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feat: add thread-safe SetExpectedState for cross-request OAuth flows #500

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Merged
merged 1 commit into from
Aug 4, 2025
Merged

feat: add thread-safe SetExpectedState for cross-request OAuth flows #500

merged 1 commit into from
Aug 4, 2025

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sd2k
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@sd2k sd2k commented Jul 22, 2025 •
edited by coderabbitai bot
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Description

This PR adds the SetExpectedState method to the OAuthHandler, which enables OAuth state management when initialization and callback steps are handled by different OAuthHandler instances, such as in web servers where separate HTTP request handlers process the auth flow stages.

It also protects the expectedState with a mutex to ensure thread-safe access and modification, and adds a test for the new method.

Type of Change

  • Bug fix (non-breaking change that fixes an issue)
  • New feature (non-breaking change that adds functionality)
  • MCP spec compatibility implementation
  • Breaking change (fix or feature that would cause existing functionality to not work as expected)
  • Documentation update
  • Code refactoring (no functional changes)
  • Performance improvement
  • Tests only (no functional changes)
  • Other (please describe):

Checklist

  • My code follows the code style of this project
  • I have performed a self-review of my own code
  • I have added tests that prove my fix is effective or that my feature works
  • I have updated the documentation accordingly

Additional Information

I'm using this code inside an MCP client already, so it has some real-world usage, if that helps with justification!

Summary by CodeRabbit

  • Bug Fixes

    • Improved the reliability of OAuth authentication by ensuring safe handling of state values during concurrent OAuth flows.

  • Tests

    • Added tests to verify correct management of OAuth state across multiple authentication requests.

@sd2k
feat: add thread-safe SetExpectedState for cross-request OAuth flows
7d0613f 
Enables OAuth state management when initialization and callback steps
are handled by different OAuthHandler instances, such as in web servers
where separate HTTP request handlers process the auth flow stages.

- Add SetExpectedState method for explicit state configuration
- Add mutex protection for thread-safe expectedState access
- Add comprehensive test for cross-request scenario validation
@coderabbitai coderabbitai
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coderabbitai bot commented Jul 22, 2025 •
edited
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Walkthrough

Thread-safe synchronization was added to the OAuthHandler's expectedState field in the OAuth flow implementation. A mutex now protects concurrent access, with new methods for safely setting and retrieving the state. Tests were added to verify correct state handling across multiple handler instances, simulating real-world OAuth request flows.

Changes

File(s) Change Summary
client/transport/oauth.go Added RWMutex to OAuthHandler; introduced SetExpectedState method; updated methods for thread-safe access to expectedState.
client/transport/oauth_test.go Added test for cross-request expectedState handling across multiple OAuthHandler instances.

Estimated code review effort

2 (~15 minutes)

📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 7c38b56 and 7d0613f.

📒 Files selected for processing (2)
  • client/transport/oauth.go (4 hunks)
  • client/transport/oauth_test.go (1 hunks)
🧠 Learnings (1)
client/transport/oauth_test.go (1)

Learnt from: octo
PR: #149
File: mcptest/mcptest.go:0-0
Timestamp: 2025-04-21T21:26:32.945Z
Learning: In the mcptest package, prefer returning errors from helper functions rather than calling t.Fatalf() directly, giving callers flexibility in how to handle errors.

🧰 Additional context used
🧠 Learnings (1)
client/transport/oauth_test.go (1)

Learnt from: octo
PR: #149
File: mcptest/mcptest.go:0-0
Timestamp: 2025-04-21T21:26:32.945Z
Learning: In the mcptest package, prefer returning errors from helper functions rather than calling t.Fatalf() directly, giving callers flexibility in how to handle errors.

🔇 Additional comments (7)
client/transport/oauth.go (6)

13-13: LGTM: Sync import added for mutex support.

The addition of the sync package import is necessary for the new mutex-based thread synchronization.

119-121: LGTM: Thread-safe protection added for expectedState.

The addition of the RWMutex and updated comment correctly establishes thread-safe access patterns for the expectedState field, which is critical for CSRF protection in concurrent OAuth flows.

268-271: LGTM: Thread-safe read access implemented correctly.

The GetExpectedState method properly uses RLock for concurrent read access while maintaining thread safety.

273-287: LGTM: Well-documented SetExpectedState method with proper thread safety.

The implementation is excellent:

  • Comprehensive documentation explaining the cross-request use case
  • Proper write lock usage for thread-safe state modification
  • Clear method signature and purpose

The documentation effectively addresses the key scenario where OAuth initialization and callback are handled by different handler instances.

570-584: LGTM: Atomic state validation and clearing implemented correctly.

The locking strategy is well-implemented:

  • Single write lock acquisition for atomic read-validate-clear operation
  • Early unlock on validation failure to avoid holding lock unnecessarily
  • State cleared after successful validation to prevent reuse

This prevents race conditions during concurrent authorization response processing.

655-655: LGTM: Consistent use of SetExpectedState method.

The change from direct assignment to using the SetExpectedState method ensures consistent thread-safe access patterns throughout the codebase.

client/transport/oauth_test.go (1)

304-395: LGTM: Comprehensive test coverage for cross-request OAuth scenario.

This test excellently validates the new SetExpectedState functionality:

Strengths:

  • Simulates realistic multi-request OAuth flow with separate handler instances
  • Tests state transfer, validation, and clearing behavior
  • Includes both positive (correct state) and negative (wrong state) test cases
  • Verifies proper error types (ErrInvalidState vs other errors)
  • Confirms state is cleared after processing to prevent reuse

Test Flow:

  1. ✅ Handler1 generates and stores state during authorization URL creation
  2. ✅ Handler2 starts with empty state (separate instance simulation)
  3. ✅ State transfer using SetExpectedState
  4. ✅ Validation with correct state (passes CSRF check, fails at token exchange as expected)
  5. ✅ State clearing verification
  6. ✅ Validation with incorrect state (proper ErrInvalidState)

The test comprehensively covers the thread-safe state management functionality and the cross-request scenario described in the PR objectives.

✨ Finishing Touches
  • 📝 Generate Docstrings

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@ezynda3 ezynda3 merged commit 9259d32 into mark3labs:main Aug 4, 2025
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@gramidt gramidt gramidt approved these changes

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@sd2k @gramidt @ezynda3