Edit report at http://bugs.php.net/bug.php?id=54114&edit=1
ID: 54114
User updated by: danhstevens at gmail dot com
Reported by: danhstevens at gmail dot com
Summary: Output Buffer Dumps Data On Error
Status: Open
Type: Bug
Package: Output Control
Operating System: all
PHP Version: 5.3.5
Block user comment: N
Private report: N
New Comment:
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
Previous Comments:
------------------------------------------------------------------------
[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.
------------------------------------------------------------------------
[2011-02-28 21:40:36] danhstevens at gmail dot com
Hi Rasmus,
I was still able to create the problem by calling on a non-existing
class to create a fatal error. Here is a variation of your code:
function eh($errno, $errstr, $errfile, $errline) {
$contents = ob_get_contents();
ob_end_clean();
echo "Error: $errno, $errstr, $errfile, $errline\n";
}
set_error_handler('eh');
ob_start();
echo 123;
nonExistantClass::nonExistantMethod();
echo "After error\n";
Output is:
123
Fatal error: Class 'nonExistantClass' not found in ...
Hopefully the above should more accurately illustrate the issue.
------------------------------------------------------------------------
[2011-02-28 19:37:32] ras...@php.net
I am unable to reproduce this. My test script:
<?php
function eh($errno, $errstr, $errfile, $errline) {
$contents = ob_get_contents();
ob_end_clean();
echo "Error: $errno, $errstr, $errfile, $errline\n";
}
set_error_handler('eh');
ob_start();
echo 123;
trigger_error('test error', E_USER_ERROR);
echo "After error\n";
And my output is:
Error: 256, test error, /var/www/testing/o.php, 10
After error
No sign of "123" there.
------------------------------------------------------------------------
[2011-02-28 07:43:46] danhstevens at gmail dot com
Description:
------------
When output buffering is turned on (via ob_start()) and an error is
encountered before a call to ob_end_* is called the entire contents of
the output buffer is dumped (to STDOUT) and there appears to be no way
to prevent the buffer from dumping - not even by setting an error
handler, etc.
This is a security issue since the output buffer may contain sensitive
information that is them dumped over to the user. Using
set_error_handler does not stop the dump - it appears the dump simply
happens with no way to intercept or prevent it.
Test script:
---------------
<?php
ob_start();
echo 123;
trigger_error('test error', E_USER_ERROR);
$contents = ob_get_contents();
ob_end_clean();
?>
Expected result:
----------------
(no output)
Actual result:
--------------
123
Fatal error: test error in ...
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=54114&edit=1
