anestisb / Melkor Android

--------------------------------~ | -- DESCRIPTION -- | --------------------------------~

Melkor - An ELF File Format Fuzzer

Melkor, a fictional character from J. R. R. Tolkien's Middle-earth legendarium, was the first Dark Lord and master of Sauron. He's mentioned briefly in The Lord of the Rings and is known for:

"... Melkor had captured a number of ELVES before the Valar attacked him, and he tortured and corrupted them, breeding the first Orcs." (http://en.wikipedia.org/wiki/Morgoth)

"... Melkor was cunning and more filled with malice than ever. Seeing the bliss of the ELVES and remembering that it was for their sake that he was overthrown, Melkor desired above all things to corrupt them." (http://lotr.wikia.com/wiki/Melkor)

"Orcs...This has been so from the day they were bred by Melkor from corrupted, tortured and mutilated ELVES that may also have been forced to breed with other unnatural abominations in the dominion of the Dark Powers." (http://lotr.wikia.com/wiki/Orcs)

To honor his name, this piece of code takes an ELF, corrupts it and creates as much Orcs as you want.

Melkor is a hybrid fuzzer (mutation-based and generation-based). It mutates the existing data in an ELF sample given to create orcs (malformed ELFs), however, it doesn't change values randomly (dumb fuzzing), instead, it fuzzes certain metadata with semi-valid values through the use of fuzzing rules (knowledge base). Written in C, Melkor is a very intuitive and easy-to-use fuzzer to find functional (and security) bugs in ELF parsers.

The fuzzing rules were designed with the following inputs in mind:

• ELF Specification violations
  • TIS ELF Specification 1.2 (May, 1995)
  • ELF-64 Object File Format 1.5 (May 1998)
• Misc ideas & considerations
• Parsing patterns in ELF software

You will find the fuzzing rules in detail and some other schematics in the docs/ directory.

--------------------------------~ | -- REQUIREMENTS -- | --------------------------------~

• make
• gcc

--------------------------------~ | -- COMPILATION & USAGE -- | --------------------------------~ The compilation is very straightforward, just type: $make

It will create the file 'melkor', which is the fuzzer itself, and some other ELF files inside the templates/ folder, including normal ELF files such as a normal ELF executable, some shared libraries, an static ELF (standalone executable) and some others.

By running melkor, a list of options will be shown and you will realize that it's very intuitive and easy-to-use. All you have to supply is the name of an ELF to be used as a template, which could be any of the ones inside the templates/ dir.

Depending on what kind of software you want to test, you have to choose which metadata you want to fuzz. For example, if you want to test an OS loader, you probably might want to fuzz only the Program Header Table (-P) and/or the Dynamic Section (-D). On the other hand, perhaps you might want to fuzz the Section Header Table and the ELF Header to test any antivirus engine or debugger. Fuzzing the Symbols Tables (-s) and/or Relocations Tables (-R) on relocatable files (.o) or shared libraries (.so) to test compilers and/or linkers. The String Tables could be fuzzed as well (-Z). It's up to you to decide how badly you want to corrupt an ELF }:-)

Once the orcs have been created inside the orcs_*/ dir, it's time to test them with the help of test_fuzzed.sh, where you can simply specify the name of the folder with the orcs to be run (OS loader testing) or add an extra parameter to specify which program (and its parameters) you'd like to test against every malformed ELF within the orcs folder. This script has the option to fuzz some environment variables (defined as fuzzing rules as well). Showing logs with #dmesg after running the script could be useful to identify which program/library crashed and where that crash was. Some examples are shown running the script without parameters.

If you want test the malformed ELFs (orcs) automatically on Windows environment, there is included a batch script (win_test_fuzzed.bat) with almost the same functionality of the script for *NIX.

Happy Fuzzing !

--------------------------------~ | -- DIRS -- | --------------------------------~

• docs/ Contains related documentation such as the detailed list of fuzzing rules as well as the list of ELF metadata dependencies.

• templates/ It has some ELF files compiled at the same time than melkor and could be used to feed melkor: foo.c -> foo.o (ELF object)-> foo (ELF executable) foo.c -> foo_static (ELF static executable) libfoo.c -> libfoo.so (ELF shared object) and some others. Type "$make templ" to see in detail which other ELF templates are created.

• orcs_*/ Will contain the malformed ELF files (based on the given template file) created after the fuzzing process.

• src/ Melkor source code.

--------------------------------~ | -- BUGS -- | --------------------------------~

Please read BUGS.txt

--------------------------------~ | -- CONTACT -- | --------------------------------~

Name: Alejandro Hernandez H. [nitr0us] Twitter: http://twitter.com/nitr0usmx Email: nitrousenador [at] gmail [dot] com Website: http://www.brainoverflow.org Blog: http://chatsubo-labs.blogspot.com

--------------------------------~ | -- IN MEMORIAL -- | --------------------------------~

This project is dedicated to the memory of one of my best friends, Aaron Alba.

--------------------------------~ | -- LICENSE -- | --------------------------------~

Melkor - An ELF File Format Fuzzer Copyright (C) 2014 Alejandro Hernandez H. (nitr0us)

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.