Edit report at https://bugs.php.net/bug.php?id=54114&edit=1
ID: 54114
Comment by: nicolas dot grekas+php 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:
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', '******', $b);
}
register_shutdown_function('my_shutdown');
ob_start('ob_custom_filter');
?>
Previous Comments:
------------------------------------------------------------------------
[2011-03-10 19:41:28] danhstevens at gmail dot com
I've found a viable work-around for this bug (although a patch of the core
would still be ideal so people don't discover this potential security issue the
hard-way).
By registering the following shutdown handler before any output buffering the
dump of data can be prevented:
<?php
function shutdown_fn()
{
//If ob_start has been called at least once
if(ob_get_level() > 1)
{
//Prevent data in buffer from dumping
ob_end_clean();
}
}
register_shutdown_function('shutdown_fn');
Now when using the examples above that normally cause the buffer to dump to the
client the buffer data is disposed of. Of course, this can be extended to use
ob_get_contents and redirect the data to file or other means if necessary. This
approach is working for me (on PHP 5.3.5).
~Dan
------------------------------------------------------------------------
[2011-03-06 16:51:52] neweracracker at gmail dot com
I've managed to reproduce this in Windows 7 running php 5.2.17 (with
php.ini-dist) and php 5.3.5 (with php.ini-development).
Here is my test script:
<?php
set_time_limit(1);
ob_start();
echo "You shouldn't see this!";
sleep(2); //comment this and you won't see the line above in output ;)
ob_end_clean();
?>
I've reported this as bug #54174 which got closed due being a dupe of this one
so I am leaving this comment here for reference purposes.
Regards,
NewEraCracker.
------------------------------------------------------------------------
[2011-02-28 21:40:36] danhstevens at gmail dot com
Hi Rasmus,
I was still able to create the problem by calling on a non-existing class to
create a fatal error. Here is a variation of your code:
function eh($errno, $errstr, $errfile, $errline) {
$contents = ob_get_contents();
ob_end_clean();
echo "Error: $errno, $errstr, $errfile, $errline\n";
}
set_error_handler('eh');
ob_start();
echo 123;
nonExistantClass::nonExistantMethod();
echo "After error\n";
Output is:
123
Fatal error: Class 'nonExistantClass' not found in ...
Hopefully the above should more accurately illustrate the issue.
------------------------------------------------------------------------
[2011-02-28 19:37:32] [email protected]
I am unable to reproduce this. My test script:
<?php
function eh($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 https://bugs.php.net/bug.php?id=54114&edit=1
