How to use sha256 in php5.3.0


Question

I'm using sha256 to encrypt the password. I can save the sha256 encrypted password in mysql. But i can't login with the same clause.

Insert code:

<?php
error_reporting(E_ALL ^ E_NOTICE);
$username = $_POST['uusername'];
$passcode = $_POST['ppasscode'];
$userflag = $_POST['uuserflag'];
//$passcodeen = hash('sha256',$passcode);
$passcodeen = hash('sha256', (get_magic_quotes_gpc() ? stripslashes($ppasscode) : $ppasscode));
$conn = mysql_connect("localhost","charles","charles") or die("connection failed with DB:".mysql_error());
mysql_select_db("sessiondb");
$query = "INSERT INTO users(username,passcode,userflag) values('$username','$passcodeen','$userflag')";

Select code:

<?php 
error_reporting(E_ALL ^ E_NOTICE);

    @mysql_connect("localhost","charles","charles") or die("Connection failed".mysql_error());
    @mysql_select_db("sessiondb") or die("Database doesn't exist".mysql_error());
    //get user input
    $username = $_POST['username'];
    $ppasscode = $_POST['ppasscode'];
    //$passcodeen = hash('sha256', $ppasscode);
    $passcodeen = hash('sha256', (get_magic_quotes_gpc() ? stripslashes($ppasscode) : $ppasscode));
    //get session value from mysql
    $query = @mysql_query("select username, userflag from users where username ='$username' and passcode = '$passcodeen'") or die("Query execution failed".mysql_error());

Is there something wrong? I'm very confused. Thanks.

1
37
11/17/2009 11:36:06 PM

Accepted Answer

Could this be a typo? (two Ps in ppasscode, intended?)

$_POST['ppasscode'];

I would make sure and do:

print_r($_POST);

and make sure the data is accurate there, and then echo out what it should look like:

echo hash('sha256', $_POST['ppasscode']);

Compare this output to what you have in the database (manually). By doing this you're exploring your possible points of failure:

  1. Getting password from form
  2. hashing the password
  3. stored password
  4. comparison of the two.
59
11/17/2009 11:23:57 PM

First of all, sha256 is a hashing algorithm, not a type of encryption. An encryption would require having a way to decrypt the information back to its original value (collisions aside).

Looking at your code, it seems it should work if you are providing the correct parameter.

  • Try using a literal string in your code first, and verify its validity instead of using the $_POST[] variable

  • Try moving the comparison from the database query to the code (get the hash for the given user and compare to the hash you have just calculated)

But most importantly before deploying this in any kind of public fashion, please remember to sanitize your inputs. Don't allow arbitrary SQL to be insert into the queries. The best idea here would be to use parameterized queries.


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