Chunked requests to bypass ModSecurity and mod_headers

[Martin Holst Swende <martin () swende se>]

Hi list,

While playing with requests that used chunked encoding, I found one way 
to sneak headers through Apache mod_headers removal mechanism. I also 
found a way to sneak pretty much anything through ModSecurity.

More details here:
http://martin.swende.se/blog/HTTPChunked.html

## Timeline

* 2013-09-05 Notified ModSecurity (security () modsecurity org) about the 
problem.
* 2013-09-05 ModSecurity responded; will investigate/patch.
* 2013-09-06 Notified Apache Software Foundation about the problem.
* 2013-09-08 Apache responded; confirmed and looking into the issue.
* 2013-09-09 ModSecurity responded with patch.
* 2013-10-19 Apache security raised the issue on dev@httpd instead, it 
was "languishing on the private list". 
[Mail](http://marc.info/?l=apache-httpd-dev&m=138219203120175&w=2)
* 2013-12-16 ModSecurity released version 2.7.6, with 
[patch](https://github.com/SpiderLabs/ModSecurity/commit/f8d441cd25172fdfe5b613442fedfc0da3cc333d). 
Uncredited.
* 2014-03-31 Published details

### Status as of february 2014

The Ubuntu-packaged version of Modsecurity is 2.7.4, both for 13.10 and 
earlier. This version is vulnerable.

The latest LTS server version - Ubuntu 12.04 uses Apache 2.2.22, which 
*is* vulnerable.
Ubuntu 13.10 repositories contains Apache 2.4.6, which was found *not* 
to be vulnerable.

Regards,
Martin Holst Swende (and thanks to Fyodor!)

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