Change Linux or UNIX system password using PHP script

Posted on in Categories Apache, lighttpd, php, Shell scripting last updated August 3, 2006

If you just wanted to change your own password or other user passwords use passwd command.

I was asked to setup a PHP based interface to change the password. Since my knowledge of php is limited. Here is what I did:

Warning: This is an outdated and insecure information. Please see the official php.net document for more information. You have been warned to ignore this post.

Required tools/setup:

You must have following tools/software installed

=> Shell script to change password

=> Sudo access

=> Apache or Lighttpd web server

=> PHP server side

Step # 1: Setup a shell script to change password

This shell script use expect tool to change the password (see more about expect tool here).

Sample shell script code

#!/bin/sh
# \
exec expect -f "$0" ${1+"[email protected]"}
set password [lindex $argv 1]
spawn passwd [lindex $argv 0]
sleep 1
expect "assword:"
send "$password\r"
expect "assword:"
send "$password\r"
expect eof

You can execute this script as follows (dowload link):
$ chpasswd username password

Download script and copy to your webroot or location where webserver can read this script file:
$ cp chpasswd /var/www/

ALTERNATIVELY, if you are using Ligtttpd web server:
$ cp chpasswd /home/lighttpd

Step # 2: Setup sudo to execute a command as root user

Apache or Lighttpd web server drops root privileges as soon as they go into background. This makes changing password scenario difficult as passwd command needs root privileges to change other user account password.

Typically, Apache 2 use www-data user and Lighttpd use lighttppd username to drop privileges. Login as root user and type the following command:
# visudo

Now allow your web server to execute a script (chpasswd) w/o password. If you are using Apache web server, type the following command:
www-data ALL=NOPASSWD: /var/www/chpasswd

ALTERNATIVELY, if you are using Ligtttpd web server, type the following command:
lighttpd ALL=NOPASSWD: /home/lighttpd/chpasswd

Save and close the file.

Step # 3: Create a PHP based interface

Now you need to write a php script. Here is sample php script. This is a demo script. You should modify it according to your requirement or setup. At minimum, you need to setup correct shell script location so that it will work for you out of box. Open php script and locate line:
$shellscript = "sudo /home/lighttpd/chpasswd";

Change it to point to correct location. PHP Source code:

<?php
// change .. me! - shell script name
$shellscript = "sudo /home/lighttpd/chpasswd";
 
// Make sure form is submitted by user
if(!(isset($_POST['pwdchange']))) {
 // if not display them form
 writeHead("Change password");
 writeForm();
 writeFoot();
}
else {
 // try to change the password
 $callshell=true;
 // get username and password
 $_POST['username'] = stripslashes(trim($_POST['username']));
 $_POST['passwd'] = stripslashes(trim($_POST['passwd']));
 
// if user skip our javascript ...
// make sure we can only change password if we have both username and password
 if(empty($_POST['username'])) {
   $callshell=false;
 }
 if(empty($_POST['passwd'])) {
   $callshell=false;
 }
 if ( $callshell == true ) {
  // command to change password
  $cmd="$shellscript " . $_POST['username'] . " " . $_POST['passwd'];
  // call command
  // $cmd - command, $output - output of $cmd, $status - useful to find if command failed or not
   exec($cmd,$output,$status);
   if ( $status == 0 ) { // Success - password changed
   writeHead("Password changed");
   echo '<h3>Password changed</h3>Setup a new password';
   writeFoot();
   }
   else { // Password failed
      writeHead("Password change failed");
      echo '<h3>Password change failed</h3>';
      echo '<p>System returned following information:</p>';
      print_r($output);
      echo '<p><em>Please contact tech-support for more info! Or try <a href='.$_SERVER['PHP_SELF'].'again</a></em></p>';
      writeFoot();
   }
 }
 else {
   writeHead("Something was wrong -- Please try again");
   echo 'Error - Please enter username and password';
   writeForm();
   writeFoot();
 }
}
 
// display html head
function writeHead($title) {
echo '
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title> ' .$title. '</title>
<style type="text/css" media="screen">
.passwdform {
	position: static;
	overflow: hidden;
}
 
.passwdleft {
	width: 25%;
	text-align: right;
	clear: both;
	float: left;
	display: inline;
	padding: 4px;
	margin: 5px 0;
}
 
.passwdright {
	width: 70%;
	text-align: left;
	float: right;
	display: inline;
	padding: 4px;
	margin: 5px 0;
}
 
.passwderror {
	border: 1px solid #ff0000;
}
 
.passwdsubmit {
}
</style>
 
</head>
 
<body>';
 
}
// display html form
function writeForm() {
echo '
<h3>Use following form to change password:</h3>
 
<script>
function checkForm() {
if (document.forms.changepassword.elements[\'username\'].value.length == 0) {
    alert(\'Please enter a value for the "User name" field\');
    return false;
}
if (document.forms.changepassword.elements[\'passwd\'].value.length == 0) {
    alert(\'Please enter a value for the "Password" field\');
    return false;
}
  return true;
}
</script>
 
<div class="contactform">
<form action="' . $_SERVER[PHP_SELF]. '" method="post" onSubmit="return checkForm()" name="changepassword">
<div class="passwdleft"><label for="lblusername">User Name: </label></div>
<div class="passwdright"><input type="text" name="username" id="lblusername" size="30" maxlength="50" value="" /> (required)</div>
<div class="passwdleft"><label for="lblpasswd">Password: </label></div>
<div class="passwdright"><input type="password" name="passwd" id="lblpasswd" size="30" maxlength="50" value="" /> (required)</div>
<div class="passwdright"><input type="submit" name="Submit" value="Change password" id="passwdsubmit" />
<input type="hidden" name="pwdchange" value="process" /></div>
</form>
</div>
';
 
}
// display footer
function writeFoot(){
echo '</body>
</html>
';
}
?>

Step # 4: Run the script

Point a web browser to your server url – https://mydomain.com/changepassword.php. You should see a username and password form as follows:

changepassword php script output # 1

If a password is changed successfully, you should get confirmation as follows:

changepassword php script output # 2

For some reason if a password failed to change, you should get detailed error message as follows:

changepassword php script output # 3

Step # 5: Security

Note this is an example and not final solution as it is little insecure.

  • Never ever run this script over http session. Always run over https session.
  • Put script in a password protected directory (see how to setup Apache or Lighttpd web server password protected directory).
  • Never ever, trust user input. Above php script is just a sample, for real life production you should consider more powerful user input validation. Discussion regarding PHP programming security is beyond the scope of this article. You can consult a good PHP book or search a web using your favorite search engine 🙂

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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74 comment

  1. Ready to use tools or webmin are not useful for custom-made control panel or other solution. Every situation is different hence; you need to develop your own methods.

    No, it is not a pain. We simply call it hacks 😛

  2. Pipacs,

    Thanks for your concern. I agree with you. At the movement, this box can be access by admins only and other user change password using above solution.

    But if you need to give shell access –
    On FreeBSD with secure runlevel prevents other users from monitoring command/script arguments from ps, w, who, top etc commands.

    On Linux system you need to apply a special patch to kernel (LINUX BSD LSM) or disable other user shell login all together

    If you have any other, solution then please let me know…

    Appreciate your post.

  3. Chadrick,

    As name, suggest sleep command puts pause for NUMBER seconds (1 second). If you are using Debian Linux you need to use sleep to slow down few things. However, on RHEL or CentOS or FreeBSD it works w/o sleep command.

  4. @Boo, you ssl and Password protected directory is must

    @Sven, thanks for link i will update my code!

    As I said earlier, my knowledge of php is limited. At the movement, script is protected using SSL and a password-protected directory.

    And I must add protection for root user… in php itself

    Appreciate all of your posts.

  5. thx for the script, very close what i needed quick-and-dirty here, got it up and running for my purpose within 10 minutes.

    And yep, its extremely dangerous, but the box running it isn’t designed to be overly safe or even public anyway ^^

  6. As written, this script allows any user’s password to be changed, which may not be a good thing. By placing this script in a secure, password-protected directory, you can avoid having to request the username on the form & instead use the $_SERVER[‘PHP_AUTH_USER’] variable to get the name of the currently-authenticated user. That will restrict password changes to the authenticated user only.

  7. hi,
    thank you for sharing your code with us.i want to do the samething but i have to confirm the password first.And this is not working at this point.I think confirming password first needs to edit the shell script at step one.And i dont know about shell scripts.If you have a solution for this problem or anyone knows,please share with us.
    thank you again

  8. I’m having a problem with this script, sometimes if i execute it, it doesn’t return “passwd: all authentication tokens updated successfully.” but i can’t check this from my php so the password isn’t updated and my clients can’t use their ftp logins…
    Is it possible to like expect “successfully.” or else restart the script? I haven’t got a clue how to do this so all ideas are welcome.

  9. Thanks!

    I have a serer running Fedora Core 3. I was having problems with an expect script that I wrote, so I found your site. The chpasswd script worked with one minor modification: instead of “r” an the end of the send lines, it wanted “rn” on my system.

    Thanks again!
    Herb

  10. My system is Redhat Linux9.
    I try to execute chpasswd script to change password.
    But the script didn’t change password successfully.

    And I try to open the PHP file.
    After I input username and password that also display error message.

    =========
    Password change failed
    System returned following information…..:

    Array
    (
    )

    Please contact tech-support for more info! Or try

    =========
    What can I do and resolve his problem?

  11. Hello
    I got this error when I try to run the php script

    Parse error: parse error, unexpected T_STRING, expecting ‘,’ or ‘;’ in /srv/www/htdocs/changepassword.php on line 108

    here you have line 108
    if (document.forms.changepassword.elements[‘username’].value.length == 0) {

    Thanks for your help

  12. I’m new to PHP, so don’t expect this to be perfect. It gives me a parse error with the following (very simple) code:

    I’m using this to scare the guys in the server room (where we have a Mac Pro).

    I don’t even think the syntax is correct either…

  13. This solution involves giving the web user full control over a script that can change any system user’s password, without verification. You might as well just run apache as root.

  14. Hello everyone,

    I need to know how to change linux system time zone using php script.

    used this in shell,that is
    $ export TZ=MST, then timezone changed to MST,
    but i tried this using php script,
    that is,

    but this is not working.
    can anyone tell me what is the reason for this

  15. When I run the PHP script, I get
    sudo: unable to execute /var/www/chpasswd: No such file or directory

    My /etc/sudoers contains the following entry
    www-data ALL=NOPASSWD: /var/www/chpasswd

    I have tested this with permission on /var/www/chpasswd set to 744 and 777 but with no luck.

    I call the script from PHP using the following:

    // set the user's password
    $command = 'sudo /var/www/chpasswd'.
    $user_info['username'].' '.
    $user_info['password'];
    shell_exec($command);

    Any help would be greatly appreciated

  16. pipacs: “The expect script proposed here is extremely dangerous. Any user monitoring commands with “ps” could capture user names and passwords.”

    instead of executing “$ chpasswd username password” you can save the password in a tmp file, unreadable for users – that’s what I’ll do 😉

    Great script!

  17. The script works with Fedora/CentOS but requires some edits.

    As always read the logs!

    Check the apache/httpd error logs.

    If it states “sudo: sorry, you must have a tty to run sudo”

    You will need to comment out “Defaults requiretty” using visudo.

    This solution address kevin_cn and Alex’s posts.

  18. i’m trying to do the similar thing to access iptables. my shell script only contains iptables-L, but i still cant run it from my web.
    i already change the visudo and adding the “www-data ALL=NOPASSWD: ALL” line.
    all im seeing in the error_log is : Permission denied

  19. Congratulations on your high Google score with the keywords php+change+linux+password 🙂

    Inspired by your script I decided to make this just a little bit safer by eliminating the need for sudo:

    #!/bin/sh
    # 
    exec expect -f "$0" ${1+"[email protected]"}
    
    set name    [lindex $argv 0]
    set curpass [lindex $argv 1]
    set newpass [lindex $argv 2]
    set chkpass [lindex $argv 3]
    
    spawn su $name -c passwd
    sleep 0.5
    expect "assword:"
    sleep 0.25
    send "$curpassr"
    expect "assword:"
    sleep 0.25
    send "$curpassr"
    expect "assword:"
    sleep 0.25
    send "$newpassr"
    expect "assword:"
    sleep 0.25
    send "$chkpassr"
    expect eof
    

    Never mind the many sleep commands in there, but I found that at least it works this way.

  20. Hi
    After I try to run Step 1 I have some problem
    password show change ok but not change realy

    I try run below on my sytem
    [[email protected] Code]# sh chpasswd admin mvc123
    spawn passwd admin
    Changing password for user admin.
    New UNIX password: mvc123

    Retype new UNIX password: mvc123

    [[email protected] Code]#

    That finish I think it ok
    I try to login by name = admin and newpass
    login not ok but old password still work
    I don’ know why?

    my system ES3

  21. I try to execute chpasswd script to change password.
    But the script didn’t change password successfully.

    whn i use sh chpassword test test123 its working.

    And I try to open the PHP file.
    After I input username and password that also display error message.

    =========
    Password change failed
    System returned following information…..:

    Array
    (
    )

    Please contact tech-support for more info! Or try

    =========
    in my /var/log/messages error shown as

    authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= user=apache

    What can I do to resolve this problem?

  22. I’ve written a function which doesn’t need an external script, and does not need sudo access. This eliminated the concern of someone capturing the password by monitoring ps, and allows everything to be done without the need for external files. A log file is created during the password change procedure, though this does not contain any passwords, it’s used to verify the password being successfully changed, and it’s deleted on completion.

    Note: you may need to modify the expect strings, depending on your systems password chat.

    function changePassword($user, $currpwd, $newpwd) {
    	// Open a handle to expect in write mode
    	$p = popen('/usr/bin/expect','w');
    
    	// Log conversation for verification
    	$log = '/tmp/passwd_' . $user . '_' . time();
    	$cmd .= "log_file -a "$log"; ";
    
    	// Spawn a shell as $user
    	$cmd .= "spawn /bin/su $user; ";
    	$cmd .= "expect "Password:"; ";
    	$cmd .= "send "$currpwd\r"; ";
    	$cmd .= "expect "[email protected]"; ";
    
    	// Change the unix password
    	$cmd .= "send "/usr/bin/passwd\r"; ";
    	$cmd .= "expect "(current) UNIX password:"; ";
    	$cmd .= "send "$currpwd\r"; ";
    	$cmd .= "expect "Enter new UNIX password:"; ";
    	$cmd .= "send "$newpwd\r"; ";
    	$cmd .= "expect "Retype new UNIX password:"; ";
    	$cmd .= "send "$newpwd\r"; ";
    	$cmd .= "expect "passwd: password updated successfully"; ";
    
    	// Commit the command to expect & close
    	fwrite($p, $cmd); pclose ($p);
    
    	// Read & delete the log
    	$fp = fopen($log,r);
    	$output = fread($fp, 2048);
    	fclose($fp); unlink($log);
    	$output = explode("n",$output);
    
    	return (trim($output[count($output)-2]) == 'passwd: password updated successfully') ? true : false;
    }
    
  23. Terry,

    I’ve worked on combining your changePassword function with the original script. Unfortunately this expect script does not gracefully handle the case of a nonexistent user. I get the user’s typed-in password printed (in clear) in my http error_log:

    send: spawn id exp16 not open
    while executing
    “send “xxxr””

    1. if I may suggest, you can replace the end of the script like this:

      # send passwd command
      send — “passwd $userr”
      expect “assword:” {
      send “$passwordr”
      expect “assword:”
      send “$passwordr”
      send “r”
      send “exitr”
      expect eof
      } “Unknown user” {
      send “r”
      send “exitr”
      expect eof
      }
      if expect doesnt find the password, it will change to the unknown user statement and exit… you can treat the log later.

      another suggestion would be to not allowing the webserver to have root and instead, save the command to a file and use chron to execute it later. this file can be outside the scope of webserver and you can block root change, etc.

  24. Has anyone thought about adding a secret question onto the php webpage? That way, you could use this script as a backend password change once the user has answered the secret question properly.

    With such a system in place, the user can change there own password…. using presetup authentication.

    any ideas?

  25. Thanks a lot
    Your script help a lot but I have to do more configuration in linux for run it.
    the aditional configuration is

    use command chown in the script!!!
    and watch the error_log of httpd

    thanks again

  26. Thank you.

    One note for CentOS/RHEL users is that ‘requiretty’ is enabled by default in the sudoers file. To get around this add:

    Defaults:www-data !requiretty

    before the “www-data ALL=NOPASSWD: /var/www/chpasswd” line. Obviously you’ll need substitute the name of the user that the webserver runs under if it isn’t www-data (in CentOS it seems to be ‘apache’ by default).

    Thanks again!

  27. @Terry

    That’s a nice little function but it looks like it only works for users who have shell access. For instance, it looks like it won’t work for users with /sbin/nologin as a shell, such as is typical for FTP users.

  28. Hi; i m having problem with my php installation in linux on my pc. Whenever i try to start the service of php, it throws an error “service failed”. but it installs without any error if I connect my hard disk to someone else’s computer. can anyone has solution for this problem?????

  29. The file in /tmp will contain the password briefly, allowing an attack vector. How about an interactive ssh shell through php?

    [code]

    Password Update Utility

    Username

    Current Password

    New Password

    Confirm New Password

    <?php

    if ($_POST['submitChangePassword'])
    {
    $error = "0";
    # Die on root user
    if ($_POST['username'] == 'root')
    {
    echo ('Authentication Failed');
    }
    else
    {
    # Connect and reset password
    $connection = ssh2_connect($targetHost, $targetPort);

    if (!ssh2_auth_password($connection, $_POST['username'], $_POST['OldPassword']))
    {
    echo ('Authentication Failed');
    }
    else
    {
    $out = '';
    $last_line = '';
    $cmds[0] = "passwd";
    $cmds[1] = $_POST['OldPassword'];
    $cmds[2] = $_POST['NewPassword'];
    $cmds[3] = $_POST['NewPassword2'];
    $shell = ssh2_shell($connection);

    for($i=0; $i

    [/code]

  30. Or you could just do the hash right in PHP using crypt, and then change the password in one command using perl:
    usermod -p `perl -e ‘print crypt(“password”, “user”)’` user

    Here’s an example of a PHP script to do it. This is part of a CGI I wrote. This is NOT how the actual CGI works. I stripped out the GET and PUT methods for clarity’s sake. Also, the real CGI doesn’t have root access. Instead, it communicates with another process that does. That combined with the fact that this script validates the current user and password makes it more secure.

    Please do not grant CGI access to a script based on this example and place it on a Web site.

     "peter", "old" => "oldpassword", "new" => "newpassword");
    
        // Get the old password and new password
        $user = $data["user"];
        $old = $data["old"];
        $new = $data["new"];
    	// Get the current password hash to compare
    	// Read the file and return the data
    	$old_hash = @file_get_contents($pw_path);
    	if (!$old_hash)	// Couldn't access the file
        {
            printf("Cannot read password file: ".$pw_path."n");
            return;
        }
        // Parse out the hash
        $old_hash = strstr($old_hash, $user);
    	if (!$old_hash) // The user doesn't exist
        {
            printf("No user named ".$user." in ".$pw_path."n");
            return;
    	}
        // Get everything in front of the next ccarriage return
        $old_hash2 = strstr($old_hash, "n", TRUE);
        // If it's the last line, that's ok too
        if (!$old_hash2)
            $old_hash2 = $old_hash;
        $old_hash = trim($old_hash2);
        // Could use explode, but this is just as easy
        $old_hash = strstr($old_hash, ":");
        $old_hash = substr($old_hash, 1);
        // PHP's crypt guesses the encryption alogrithm based on the "salt"
        // Linux passwords typically use MD5, so we'll just use the old hash.
        // Apache's htpasswd, for example, typically uses DES, so we would use
        // just the first to characters; $salt = substr($old_hash, 0, 2);
        $salt = $old_hash;
        // Now get a hash to match the existing password
        $new_hash = crypt($old, $salt);
        if ($new_hash != $old_hash)
        {
            printf("The entered password doesn't match the current passwordn");
            return;
        }
        // Now change new passwords
    	$command = sprintf($change_script, $new, $new, $new);
        $output = ExecuteCommand($command);
    
    	// Now send the result
        printf($output."n");
    
    ?>
  31. Sorry, that previous code listing was a bad cut and paste:

     "peter", "old" => "oldpassword", "new" => "newpassword");
    
        // Get the old password and new password
        $user = $data["user"];
        $old = $data["old"];
        $new = $data["new"];
    	// Get the current password hash to compare
    	// Read the file and return the data
    	$old_hash = @file_get_contents($pw_path);
    	if (!$old_hash)	// Couldn't access the file
        {
            printf("Cannot read password file: ".$pw_path."n");
            return;
        }
        // Parse out the hash
        $old_hash = strstr($old_hash, $user);
    	if (!$old_hash) // The user doesn't exist
        {
            printf("No user named ".$user." in ".$pw_path."n");
            return;
    	}
        // Get everything in front of the next ccarriage return
        $old_hash2 = strstr($old_hash, "n", TRUE);
        // If it's the last line, that's ok too
        if (!$old_hash2)
            $old_hash2 = $old_hash;
        $old_hash = trim($old_hash2);
        // Could use explode, but this is just as easy
        $old_hash = strstr($old_hash, ":");
        $old_hash = substr($old_hash, 1);
        // PHP's crypt guesses the encryption alogrithm based on the "salt"
        // Linux passwords typically use MD5, so we'll just use the old hash.
        // Apache's htpasswd, for example, typically uses DES, so we would use
        // just the first to characters; $salt = substr($old_hash, 0, 2);
        $salt = $old_hash;
        // Now get a hash to match the existing password
        $new_hash = crypt($old, $salt);
        if ($new_hash != $old_hash)
        {
            printf("The entered password doesn't match the current passwordn");
            return;
        }
        // Now change new passwords
    	$command = sprintf($change_script, $new, $new, $new);
        $output = ExecuteCommand($command);
    
    	// Now send the result
        printf($output."n");
    
    ?>

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