zzuf - multi-purpose fuzzer

zzuf is a transparent application input fuzzer. Its purpose is to find bugs in applications by corrupting their user-contributed data (which more than often comes from untrusted sources on the Internet). It works by intercepting file and network operations and changing random bits in the program’s input. zzuf’s behaviour is deterministic, making it easier to reproduce bugs. Its main areas of use are:

• quality assurance: use zzuf to test existing software, or integrate it into your own software’s testsuite
• security: very often, segmentation faults or memory corruption issues mean a potential security hole, zzuf helps exposing some of them
• code coverage analysis: use zzuf to maximise code coverage

zzuf’s primary target is media players, image viewers and web browsers, because the data they process is inherently insecure, but it was also successfully used to find bugs in system utilities such as objdump.

zzuf is not rocket science: the idea of fuzzing input data is barely new, but zzuf’s main purpose is to make things easier and automated. You can see an impressive list of bugs found with zzuf.

Downloads

Supported platforms are: Linux (glibc), FreeBSD, OpenBSD, Mac OS X and OpenSolaris.

• Source code: zzuf-0.13.tar.gz (31 January 2010).
• Mac OS X universal binary: zzuf-osx-0.13.tar.gz (7 February 2010).

There is no Windows port yet and NetBSD is almost working. Help is sought for the Win32 port, see ticket #62.

Documentation

The zzuf tutorial is a hands-on guide to the most important zzuf features. It starts with the working principles but goes on with very advanced uses of the tool.

Warning: this tutorial requires zzuf version 0.11 or later.

1. Basic zzuf usage
   1.1. Launching zzuf
   1.2. Invoking different programs
   1.3. The fuzzing ratio
   1.4. The random seed
   1.5. Creating fuzzed files
2. zzuf as a batch testing tool
   2.1. Debug mode
   2.2. Include and exclude patterns
   2.3. Seed ranges
   2.4. Ratio ranges
3. WORK IN PROGRESS

Presentations

Sam gave a few talks about zzuf. The slides contain information you may find useful:

• ​FOSDEM 2007 (Sam actually missed that talk) - PDF or OpenOffice
• ​Hacker Space Festival 2008 - PDF or OpenOffice

Internals documentation

zzuf is full of black magic and can be pretty difficult to hack with. The internals documentation tries to shed light on the global architecture and some specific tricks.

Development

Development happens in a centralised Subversion repository:

• ​svn://svn.zoy.org/caca/zzuf/trunk
• associated web interface

There is also a Git repository that mirrors the central one:

• using the Git protocol: ​git://git.zoy.org/zzuf.git
• using HTTP: http://caca.zoy.org/git/zzuf.git

If you want to discuss zzuf or report bugs, you can write to ​sam@hocevar.net or join #libcaca on irc.freenode.net.

They use zzuf

• ​Goatse Security uses zzuf to find issues in various third-party applications.
• Security researchers at ​Adobe use zzuf to stress test their applications and libraries.
• The ​CERT Basic Fuzzing Framework (BFF) is based on zzuf.