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Continuous Integration

OSS-Fuzz offers CIFuzz, which will run your fuzz targets each time a pull request is submitted, for projects hosted on GitHub. This allows you to detect and fix bugs before they make it into your codebase.

How it works

CIFuzz works by checking out a repository at the head of a pull request. For projects that support code coverage, fuzzers coverage is compared with PR diffs to determine which fuzzers should be used. For projects that do not support code coverage, all fuzzers are run for an even length of time. If no bugs are found and the allotted time is up (default is 10 minutes), the CI test passes with a green check. But if a bug is found, the bug is checked for reproducability and against old OSS-Fuzz builds to prevent the reporting of pre-existing bugs. If the bug is both new and reproducible, it is reported and the stack trace as well as the test case are made available for download.

Requirements

  1. Your project must be integrated in OSS-Fuzz.
  2. Your project is hosted on GitHub.

Integrating into your repository

You can integrate CIFuzz into your project using the following steps:

  1. Create a .github directory in the root of your project.
  2. Create a workflows directory inside of your .github directory.
  3. Copy the example main.yml file over from the OSS-Fuzz repository to the workflows directory.
  4. Change the oss-fuzz-project-name value in main.yml from example to the name of your OSS-Fuzz project. It is very important that you use your OSS-Fuzz project name which is case sensitive. This name is the name of your project’s subdirectory in the projects directory of OSS-Fuzz.
  5. Set the value of fuzz-seconds. The longest time that the project maintainers are acceptable with should be used. This value should be at minimum 600 seconds and scale with project size.

Your directory structure should look like the following:

project
|___ .github
|    |____ workflows
|          |____ main.yml
|___ other-files

main.yml for an example project:

name: CIFuzz
on: [pull_request]
jobs:
 Fuzzing:
   runs-on: ubuntu-latest
   steps:
   - name: Build Fuzzers
     id: build
     uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
     with:
       oss-fuzz-project-name: 'example'
       dry-run: false
   - name: Run Fuzzers
     uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
     with:
       oss-fuzz-project-name: 'example'
       fuzz-seconds: 600
       dry-run: false
   - name: Upload Crash
     uses: actions/upload-artifact@v1
     if: failure() && steps.build.outcome == 'success'
     with:
       name: artifacts
       path: ./out/artifacts

Optional configuration

Configurable Variables

fuzz-time: Determines how long CIFuzz spends fuzzing your project in seconds. The default is 600 seconds. The GitHub Actions max run time is 21600 seconds (6 hours).

dry-run: Determines if CIFuzz surfaces errors. The default value is false. When set to true, CIFuzz will never report a failure even if it finds a crash in your project. This requires the user to manually check the logs for detected bugs. If dry run mode is desired, make sure to set the dry-run parameters in both the Build Fuzzers and Run Fuzzers action step.

allowed-broken-targets-percentage: Can be set if you want to set a stricter limit for broken fuzz targets than OSS-Fuzz’s check_build. Most users should not set this.

sanitizer: Determines a sanitizer to build and run fuzz targets with. The choices are 'address', 'memory' and 'undefined'. The default is 'address'. It is important to note that the Build Fuzzers and the Run Fuzzers sanitizer field needs to be the same. To specify a list of sanitizers a matrix can be used. To use a sanitizer add it to the list of sanitizers in the matrix field below:


name: CIFuzz
on: [pull_request]
jobs:
 Fuzzing:
   runs-on: ubuntu-latest
   strategy:
     fail-fast: false
     matrix:
       sanitizer: [address, undefined, memory]
   steps:
   - name: Build Fuzzers (${{ matrix.sanitizer }})
     id: build
     uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
     with:
       oss-fuzz-project-name: 'example'
       dry-run: false
       sanitizer: ${{ matrix.sanitizer }}
   - name: Run Fuzzers (${{ matrix.sanitizer }})
     uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
     with:
       oss-fuzz-project-name: 'example'
       fuzz-seconds: 600
       dry-run: false
       sanitizer: ${{ matrix.sanitizer }}
   - name: Upload Crash
     uses: actions/upload-artifact@v1
     if: failure() && steps.build.outcome == 'success'
     with:
       name: ${{ matrix.sanitizer }}-artifacts
       path: ./out/artifacts

Understanding results

The results of CIFuzz can be found in two different places.

  • Run fuzzers log:
    1. This log can be accessed in the actions tab of a CIFuzz integrated repo.
    2. Click on the CIFuzz button in the workflow selector on the left hand side.
    3. Click on the event triggered by your desired pull request.
    4. Click the Fuzzing workflow.
    5. Select the Run Fuzzer drop down. It should show the timestamps and results from each of the fuzz targets.

Finding fuzzer output

  • Artifacts:
    1. When a crash is found by CIFuzz the Upload Artifact event is triggered.
    2. This will cause a pop up in the right hand corner, allowing you to download a zip file called artifacts.
    3. artifacts contains two files:
      • test_case - a test case that can be used to reproduce the crash.
      • bug_summary - the stack trace and summary of the crash.

Finding uploaded artifacts

Feedback/Questions/Issues

Create an issue in OSS-Fuzz if you have questions of any other feedback on CIFuzz.