How to execute a shell command from a php script

Question

I would like to create a php script to execute a shell command and return its output. The server requires a private key. When I first decided to test this out I created this:

<?php
$command = "ls";
$output = shell_exec($command);
echo "<pre>$output</pre>";
?>

That worked just fine. But when I changed $command to the command I really wanted to run:

$command = "/etc/init.d/mycontrollerd status /etc/mycontrollerconfig";

it gave me this output:

You need root privileges to run this script

My guess is I need to use sudo. Of course that will require putting the pem file somewhere on the server. Assuming I do that, what exactly should $command be? Should I use shell_exec(), exec(), system() or something else?

phihag · Accepted Answer · 2011-07-13 21:42:23Z

4

It does not matter which php function you use to start the script - what lacks is the authorization of your user account.

Either use sudo (preconfigure the web server user to run the exact command without password via visudo, and prefix the command with sudo) or set up a setuid script that executes the command on itself.

answered Jul 13, 2011 at 21:42

phihag

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2 Comments

Kenneth Vogt Over a year ago

While it also matters that the user account must be authorized, that doesn't mean there isn't a best choice for the PHP function to use. Which is best?

phihag Over a year ago

@Kenneth Vogt exec, since it doesn't needlessly involve the shell and returns the result, or passthru, which directly outputs the result, but would require some modification of the original code.

Community · Accepted Answer · 2017-05-23 10:27:45Z

3

What you really need to do is set your web server to run as a specific user (other than 'nobody' for example), or give that user permissions to what you want to execute.

See also: PHP shell_exec() and sudo: must be setuid root

edited May 23, 2017 at 10:27

CommunityBot

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answered Jul 13, 2011 at 21:27

Brad

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2 Comments

Kenneth Vogt Over a year ago

This begs the question: How do you "set your web server to run as a specific user other than 'nobody'"?

Brad Over a year ago

@Kenneth Vogt, how should I know, you didn't specify which server you were using. If you are using Apache, check the User and Group configuration directives. (httpd.apache.org/docs/1.3/mod/core.html#user) If you can't get that working, the appropriate place to ask is ServerFault.com.

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