π‘οΈ Sentinel: [MEDIUM] Fix TOCTOU in index generation#247
π‘οΈ Sentinel: [MEDIUM] Fix TOCTOU in index generation#247seonghobae wants to merge 1 commit into
Conversation
β¦on via Atomic Move with Fallback
|
π Jules, reporting for duty! I'm here to lend a hand with this pull request. When you start a review, I'll add a π emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down. I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job! For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with New to Jules? Learn more at jules.google/docs. For security, I will only act on instructions from the user who triggered this task. |
There was a problem hiding this comment.
Pull request overview
This PR hardens html4treeβs index.html generation by attempting an atomic replace (to avoid readers seeing a partially updated index) and providing a safe fallback path when the filesystem does not support atomic moves.
Changes:
- Updated
write_index_fileto preferFiles.move(..., ATOMIC_MOVE, REPLACE_EXISTING)and fall back toREPLACE_EXISTINGwhenAtomicMoveNotSupportedExceptionis thrown. - Added a unit test that forces the atomic-move-not-supported path to exercise the fallback logic.
- Documented the βatomic move + fallbackβ learning in
.jules/sentinel.md.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/main/kotlin/html4tree/main.kt | Uses ATOMIC_MOVE for index replacement with a fallback when atomic moves arenβt supported. |
| src/test/kotlin/html4tree/MainTest.kt | Adds coverage for the AtomicMoveNotSupportedException fallback path. |
| .jules/sentinel.md | Records the atomic move mitigation guidance for future prevention. |
π‘ Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
| val testFile = File(tempDir, "testWriteIndexDir") | ||
| testFile.mkdir() |
| try { | ||
| moveFile(tempPath, indexPath) | ||
| } catch (e: AtomicMoveNotSupportedException) { | ||
| Files.move(tempPath, indexPath, StandardCopyOption.REPLACE_EXISTING) | ||
| } |
| **Vulnerability:** νμΌμ΄ μ°μ¬μ§λ λμ(μ: `index.html` μμ± μ€) λΆλΆμ μΌλ‘ μμ±λ νμΌμ λ€λ₯Έ νλ‘μΈμ€κ° μ½κ² λμ΄ λ°μν μ μλ λ μ΄μ€ 컨λμ λ° TOCTOU μ·¨μ½μ . | ||
| **Learning:** μ μ νμΌ μμ± κ³Όμ μμ μμ νμΌμ μ΄λμν¬ λ λ¨μν `REPLACE_EXISTING`λ§ μ¬μ©νλ©΄ νμΌ μμ€ν μ λ°λΌ μμ ν μμμ μΌλ‘ 볡μ¬/μ΄λλμ§ μμ μ μμ΅λλ€. | ||
| **Prevention:** `Files.move` μ `StandardCopyOption.ATOMIC_MOVE`λ₯Ό μ¬μ©νκ³ , ν΄λΉ μ΅μ μ μ§μνμ§ μλ νμΌ μμ€ν μ μν΄ `AtomicMoveNotSupportedException` λ°μ μ `REPLACE_EXISTING`μΌλ‘ λ체νλ Fallback λ‘μ§μ ꡬννμ¬ μμ ν νμΌ μ λ°μ΄νΈλ₯Ό 보μ₯ν΄μΌ ν©λλ€. |
π¨ Severity: MEDIUM
π‘ Vulnerability: A Time-of-Check to Time-of-Use (TOCTOU) race condition could occur during the generation of
index.html. External processes might read a partially written file becauseFiles.movewith justREPLACE_EXISTINGdoes not guarantee atomic operation across all filesystems.π― Impact: Partially written HTML indexes could be served to users, potentially causing broken pages or unexpected behavior in automated systems parsing the directory index.
π§ Fix: Upgraded the
Files.moveoperation to useStandardCopyOption.ATOMIC_MOVE. To maintain cross-platform compatibility and prevent crashes on filesystems that do not support atomic moves, wrapped the call in atry-catchblock that gracefully falls back to a standardREPLACE_EXISTINGmove if anAtomicMoveNotSupportedExceptionis thrown.β Verification: Tested via unit tests ensuring 100% JaCoCo instruction coverage of the fallback logic. All tests pass successfully.
PR created automatically by Jules for task 13512999805702888854 started by @seonghobae