full-disclosure - Re: linux rootkit in combination with nginx

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Date: Tue, 27 Nov 2012 12:50:50 -0500
From: Jeffrey Walton <noloader@...il.com>
To: "Gregor S." <rc46fi@...glemail.com>
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: linux rootkit in combination with nginx

On Tue, Nov 27, 2012 at 10:41 AM, Gregor S. <rc46fi@...glemail.com> wrote:
> More interesting than the rootkit itself is how it found it's way into the
> box.
>
> Chances are that Squeeze has a non-disclosed 0day, and that's worring me a
> bit...
Its based on Linux, so there are probably a lot of non-disclosed 0-days.

Folks like Dan Rosenberg have made a career out of finding Comp Sci
101 bugs because some of the developers are too l33t to use tools and
analysis to find their mistakes. The OS's namesake is too arrogant for
his own good (cf., "GCC is crap",
http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-11/msg08325.html).

Jeff

> On Mon, Nov 26, 2012 at 11:04 AM, dxp <dxp2532@...il.com> wrote:
>>
>> Looks like a new rootkit according to Kaspersky [1] and some analysis
>> released by CrowdStrike [2].
>>
>> [1]
>> https://www.securelist.com/en/blog/208193935/New_64_bit_Linux_Rootkit_Doing_iFrame_Injections
>> [2]
>> http://blog.crowdstrike.com/2012/11/http-iframe-injecting-linux-rootkit.html
>>
>> PS: Interesting to know if others found this on their servers or is this
>> an isolated incident !?
>>
>>
>> On Tue, Nov 13, 2012 at 10:19 AM, stack trace <stacktrace44@...il.com>
>> wrote:
>>>
>>> Hi there,
>>>
>>> We've discovered something which looks to us like a rootkit working
>>> together with proxy software like nginx. Our OS is debian squeeze and nginx
>>> 1.2.3.
>>>
>>> Here is what happened:
>>>
>>> We are running a web service and we got notified by some customers of us
>>> that they are getting redirected to some malicious sites. Somehow a hacker
>>> managed to inject an iframe into our http responses.
>>>
>>> I tried to do a telnet test on our nginx proxy and saw that even the "bad
>>> request" response which gets served directly from nginx contained the
>>> malicious iframe code.
>>>
>>> server {
>>>     listen          80 default backlog=2048;
>>>     listen          443 default backlog=2048 ssl;
>>>     server_name     _;
>>>     access_log      off;
>>>     (...)
>>>     location / {
>>>         return  400;
>>>     }
>>> }
>>>
>>> Doing a bad request nginx doesn't go to cache in this case - the "return
>>> 400" makes nginx reply with a predefined response (a string in memory).
>>>
>>> Even this response contained an iframe like this:
>>> HTTP/1.1 400 Bad Request
>>> Server: nginx/1.2.3
>>> Date: Wed, 07 Nov 2012 00:01:24 GMT
>>> Content-Type: text/html
>>> Content-Length: 353
>>> Connection: close
>>>
>>> <html>
>>> <head><title>400 Bad Request</title></head>
>>> <body bgcolor="white"><style><iframe
>>> src="http://malware-site/index.php"></iframe></div>
>>> <center><h1>400 Bad Request</h1></center>
>>> <hr><center>nginx/1.2.3</center>
>>>
>>> We've done an strace on the running nginx process and discovered that the
>>> reply of the process actually didn't contain the malicious iframe.
>>>
>>> writev(3, [{"HTTP/1.1 400 Bad Request\r\nServer"..., 151},
>>> {"<html>\r\n<head><title>400 Bad Req"..., 120},
>>> {"<hr><center>nginx/1.2.4</center>"..., 52}], 3) = 323
>>>
>>> After a bit deeper digging we've found some kernel rootkit I've attached
>>> to this email and also some hidden processes were running on our proxy
>>> machine with names like write_startup_c and get_http_inj_fr (which sounds
>>> like what happened to us).
>>>
>>> Is this a known attack / rootkit etc or did we discover something new?

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