello,

I've tried doing a whoami using PHP exec and got the user 'nobody' on my box. I edited the passwd file and provided nobody with bash access (I'm aware of the security risk here). I edited the sudoers file using visudo and created an entry for nobody to run ALL commands using root (again, I know the security risk but it doesn't matter in my case).

In SSH, after a 'su - nobody' while I'm on root I can run any command using sudo. Say :

Code:

root@server [~]# su - nobody
-bash-3.1$ sudo whoami
root
-bash-3.1$ sudo foo
sudo: foo: command not found

But when I do the same with a PHP file using the code :

Code:

<?php
echo shell_exec('sudo foo');
echo system('sudo foo');
echo passthru('sudo foo');
echo exec('sudo foo');
echo system('id');
echo system('uname');
?>

I get NO output for any of the line containing sudo, but I get output for the last two lines (id and uname).

I don't know where I'm wrong here, my sudoers entry reads ->

Code:

nobody ALL=(root) NOPASSWD: ALL

So, there's no hostname/FQDN restriction. I've also tried executing the script from an IP instead of a FQDN. There might be some other restriction or problem which I'm overlooking or of which I'm not aware of. Please help me.

Thanks your for inputs.

5ury4 · 05-25-2008, 05:28 PM

I got it working. It was a statement in the sudoers 'Defaults requiretty' which required a real tty to operate sudo. Using an exec() with php for the command 'tty' printed 'not a tty'. Therefore removing/commenting that line solved the problem. There's still no output, however the sudo action/command is carried out and I've also seen that the php waits for the execution to complete before carrying out other commands beyond that line.