Bug #69833 [Com]: mcrypt broken in 5.6.10 fd caching not working

From: Date: Mon, 22 Jun 2015 17:55:13 +0000
Subject: Bug #69833 [Com]: mcrypt broken in 5.6.10 fd caching not working
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-193766@lists.php.net to get a copy of this message
Edit report at https://bugs.php.net/bug.php?id=69833&edit=1

 ID:                 69833
 Comment by:         info at regioconnect dot net
 Reported by:        iand at ekit-inc dot com
 Summary:            mcrypt broken in 5.6.10 fd caching not working
 Status:             Assigned
 Type:               Bug
 Package:            mcrypt related
 Operating System:   Solaris 9,10
 PHP Version:        5.6.10
 Assigned To:        leigh
 Block user comment: N
 Private report:     N

 New Comment:

Can confirm this problem on debian 7 on xen PV.
apache 2.4.12, both for php 5.5.26 and 5.6.10
underlying distro is debian wheezy, but apache and php were source compiled.

happens with mediawiki 1.25.1:

in includes/MWCryptRand.php
$iv = mcrypt_create_iv( $rem, MCRYPT_DEV_URANDOM );

changing 2nd parameter to MCRYPT_RAND makes the problem go away.


Previous Comments:
------------------------------------------------------------------------
[2015-06-16 06:16:20] compi at stz-bg dot com

Have the same problem on test server Linux Slackware x64 current. Interesting on produce servers are
the same like test server (packages) this problem does not exists, but my test server run on
apache2, produce servers on nginx with php-fpm.

------------------------------------------------------------------------
[2015-06-15 08:53:37] iand at ekit-inc dot com

Hi Leigh; can you elaborate on how I can test that please.
Thanks.

Ian D

------------------------------------------------------------------------
[2015-06-15 07:11:53] nikic@php.net

@leigh: Please also check whether this applies to the CSPRNG as well.

------------------------------------------------------------------------
[2015-06-15 04:40:16] iand at ekit-inc dot com

Description:
------------
mcrypt has broken in 5.6.10 on my platform under apache 2.4.12
running with threaded mpm.

$ /opt/local/apache/bin/httpd  -M |grep mpm
 mpm_worker_module (static)

Symptoms are that under apache, php's use of mcrypt runs into time limits...
but if you run the same code from php command line it works fine.



Fatal error: Maximum execution time of 30 seconds exceeded in /opt/local/apache/htdocs/mcr.php on
line 7

Inspection with truss shows it is failing to open /dev/urandom

This is a truss from apache 2.4.12 with php 5.6.9:

24686/27:       munmap(0xCD3B0000, 4096)                        = 0
24686/27:       munmap(0xCD390000, 7880)                        = 0
24686/27:       munmap(0xCD3A1000, 5040)                        = 0
24686/27:       munmap(0xCD370000, 2724)                        = 0
24686/27:       munmap(0xCD380000, 3028)                        = 0
24686/27:       open("/dev/urandom", O_RDONLY)                  = 17
24686/27:       read(17, "02F7F1F1 3CA $A8", 8)                 = 8
24686/27:       close(17)                                       = 0
24686/27:       open("/opt/local/lib/libmcrypt/tripledes.la", O_RDONLY) = 17

whereas on apache 2.4.12/php 5.6.10 (below) it keeps reading from fd #0 
(lsof says this is /dev/null)  until the timeout is reached.

25529/27:       munmap(0xCD3B0000, 4096)                        = 0
25529/27:       munmap(0xCD390000, 7880)                        = 0
25529/27:       munmap(0xCD3A1000, 5040)                        = 0
25529/27:       munmap(0xCD370000, 2724)                        = 0
25529/27:       munmap(0xCD380000, 3028)                        = 0
25529/27:       read(0, 0x0853CF78, 8)                          = 0
25529/27:       read(0, 0x0853CF78, 8)                          = 0
25529/27:       read(0, 0x0853CF78, 8)                          = 0
25529/27:       read(0, 0x0853CF78, 8)                          = 0
25529/27:       read(0, 0x0853CF78, 8)                          = 0

Looking at the php change log for 5.6.10 and the related changes in mcrypt.c
it would seem that the changes here have caused this fail.


Looking at these changes, I can spot one obvious error; the close code
doesn't consider fd#0 an open fd.  Patch for this below.  

However I suspect there is something else going on perhaps related to 
the multi-threaded environment.

$ diff -c mcrypt.c.orig mcrypt.c
*** mcrypt.c.orig       Wed Jun 10 07:42:27 2015
--- mcrypt.c    Mon Jun 15 03:33:18 2015
***************
*** 450,461 ****
        php_stream_filter_unregister_factory("mcrypt.*" TSRMLS_CC);
        php_stream_filter_unregister_factory("mdecrypt.*" TSRMLS_CC);
  
!       if (MCG(fd[RANDOM]) > 0) {
                close(MCG(fd[RANDOM]));
        }
  
!       if (MCG(fd[URANDOM]) > 0) {
                close(MCG(fd[URANDOM]));
        }
  
        UNREGISTER_INI_ENTRIES();
--- 450,463 ----
        php_stream_filter_unregister_factory("mcrypt.*" TSRMLS_CC);
        php_stream_filter_unregister_factory("mdecrypt.*" TSRMLS_CC);
  
!       if (MCG(fd[RANDOM]) >= 0) {
                close(MCG(fd[RANDOM]));
+               MCG(fd[RANDOM]) = -1;
        }
  
!       if (MCG(fd[URANDOM]) >= 0) {
                close(MCG(fd[URANDOM]));
+               MCG(fd[URANDOM]) = -1;
        }
  
        UNREGISTER_INI_ENTRIES();

-----------

So further debugging is required.



Test script:
---------------
<?php
$plaintext="hello world";

$key = "1;lk23GH2KJ:l*&^$^%$913S";


$encrypted =
bin2hex(mcrypt_encrypt(MCRYPT_3DES,$key,$plaintext,MCRYPT_MODE_ECB,mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_3DES,MCRYPT_MODE_CFB))));

$decrypted_data =
trim(mcrypt_decrypt(MCRYPT_3DES,$key,hex2bin($encrypted),MCRYPT_MODE_ECB,mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_3DES,MCRYPT_MODE_CFB))),
"\0");

print "orig=".$plaintext."\n";
print "encr=".$encrypted."\n";
print "decrypted=".$decrypted_data."\n";
if($plaintext != $decrypted_data) {
        print "MISMATCH\n";
}
else {
        print "MATCH\n";
}

?>


Expected result:
----------------
Instant; no timeout

Actual result:
--------------
timeout


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



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