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4 Commits
Author SHA1 Message Date
Bobby Ho 209d1ca498 fix: reject PKCE code_verifier below RFC 7636 length floor (#28003) 
The token endpoint accepted any non-empty `code_verifier`, so a
one-character verifier was enough to authenticate. RFC 7636 §4.1
requires 43 to 128 characters from the unreserved set.

That fix plus the related gaps review surfaced in the same path:

- Enforce the length and charset floor on the verifier before the S256
comparison runs.
- Validate the challenge at the authorize endpoint too. It was only
checked for non-emptiness, so a malformed challenge was stored and then
failed late at token exchange, blaming the wrong parameter.
- A malformed verifier now returns `invalid_request` (RFC 6749 §5.2); a
well-formed but wrong one still returns `invalid_grant` (RFC 7636 §4.6).
Both looked identical before, so a client had no way to tell a syntax
error from a hash mismatch and would retry the same bad verifier
forever.
- Revoke the authorization code when a PKCE check fails. Without that, a
leaked code could be replayed with unlimited verifier guesses for its
remaining lifetime, and RFC 6749 §10.5 requires codes to be single use.
- Fix verifier generation in `scripts/oauth2/*.sh` and the docs example.
They deleted reserved base64 characters instead of translating them to
the URL-safe alphabet, so most runs produced verifiers under the new
floor.

Also carries #28041, which merged into this branch: public clients may
register bare custom schemes such as `vscode://` again, with `mailto`,
`tel`, and `sms` rejected.

Split out of #27873 (public OAuth2 client support). PKCE is already
mandatory for every client, so this stands on its own.

<details>
<summary>Manual verification</summary>

Ran against a local dev server on this branch, using a session token and
a throwaway app from `scripts/oauth2/setup-test-app.sh`.

1. Happy path unchanged: HTTP 200, verifier length 43.
2. `code_verifier=short`, and a 43-character verifier ending in `!`:
both HTTP 400 `invalid_request`, so charset is enforced and not just
length.
3. `code_challenge=tooshort` at authorize: HTTP 400 `invalid_request`,
no code issued. An empty challenge still hits the older "required and
cannot be empty" message.
4. Well-formed but wrong verifier: HTTP 400 `invalid_grant`, distinct
from the cases above.
5. Retrying that same code with the correct verifier: HTTP 400, code
already revoked by the failed check.
6. `generate-pkce.sh` produces a 43-character verifier (20 out of 20
runs); the docs example produces 128.
7. `scripts/oauth2/test-mcp-oauth2.sh` passes end to end. The two
bearer-token failures in its output are a pre-existing script bug
(`09c50559f3`, July 2025) that reuses a resource-scoped token against
the real API, not a regression here.

</details>
 2026-08-12 13:36:52 -07:00
Bobby Ho 608bc6e837 fix(scripts/oauth2): fix test-mcp-oauth2.sh for macOS and OAuth 2.1 compliance (#26825) 
The `test-mcp-oauth2.sh` script had three bugs that caused tests 2, 3,
and 4 to fail when run on macOS.

`grep -oP` uses PCRE lookbehind (`\K`), which is not supported by BSD
grep on macOS. Replaced with `grep -oE … | sed 's/code=//'` which works
on both platforms.

The token exchange requests in tests 2, 3, and 4 omitted `redirect_uri`,
which is required by RFC 6749 §4.1.3 whenever `redirect_uri` was
included in the authorization request. The server correctly rejects
these with `invalid_grant`, masking the actual PKCE validation.

Test 4's resource parameter flow was missing PKCE parameters entirely.
The server enforces PKCE on all authorization code flows per OAuth 2.1,
so the authorization request returned 400 and the script exited silently
due to `set -euo pipefail`.
 2026-06-30 08:02:55 -07:00
Thomas Kosiewski 09c50559f3 feat: implement RFC 6750 Bearer token authentication (#18644) 
# Add RFC 6750 Bearer Token Authentication Support

This PR implements RFC 6750 Bearer Token authentication as an additional authentication method for Coder's API. This allows clients to authenticate using standard OAuth 2.0 Bearer tokens in two ways:

1. Using the `Authorization: Bearer <token>` header
2. Using the `access_token` query parameter

Key changes:

- Added support for extracting tokens from both Bearer headers and access_token query parameters
- Implemented proper WWW-Authenticate headers for 401/403 responses with appropriate error descriptions
- Added comprehensive test coverage for the new authentication methods
- Updated the OAuth2 protected resource metadata endpoint to advertise Bearer token support
- Enhanced the OAuth2 testing script to verify Bearer token functionality

These authentication methods are added as fallback options, maintaining backward compatibility with Coder's existing authentication mechanisms. The existing authentication methods (cookies, session token header, etc.) still take precedence.

This implementation follows the OAuth 2.0 Bearer Token specification (RFC 6750) and improves interoperability with standard OAuth 2.0 clients.
 2025-07-02 19:14:54 +02:00
Thomas Kosiewski 6f2834f62a feat: oauth2 - add authorization server metadata endpoint and PKCE support (#18548) 
## Summary

  This PR implements critical MCP OAuth2 compliance features for Coder's authorization server, adding PKCE support, resource parameter handling, and OAuth2 server metadata discovery. This brings Coder's OAuth2 implementation significantly closer to production readiness for MCP (Model Context Protocol)
  integrations.

  ## What's Added

  ### OAuth2 Authorization Server Metadata (RFC 8414)
  - Add `/.well-known/oauth-authorization-server` endpoint for automatic client discovery
  - Returns standardized metadata including supported grant types, response types, and PKCE methods
  - Essential for MCP client compatibility and OAuth2 standards compliance

  ### PKCE Support (RFC 7636)
  - Implement Proof Key for Code Exchange with S256 challenge method
  - Add `code_challenge` and `code_challenge_method` parameters to authorization flow
  - Add `code_verifier` validation in token exchange
  - Provides enhanced security for public clients (mobile apps, CLIs)

  ### Resource Parameter Support (RFC 8707)
  - Add `resource` parameter to authorization and token endpoints
  - Store resource URI and bind tokens to specific audiences
  - Critical for MCP's resource-bound token model

  ### Enhanced OAuth2 Error Handling
  - Add OAuth2-compliant error responses with proper error codes
  - Use standard error format: `{"error": "code", "error_description": "details"}`
  - Improve error consistency across OAuth2 endpoints

  ### Authorization UI Improvements
  - Fix authorization flow to use POST-based consent instead of GET redirects
  - Remove dependency on referer headers for security decisions
  - Improve CSRF protection with proper state parameter validation

  ## Why This Matters

  **For MCP Integration:** MCP requires OAuth2 authorization servers to support PKCE, resource parameters, and metadata discovery. Without these features, MCP clients cannot securely authenticate with Coder.

  **For Security:** PKCE prevents authorization code interception attacks, especially critical for public clients. Resource binding ensures tokens are only valid for intended services.

  **For Standards Compliance:** These are widely adopted OAuth2 extensions that improve interoperability with modern OAuth2 clients.

  ## Database Changes

  - **Migration 000343:** Adds `code_challenge`, `code_challenge_method`, `resource_uri` to `oauth2_provider_app_codes`
  - **Migration 000343:** Adds `audience` field to `oauth2_provider_app_tokens` for resource binding
  - **Audit Updates:** New OAuth2 fields properly tracked in audit system
  - **Backward Compatibility:** All changes maintain compatibility with existing OAuth2 flows

  ## Test Coverage

  - Comprehensive PKCE test suite in `coderd/identityprovider/pkce_test.go`
  - OAuth2 metadata endpoint tests in `coderd/oauth2_metadata_test.go`
  - Integration tests covering PKCE + resource parameter combinations
  - Negative tests for invalid PKCE verifiers and malformed requests

  ## Testing Instructions

  ```bash
  # Run the comprehensive OAuth2 test suite
  ./scripts/oauth2/test-mcp-oauth2.sh

  Manual Testing with Interactive Server

  # Start Coder in development mode
  ./scripts/develop.sh

  # In another terminal, set up test app and run interactive flow
  eval $(./scripts/oauth2/setup-test-app.sh)
  ./scripts/oauth2/test-manual-flow.sh
  # Opens browser with OAuth2 flow, handles callback automatically

  # Clean up when done
  ./scripts/oauth2/cleanup-test-app.sh

  Individual Component Testing

  # Test metadata endpoint
  curl -s http://localhost:3000/.well-known/oauth-authorization-server | jq .

  # Test PKCE generation
  ./scripts/oauth2/generate-pkce.sh

  # Run specific test suites
  go test -v ./coderd/identityprovider -run TestVerifyPKCE
  go test -v ./coderd -run TestOAuth2AuthorizationServerMetadata
```

  ### Breaking Changes

  None. All changes maintain backward compatibility with existing OAuth2 flows.

---

Change-Id: Ifbd0d9a543d545f9f56ecaa77ff2238542ff954a
Signed-off-by: Thomas Kosiewski <tk@coder.com>
 2025-07-01 15:39:29 +02:00