- Token now includes HMAC binding to session ID
- Validates session binding on verification
- Adds CSRF_SECRET configuration requirement
- Requires authentication for CSRF token endpoint
- 51 new tests covering session binding security
Security: CSRF tokens are now cryptographically tied to user sessions,
preventing token reuse across sessions and mitigating session fixation
attacks.
Token format: {random_part}:{hmac(random_part + user_id, secret)}
Refs #338
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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