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

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Message-ID: <CAC7UXK8uacWiVieCcFM0anmCCEpJsKg5GSHt7siN8uemBty6AA@mail.gmail.com>
Date: Tue, 27 Nov 2012 16:41:30 +0100
From: "Gregor S." <rc46fi@...glemail.com>
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: linux rootkit in combination with nginx

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...


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?
>>
>> Cheers,
>> -stacktrace
>>
>> _______________________________________________
>> Full-Disclosure - We believe in it.
>> Charter: http://lists.grok.org.uk/full-disclosure-charter.html
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>>
>
>
>
> --
> dxp
>
> _______________________________________________
> Full-Disclosure - We believe in it.
> Charter: http://lists.grok.org.uk/full-disclosure-charter.html
> Hosted and sponsored by Secunia - http://secunia.com/
>



-- 
just because you're paranoid, don't mean they're not after you...
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