Fix #64745 hash_pbkdf2 truncation issue

When using hash_pbkdf2 with hex output and 0 length (auto), it incorrectly
truncates the result to 1/2 the expected result.

NEWS

@@ -5,6 +5,10 @@ PHP                                                                        NEWS
 -FPM:
   . Fixed Bug #64915 (error_log ignored when daemonize=0). (Remi)
 
+- Hash:
+  . Fixed Bug #64745 (hash_pbkdf2() truncates data when using default length
+    and hex output). (Anthony Ferrara)
+
 23 May 2013, PHP 5.5.0 Release Candidate 2
 
 - Core:

ext/hash/hash.c

@@ -659,6 +659,9 @@ PHP_FUNCTION(hash_pbkdf2)
 	/* Setup Main Loop to build a long enough result */
 	if (length == 0) {
 		length = ops->digest_size;
+		if (!raw_output) {
+			length = length * 2;
+		}
 	}
 	digest_length = length;
 	if (!raw_output) {

ext/hash/tests/bug64745.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Bug #64745 hash_pbkdf2() truncates data when using default length and hex output
+--SKIPIF--
+<?php extension_loaded('hash') or die('skip'); ?>
+--FILE--
+<?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));
+
+?>
+--EXPECT--
+string(40) "0c60c80f961f0e71f3a9b524af6012062fe037a6"
+string(40) "0c60c80f961f0e71f3a9b524af6012062fe037a6"
+