Feature Requirements: security-hardening-addendum

Feature Requirements: security-hardening-addendum

Metadata

• Feature: security-hardening-addendum
• Status: APPROVED
• Created: 2026-02-15
• Author: Factory Plan Mode
• Parent: fix/codeql-scanning-alerts (addendum to existing branch)

1. Problem Statement

1.1 Background

Security review of review-fixes-before-merge identified 2 pre-existing low-severity hardening opportunities. Neither is exploitable in the current deployment context, but both violate defense-in-depth principles.

1.2 Problem

• PR title not sanitized: _generate_title() returns raw commit.message data. While the title is passed as a list element to subprocess.run() (no shell injection) and GitHub sanitizes server-side, the PR body is sanitized at output boundary but the title is not — an asymmetry that could become exploitable if the code is adapted for non-GitHub platforms.
• Temp file permission race window: tempfile.NamedTemporaryFile(delete=False) creates files with system default umask (commonly 0o644), then os.chmod(script_path, 0o700) tightens permissions after the write. Brief window where file is world-readable.

1.3 Impact

Low. Neither is currently exploitable. Fixes bring consistency with OWASP defense-in-depth and CWE-377 best practices.

2. Users

2.1 Primary Users

• ZERG maintainers creating PRs via zerg git pr
• ZERG maintainers using zerg git rewrite

2.2 User Stories

• As a maintainer, I want PR titles sanitized at output boundary for defense-in-depth consistency
• As a maintainer, I want temp rebase scripts created with owner-only permissions from the start

3. Functional Requirements

3.1 Detailed Changes

FR-001 (pr_engine.py:509):

# BEFORE:
title = pr_data.get("title", "Update")

# AFTER:
title = _sanitize_pr_content(pr_data.get("title", "Update"))

FR-002 (pr_engine.py:586):

# BEFORE:
content = f"# {pr_data.get('title', 'PR Draft')}\n\n{pr_data.get('body', '')}"

# AFTER:
content = f"# {_sanitize_pr_content(pr_data.get('title', 'PR Draft'))}\n\n{pr_data.get('body', '')}"

FR-003 (history_engine.py:546-570) — replace NamedTemporaryFile with secure creation:

# BEFORE:
with tempfile.NamedTemporaryFile(
    mode="w", suffix=".py", delete=False, prefix="zerg_rebase_",
) as script_file:
    script_path = script_file.name
    # ... write content ...
os.chmod(script_path, 0o700)

# AFTER:
script_dir = tempfile.gettempdir()
fd, script_path = tempfile.mkstemp(suffix=".py", prefix="zerg_rebase_", dir=script_dir)
os.fchmod(fd, 0o700)
with os.fdopen(fd, "w") as script_file:
    # ... write content (unchanged) ...
# Remove os.chmod(script_path, 0o700) — already set via fchmod

FR-004 (history_engine.py:633-662) — same pattern for reorder:

# BEFORE:
with tempfile.NamedTemporaryFile(
    mode="w", suffix=".py", delete=False, prefix="zerg_reorder_",
) as script_file:
    script_path = script_file.name
    # ... write content ...
os.chmod(script_path, 0o700)

# AFTER:
script_dir = tempfile.gettempdir()
fd, script_path = tempfile.mkstemp(suffix=".py", prefix="zerg_reorder_", dir=script_dir)
os.fchmod(fd, 0o700)
with os.fdopen(fd, "w") as script_file:
    # ... write content (unchanged) ...
# Remove os.chmod(script_path, 0o700) — already set via fchmod

3.2 Business Rules

• No behavioral changes — output remains identical
• Temp script content unchanged; only creation mechanism changes
• PR title sanitization mirrors existing body sanitization pattern
• _sanitize_pr_content() uses html.escape() — safe for all text content

4. Non-Functional Requirements

4.1 Performance

• No performance impact

4.2 Security

• Eliminates CWE-79 asymmetry in PR title vs body sanitization
• Eliminates CWE-377 temp file permission race window
• Defense-in-depth improvements only — no active exploit path existed

4.3 Reliability

• All existing tests must pass
• ruff check must show no new lint errors

5. Scope

5.1 In Scope

• pr_engine.py: Sanitize PR title at 2 output boundaries
• history_engine.py: Secure temp file creation at 2 locations
• CHANGELOG.md update

5.2 Out of Scope

• Refactoring _sanitize_pr_content() itself
• Adding new tests (existing test suite covers these paths)
• Any other security findings

5.3 Constraints

• Changes go on existing fix/codeql-scanning-alerts branch
• Must not break any existing tests

6. Dependencies

7. Acceptance Criteria

• PR title sanitized via _sanitize_pr_content() at create() line 509
• PR title sanitized in draft save content at line 586
• Temp rebase script (squash) created with 0o700 from start via mkstemp+fchmod
• Temp rebase script (reorder) created with 0o700 from start via mkstemp+fchmod
• python -m pytest tests/ --timeout=120 — green
• ruff check zerg/git/pr_engine.py zerg/git/history_engine.py — clean

8. Open Questions

9. Approval

10. Documentation Impact Analysis

11. Estimated Effort

2 files changed, ~12 lines modified. Minimal risk. ~5 minutes implementation.