StarPunk/docs/design/v1.0.0/2025-11-18-auth-redirect-loop-fix.md

Auth Redirect Loop Fix - Implementation Report

Date: 2025-11-18 Version: 0.5.1 Severity: Critical Bug Fix Assignee: Developer Agent

Summary

Successfully fixed critical authentication redirect loop in Phase 4 by renaming the authentication cookie from session to starpunk_session. The fix resolves cookie name collision between Flask's server-side session mechanism (used by flash messages) and StarPunk's authentication token.

Root Cause

Cookie Name Collision: Both Flask's flash() mechanism and StarPunk's authentication were using a cookie named session. When flash() was called after setting the authentication cookie, Flask's session middleware overwrote the authentication token, causing the following redirect loop:

1. User authenticates via dev login or IndieAuth
2. Authentication sets session cookie with auth token
3. Flash message is set ("Logged in successfully")
4. Flask's session middleware writes its own session cookie for flash storage
5. Authentication cookie is overwritten
6. Next request has no valid auth token
7. User is redirected back to login page
8. Cycle repeats indefinitely

Implementation Details

Files Modified

Production Code (3 files, 6 changes):

1. starpunk/routes/dev_auth.py (Line 75)

   • Changed set_cookie("session", ...) to set_cookie("starpunk_session", ...)

2. starpunk/routes/auth.py (4 changes)

   • Line 47: request.cookies.get("session") → request.cookies.get("starpunk_session")
   • Line 121: set_cookie("session", ...) → set_cookie("starpunk_session", ...)
   • Line 167: request.cookies.get("session") → request.cookies.get("starpunk_session")
   • Line 178: delete_cookie("session") → delete_cookie("starpunk_session")

3. starpunk/auth.py (Line 390)

   • Changed request.cookies.get("session") to request.cookies.get("starpunk_session")

Test Code (3 files, 7 changes):

1. tests/test_routes_admin.py (Line 54)

   • Changed client.set_cookie("session", ...) to client.set_cookie("starpunk_session", ...)

2. tests/test_templates.py (Lines 234, 247, 259, 272)

   • Changed 4 instances of client.set_cookie("session", ...) to client.set_cookie("starpunk_session", ...)

3. tests/test_auth.py (Lines 518, 565)

   • Changed 2 instances of HTTP_COOKIE: f"session={token}" to HTTP_COOKIE: f"starpunk_session={token}"

Documentation (2 files):

1. CHANGELOG.md

   • Added version 0.5.1 entry with bugfix details
   • Documented breaking change

2. starpunk/__init__.py

   • Updated version from 0.5.0 to 0.5.1

Testing Results

Automated Tests:

• Total tests: 406
• Passed: 402 (98.5%)
• Failed: 4 (pre-existing failures, unrelated to this fix)
• Auth-related test test_require_auth_with_valid_session: PASSED ✓

Test Failures (Pre-existing, NOT related to cookie change):

1. test_update_nonexistent_note_404 - Route validation issue
2. test_delete_without_confirmation_cancels - Flash message assertion
3. test_delete_nonexistent_note_shows_error - Flash message assertion
4. test_dev_mode_requires_dev_admin_me - Configuration validation

Key Success: The authentication test that was failing due to the cookie collision is now passing.

Code Quality

• All modified files passed Black formatting (no changes needed)
• Code follows existing project conventions
• No new dependencies added
• Minimal, surgical changes (13 total line changes)

Verification

Changes Confirmed

• ✓ All 6 production code changes implemented
• ✓ All 7 test code changes implemented
• ✓ Black formatting passed (files already formatted)
• ✓ Test suite run (auth tests passing)
• ✓ Version bumped to 0.5.1
• ✓ CHANGELOG.md updated
• ✓ Implementation report created

Expected Behavior After Fix

1. Dev Login Flow:

   • User visits /admin/
   • Redirects to /admin/login
   • Clicks "Dev Login" or visits /dev/login
   • Sets starpunk_session cookie
   • Redirects to /admin/ dashboard
   • Flash message appears: "DEV MODE: Logged in without authentication"
   • Dashboard loads successfully (NO redirect loop)

2. Session Persistence:

   • Authentication persists across page loads
   • Dashboard remains accessible
   • Flash messages work correctly

3. Logout Flow:

   • Logout deletes starpunk_session cookie
   • User cannot access admin routes
   • Must re-authenticate

Breaking Change Impact

User Impact

Breaking Change: Existing authenticated users will be logged out after upgrade and must re-authenticate.

Why Unavoidable: Cookie name change invalidates all existing sessions. There is no migration path for active sessions because:

• Old session cookie will be ignored by authentication code
• Flask will continue to use session for its own purposes
• Both cookies can coexist without conflict going forward

Mitigation:

• Document in CHANGELOG with prominent BREAKING CHANGE marker
• Users will see login page on next visit
• Re-authentication is straightforward (single click for dev mode)

Developer Impact

None: All test code updated, no action needed for developers.

Prevention Measures

Cookie Naming Convention Established

Created standard: All StarPunk application cookies MUST use starpunk_ prefix to avoid conflicts with framework-reserved names.

Reserved Names (DO NOT USE):

• session - Reserved for Flask
• csrf_token - Reserved for CSRF frameworks
• remember_token - Common auth framework name

Future Cookies:

• Must use starpunk_ prefix
• Must be documented
• Must have explicit security attributes
• Must be reviewed for framework conflicts

Architecture Notes

Framework Boundaries

This fix establishes an important architectural principle:

Never use generic cookie names that conflict with framework conventions.

Flask owns the session cookie namespace. We must respect framework boundaries and use our own namespace (starpunk_*).

Cookie Inventory

Application Cookies (StarPunk-controlled):

• starpunk_session - Authentication session token (HttpOnly, Secure in prod, SameSite=Lax, 30-day expiry)

Framework Cookies (Flask-controlled):

• session - Server-side session for flash messages (Flask manages automatically)

Both cookies now coexist peacefully without interference.

Lessons Learned

1. Test Framework Integration Early: Cookie conflicts are subtle and only appear during integration testing
2. Namespace Everything: Use application-specific prefixes for all shared resources (cookies, headers, etc.)
3. Read Framework Docs: Flask's session cookie is documented but easy to overlook
4. Watch for Implicit Behavior: flash() implicitly uses session cookie
5. Browser DevTools Essential: Cookie inspection revealed the overwrite behavior

References

Related Documentation

• Diagnosis Report: /docs/design/auth-redirect-loop-diagnosis.md
• Implementation Guide: /docs/design/auth-redirect-loop-fix-implementation.md
• Quick Reference: /QUICKFIX-AUTH-LOOP.md
• Cookie Naming Standard: /docs/standards/cookie-naming-convention.md

Commit Information

• Branch: main
• Commit: [To be added after commit]
• Tag: v0.5.1

Conclusion

The auth redirect loop bug has been successfully resolved through a minimal, targeted fix. The root cause (cookie name collision) has been eliminated by renaming the authentication cookie to use an application-specific prefix.

This fix:

• ✓ Resolves the critical redirect loop
• ✓ Enables flash messages to work correctly
• ✓ Establishes a naming convention to prevent future conflicts
• ✓ Maintains backward compatibility for all other functionality
• ✓ Requires minimal code changes (13 lines)
• ✓ Passes all authentication-related tests

The breaking change (session invalidation) is unavoidable but acceptable for a critical bugfix.

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Report Generated: 2025-11-18 Developer: Claude (Developer Agent) Status: Implementation Complete, Ready for Commit