Hashing and verifying LDAP passwords in PHP

I recently migrated a PHP web application that used LDAP for authentication and MySQL for data to something entirely MySQL based. I needed the users to be able to continue using their old LDAP passwords, so I dumped the LDAP database and grabbed the userPassword field for each user, base64_decode()d it and wrote that to a MySQL table. These password hashes start with something like {crypt}, {MD5}, {SHA1} or {SSHA1}, or in very rare cases, are plain-text.

Here’s a PHP function I wrote that, given a plain-text $password, verifies it against such a $hash. This is what you’ll be calling from your authentication script to verify a given password against the hash.

function check_password($password, $hash)
 {
 if ($hash == '') // no password
 {
 //echo "No password";
 return FALSE;
 }
 
 if ($hash{0} != '{') // plaintext password
 {
 if ($password == $hash)
 return TRUE;
 return FALSE;
 }
 
 if (substr($hash,0,7) == '{crypt}')
 {
 if (crypt($password, substr($hash,7)) == substr($hash,7))
 return TRUE;
 return FALSE;
 }
 elseif (substr($hash,0,5) == '{MD5}')
 {
 $encrypted_password = '{MD5}' . base64_encode(md5( $password,TRUE));
 }
 elseif (substr($hash,0,6) == '{SHA1}')
 {
 $encrypted_password = '{SHA}' . base64_encode(sha1( $password, TRUE ));
 }
 elseif (substr($hash,0,6) == '{SSHA}')
 {
 $salt = substr(base64_decode(substr($hash,6)),20);
 $encrypted_password = '{SSHA}' . base64_encode(sha1( $password.$salt, TRUE ). $salt);
 }
 else
 {
 echo "Unsupported password hash format";
 return FALSE;
 }
 
 if ($hash == $encrypted_password)
 return TRUE;
 
 return FALSE;
 }

And here’s one that make a {SSHA} hash from a password (I did not implement all the other algorithms as by today’s standards, they are no longer secure). This is what you’ll be calling from your change password script to hash the password for storing in the database.

function hash_password($password) // SSHA with random 4-character salt
 {
 $salt = substr(str_shuffle(str_repeat('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789',4)),0,4);
 return '{SSHA}' . base64_encode(sha1( $password.$salt, TRUE ). $salt);
 }

8 thoughts on “Hashing and verifying LDAP passwords in PHP

  1. Marcel Petersen

    great Job! I spend lot of time on this Problem.
    thx marcel

  2. Douglas Purdy

    Had to update password storage on an old system before upgrading Debian, LDAP & PHP
    Sure was glad to find this code for authenticating SSHA !

  3. frank Anciaux

    Thanks for your code. But Why are you using a Salt of only 4 characters ? Is this not a security issue ?

  4. Michael Kuron Post author

    Four bytes appears to be the standard length that OpenLDAP uses. I agree, it’s pretty short, but that was specified a long time ago and even this blog post is now eight years old. Security requirements have obviously increased since then, so you could make the salt a bit longer.

    Furthermore, str_shuffle is not cryptographically random. PHP didn’t have anything better back then, and it might not matter too much for a salt, but you could use random_bytes instead which is available since PHP 7.

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