posix_getpwnam

Didar Hossain (2007-09-19 03:05:05)

My original code is an example of stupid code leading to a security vulnerability. The username and password can be viewed using the *NIX command `ps'.

Here is a better approach:

<?php
 $desc = array(
                0 => array("pipe","r"),
                1 => array("pipe","w"),
                2 => array("file","/tmp/error.out","a")
        );
        
        $proc = proc_open('/opt/webpanel/bin/pam_auth -o -1',$desc, $pipes);
                
        if (is_resource($proc)) {
                fwrite($pipes[0],$_POST['usr']);
                fwrite($pipes[0]," ");
                fwrite($pipes[0],$_POST['pass']);
                fwrite($pipes[0],"\n");
                fclose($pipes[0]);
                echo stream_get_contents($pipes[1]);
                fclose($pipes[1]);
        }
        $retval = proc_close($proc);
?>

Example code is mostly a verbatim copy from the proc_open() page.

http://php.net/manual/en/function.proc-open.php

Didar Hossain (2006-08-06 06:50:52)

Okay, this is a DIRTY HACK that I came up with

I am not a regular coder, so please weigh the relevant security considerations

<?php
$cmdstr = 'echo ' . $_POST['user'] . ' ' . $_POST['pass'];
$cmdstr .= ' | /home/didar/pam_auth -n common-auth ';

exec($cmdstr,$read);

if (strstr($read[0],"OK")) {
      echo "Success";
} else {
      echo "Failed";
}
?>

The code above makes use of the "pam_auth" or "squid_pam_auth" helper program from Squid package. Go to the following link for more information about it -

http://devel.squid-cache.org/hno/pam_auth-2.0.txt

WARNING: This is simply a hack. Always USE SSL/TLS in the orignating submit form. Also, always do sanity checks on the user input data.

bau at kg-fds dot de (2006-02-18 09:29:05)

bau at kg-fds dot de (2006-02-18 09:22:45)

bau at kg-fds dot de (2006-02-14 11:24:49)

If you are running a pop3-daemon, so you can do authentification on pop3 by using fsockopen :-) and checking whether it returns +OK or -ERR

corychristison at lavacube dot net (2004-10-17 04:33:38)

For those of you who are writing daemons with PHP and are one for security. This function will not return any info if you have called PHP's chroot() function.
Took me a few minutes why it wouldn't find the user it was searching for.

marcus at nospamsynchromedia dot co dot uk (2002-08-23 13:12:15)

Given a non-existent username, this function returns a boolean FALSE.

perreal at lyon dot cemagref dot fr (2002-04-18 08:47:05)

To check passwords on a Unix-box, look at the mod_auth_external module for Apache, it uses external programs to do the real job. The server won't ever read the encrypted password.
One of them, pwauth, can be configured to use PAM or whatever is used on your system. Users that can run this program are configured at compile time. And this program can be called from PHP with exec(...).

vision_1967 at hotmail dot com (2001-11-20 11:23:09)

I needed to get access to the user information to do login/validation via an SSL connection and encountered the same problem with receiving '*' in the password field. After checking the documentation on posix_getpwnam, I saw a previous solution involving coding a C program. This was a bit bulky for me so I came up with my own solution.
Variations on this theme can probably be done to make the solution more programmer/reader friendly, but the way I did it accomplished the task that I needed to do.
IF the information you need to get from posix_getpwnam comes from a host participating in an NIS network, you can accomplish the same thing with the following command:
$autharray = split(":",`ypmatch $USER passwd`);
(pretty long explanation for such a short solution huh?)
You'll have to get at the fields by their index number ($autharray[0], $autharray[1], ...) using this method.
To create an associative array that is plug-in compatible with the posix_getpwnam function, you'll probably need to use the 'list' specifier to do the assignments.
I hope this helps someone.
--S

darryl at pointclark dot net (2001-10-17 22:43:21)

If you need to validate a *real* unix password on a system using shadowed passwords, the posix_getpwnam() function in PHP won't work (as mentioned, 'x', or '*', will be in the password field).
I have a need to verify a user/pass within PHP (using SSL!). I don't know if this is the best way, but it's what I'm doing at the moment (works well!).
First, you need some help from the OS. I wrote a tiny C utility that does the shadow look-up for me... It requires root access to read /etc/shadow. So after you compile (gcc -O2 -s -o spasswd -lcrypt spasswd.c), you need to either use sudo to run it, or
# chown root spasswd && chmod u+s spasswd
To code that I'm using to authenticate a user/pass from PHP looks like:
function Authenticate($realm)
{
global $PHP_AUTH_USER;
global $PHP_AUTH_PW;
if(!isset($PHP_AUTH_USER))
{
header("WWW-Authenticate: Basic realm=\"$realm\"");
header("HTTP/1.0 401 Unauthorized");
return false;
}
else
{
if(($fh = popen("/usr/sbin/spasswd", "w")))
{
fputs($fh, "$PHP_AUTH_USER $PHP_AUTH_PW");
$r = pclose($fh);
if(!$r)
return true;
}
}
header("WWW-Authenticate: Basic realm=\"$realm\"");
header("HTTP/1.0 401 Unauthorized");
return false;
}
The C source for spasswd.c:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <crypt.h>
#include <shadow.h>
static char salt[12], user[128], pass[128];
void die(void)
{
memset(salt, '\0', 12);
memset(user, '\0', 128);
memset(pass, '\0', 128);
}
int main(int argc, char *argv[])
{
struct spwd *passwd;
atexit(die); die();
if(fscanf(stdin, "%127s %127s", user, pass) != 2)
return 1;
if(!(passwd = getspnam(user)))
return 1;
strncpy(salt, passwd->sp_pwdp, 11);
strncpy(pass, crypt(pass, salt), 127);
if(!strncmp(pass, passwd->sp_pwdp, 127))
return 0;
return 1;
}
Hope this helps someone...

sezery at damla dot net (2001-10-03 14:09:30)

User and group functions do not work on recent Redhat systems since these functions are based on /etc/group file but new redhat does not put group members' list into this file. Instead you need to examine /etc/passwd file and find members of a group by checking group id.