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ThomasK33ThomasK33
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feat(oauth2): implement RFC 6750 Bearer Token Support for MCP compliance
- Add RFC 6750 bearer token extraction to APITokenFromRequest as fallback methods - Support Authorization: Bearer <token> header and access_token query parameter - Maintain backward compatibility by prioritizing existing custom methods first - Add WWW-Authenticate headers to 401/403 responses per RFC 6750 - Update Protected Resource Metadata to advertise bearer_methods_supported - Add comprehensive test suite for RFC 6750 compliance in rfc6750_test.go - Update MCP test scripts with bearer token authentication tests - Enhance CLAUDE.md with improved Go LSP tool usage guidelines Implements RFC 6750 Section 2.1 (Authorization Request Header Field) and 2.3 (URI Query Parameter). Maintains full backward compatibility with existing Coder authentication methods. Completes major MCP OAuth2 compliance milestone. Change-Id: Ic9c9057153b40728ad91b377d753a7ffd566add7 Signed-off-by: Thomas Kosiewski <tk@coder.com>
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‎coderd/httpmw/apikey.go

Lines changed: 42 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -214,6 +214,31 @@ func ExtractAPIKey(rw http.ResponseWriter, r *http.Request, cfg ExtractAPIKeyCon
214214
return nil, nil, false
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}
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217+
// Add WWW-Authenticate header for 401/403 responses (RFC 6750)
218+
if code == http.StatusUnauthorized || code == http.StatusForbidden {
219+
var wwwAuth string
220+
221+
switch code {
222+
case http.StatusUnauthorized:
223+
// Map 401 to invalid_token with specific error descriptions
224+
switch {
225+
case strings.Contains(response.Message, "expired") || strings.Contains(response.Detail, "expired"):
226+
wwwAuth = `Bearer realm="coder", error="invalid_token", error_description="The access token has expired"`
227+
case strings.Contains(response.Message, "audience") || strings.Contains(response.Message, "mismatch"):
228+
wwwAuth = `Bearer realm="coder", error="invalid_token", error_description="The access token audience does not match this resource"`
229+
default:
230+
wwwAuth = `Bearer realm="coder", error="invalid_token", error_description="The access token is invalid"`
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}
232+
case http.StatusForbidden:
233+
// Map 403 to insufficient_scope per RFC 6750
234+
wwwAuth = `Bearer realm="coder", error="insufficient_scope", error_description="The request requires higher privileges than provided by the access token"`
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default:
236+
wwwAuth = `Bearer realm="coder"`
237+
}
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rw.Header().Set("WWW-Authenticate", wwwAuth)
240+
}
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217242
httpapi.Write(ctx, rw, code, response)
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return nil, nil, false
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}
@@ -653,9 +678,14 @@ func UserRBACSubject(ctx context.Context, db database.Store, userID uuid.UUID, s
653678
// 1: The cookie
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// 2. The coder_session_token query parameter
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// 3. The custom auth header
681+
// 4. RFC 6750 Authorization: Bearer header
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// 5. RFC 6750 access_token query parameter
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//
657684
// API tokens for apps are read from workspaceapps/cookies.go.
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func APITokenFromRequest(r *http.Request) string {
686+
// Prioritize existing Coder custom authentication methods first
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// to maintain backward compatibility and existing behavior
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659689
cookie, err := r.Cookie(codersdk.SessionTokenCookie)
660690
if err == nil && cookie.Value != "" {
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return cookie.Value
@@ -671,7 +701,18 @@ func APITokenFromRequest(r *http.Request) string {
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return headerValue
672702
}
673703

674-
// TODO(ThomasK33): Implement RFC 6750
704+
// RFC 6750 Bearer Token support (added as fallback methods)
705+
// Check Authorization: Bearer <token> header (case-insensitive per RFC 6750)
706+
authHeader := r.Header.Get("Authorization")
707+
if strings.HasPrefix(strings.ToLower(authHeader), "bearer ") {
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return authHeader[7:] // Skip "Bearer " (7 characters)
709+
}
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711+
// Check access_token query parameter
712+
accessToken := r.URL.Query().Get("access_token")
713+
if accessToken != "" {
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return accessToken
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}
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return ""
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}

‎coderd/httpmw/csrf.go

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -102,6 +102,12 @@ func CSRF(cookieCfg codersdk.HTTPCookieConfig) func(next http.Handler) http.Hand
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return true
103103
}
104104

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// RFC 6750 Bearer Token authentication is exempt from CSRF
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// as it uses custom headers that cannot be set by malicious sites
107+
if authHeader := r.Header.Get("Authorization"); strings.HasPrefix(strings.ToLower(authHeader), "bearer ") {
108+
return true
109+
}
110+
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// If the X-CSRF-TOKEN header is set, we can exempt the func if it's valid.
106112
// This is the CSRF check.
107113
sent := r.Header.Get("X-CSRF-TOKEN")

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