cwe_checker is a suite of tools to detect common bug classes such as use of dangerous functions and simple integer overflows. These bug classes are formally known as Common Weakness Enumerations (CWEs). Its main goal is to aid analysts to quickly find vulnerable code paths.
Its main focus are ELF binaries that are commonly found on Linux and Unix operating systems. cwe_checker is built on top of BAP(Binary Analysis Platform). By using BAP, we are not restricted to one low level instruction set architectures like Intel x86. BAP lifts several of them to one common intermediate representation (IR). cwe_checker implements its analyses on this IR. At time of writing, BAP 1.6 supports Intel x86/x64, ARM, MIPS, and PPC amongst others. Hence, this makes cwe_checker a valuable tool for firmware analysis.
cwe_checker implements a modular architecture that allows to add new analyses with ease. So far the following analyses are implemented across several BAP plugins:
- CWE-125: Out-of-bounds read (via emulation)
- CWE-190: Integer Overflow or Wraparound
- CWE-215: Information Exposure Through Debug Information
- CWE-243: Creation of chroot Jail Without Changing Working Directory
- CWE-248: Uncaught Exception
- CWE-332: Insufficient Entropy in PRNG
- CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
- CWE-415: Double Free (via emulation)
- CWE-416: Use After Free (UAF) (via emulation)
- CWE-426: Untrusted Search Path
- CWE-457: Use of Uninitialized Variable
- CWE-467: Use of sizeof() on a Pointer Type
- CWE-476: NULL Pointer Dereference
- CWE-560: Use of umask() with chmod-style Argument
- CWE-676: Use of Potentially Dangerous Function
- CWE-782: Exposed IOCTL with Insufficient Access Control
- CWE-787: Out-of-bounds Write (via emulation)
Please note that some of the above analyses only are partially implemented at the moment. Furthermore, false positives are to be expected due to shortcuts and the nature of static analysis as well as over-approximation. For more information about the individual checks you can look at the online documentation.
cwe_checker comes with scripts for IDA Pro and Ghidra, which parse the output of cwe_checker and annotate the found CWEs in the disassembler for easier manual analysis. See the online documentation for their usage. The IDA Pro plugin also uses colors to represent the severeness of the found issues (yellow, orange, or red). The following screenshot shows some results:
The following arguments should convince you to give cwe_checker a try:
- it is very easy to setup, just build the Docker container!
- it analyzes ELF binaries of several CPU architectures including x86, ARM, MIPS, and PPC
- it is extensible due to its plugin-based architecture
- it is configureable, e.g. apply analyses to new APIs
- view results annotated in IDA Pro and Ghidra
- cwe_checker can be integrated as a plugin into FACT
There are several ways to install cwe_checker. The recommended way is to get cwe_checker from the Ocaml package manager Opam. You can install cwe_checker via the package cwe_checker (opam install cwe_checker
). This gives you a stable version of cwe_checker.
Another option is to pull the latest Docker image from dockerhub:
docker pull fkiecad/cwe_checker:latest
yields an image based on the current master branch.docker pull fkiecad/cwe_checker:stable
yields an image based on the latest stable release version.
If you plan to develop cwe_checker, it is recommended to build it using the provided Makefile
. In this case you must ensure that all dependencies are fulfilled:
- Ocaml 4.07.1
- Opam 2.0.2
- dune >= 1.6
- BAP (and its dependencies). Development on the master branch depends on the master branch of BAP which can be added with
opam repo add bap-testing git+https://github.com/BinaryAnalysisPlatform/opam-repository#testing
to the sources of the Opam package manager. The stable release of the cwe_checker depends on BAP 1.6. - yojson >= 1.6.0
- ppx_deriving_yojson >= 3.5.1
- alcotest >= 0.8.3 (for tests)
- Sark (latest) for IDA Pro annotations
- pytest >= 3.5.1 (for tests)
- SCons >= 3.0.5 (for tests)
- odoc >= 1.4 (for documentation)
Just run make all
to compile and register the plugin with BAP. You can run the test suite via make test
. Documentation can be built via make documentation
.
The usage is straight forward: adjust the config.json
(if needed) and call BAP with cwe_checker as a pass.
bap PATH_TO_BINARY --pass=cwe-checker --cwe-checker-config=src/config.json
For further information see the online documentation. You can also build the documentation locally via make documentation
and then browse it in the doc/html/ folder.
You can find some information about how to write your own check here
If you plan to open a PR, please utilize precommit in your development environment to catch many issues before the code review.
Contributions are always welcome. Just fork it and open a pull request!
See the online documentation or build it locally via make documentation
and then browse it in the doc/html/ folder. But the most accurate documentation is still the source code. We also provide some slides of conference presentations on cwe_checker in doc. These should be of special interest for those who would like to get a quick/initial overview of its internals.
We presented cwe_checker at the following conferences so far:
This project is partly financed by German Federal Office for Information Security (BSI).
A special thanks goes out to the BAP community (especially the official gitter) for answering questions and discussing solutions.
Copyright (C) 2018 - Fraunhofer FKIE (firmware-security@fkie.fraunhofer.de)
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library 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
Library 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/>.