Alternate way to Kerberos NTLM auth in pure PHP [EN]

Regarding to a recent post I put here about Kerberos and Apache, there is a way to replace Kerberos when the Active Directory cannot be properly configured to accept Kerberos connections. You can simulate the NTLM auth process with the browser by 6 steps in PHP :

function get_login() {

   /*
   step:  | type:
   -------|----------------|------------------------------------
   1      | C --> S        | GET ...
   -------|----------------|------------------------------------
   2      | C <-- S        | 401 Unauthorized
          |                | WWW-Authenticate: NTLM
   -------|----------------|------------------------------------
   3      | C --> S        | GET ...
          |                | Authorization: NTLM
          |                | <base64-encoded type-1-message>
   -------|----------------|------------------------------------
   4      | C <-- S        | 401 Unauthorized
          |                | WWW-Authenticate: NTLM
          |                | <base64-encoded type-2-message>
   -------|----------------|------------------------------------
   5      | C --> S        | GET ...
          |                | Authorization: NTLM <base64-encoded type-3-message>
   -------|----------------|------------------------------------
   6      | C <-- S        | 200 Ok
   -------|----------------|------------------------------------
   */

   $headers = apache_request_headers();
   if($headers['Authorization'] == NULL) { // step 1
       header( "HTTP/1.1 401 Unauthorized" ); // step 2
       header( "WWW-Authenticate: NTLM" );
       exit;
   };
   if(isset($headers['Authorization'])
         && substr($headers['Authorization'],0,5) == 'NTLM ') {
            // step 3 to 6
       $chaine=$headers['Authorization'];
       $chaine=substr($chaine, 5); // type1 message
       $chained64=base64_decode($chaine);
       if(ord($chained64{8}) == 1) { // step 3
           // check NTLM flag "0xb2",
          // offset 13 in type-1-message :
           if (ord($chained64[13]) != 178) {
                echo "Please use NTLM compatible browser";
                   return null;
           }
           $retAuth = "NTLMSSP";
           $retAuth .= chr(0).chr(2).chr(0).chr(0);
          $retAuth .= chr(0).chr(0).chr(0).chr(0);
           $retAuth .= chr(0).chr(40).chr(0).chr(0);
          $retAuth .= chr(0).chr(1).chr(130).chr(0);
           $retAuth .= chr(0).chr(0).chr(2).chr(2);
          $retAuth .= chr(2).chr(0).chr(0).chr(0);
           $retAuth .= chr(0).chr(0).chr(0).chr(0);
          $retAuth .= chr(0).chr(0).chr(0).chr(0).chr(0);

           $retAuth64 =base64_encode($retAuth);
           $retAuth64 = trim($retAuth64);
           header( "HTTP/1.1 401 Unauthorized" ); // step 4
           header( "WWW-Authenticate: NTLM $retAuth64" );
           exit;
       }
       else if(ord($chained64{8}) == 3) { // step 5
           $lenght_domain = (ord($chained64[31])*256 + ord($chained64[30]));
           $offset_domain = (ord($chained64[33])*256 + ord($chained64[32]));
           $domain = substr($chained64, $offset_domain, $lenght_domain);
           $lenght_login = (ord($chained64[39])*256 + ord($chained64[38]));
           $offset_login = (ord($chained64[41])*256 + ord($chained64[40]));
           $login = substr($chained64, $offset_login, $lenght_login);
           $lenght_host = (ord($chained64[47])*256 + ord($chained64[46]));
           $offset_host = (ord($chained64[49])*256 + ord($chained64[48]));
           $host = substr($chained64, $offset_host, $lenght_host);
       }

   }
   $login = preg_replace("/(.)(.)/","$1",$login);
   $domain = preg_replace("/(.)(.)/","$1",$domain);
   $login = strtolower($login);
   $domain = strtoupper($domain);
   return array($login,$domain); // step 6 : accept
}

Warning : this code must be exectuted not only for the auth process when you want to login the user, but for each HTTP request to your application (so on each page).

It is very important to put HTTP 1.1 protocole in HTTP headers because HTTP 1.0 does not support Keep-alive connection and so NTLM auth. For some unknown reasons, even if some Apache versions change automatically the protocole version to 1.1 in your headers, other versions don't (for example 2.2.3 can do it and 2.2.9 can't).

Finally, keep in mind that this code is not as secure as Kerberos Apache module, because this code will never check Active Directory permission to accept the user. This function is just to retrieve login and domain, you have to make the account check yourself.

Good luck !