Gondulf/docs/reports/2025-11-22-dns-verification-bug-fix.md

Implementation Report: DNS Verification Bug Fix

Date: 2025-11-22 Developer: Claude (Developer Agent) Design Reference: /docs/designs/dns-verification-bug-fix.md

Summary

Fixed a critical bug in the DNS TXT record verification that caused domain verification to always fail. The code was querying the base domain (e.g., example.com) instead of the _gondulf.{domain} subdomain (e.g., _gondulf.example.com) where users are instructed to place their TXT records. The fix modifies the verify_txt_record method in src/gondulf/dns.py to prefix the domain with _gondulf. when the expected value is gondulf-verify-domain. All tests pass with 100% coverage on the DNS module.

What Was Implemented

Components Modified

1. src/gondulf/dns.py - DNSService class

   • Modified verify_txt_record method to query the correct subdomain
   • Updated docstring to document the Gondulf-specific behavior
   • Updated all logging statements to include both the requested domain and the queried domain

2. tests/unit/test_dns.py - DNS unit tests

   • Added new test class TestGondulfDomainVerification with 7 test cases
   • Tests verify the critical bug fix behavior
   • Tests ensure backward compatibility for non-Gondulf TXT verification

Key Implementation Details

The fix implements Option A from the design document - modifying the existing verify_txt_record method rather than creating a new dedicated method. This keeps the fix localized and maintains backward compatibility.

Core logic added:

# For Gondulf domain verification, query _gondulf subdomain
if expected_value == "gondulf-verify-domain":
    query_domain = f"_gondulf.{domain}"
else:
    query_domain = domain

Logging updates:

• Success log now shows: "TXT record verification successful for domain={domain} (queried {query_domain})"
• Failure log now shows: "TXT record verification failed: expected value not found for domain={domain} (queried {query_domain})"
• Error log now shows: "TXT record verification failed for domain={domain} (queried {query_domain}): {e}"

How It Was Implemented

Approach

1. Reviewed design document - Confirmed Option A (modify existing method) was the recommended approach
2. Reviewed standards - Checked coding.md and testing.md for requirements
3. Implemented the fix - Single edit to verify_txt_record method
4. Added comprehensive tests - Created new test class covering all scenarios from design
5. Ran full test suite - Verified no regressions

Deviations from Design

No deviations from design.

The implementation follows the design document exactly:

• Used Option A (modify verify_txt_record method)
• Added the domain prefixing logic as specified
• Updated logging to show both domains
• No changes needed to authorization router or templates

Issues Encountered

No significant issues encountered.

The fix was straightforward as designed. The existing code structure made the change clean and isolated.

Test Results

Test Execution

============================= test session starts ==============================
platform linux -- Python 3.11.14, pytest-9.0.1, pluggy-1.6.0
plugins: anyio-4.11.0, asyncio-1.3.0, mock-3.15.1, cov-7.0.0, Faker-38.2.0
collected 487 items

[... all tests ...]

================= 482 passed, 5 skipped, 36 warnings in 20.00s =================

Test Coverage

• Overall Coverage: 90.44%
• DNS Module Coverage: 100% (src/gondulf/dns.py)
• Coverage Tool: pytest-cov 7.0.0

Test Scenarios

New Unit Tests Added (TestGondulfDomainVerification)

1. test_gondulf_verification_queries_prefixed_subdomain - Critical test verifying the bug fix

   • Verifies verify_txt_record("example.com", "gondulf-verify-domain") queries _gondulf.example.com

2. test_gondulf_verification_with_missing_txt_record - Tests NoAnswer handling

   • Verifies returns False when no TXT records exist at _gondulf.{domain}

3. test_gondulf_verification_with_wrong_txt_value - Tests value mismatch

   • Verifies returns False when TXT value doesn't match

4. test_non_gondulf_verification_queries_base_domain - Backward compatibility test

   • Verifies other TXT verification still queries base domain (not prefixed)

5. test_gondulf_verification_with_nxdomain - Tests NXDOMAIN handling

   • Verifies returns False when _gondulf.{domain} doesn't exist

6. test_gondulf_verification_among_multiple_txt_records - Tests multi-record scenarios

   • Verifies correct value found among multiple TXT records

7. test_gondulf_verification_with_subdomain - Tests subdomain handling

   • Verifies blog.example.com queries _gondulf.blog.example.com

Existing Tests (All Pass)

All 22 existing DNS tests continue to pass, confirming no regressions:

• TestDNSServiceInit (1 test)
• TestGetTxtRecords (7 tests)
• TestVerifyTxtRecord (7 tests)
• TestCheckDomainExists (5 tests)
• TestResolverFallback (2 tests)

Test Results Analysis

• All 29 DNS tests pass (22 existing + 7 new)
• 100% coverage on dns.py module
• Full test suite (487 tests) passes with no regressions
• 5 skipped tests are unrelated (SQL injection tests awaiting implementation)
• Deprecation warnings are unrelated to this change (FastAPI/Starlette lifecycle patterns)

Technical Debt Created

No technical debt identified.

The fix is clean, well-tested, and follows the existing code patterns. The implementation matches the design exactly.

Next Steps

1. Manual Testing - Per the design document, manual testing with a real DNS record is recommended:

   • Configure real DNS record: _gondulf.yourdomain.com with value gondulf-verify-domain
   • Test authorization flow
   • Verify successful DNS verification
   • Check logs show correct domain being queried

2. Deployment - This is a P0 critical bug fix that should be deployed to production as soon as testing is complete.

Sign-off

Implementation status: Complete Ready for Architect review: Yes