OIDC: Check static client registration and add login flow (#11088)

* util functions to get static client id

* check static client ids in login flow

* remove dead code

* add trailing slash

* comment error enum

* spacing

* PR tidying

* more comments

* add ValidatedDelegatedAuthConfig type

* Update src/Login.ts

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Update src/Login.ts

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Update src/utils/ValidatedServerConfig.ts

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* rename oidc_static_clients to oidc_static_client_ids

* comment

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

test/utils/oidc/registerClient-test.ts

@@ -0,0 +1,86 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import fetchMockJest from "fetch-mock-jest";
+
+import { OidcClientError } from "../../../src/utils/oidc/error";
+import { getOidcClientId } from "../../../src/utils/oidc/registerClient";
+
+describe("getOidcClientId()", () => {
+    const issuer = "https://auth.com/";
+    const registrationEndpoint = "https://auth.com/register";
+    const clientName = "Element";
+    const baseUrl = "https://just.testing";
+    const dynamicClientId = "xyz789";
+    const staticOidcClients = {
+        [issuer]: "abc123",
+    };
+    const delegatedAuthConfig = {
+        issuer,
+        registrationEndpoint,
+        authorizationEndpoint: issuer + "auth",
+        tokenEndpoint: issuer + "token",
+    };
+
+    beforeEach(() => {
+        fetchMockJest.mockClear();
+        fetchMockJest.resetBehavior();
+    });
+
+    it("should return static clientId when configured", async () => {
+        expect(await getOidcClientId(delegatedAuthConfig, clientName, baseUrl, staticOidcClients)).toEqual(
+            staticOidcClients[issuer],
+        );
+        // didn't try to register
+        expect(fetchMockJest).toHaveFetchedTimes(0);
+    });
+
+    it("should throw when no static clientId is configured and no registration endpoint", async () => {
+        const authConfigWithoutRegistration = {
+            ...delegatedAuthConfig,
+            issuer: "https://issuerWithoutStaticClientId.org/",
+            registrationEndpoint: undefined,
+        };
+        expect(
+            async () => await getOidcClientId(authConfigWithoutRegistration, clientName, baseUrl, staticOidcClients),
+        ).rejects.toThrow(OidcClientError.DynamicRegistrationNotSupported);
+        // didn't try to register
+        expect(fetchMockJest).toHaveFetchedTimes(0);
+    });
+
+    it("should handle when staticOidcClients object is falsy", async () => {
+        const authConfigWithoutRegistration = {
+            ...delegatedAuthConfig,
+            registrationEndpoint: undefined,
+        };
+        expect(async () => await getOidcClientId(authConfigWithoutRegistration, clientName, baseUrl)).rejects.toThrow(
+            OidcClientError.DynamicRegistrationNotSupported,
+        );
+        // didn't try to register
+        expect(fetchMockJest).toHaveFetchedTimes(0);
+    });
+
+    it("should throw while dynamic registration is not implemented", async () => {
+        fetchMockJest.post(registrationEndpoint, {
+            status: 200,
+            body: JSON.stringify({ client_id: dynamicClientId }),
+        });
+
+        expect(async () => await getOidcClientId(delegatedAuthConfig, clientName, baseUrl)).rejects.toThrow(
+            OidcClientError.DynamicRegistrationNotSupported,
+        );
+    });
+});