Show the error_description when it is included in authorization response

pkg/oidcclient/login.go

@@ -423,9 +423,15 @@ func (h *handlerState) cliBasedAuth(authorizeOptions *[]oauth2.AuthCodeOption) (
 		return nil, fmt.Errorf("error getting authorization: redirected to the wrong location: %s", rawLocation)
 	}
 
+	// Validate OAuth2 state and fail if it's incorrect (to block CSRF).
+	if err := h.state.Validate(location.Query().Get("state")); err != nil {
+		return nil, fmt.Errorf("missing or invalid state parameter in authorization response: %s", rawLocation)
+	}
+
 	// Get the auth code or return the error from the server.
 	authCode := location.Query().Get("code")
 	if authCode == "" {
+		// Check for error response parameters. See https://openid.net/specs/openid-connect-core-1_0.html#AuthError.
 		requiredErrorCode := location.Query().Get("error")
 		optionalErrorDescription := location.Query().Get("error_description")
 		if optionalErrorDescription == "" {
@@ -434,11 +440,6 @@ func (h *handlerState) cliBasedAuth(authorizeOptions *[]oauth2.AuthCodeOption) (
 		return nil, fmt.Errorf("login failed with code %q: %s", requiredErrorCode, optionalErrorDescription)
 	}
 
-	// Validate OAuth2 state and fail if it's incorrect (to block CSRF).
-	if err := h.state.Validate(location.Query().Get("state")); err != nil {
-		return nil, fmt.Errorf("missing or invalid state parameter in authorization response: %s", rawLocation)
-	}
-
 	// Exchange the authorization code for access, ID, and refresh tokens and perform required
 	// validations on the returned ID token.
 	tokenCtx, tokenCtxCancelFunc := context.WithTimeout(context.Background(), httpRequestTimeout)
@@ -655,10 +656,11 @@ func (h *handlerState) handleAuthCodeCallback(w http.ResponseWriter, r *http.Req
 		return httperr.New(http.StatusForbidden, "missing or invalid state parameter")
 	}
 
-	// Check for error response parameters.
+	// Check for error response parameters. See https://openid.net/specs/openid-connect-core-1_0.html#AuthError.
 	if errorParam := params.Get("error"); errorParam != "" {
-		// TODO This should also show the value of the optional "error_description" param if it exists.
+		if errorDescParam := params.Get("error_description"); errorDescParam != "" {
-		//  See https://openid.net/specs/openid-connect-core-1_0.html#AuthError
+			return httperr.Newf(http.StatusBadRequest, "login failed with code %q: %s", errorParam, errorDescParam)
+		}
 		return httperr.Newf(http.StatusBadRequest, "login failed with code %q", errorParam)
 	}
 

pkg/oidcclient/login_test.go

@@ -724,7 +724,7 @@ func TestLogin(t *testing.T) { // nolint:gocyclo
 					return defaultLDAPTestOpts(t, h, &http.Response{
 						StatusCode: http.StatusFound,
 						Header: http.Header{"Location": []string{
-							"http://127.0.0.1:0/callback?error=access_denied&error_description=optional-error-description",
+							"http://127.0.0.1:0/callback?error=access_denied&error_description=optional-error-description&state=test-state",
 						}},
 					}, nil)
 				}
@@ -756,7 +756,7 @@ func TestLogin(t *testing.T) { // nolint:gocyclo
 					return defaultLDAPTestOpts(t, h, &http.Response{
 						StatusCode: http.StatusFound,
 						Header: http.Header{"Location": []string{
-							"http://127.0.0.1:0/callback?error=access_denied",
+							"http://127.0.0.1:0/callback?error=access_denied&state=test-state",
 						}},
 					}, nil)
 				}
@@ -1279,6 +1279,12 @@ func TestHandleAuthCodeCallback(t *testing.T) {
 			wantErr:        `login failed with code "some_error"`,
 			wantHTTPStatus: http.StatusBadRequest,
 		},
+		{
+			name:           "error code with a description from provider",
+			query:          "state=test-state&error=some_error&error_description=optional%20error%20description",
+			wantErr:        `login failed with code "some_error": optional error description`,
+			wantHTTPStatus: http.StatusBadRequest,
+		},
 		{
 			name:           "invalid code",
 			query:          "state=test-state&code=invalid",