- Replace == HMAC comparisons with hmac.compare_digest (Python) and
hmac.Equal (Go) in ledger.py, verify.py, and audit.go to prevent
timing oracle attacks (Fixes 1-6)
- Increase PBKDF2 iterations from 100K to 210K in both ledger.py and
audit.go — must match for cross-language verification (Fix 7)
- Return chain_valid: null when offset > 0 (paginated views cannot
verify a truncated chain; null means "not computed") (Fix 8)
- Remove module-level AUDIT_LEDGER_SALT attribute from ledger.py; read
the secret exclusively from os.environ inside _get_hmac_key() so the
salt is not exposed in the module namespace (Fix 9)
- Update tests: use monkeypatch.setenv/delenv instead of setattr on the
removed AUDIT_LEDGER_SALT attribute; update testAuditKey helper to
use 210K iterations; add TestAuditQuery_PaginatedOffsetReturnsNullChainValid
- Fix migration 028: workspace_id column type TEXT → UUID to match
workspaces.id UUID primary key
All tests pass: 1043 pytest + 0 Go test failures.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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