Bug #54114 [Nab]: Output Buffer Dumps Data On Error

Edit report at https://bugs.php.net/bug.php?id=54114&edit=1 ID: 54114 Updated by: mike@php.net Reported by: danhstevens at gmail dot com Summary: Output Buffer Dumps Data On Error Status: Not a bug Type: Bug Package: Output Control Operating System: all PHP Version: 5.3.5 Block user comment: N Private report: N New Comment: Well, this is pretty much the wrong way then, IMO. Is this about Symfony 1 or 2? Previous Comments: ------------------------------------------------------------------------ [2013-09-30 14:58:14] danhstevens at gmail dot com Mike, this is a security issue because users of frameworks like Symfony are highly exposed to this bug. Symfony uses OB for parsing configuration files which often contain sensitive information. One syntax error in your config file and all your config params are on display to the www. It's unexpected behavior, and it can (and in my case, has) caused the release of sensitive information. ------------------------------------------------------------------------ [2013-09-30 12:11:25] mike@php.net I'm not sure why this should be security related? Why even output security sensitive information at all? ------------------------------------------------------------------------ [2011-08-17 13:44:19] nicolas dot grekas+php at gmail dot com Here is an other example that can't be workaround using danhstevens' technique: <?php function my_shutdown() { echo "secret\n"; throw new Exception; } function ob_custom_filter($b) { return str_replace('secret', '******', $b); } register_shutdown_function('my_shutdown'); ob_start('ob_custom_filter'); ?> ------------------------------------------------------------------------ [2011-03-10 19:41:28] danhstevens at gmail dot com I've found a viable work-around for this bug (although a patch of the core would still be ideal so people don't discover this potential security issue the hard-way). By registering the following shutdown handler before any output buffering the dump of data can be prevented: <?php function shutdown_fn() { //If ob_start has been called at least once if(ob_get_level() > 1) { //Prevent data in buffer from dumping ob_end_clean(); } } register_shutdown_function('shutdown_fn'); Now when using the examples above that normally cause the buffer to dump to the client the buffer data is disposed of. Of course, this can be extended to use ob_get_contents and redirect the data to file or other means if necessary. This approach is working for me (on PHP 5.3.5). ~Dan ------------------------------------------------------------------------ [2011-03-06 16:51:52] neweracracker at gmail dot com I've managed to reproduce this in Windows 7 running php 5.2.17 (with php.ini-dist) and php 5.3.5 (with php.ini-development). Here is my test script: <?php set_time_limit(1); ob_start(); echo "You shouldn't see this!"; sleep(2); //comment this and you won't see the line above in output ;) ob_end_clean(); ?> I've reported this as bug #54174 which got closed due being a dupe of this one so I am leaving this comment here for reference purposes. Regards, NewEraCracker. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=54114 -- Edit this bug report at https://bugs.php.net/bug.php?id=54114&edit=1