🛡️ Sentinel: [HIGH] 이메일 헤더의 CRLF 인젝션 취약점 수정

[seonghobae]

Security defect

SendEmailRequest did not apply one explicit CR/LF rejection rule consistently across all user-controlled SMTP header fields. The API must fail before dispatch when to, subject, in_reply_to, or references contains an isolated CR or LF.

Root-cause fix

• run a mode="before" field validator across all four fields;
• reject both chr(13) and chr(10);
• exercise eight route-level cases (four fields × two newline characters);
• assert HTTP 422 and that send_email is never called;
• keep the security decision record aligned with the implemented field set.

CodeRabbit identified the missing to alignment on predecessor head e7fd1b994f7be7c43494aca6cf92b4fc64285dfc. Commits 6059aa56ca7c3a5ea8b1dedf5ad4d22ec82be886 and 0b41c9677d33a5cfe73ad9062c9124b8ee8fa90b added the recipient boundary and tests; all three review threads are resolved and CodeRabbit approved the exact current head.

Exact-head evidence

For 0b41c9677d33a5cfe73ad9062c9124b8ee8fa90b against live develop@f781701f108cacae08bf1b0749b62ddb8b8385fd:

• Bandit 31468086850: success;
• Dependency Review 31468086882: success;
• SAST Semgrep 31468086887: success;
• Security Scan 31468086893: success;
• Application CI 31468086892: backend and frontend jobs success;
• container build 31468087100: still in progress.

Pending, predecessor, or status-only evidence is not merge approval. Merge only after the unchanged head satisfies the remaining container, repository policy, and independent review gates.

[google-labs-jules]

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[coderabbitai]

📝 Walkthrough

Walkthrough

The email request model now rejects CR/LF characters in subject, in_reply_to, and references. Parameterized tests cover all injection cases and confirm that sending is blocked. Security documentation records the validation requirement.

Changes

Email header validation

Layer / File(s)	Summary
CRLF validation backend/api/emails.py	SendEmailRequest validates subject, in_reply_to, and references and rejects carriage-return or line-feed characters.
Validation coverage and security record backend/tests/test_emails_api.py, .jules/sentinel.md	Parameterized tests cover CR and LF injection in each validated field. The security finding documents the required early validation.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: codex

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the CRLF injection vulnerability fix in email headers, which matches the main change.

✨ 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 sentinel-fix-crlf-14919358368017569235

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[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In @.jules/sentinel.md:
- Around line 132-135: Update the prevention record in the CRLF injection
documentation to match the implementation: either extend the SendEmailRequest
validator and API tests to cover the to field alongside subject, in_reply_to,
and references, or revise the record to list only the fields currently
validated. Keep the documented guarantee consistent with the actual model and
test coverage.

In `@backend/api/emails.py`:
- Around line 696-703: Extend reject_crlf to validate the to field, then add CR
and LF API cases in backend/tests/test_emails_api.py lines 1822-1848 matching
the existing 422 and no-dispatch assertions. Keep the four-field prevention rule
in .jules/sentinel.md lines 132-135, since implementation and tests must enforce
all four headers.

In `@backend/tests/test_emails_api.py`:
- Around line 1822-1848: Extend the parameterization in
test_send_email_endpoint_rejects_header_injection to include both CR and LF
newline cases for the to field. Preserve the existing expected 422 response and
mock_send_email.assert_not_called() assertions so the API boundary is explicitly
covered.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 4b96bfad-8e70-4080-bb7d-26143d82d4ae

📥 Commits

Reviewing files that changed from the base of the PR and between f781701 and e7fd1b9.

📒 Files selected for processing (3)

• .jules/sentinel.md
• backend/api/emails.py
• backend/tests/test_emails_api.py

[github-actions]

PR governance metadata gate update for 0b41c9677d33a5cfe73ad9062c9124b8ee8fa90b: no current blocking failures remain.

PR governance metadata gate is ready; all current-head requirements passed.