Support registering a new authenticator

This adds Yubico's FIDO2 library and two APIs for working with the
"navigator.credentials.create()" function in JavaScript. The GET
API uses the library to generate options for the "create()" function,
and the POST API decodes and verifies the resulting credential. While
the options and response are dict-like, CBOR is necessary to encode
some of the byte-level values, which can't be represented in JSON.

Much of the code here is based on the Yubico library example [1][2].

Implementation notes:

- There are definitely better ways to alert the user about failure, but
window.alert() will do for the time being. Using location.reload() is
also a bit jarring if the page scrolls, but not a major issue.

- Ideally we would use window.fetch() to do AJAX calls, but we don't
have a polyfill for this, and we use $.ajax() elsewhere [3]. We need
to do a few weird tricks [6] to stop jQuery trashing the data.

- The FIDO2 server doesn't serve web requests; it's just a "server" in
the sense of WebAuthn terminology. It lives in its own module, since it
needs to be initialised with the app / config.

- $.ajax returns a promise-like object. Although we've used ".fail()"
elsewhere [3], I couldn't find a stub object that supports it, so I've
gone for ".catch()", and used a Promise stub object in tests.

- WebAuthn only works over HTTPS, but there's an exception for "localhost"
[4].  However, the library is a bit too strict [5], so we have to disable
origin verification to avoid needing HTTPS for dev work.

[1]: c42d9628a4/examples/server/server.py
[2]: c42d9628a4/examples/server/static/register.html
[3]: 91453d3639/app/assets/javascripts/updateContent.js (L33)
[4]: https://stackoverflow.com/questions/55971593/navigator-credentials-is-null-on-local-server
[5]: c42d9628a4/fido2/rpid.py (L69)
[6]: https://stackoverflow.com/questions/12394622/does-jquery-ajax-or-load-allow-for-responsetype-arraybuffer

tests/app/main/views/test_webauthn_credentials.py

@@ -0,0 +1,108 @@
+import pytest
+from fido2 import cbor
+from flask import url_for
+
+from app import webauthn_server
+
+
+@pytest.mark.parametrize('endpoint', [
+    'webauthn_begin_register',
+])
+def test_register_forbidden_for_non_platform_admins(
+    client_request,
+    endpoint,
+):
+    client_request.get(f'main.{endpoint}', _expected_status=403)
+
+
+def test_begin_register_returns_encoded_options(
+    app_,
+    mocker,
+    platform_admin_user,
+    platform_admin_client,
+):
+    # override base URL so it's consistent on CI and locally
+    mocker.patch.dict(
+        app_.config,
+        values={'ADMIN_BASE_URL': 'http://localhost:6012'}
+    )
+    webauthn_server.init_app(app_)
+
+    response = platform_admin_client.get(
+        url_for('main.webauthn_begin_register')
+    )
+
+    assert response.status_code == 200
+
+    webauthn_options = cbor.decode(response.data)['publicKey']
+    assert webauthn_options['attestation'] == 'direct'
+    assert webauthn_options['timeout'] == 30_000
+
+    auth_selection = webauthn_options['authenticatorSelection']
+    assert auth_selection['authenticatorAttachment'] == 'cross-platform'
+    assert auth_selection['userVerification'] == 'discouraged'
+
+    user_options = webauthn_options['user']
+    assert user_options['name'] == platform_admin_user['email_address']
+    assert user_options['id'] == bytes(platform_admin_user['id'], 'utf-8')
+
+    relying_party_options = webauthn_options['rp']
+    assert relying_party_options['name'] == 'GOV.UK Notify'
+    assert relying_party_options['id'] == 'localhost'
+
+
+def test_begin_register_stores_state_in_session(
+    platform_admin_client,
+):
+    platform_admin_client.get(
+        url_for('main.webauthn_begin_register')
+    )
+
+    with platform_admin_client.session_transaction() as session:
+        assert session['webauthn_registration_state'] is not None
+
+
+def test_complete_register_creates_credential(
+    platform_admin_user,
+    platform_admin_client,
+    mocker,
+):
+    with platform_admin_client.session_transaction() as session:
+        session['webauthn_registration_state'] = 'state'
+
+    user_api_mock = mocker.patch(
+        'app.user_api_client.create_webauthn_credential_for_user'
+    )
+
+    credential_mock = mocker.patch(
+        'app.models.webauthn_credential.WebAuthnCredential.from_registration',
+        return_value='cred'
+    )
+
+    response = platform_admin_client.post(
+        url_for('main.webauthn_complete_register'),
+        data=cbor.encode('public_key_credential'),
+    )
+
+    assert response.status_code == 200
+    credential_mock.assert_called_once_with('state', 'public_key_credential')
+    user_api_mock.assert_called_once_with(platform_admin_user['id'], 'cred')
+
+
+def test_complete_register_clears_session(
+    platform_admin_client,
+    mocker,
+):
+    with platform_admin_client.session_transaction() as session:
+        session['webauthn_registration_state'] = 'state'
+
+    mocker.patch('app.user_api_client.create_webauthn_credential_for_user')
+    mocker.patch('app.models.webauthn_credential.WebAuthnCredential.from_registration')
+
+    platform_admin_client.post(
+        url_for('main.webauthn_complete_register'),
+        data=cbor.encode('public_key_credential'),
+    )
+
+    with platform_admin_client.session_transaction() as session:
+        assert 'webauthn_registration_state' not in session

tests/app/models/test_webauthn_credential.py

@@ -0,0 +1,40 @@
+import base64
+
+from fido2 import cbor
+from fido2.cose import ES256
+
+from app import webauthn_server
+from app.models.webauthn_credential import WebAuthnCredential
+
+# noqa adapted from https://github.com/duo-labs/py_webauthn/blob/90e3d97e0182899a35a70fc510280b4082cce19b/tests/test_webauthn.py#L14-L24
+SESSION_STATE = {'challenge': 'bPzpX3hHQtsp9evyKYkaZtVc9UN07PUdJ22vZUdDp94', 'user_verification': 'discouraged'}
+CLIENT_DATA_JSON = b'{"type": "webauthn.create", "clientExtensions": {}, "challenge": "bPzpX3hHQtsp9evyKYkaZtVc9UN07PUdJ22vZUdDp94", "origin": "https://webauthn.io"}'  # noqa
+
+# had to use the cbor2 library to re-encode the attestationObject due to implementation differences
+ATTESTATION_OBJECT = base64.b64decode(b'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')  # noqa
+
+
+def test_from_registration_verifies_response(app_, mocker):
+    mocker.patch.dict(
+        app_.config, values={
+            'NOTIFY_ENVIRONMENT': 'development',
+            'ADMIN_BASE_URL': 'https://webauthn.io',
+        }
+    )
+
+    # disable origin verification for non-HTTPS test
+    webauthn_server.init_app(app_)
+
+    registration_response = {
+       'clientDataJSON': CLIENT_DATA_JSON,
+       'attestationObject': ATTESTATION_OBJECT,
+    }
+
+    credential = WebAuthnCredential.from_registration(SESSION_STATE, registration_response)
+    assert credential.name == 'Unnamed key'
+    assert credential.registration_response == base64.b64encode(cbor.encode(registration_response))
+
+    credential_data = credential.to_credential_data()
+    assert type(credential_data.credential_id) is bytes
+    assert type(credential_data.aaguid) is bytes
+    assert credential_data.public_key[3] == ES256.ALGORITHM

tests/app/notify_client/test_user_client.py

@@ -4,6 +4,7 @@ from unittest.mock import call
 import pytest
 
 from app import invite_api_client, service_api_client, user_api_client
+from app.models.webauthn_credential import WebAuthnCredential
 from tests import sample_uuid
 from tests.conftest import SERVICE_ONE_ID
 
@@ -243,3 +244,9 @@ def test_add_user_to_service_calls_correct_endpoint_and_deletes_keys_from_cache(
 def test_get_webauthn_credentials_for_user_returns_stubbed_data():
     credentials = user_api_client.get_webauthn_credentials_for_user('id')
     assert credentials[0]['name'] == 'Ben test'
+
+
+def test_create_webauthn_credential_for_user_stores_stubbed_data(webauthn_credential):
+    credential = WebAuthnCredential(webauthn_credential)
+    user_api_client.create_webauthn_credential_for_user('id', credential)
+    assert len(user_api_client.credentials) == 1

tests/app/test_navigation.py

@@ -332,6 +332,8 @@ EXCLUDED_ENDPOINTS = tuple(map(Navigation.get_endpoint_with_blueprint, {
     'view_template',
     'view_template_version',
     'view_template_versions',
+    'webauthn_begin_register',
+    'webauthn_complete_register',
     'who_can_use_notify',
     'who_its_for',
     'write_new_broadcast',

tests/app/test_webauthn_server.py

@@ -0,0 +1,35 @@
+import pytest
+
+from app import webauthn_server
+
+
+@pytest.mark.parametrize(('environment, allowed'), [
+    ('development', True),
+    ('production', False)
+])
+def test_server_origin_verification(
+    app_,
+    mocker,
+    environment,
+    allowed
+):
+    mocker.patch.dict(
+        app_.config,
+        values={'NOTIFY_ENVIRONMENT': environment}
+    )
+
+    webauthn_server.init_app(app_)
+    assert app_.webauthn_server._verify('fake-domain') == allowed
+
+
+def test_server_relying_party_id(
+    app_,
+    mocker,
+):
+    mocker.patch.dict(
+        app_.config,
+        values={'ADMIN_BASE_URL': 'https://www.notify.works'}
+    )
+
+    webauthn_server.init_app(app_)
+    assert app_.webauthn_server.rp.id == 'www.notify.works'

tests/conftest.py

@@ -4485,5 +4485,7 @@ def mock_get_invited_org_user_by_id(mocker, sample_org_invite):
 def webauthn_credential():
     return {
         'name': 'Test credential',
+        'credential_data': 'credential_data',
+        'registration_response': 'anything',
         'created_at': '2017-10-18T16:57:14.154185Z',
     }

tests/javascripts/registerSecurityKey.test.js

@@ -1,26 +1,147 @@
 beforeAll(() => {
-  require('../../app/assets/javascripts/registerSecurityKey.js');
+  window.CBOR = require('../../node_modules/cbor-js/cbor.js')
+  require('../../app/assets/javascripts/registerSecurityKey.js')
+
+  // disable console.error() so we don't see it in test output
+  // you might need to comment this out to debug some failures
+  jest.spyOn(console, 'error').mockImplementation(() => {})
 })
 
 afterAll(() => {
-  require('./support/teardown.js');
+  require('./support/teardown.js')
 })
 
 describe('Register security key', () => {
+  let button
+
   beforeEach(() => {
     document.body.innerHTML = `
       <a href="#" role="button" draggable="false" class="govuk-button govuk-button--secondary" data-module="register-security-key">
         Register a key
-      </a>`;
+      </a>`
+
+    button = document.querySelector('[data-module="register-security-key"]')
+    window.GOVUK.modules.start()
   })
 
-  test('it is not implemented yet', () => {
-    window.GOVUK.modules.start();
-    jest.spyOn(window, 'alert').mockImplementation(() => {});
+  test('creates a new credential and reloads', (done) => {
+    // pretend window.navigator.credentials exists in test env
+    // defineProperty is used as window.navigator is read-only
+    Object.defineProperty(window.navigator, 'credentials', {
+      value: {
+        // fake PublicKeyCredential response from WebAuthn API
+        // both of the nested properties are Array(Buffer) objects
+        create: (options) => {
+          expect(options).toEqual('options')
 
-    button = document.querySelector('[data-module="register-security-key"]');
-    button.click();
+          return Promise.resolve({
+            response: {
+              attestationObject: [1, 2, 3],
+              clientDataJSON: [4, 5, 6],
+            }
+          })
+        }
+      },
+      // allow global property to be redefined in other tests
+      writable: true,
+    })
 
-    expect(window.alert).toBeCalledWith('not implemented')
+    // pretend window.location exists in test env
+    // defineProperty is used as window.location is read-only
+    Object.defineProperty(window, 'location', {
+      // signal that the async promise chain was called
+      value: { reload: () => done() },
+      // allow global property to be redefined in other tests
+      writable: true,
+    })
+
+    jest.spyOn(window.$, 'ajax').mockImplementation((options) => {
+      // initial fetch of options from the server
+      if (!options.method) {
+        // options from the server are CBOR-encoded
+        webauthnOptions = window.CBOR.encode('options')
+        return Promise.resolve(webauthnOptions)
+
+      // subsequent POST of credential data to server
+      } else {
+        decodedData = window.CBOR.decode(options.data)
+        expect(decodedData.clientDataJSON).toEqual(new Uint8Array([4,5,6]))
+        expect(decodedData.attestationObject).toEqual(new Uint8Array([1,2,3]))
+        expect(options.headers['X-CSRFToken']).toBe()
+        return Promise.resolve()
+      }
+    })
+
+    button.click()
+  })
+
+  test('alerts if fetching WebAuthn options fails', (done) => {
+    jest.spyOn(window.$, 'ajax').mockImplementation((options) => {
+      return Promise.reject('error')
+    })
+
+    jest.spyOn(window, 'alert').mockImplementation((msg) => {
+      done()
+      expect(msg).toEqual('Error during registration. Please try again.')
+    })
+
+    button.click()
+  })
+
+  test('alerts if sending WebAuthn credentials fails', (done) => {
+    Object.defineProperty(window.navigator, 'credentials', {
+      value: {
+        // fake PublicKeyCredential response from WebAuthn API
+        create: (options) => {
+          return Promise.resolve({ response: {} })
+        }
+      },
+      // allow global property to be redefined in other tests
+      writable: true,
+    })
+
+    jest.spyOn(window.$, 'ajax').mockImplementation((options) => {
+      // initial fetch of options from the server
+      if (!options.method) {
+        webauthnOptions = window.CBOR.encode('options')
+        return Promise.resolve(webauthnOptions)
+
+      // subsequent POST of credential data to server
+      } else {
+        return Promise.reject('error')
+      }
+    })
+
+    jest.spyOn(window, 'alert').mockImplementation((msg) => {
+      done()
+      expect(msg).toEqual('Error during registration. Please try again.')
+    })
+
+    button.click()
+  })
+
+  test('alerts if comms with the authenticator fails', (done) => {
+    Object.defineProperty(window.navigator, 'credentials', {
+      value: {
+        create: () => {
+          return Promise.reject(new DOMException('error'))
+        }
+      },
+      // allow global property to be redefined in other tests
+      writable: true,
+    })
+
+    jest.spyOn(window.$, 'ajax').mockImplementation((options) => {
+      // initial fetch of options from the server
+      webauthnOptions = window.CBOR.encode('options')
+      return Promise.resolve(webauthnOptions)
+    })
+
+    jest.spyOn(window, 'alert').mockImplementation((msg) => {
+      done()
+      expect(msg).toEqual('Error communicating with device.\n\nerror')
+    })
+
+    button.click()
   })
 })