Question

How can i verify if a user is root in a PHP script ? What is the command ?
I tried something like that :

exec("su -l login < `echo password`");

but the su command can not receive password…

Note that the machine is isolated from internet so I can run PHP as root if needed.

EDIT:
I don’t want to know if the current user who run the script is root or not.
I have a list of users in my PHP script and I want to know for each login if he has root privileges.

Answer 1

First, ask yourself what exactly defines a login “having root privileges”. AFAICT there are 2 basic solutions.

The old-school way, where sysadmins create multiple accounts with uid 0, which I – and I’m certainly not alone in this – consider to be a nightmare. In this scenario you could check all users in your list using posix_getpwnam and see if their uid matches 0.

The following code snippet does just that, $privileged will contain the users with root privileges :

$logins = array('root', 'john', 'guest', 'foo');
$privileged = array();
foreach($logins as $login) {
    $userInfo = posix_getpwnam($login);
    if ($userInfo !== FALSE) {
        if ($userInfo['uid'] == 0) {
          $privileged[] = $login;
        }
    }
}

The other (and imho only sane) way to do this is to add all users with root/administrative privileges to a specific group (wheel or admin are already used in different Linux distributions, find out which one works for you). This scenario is even simpler, since you can use posix_getgrnam to fetch all members in a specific group.

The following code snippet will match an array of logins you provide, and see who’s a member with specific privileges, again $privileged will contain the result (ie. the users in your list that are a member of the group you specified) :

$logins = array('root', 'john', 'guest', 'foo');
$privileged = array();
$groupInfo = posix_getgrnam('admins');
if ($groupInfo !== FALSE) {
    $privileged = array_intersect($logins, $groupInfo['members']);
}