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This is "flawfinder" by David A. Wheeler.
Flawfinder is a simple program that scans C/C++ source code and reports potential security flaws. It can be a useful tool for examining software for vulnerabilities, and it can also serve as a simple introduction to static source code analysis tools more generally. It is designed to be easy to install and use. Flawfinder supports the Common Weakness Enumeration (CWE) and is officially CWE-Compatible.
For more information, see the project website
Flawfinder is designed for use on Unix/Linux/POSIX systems (including Cygwin, Linux-based systems, MacOS, and various BSDs) as a command line tool. It requires either Python 2.7 or Python 3.
If you just want to use it, you can install flawfinder with
Python's "pip" or with your system's package manager (flawfinder has
packages for many systems). It also supports easy installation
make install source installation conventions.
The file INSTALL.md has more detailed installation instructions.
You don't HAVE to install it to run it, but it's easiest that way.
To run flawfinder, just give it a list of source files or directories to example. For example, to examine all files in "src/" and down recursively:
To examine all files in the current directory and down recursively:
Hits (findings) are given a risk level from 0 (very low risk) to 5 (high risk), By default, findings of risk level 1 or higher are shown. You can show only the hits of risk level 4 or higher in the current directory and down this way:
flawfinder --minlevel 4 ./
The manual page (flawfinder.1 or flawfinder.pdf) describes how to use
flawfinder (including its various options) and related information
(such as how it supports CWE). For example, the
--html option generates
output in HTML format. The
--help option gives a brief list of options.
Character Encoding Errors
Flawfinder must be able to correctly interpret your source code's character encoding. In the vast majority of cases this is not a problem, especially if the source code is correctly encoded using UTF-8 and your system is configured to use UTF-8 (the most common situation by far).
However, it's possible for flawfinder to halt if there is a
character encoding problem and you're running Python3.
The usual symptom is error messages like this:
Error: encoding error in FILENAME 'ENCODING' codec can't decode byte ... in position ...: invalid start byte
Unfortunately, Python3 fails to provide useful built-ins to deal with this. Thus, it's non-trivial to deal with this problem without depending on external libraries (which we're trying to avoid).
If you have this problem, see the flawfinder manual page for a collection
of various solutions.
One of the simplest is to simply convert the source code and system
configuration to UTF-8.
You can convert source code to UTF-8 using tools such as the
iconv or the Python program
you can install
pip install cvt2utf.
Under the hood
More technically, flawfinder uses lexical scanning to find tokens (such as function names) that suggest likely vulnerabilities, estimates their level of risk (e.g., by the text of function calls), and reports the results. Flawfinder does not use or have access to information about control flow, data flow, or data types. Thus, flawfinder will necessarily produce many false positives for vulnerabilities and fail to report many vulnerabilities. On the other hand, flawfinder can find vulnerabilities in programs that cannot be built or cannot be linked. Flawfinder also doesn't get as confused by macro definitions and other oddities that more sophisticated tools have trouble with.
Flawfinder GitHub Action
There's a GitHub action available for those who use GitHub.
Create a .yml file under .github/workflows with the following contents:
- name: flawfinder_scan uses: firstname.lastname@example.org with: arguments: '--sarif ./' output: 'flawfinder_results.sarif'
You can add many other additions to the arguments.
--error-level=4 will cause an error to be returned if
flawfinder finds a vulnerability of level 4 or higher.
Notice the version number after the
@ symbol; you can select a
You can find the action name and version string from Marketplace by clicking "Use latest/xxx version" button.
- arguments: Flawfinder command arguments
- output: Flawfinder output file name. Can be uploaded to GitHub.
We love contributions! For more information on contributing, see the file CONTRIBUTING.md.
Flawfinder is released under the GNU GPL license version 2 or later (GPL-2.0+). See the COPYING file for license information.