fix(security): fail closed on malformed reviewer source bytes

[seonghobae]

Closes #165.

RCA / remedy

Protected main decoded exact current-head GitHub contents bytes with decode("utf-8", errors="replace"). Malformed bytes were therefore silently normalized to U+FFFD and supplied to the reviewer as if they were exact source evidence.

The narrow repair makes changed-file text decoding strict UTF-8. A malformed current-head blob is retained as an empty changed-file context plus an explicit evidence_failures entry, so the reviewer cannot produce an approval from lossy reconstructed source while normal UTF-8 and unavailable/deleted-content handling remain unchanged.

Exact test-first proof

• RED 09e2618126c12ecf7be294f2fd2d22cb957d94b8: reviewer-ci run 31494975898 checked out that exact head and failed only test_invalid_utf8_changed_file_is_not_normalized_into_review_evidence; actual source evidence was before�after instead of the required empty fail-closed context. 120 other reviewer tests passed. The RED head's application CI and central scan do not override the failing reviewer gate.
• GREEN 4889ad1d0a8d513014e63a26820d305d4f4ae926: application ci 31495630113, reviewer-ci 31495630235, and protected-base eligible central Security Scan 31495630128 all completed success.
• Exact GREEN reviewer proof: 121/121 tests pass; reviewer source totals 632 statements / 150 branches with 0 misses/partials = 100% line+branch coverage; docstring gate = 100%; real no-network CodeGraph sandbox smoke passes; authenticated distroless sandbox image scan reports 0 vulnerabilities.
• Exact base remains protected main c85d710804139c0697d7ef8fa47d02b1389e6d84.
• Fresh formal reviews: 0. Fresh review threads: 0. Green checks/scanners are not independent approval.

Evidence boundary

This repair protects reviewer source integrity only. It is not production/release/legal/acquisition evidence and does not relax the repository's live governance or independent-review requirements.

Summary by CodeRabbit

• 버그 수정

  • UTF-8로 해석할 수 없는 변경 파일이 포함되어도 전체 매니페스트 생성이 중단되지 않습니다.
  • 문제가 있는 파일은 빈 콘텐츠로 처리되고 UTF-8 관련 증거 실패가 기록됩니다.
  • 잘못된 바이트가 대체 문자로 변환되지 않아 파일 콘텐츠가 정확하게 표시됩니다.

• 테스트

  • 비 UTF-8 변경 파일 처리에 대한 회귀 테스트를 추가했습니다.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 0a4761ea-e400-4722-84e4-753bd0cf4393

📥 Commits

Reviewing files that changed from the base of the PR and between c85d710 and 4889ad1.

📒 Files selected for processing (2)

• reviewer/noema_reviewer/github_io.py
• reviewer/tests/test_github_io_utf8_boundary.py

---

📝 Walkthrough

Walkthrough

GitHub 변경 파일 콘텐츠의 UTF-8 디코딩을 엄격하게 처리합니다. 잘못된 바이트는 빈 콘텐츠와 증거 실패로 기록합니다. 다른 파일 처리는 계속합니다. 해당 동작을 검증하는 회귀 테스트를 추가합니다.

Changes

UTF-8 증거 처리

Layer / File(s)	Summary
엄격한 디코딩과 파일별 실패 처리 reviewer/noema_reviewer/github_io.py, reviewer/tests/test_github_io_utf8_boundary.py	Base64 콘텐츠를 엄격히 UTF-8로 디코딩합니다. 디코딩 오류가 발생한 파일은 경로를 유지하고 빈 콘텐츠와 증거 실패를 기록합니다. 회귀 테스트는 U+FFFD가 생성되지 않는지 검증합니다.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	제목은 잘못된 UTF-8 리뷰 소스 바이트를 fail closed로 처리하는 핵심 변경을 정확하고 간결하게 설명합니다.
Linked Issues check	✅ Passed	변경은 엄격한 UTF-8 디코딩, 명시적 evidence_failures 기록, 기존 정상·삭제 파일 처리를 포함하여 이슈 #165의 요구사항을 충족합니다.
Out of Scope Changes check	✅ Passed	변경은 GitHub 파일 디코딩 수정과 해당 회귀 테스트로 제한되며, 이슈 #165의 범위를 벗어난 변경이 없습니다.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/reviewer-strict-utf8-evidence

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}