honor redirect to SAML SSO path if user is already authenticated

web/packages/teleport/src/Login/Login.test.tsx

@@ -22,6 +22,7 @@ import { render, fireEvent, screen, waitFor } from 'design/utils/testing';
 
 import auth from 'teleport/services/auth/auth';
 import history from 'teleport/services/history';
+import session from 'teleport/services/websession';
 import cfg from 'teleport/config';
 
 import { Login } from './Login';
@@ -31,6 +32,7 @@ let user: UserEvent;
 beforeEach(() => {
   jest.restoreAllMocks();
   jest.spyOn(history, 'push').mockImplementation();
+  jest.spyOn(history, 'replace').mockImplementation();
   jest.spyOn(history, 'getRedirectParam').mockImplementation(() => '/');
   jest.spyOn(history, 'hasAccessChangedParam').mockImplementation(() => false);
   user = userEvent.setup();
@@ -194,3 +196,25 @@ describe('test MOTD', () => {
     expect(screen.getByText(/Your access has changed/i)).toBeInTheDocument();
   });
 });
+
+test('redirect to root if session is valid and path is not "/enterprise/saml-idp/sso"', () => {
+  jest.spyOn(session, 'isValid').mockImplementation(() => true);
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(
+      'http://localhost/web/login?redirect_url=http://localhost/web/cluster/localhost/resources'
+    );
+  render(<Login />);
+
+  expect(history.replace).toHaveBeenCalledWith('/web');
+});
+
+test('redirect if session is valid and path matches "/enterprise/saml-idp/sso"', () => {
+  const samlIdPPath = new URL('http://localhost' + cfg.routes.samlIdpSso);
+  jest.spyOn(session, 'isValid').mockImplementation(() => true);
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(samlIdPPath.toString());
+  render(<Login />);
+  expect(history.push).toHaveBeenCalledWith(samlIdPPath, true);
+});

web/packages/teleport/src/Login/useLogin.test.tsx

@@ -0,0 +1,100 @@
+/**
+ * Teleport
+ * Copyright (C) 2024  Gravitational, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import history from 'teleport/services/history';
+import session from 'teleport/services/websession';
+import cfg from 'teleport/config';
+
+import { renderHook } from '@testing-library/react';
+
+import useLogin from './useLogin';
+
+beforeEach(() => {
+  jest.restoreAllMocks();
+  jest.spyOn(session, 'isValid').mockImplementation(() => true);
+  jest.spyOn(history, 'push').mockImplementation();
+  jest.spyOn(history, 'replace').mockImplementation();
+  jest.mock('shared/hooks', () => ({
+    useAttempt: () => {
+      return [
+        { status: 'success', statusText: 'Success Text' },
+        {
+          clear: jest.fn(),
+        },
+      ];
+    },
+  }));
+});
+
+afterEach(() => {
+  jest.resetAllMocks();
+});
+
+it('redirect to root on path not matching "/enterprise/saml-idp/sso"', () => {
+  jest.spyOn(history, 'getRedirectParam').mockReturnValue('http://localhost');
+  renderHook(() => useLogin());
+  expect(history.replace).toHaveBeenCalledWith('/web');
+
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue('http://localhost/web/cluster/name/resources');
+  renderHook(() => useLogin());
+  expect(history.replace).toHaveBeenCalledWith('/web');
+});
+
+it('redirect to SAML SSO path on matching "/enterprise/saml-idp/sso"', () => {
+  const samlIdpPath = new URL('http://localhost' + cfg.routes.samlIdpSso);
+  cfg.baseUrl = 'http://localhost';
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(samlIdpPath.toString());
+  renderHook(() => useLogin());
+  expect(history.push).toHaveBeenCalledWith(samlIdpPath, true);
+});
+
+it('non-base domain redirects with base domain for a matching "/enterprise/saml-idp/sso"', async () => {
+  const samlIdpPath = new URL('http://different-base' + cfg.routes.samlIdpSso);
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(samlIdpPath.toString());
+  renderHook(() => useLogin());
+  const expectedPath = new URL('http://localhost' + cfg.routes.samlIdpSso);
+  expect(history.push).toHaveBeenCalledWith(expectedPath, true);
+});
+
+it('base domain with different path is redirected to root', async () => {
+  const nonSamlIdpPath = new URL('http://localhost/web/cluster/name/resources');
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(nonSamlIdpPath.toString());
+  renderHook(() => useLogin());
+  expect(history.replace).toHaveBeenCalledWith('/web');
+});
+
+it('invalid session does nothing', async () => {
+  const samlIdpPathWithDifferentBase = new URL(
+    'http://different-base' + cfg.routes.samlIdpSso
+  );
+  jest
+    .spyOn(history, 'getRedirectParam')
+    .mockReturnValue(samlIdpPathWithDifferentBase.toString());
+  jest.spyOn(session, 'isValid').mockImplementation(() => false);
+  renderHook(() => useLogin());
+  expect(history.replace).not.toHaveBeenCalled();
+  expect(history.push).not.toHaveBeenCalled();
+});

web/packages/teleport/src/Login/useLogin.ts

@@ -17,6 +17,7 @@
  */
 
 import { useState, useEffect } from 'react';
+import { matchPath } from 'react-router';
 import { useAttempt } from 'shared/hooks';
 import { AuthProvider } from 'shared/services';
 import { TrustedDeviceRequirement } from 'gen-proto-ts/teleport/legacy/types/trusted_device_requirement_pb';
@@ -69,8 +70,25 @@ export default function useLogin() {
 
   useEffect(() => {
     if (session.isValid()) {
-      history.replace(cfg.routes.root);
-      return;
+      try {
+        const redirectUrlWithBase = new URL(getEntryRoute());
+        const matched = matchPath(redirectUrlWithBase.pathname, {
+          path: cfg.routes.samlIdpSso,
+          strict: true,
+          exact: true,
+        });
+        if (matched) {
+          history.push(redirectUrlWithBase, true);
+          return;
+        } else {
+          history.replace(cfg.routes.root);
+          return;
+        }
+      } catch (e) {
+        console.error(e);
+        history.replace(cfg.routes.root);
+        return;
+      }
     }
     setCheckingValidSession(false);
   }, []);
@@ -149,6 +167,11 @@ function loginSuccess() {
   history.push(redirect, withPageRefresh);
 }
 
+/**
+ * getEntryRoute returns a base ensured redirect URL value that is safe
+ * for redirect.
+ * @returns base ensured URL string.
+ */
 function getEntryRoute() {
   let entryUrl = history.getRedirectParam();
   if (entryUrl) {

web/packages/teleport/src/config.ts

@@ -215,6 +215,9 @@ const cfg = {
     accessGraph: {
       crownJewelAccessPath: '/web/accessgraph/crownjewels/access/:id',
     },
+
+    /** samlIdpSso is an exact path of the service provider initiated SAML SSO endpoint. */
+    samlIdpSso: '/enterprise/saml-idp/sso',
   },
 
   api: {