fix: eliminate TOCTOU race conditions in ssl-bump.ts#766
fix: eliminate TOCTOU race conditions in ssl-bump.ts#766
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Replace check-then-act pattern (existsSync + writeFileSync) with atomic file creation using the 'wx' flag (O_WRONLY | O_CREAT | O_EXCL). This eliminates time-of-check-time-of-use race conditions where a file could be created between the existence check and the write operation. Fixes #174, #175. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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| Metric | Base | PR | Delta |
|---|---|---|---|
| Lines | 82.26% | 82.44% | 📈 +0.18% |
| Statements | 82.31% | 82.40% | 📈 +0.09% |
| Functions | 82.14% | 82.14% | ➡️ +0.00% |
| Branches | 74.70% | 74.60% | 📉 -0.10% |
📁 Per-file Coverage Changes (2 files)
| File | Lines (Before → After) | Statements (Before → After) |
|---|---|---|
src/ssl-bump.ts |
100.0% → 100.0% (+0.00%) | 100.0% → 96.7% (-3.28%) |
src/docker-manager.ts |
83.5% → 84.2% (+0.67%) | 83.0% → 83.6% (+0.65%) |
Coverage comparison generated by scripts/ci/compare-coverage.ts
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Pull request overview
This PR eliminates TOCTOU (time-of-check-time-of-use) race conditions in SSL certificate database initialization by replacing the check-then-act pattern (existsSync + writeFileSync) with atomic file creation using the wx flag. The wx flag combines O_WRONLY | O_CREAT | O_EXCL operations atomically, ensuring files are created only if they don't exist, and throwing EEXIST if they already exist. This is a proactive security hardening improvement.
Changes:
- Replaced
existsSync+writeFileSyncpattern with atomicwriteFileSyncusingflag: 'wx'forindex.txtfile creation - Replaced
existsSync+writeFileSyncpattern with atomicwriteFileSyncusingflag: 'wx'forsizefile creation - Added proper error handling that catches
EEXISTerrors (expected when file exists) and re-throws other errors
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| if (!fs.existsSync(sslDbPath)) { | ||
| fs.mkdirSync(sslDbPath, { recursive: true, mode: 0o700 }); | ||
| } | ||
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| // Create certs subdirectory | ||
| if (!fs.existsSync(certsPath)) { | ||
| fs.mkdirSync(certsPath, { mode: 0o700 }); | ||
| } |
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The existsSync checks before mkdirSync are unnecessary when using recursive: true, and create a minor TOCTOU pattern. While mkdirSync with recursive: true is generally safe (it succeeds silently if the directory exists), the check-then-act pattern is inconsistent with the atomic approach used for file creation below. Consider removing the existsSync checks and calling mkdirSync directly, which will handle existing directories gracefully.
See below for a potential fix:
// Create the database structure (idempotent; succeeds if it already exists)
fs.mkdirSync(sslDbPath, { recursive: true, mode: 0o700 });
// Create certs subdirectory (idempotent; succeeds if it already exists)
fs.mkdirSync(certsPath, { recursive: true, mode: 0o700 });
| try { | ||
| fs.writeFileSync(indexPath, '', { flag: 'wx', mode: 0o600 }); | ||
| } catch (e: unknown) { | ||
| if ((e as NodeJS.ErrnoException).code !== 'EEXIST') throw e; | ||
| } |
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The PR description references issues #174 and #175 as being fixed by this change, but those issues are just smoke test results that passed. There doesn't appear to be an actual issue or discussion about TOCTOU vulnerabilities in the codebase. This appears to be a proactive security improvement rather than fixing a reported bug. Consider updating the PR description to clarify that this is a security hardening improvement rather than a bug fix, or reference the correct issues if they exist.
C++ Build Test Results
Overall: PASS ✅ All C++ projects built successfully using CMake and make.
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Smoke Test ResultsLast 2 merged PRs:
Tests:
Status: PASS
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Node.js Build Test Results
Overall: PASS ✅ All Node.js projects built and tested successfully.
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✅ .NET Build Test Results
Overall: PASS All .NET projects successfully restored, built, and ran.
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Go Build Test Results
Overall: PASS ✅ All Go projects built and tested successfully.
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Build Test: Rust - ❌ FAILEDError: Rust toolchain not installed in workflow environment. The workflow requires Required FixAdd Rust toolchain setup to the workflow before running this test: - name: Install Rust
uses: dtolnay/rust-toolchain@stableTest Status
Overall: FAILED - Missing Rust toolchain
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Bun Build Test Results
Overall: PASS All Bun projects built and tested successfully.
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Deno Build Test Results ✅
Overall: PASS All Deno tests completed successfully.
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Smoke Test Results Last 2 merged PRs:
✅ GitHub MCP Status: PASS
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Chroot Test Results
Overall Status: ❌ Tests failed (1/3 passed) The chroot environment successfully detected and used Go from the host, but Python and Node.js version mismatches indicate the host binaries were not properly accessed through chroot.
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PR titles:
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@copilot bump up the test coverage so that https://github.com/github/gh-aw-firewall/actions/runs/21962659711/job/63444019960?pr=766 doesn't fail |
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Closing PR in favor of tracking issue #838. |
Summary
existsSync+writeFileSync) with atomic file creation using thewxflag (O_WRONLY | O_CREAT | O_EXCL) ininitSslDb()wxflag atomically creates and writes only if the file doesn't exist, throwingEEXISTif it already existsTest plan
npm run buildcompiles without errorsnpm test— all 748 tests pass across 19 suitesssl-bump.test.tstests continue to passFixes #174, #175.
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