Bug #64745 [Asn->Csd]: hash_pbkdf2() truncates data when using default length and hex output

From: Date: Tue, 28 May 2013 19:44:43 +0000
Subject: Bug #64745 [Asn->Csd]: hash_pbkdf2() truncates data when using default length and hex output
References: 1  Groups: php.bugs 
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Edit report at https://bugs.php.net/bug.php?id=64745&edit=1

 ID:                 64745
 Updated by:         ircmaxell@php.net
 Reported by:        ezzatron at gmail dot com
 Summary:            hash_pbkdf2() truncates data when using default
                     length and hex output
-Status:             Assigned
+Status:             Closed
 Type:               Bug
 Package:            hash related
 PHP Version:        5.5.0beta4
 Assigned To:        ircmaxell
 Block user comment: N
 Private report:     N

 New Comment:

Automatic comment on behalf of ircmaxell@gmail.com
Revision: http://git.php.net/?p=php-src.git;a=commit;h=540a5a52e89fce6da19d6f79dd1eda587a25b396
Log: Fix #64745 hash_pbkdf2 truncation issue


Previous Comments:
------------------------------------------------------------------------
[2013-05-15 13:06:14] ircmaxell@php.net

Ahh, very interesting find. Will confirm, write a test case, and push a fix for it 
later today.

Thanks for the report!

------------------------------------------------------------------------
[2013-05-01 00:18:45] ezzatron at gmail dot com

Description:
------------
When passing 0 as the length to hash_pbkdf2(), the behaviour is inconsistent 
between raw output and hex-encoded output. See the test script for a concrete 
example.

There are also no tests for the use case where length is defaulted in the current 
test suite (http://bit.ly/YcgMMu).

I'm attempting to write a compatibility library for this function for PHP versions 
earlier that 5.5, so the test suite for https://github.com/eloquent/pbkdf2-compat 
and its build history in Travis CI may also be useful, as it documents the current 
behaviour more extensively.

Test script:
---------------
<?php

$hash = hash_pbkdf2('sha1', 'password', 'salt', 1, 0);
$rawHash = hash_pbkdf2('sha1', 'password', 'salt', 1, 0, true);

var_dump($hash);
var_dump(bin2hex($rawHash));

Expected result:
----------------
string(40) "0c60c80f961f0e71f3a9b524af6012062fe037a6"
string(40) "0c60c80f961f0e71f3a9b524af6012062fe037a6"

Actual result:
--------------
string(20) "0c60c80f961f0e71f3a9"
string(40) "0c60c80f961f0e71f3a9b524af6012062fe037a6"


------------------------------------------------------------------------



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