fix(security): reject unknown MIME types in macOS image reader (#24)

[cmeans-claude-dev]

Summary

• _macos_read_image now rejects MIME types not in the UTI reverse map with ClipboardError instead of interpolating them raw into an AppleScript string literal
• Eliminates a potential script injection vector via crafted MIME types containing "
• Supported image types: image/png, image/tiff, image/jpeg (all mapped via _UTI_TO_MIME)

Test plan

• uv run pytest tests/test_server.py::test_macos_read_image_unknown_mime_rejected -v passes
• uv run pytest tests/test_server.py::test_macos_read_image_injection_rejected -v passes
• uv run pytest tests/test_server.py::test_macos_read_image -v still passes (known types work)
• uv run pytest tests/test_server.py::test_macos_read_image_jpeg_uti -v still passes (UTI mapping works)
• Full suite: uv run pytest -q -- 429 passed, 11 xfailed

Closes #24

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[cmeans]

QA Review — PR #47

Verdict: One observation. QA Failed pending a PR body edit.

Code review

Fix correctness: The old code uti = mime_to_uti.get(mime_type, mime_type) fell back to raw mime_type as the UTI, which was then interpolated into an AppleScript string literal. A crafted MIME type containing " could break out of the string and inject AppleScript commands. The new code rejects unknown types at the boundary with ClipboardError. Defense in depth — correct fix. ✓

Supported types: Only image/png, image/tiff, image/jpeg (the three types in _UTI_TO_MIME). Narrowing to known types is the right approach for a security fix. ✓

Error message: f"Unsupported image type: {mime_type}" — user input in an exception string, no injection risk in Python. ✓

Tests

Targeted (4/4 pass):

• test_macos_read_image_unknown_mime_rejected — image/webp (valid MIME, no UTI mapping) → ClipboardError ✓
• test_macos_read_image_injection_rejected — image/png"; -- (injection payload) → ClipboardError ✓
• test_macos_read_image — known type still works ✓
• test_macos_read_image_jpeg_uti — UTI mapping still works ✓

Full suite: 429 passed, 11 xfailed, 0 failed, 0 skipped ✓

The old test (test_macos_read_image_unknown_mime_passthrough) that asserted the insecure passthrough behavior is properly replaced — not just removed, but replaced with the rejection + injection tests. Good test evolution. ✓

Other checks

• CHANGELOG: ### Fixed entry, correct category (security fix), accurate description, Closes #24. ✓
• CI: test (3.11/3.12/3.13), codecov/patch SUCCESS, QA Gate pending ✓
• Diff scope: 3 files (clipboard.py, test_server.py, CHANGELOG.md), +19/-13, single commit. Clean. ✓

Finding

F1 (observation) — PR body test count is stale.

PR body says: Full suite: uv run pytest -q -- 240 passed
Actual result: 429 passed, 11 xfailed

The branch includes #44, #45, and #46 content (test_escaping.py is present, all 189+11 escaping tests run). The expected count needs updating.

Fix: Edit PR body checkbox 5 from 240 passed to 429 passed, 11 xfailed. No commit needed.

Merge coordination note

This branch includes #44, #45, #46 content. Adding merge-order: 4 — merge after all three land. The CHANGELOG diff should auto-merge cleanly since the #24 entry appends to the Fixed section whose context lines (#16, #17) are stable.

[cmeans]

Applying QA Failed — code and tests are solid, but PR body claims '240 passed' when actual is '429 passed, 11 xfailed' (branch includes #46's escaping matrix). Edit the PR body to fix the count — no commit needed.

[cmeans]

QA Re-review — PR #47 (round 2)

Verdict: F1 resolved. Zero findings. Ready for maintainer signoff.

F1: fixed ✓

PR body checkbox 5 now says 429 passed, 11 xfailed — matches actual output on head f27bbef.

Re-verification (all 5 checkboxes on new head)

CHECKBOX 1: test_macos_read_image_unknown_mime_rejected  PASSED
CHECKBOX 2: test_macos_read_image_injection_rejected     PASSED
CHECKBOX 3: test_macos_read_image                        PASSED
CHECKBOX 4: test_macos_read_image_jpeg_uti               PASSED
CHECKBOX 5: Full suite — 429 passed, 11 xfailed          PASSED (matches PR body)

Code, tests, CHANGELOG, CI all unchanged from round 1 review (which had zero code findings). Applying Ready for QA Signoff.

[cmeans]

Applying Ready for QA Signoff. F1 resolved — PR body count matches actual (429 passed, 11 xfailed). All 5 checkboxes verified on new head f27bbef. Zero findings.

[cmeans]

LGTM