Peter Van Eeckhoutte's Blog

Archive for the ‘Exploits’ Category

A few moments ago I published a detailed write-up, explaining the steps I took to build a 0day exploit for a zip file handling bug in QuickZip, on the Offensive Security blog. You can read the article here : http://www.offensive-security.com/blog/vulndev/quickzip-stack-bof-0day-a-box-of-chocolates/ Read more »

Introduction Easter is still far away, so this is probably the right time to talk about ways to hunting for eggs (so you would be prepared when the easter bunny brings you another 0day vulnerability) In the first parts of this exploit writing tutorial series, we have talked about stack based overflows and how they can lead to arbitrary code execution. In all of the exploits that we have built so far, the location of where the shellcode is placed is more or less static and/or could be referenced by using a register (instead of a hardcoded stack address), taking care of stability and reliability. In some parts of the series, I have talked about various techniques to jump to shellcode, including techniques that would use one or more trampolines to get to the shellcode.  In …

Finally … after spending a couple of weeks working on unicode and unicode exploits, I’m glad and happy to be able to release this next article in my basic exploit writing series : writing exploits for stack based unicode buffer overflows (wow – that’s a mouthful). You may (or may not) have encountered a situation where you’ve performed a stack buffer overflow, overwriting either a RET address or a SEH  record, but instead of seeing 0×41414141 in EIP, you got 0×00410041. Sometimes, when data is used in a function, some manipulations are applied. Sometimes data is converted to uppercase, to lowercase, etc…  In some situations data gets converted to unicode.  When you see 0×00410041 in EIP, in a lot of cases, this probably means that your payload had been converted to unicode before it was put on the …

Just wanted to drop a quick note about the release of another free script. This time I’ve written a simple FTP fuzzer (with a little help from HDMoore) in Metasploit. You can read more about it (and download the script) at http://www.corelan.be:8800/index.php/my-free-tools/security/metasploit/simple-ftp-fuzzer-metasploit-module/

This is why I like Metasploit so much… :-)

Update : after running some fuzzing instances against a couple of FTP servers (Win32), I have noticed that some odd folders were created in my ftp root folder, and that these folders cannot be renamed or removed anymore

(Error message : “Cannot read from the source file or disk”)

Solution : the rmdir command allow you to remove these folders using a \\?\ reference

Let’s say the ftp root is located at ftp, and the folder that cannot be removed looks like a bunch of A’s, with spaces in between, then …

Introduction In all previous tutorials in this Exploit writing tutorial series, we have looked at building exploits that would work on Windows XP / 2003 server. The success of all of these exploits (whether they are based on direct ret overwrite or exception handler structure overwrites) are based on the fact that a reliable return address or pop/pop/ret address must be found, making the application jump to your shellcode. In all of these cases, we were able to find a more or less reliable address in one of the OS dll’s or application dll’s. Even after a reboot, this address stays the same, making the exploit work reliably. Fortunately for the zillions Windows end-users out there, a number of protection mechanisms have been built-in into the Windows Operating systems. – Stack cookies (/GS Switch cookie) …

In the first parts of this exploit writing tutorial, I have mainly used Windbg as a tool to watch registers and stack contents while evaluating crashes and building exploits. Today, I will discuss some other debuggers and debugger plugins that will help you speed up this process. A typical exploit writing toolkit arsenal should at least contain the following tools : windbg (for a list of Windbg commands, click here) ollydbg immunity debugger (requires python) metasploit pyDbg (if you are using python and want to build your own custom debugger, as explained in the awesome Gray Hay Python book scripting tools …

In the first parts of the exploit writing tutorial, I have discussed some common vulnerabilities that can lead to 2 types of exploits : stack based buffer overflows (with direct EIP overwrite), and stack based buffer overflows that take advantage of SEH chains. In my examples, I have used perl to demonstrate how to build a working exploit. Obviously, writing exploits is not limited to perl only. I guess every programming language could be used to write exploits… so you can just pick the one that you are most familiar with. (python, c, c++, C#, etc) Despite the fact that these custom written exploits will work just fine, it may be nice to be able to include your own exploits in the metasploit framework in order to take advantage of some of the unique metasploit features. So …