Owning Unix and Windows systems with a (somewhat) limited vulnerability

Auditing a product recently I noticed a curious scenario where I control the following:

  • Unix based: The limited vulnerability allows one to create any file as root controlling the contents of that file. I can even overwrite existing files.
  • Windows based: The vulnerability allows one to execute an operating system command but doesn’t allow, for some reason, copying files as the Unix vulnerability allows.

In the next paragraphs I will explain how one could exploit such somewhat limited scope vulnerabilities in order to execute remote arbitrary code in the context of the running application (root under Unix and SYSTEM under Windows). In any case, I’ll also explain the opposite case: one can execute an arbitrary operating system command in Unix based systems but can’t create an arbitrary file in the system and one can create an arbitrary file anywhere in the system in Windows operating systems but cannot execute an arbitrary command.
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Malware URLs

It’s been a while since I started writing a first prototype to try to catch as much malware (URLs and samples) as possible. Today I can say my project is all grown up as it’s generating, daily, a feed with around 9.000 malware URLs and with a low rate of false positives (although there may be some).

The process of finding malware URLs  in my tool used to be only a matter of finding suspicious URLs in social networks (Twitter and Identi.ca), checking mail accounts receiving loads of bad stuff and nothing else. At first. Today I’m using crawlers, honeypots, sandboxes, thirdy party public URL feeds, private URL feeds (provided under consent), executable unpackers, heuristic engines for Flash movies, PDFs, OLE2 documents, etc… It changed a lot and became a big project that, I hope, can give useful information for malware researchers.

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A simple activity monitor with /dev/random

Today I was performing some tests in the random number generators of some browsers and found, by chance, this mail sent to Bugtraq by Michal Zalewsky called “Unix entropy source can be used for keystroke timing attacks”. While the idea of Michal is very good, I failed to find a reliable way of doing it in my house computer after some time (well, honestly, after just 1 hour…). However, a more simpler idea come to my mind: if /dev/random blocks when the entropy pool is empty and most of the events are generated when mouse or keyboard events happens, at least, I can write quite easily an activity monitor based on /dev/random.

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Patching old linux binaries to work with recent libc versions

From time to time I need to use some old binary created for older Linux versions like Redhat 6.2, for example. The problem with those binaries is that they were compiled with a very old version of the glibc and they cannot be run ‘like this’ in newer systems. Sometimes, just making a symbolic link from the new library to the old name can be enough but not always. In this brief post I will talk about how to workaround the typical relocation errors and undefined symbols problems with old binaries.

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A simple PIN tool unpacker for the Linux version of Skype

Some time ago I wanted to take a look to Skype to see how it works and get the classes diagram of this program but, surprise: It’s packed. The Windows version is protected with a crypter of their own, (UPDATE: this statement was wrong: the last time I checked it, was protected with Themida. It was Spotify the application protected with Themida). However, as I expected, the Linux version was simply packed (not protected) and with something easy to unpack. To unpack Skype and be able to analyse it in IDA and, also, to learn a bit how Intel PIN works, I have written a PIN tool to “automatically” unpack Skype.

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