Bug 84642

Summary: passthru() causes DoS
Product: [Retired] Red Hat Linux Reporter: Gigs <jgiglio>
Component: httpdAssignee: Joe Orton <jorton>
Status: CLOSED DUPLICATE QA Contact: David Lawrence <dkl>
Severity: medium Docs Contact:
Priority: high    
Version: 8.0Keywords: Security
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Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 2006-02-21 18:51:53 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Gigs 2003-02-19 23:04:29 UTC
Description of problem:
PHP's passthru function in Red Hat 8 stock PHP/Apache2 is barely functional, if the program it runs returns any significant amount of data, it causes a DoS situation, the server will become very unresponsive, and the query takes much longer than expected.  This could be remotely exploited as a system-wide DoS attack if the user has any script that uses a passthru() function to return data the user requested from an external command.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Create a small php script with one command:

passthru("cat /boot/vmlinuz");
2. Request the script through the web server.  The first time it runs it may run quickly and return the proper output, but subsequent times it will randomly take a very long time to return the output, a seeming random amount of time between 10 seconds and 10 minutes.  While the script is running, the server will be very unresponsive.

Note that /boot/vmlinuz is just an example, any command that returns a significant amount of output, (500K+ such as calling ghostscript to generate a PDF/PS file for the user) will cause the condition.  Larger outputs seem to cause the response time to scale up in an exponential growth rate.

Actual results:
Extreme slowdown of server.

Expected results:
Almost instant response with data.

Additional info:

Comment 1 Joe Orton 2003-02-20 11:53:16 UTC
passthru() did get optimized recently upstream, though this sounds like a more
serious problem.  (http://bugs.php.net/bug.php?id=22308)

Comment 2 Joe Orton 2003-10-09 08:10:00 UTC
This was a problem where httpd would sometimes buffer up dynamic content, and
was fixed by the most recent httpd erratum.

Thanks for the report.

*** This bug has been marked as a duplicate of 97111 ***

Comment 3 Red Hat Bugzilla 2006-02-21 18:51:53 UTC
Changed to 'CLOSED' state since 'RESOLVED' has been deprecated.