ElementR: Add CryptoApi.getCrossSigningKeyId (#3619)

* Add `CryptoApi.getCrossSigningKeyId`

* Rename `CrossSigningPubKey` to `CrossSigningKeyInfo`

* Remove old eslint disable

* Review changes

* Review changes

spec/integ/crypto/cross-signing.spec.ts

@@ -22,7 +22,7 @@ import { CRYPTO_BACKENDS, InitCrypto, syncPromise } from "../../test-utils/test-
 import { AuthDict, createClient, CryptoEvent, MatrixClient } from "../../../src";
 import { mockInitialApiRequests, mockSetupCrossSigningRequests } from "../../test-utils/mockEndpoints";
 import { encryptAES } from "../../../src/crypto/aes";
-import { CryptoCallbacks } from "../../../src/crypto-api";
+import { CryptoCallbacks, CrossSigningKey } from "../../../src/crypto-api";
 import { SECRET_STORAGE_ALGORITHM_V1_AES } from "../../../src/secret-storage";
 import { ISyncResponder, SyncResponder } from "../../test-utils/SyncResponder";
 import { E2EKeyReceiver } from "../../test-utils/E2EKeyReceiver";
@@ -288,4 +288,55 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("cross-signing (%s)", (backend: s
             expect(isCrossSigningReady).toBeTruthy();
         });
     });
+
+    describe("getCrossSigningKeyId", () => {
+        /**
+         * Intercept /keys/device_signing/upload request and return the cross signing keys
+         * https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3keysdevice_signingupload
+         *
+         * @returns the cross signing keys
+         */
+        function awaitCrossSigningKeysUpload() {
+            return new Promise<any>((resolve) => {
+                fetchMock.post(
+                    // legacy crypto uses /unstable/; /v3/ is correct
+                    {
+                        url: new RegExp("/_matrix/client/(unstable|v3)/keys/device_signing/upload"),
+                        name: "upload-keys",
+                    },
+                    (url, options) => {
+                        const content = JSON.parse(options.body as string);
+                        resolve(content);
+                        return {};
+                    },
+                    // Override the routes define in `mockSetupCrossSigningRequests`
+                    { overwriteRoutes: true },
+                );
+            });
+        }
+
+        it("should return the cross signing key id for each cross signing key", async () => {
+            mockSetupCrossSigningRequests();
+
+            // Intercept cross signing keys upload
+            const crossSigningKeysPromise = awaitCrossSigningKeysUpload();
+
+            // provide a UIA callback, so that the cross-signing keys are uploaded
+            const authDict = { type: "test" };
+            await bootstrapCrossSigning(authDict);
+            // Get the cross signing keys
+            const crossSigningKeys = await crossSigningKeysPromise;
+
+            const getPubKey = (crossSigningKey: any) => Object.values(crossSigningKey!.keys)[0];
+
+            const masterKeyId = await aliceClient.getCrypto()!.getCrossSigningKeyId();
+            expect(masterKeyId).toBe(getPubKey(crossSigningKeys.master_key));
+
+            const selfSigningKeyId = await aliceClient.getCrypto()!.getCrossSigningKeyId(CrossSigningKey.SelfSigning);
+            expect(selfSigningKeyId).toBe(getPubKey(crossSigningKeys.self_signing_key));
+
+            const userSigningKeyId = await aliceClient.getCrypto()!.getCrossSigningKeyId(CrossSigningKey.UserSigning);
+            expect(userSigningKeyId).toBe(getPubKey(crossSigningKeys.user_signing_key));
+        });
+    });
 });

spec/unit/rust-crypto/rust-crypto.spec.ts

@@ -168,7 +168,7 @@ describe("RustCrypto", () => {
         });
     });
 
-    it("getCrossSigningKeyId", async () => {
+    it("getCrossSigningKeyId when there is no cross signing keys", async () => {
         const rustCrypto = await makeTestRustCrypto();
         await expect(rustCrypto.getCrossSigningKeyId()).resolves.toBe(null);
     });

src/client.ts

@@ -210,7 +210,7 @@ import { LocalNotificationSettings } from "./@types/local_notifications";
 import { buildFeatureSupportMap, Feature, ServerSupport } from "./feature";
 import { CryptoBackend } from "./common-crypto/CryptoBackend";
 import { RUST_SDK_STORE_PREFIX } from "./rust-crypto/constants";
-import { BootstrapCrossSigningOpts, CryptoApi, ImportRoomKeysOpts } from "./crypto-api";
+import { BootstrapCrossSigningOpts, CrossSigningKeyInfo, CryptoApi, ImportRoomKeysOpts } from "./crypto-api";
 import { DeviceInfoMap } from "./crypto/DeviceList";
 import {
     AddSecretStorageKeyOpts,
@@ -524,13 +524,8 @@ export interface Capabilities {
     [UNSTABLE_MSC3882_CAPABILITY.altName]?: IMSC3882GetLoginTokenCapability;
 }
 
-/* eslint-disable camelcase */
-export interface ICrossSigningKey {
-    keys: { [algorithm: string]: string };
-    signatures?: ISignatures;
-    usage: string[];
-    user_id: string;
-}
+/** @deprecated prefer {@link CrossSigningKeyInfo}. */
+export type ICrossSigningKey = CrossSigningKeyInfo;
 
 enum CrossSigningKeyType {
     MasterKey = "master_key",

src/crypto-api.ts

@@ -21,6 +21,7 @@ import { UIAuthCallback } from "./interactive-auth";
 import { AddSecretStorageKeyOpts, SecretStorageCallbacks, SecretStorageKeyDescription } from "./secret-storage";
 import { VerificationRequest } from "./crypto-api/verification";
 import { KeyBackupInfo } from "./crypto-api/keybackup";
+import { ISignatures } from "./@types/signed";
 
 /**
  * Public interface to the cryptography parts of the js-sdk
@@ -503,6 +504,17 @@ export enum CrossSigningKey {
     UserSigning = "user_signing",
 }
 
+/**
+ * Information on one of the cross-signing keys.
+ * @see https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3keysdevice_signingupload
+ */
+export interface CrossSigningKeyInfo {
+    keys: { [algorithm: string]: string };
+    signatures?: ISignatures;
+    usage: string[];
+    user_id: string;
+}
+
 /**
  * Recovery key created by {@link CryptoApi#createRecoveryKeyFromPassphrase}
  */

src/rust-crypto/rust-crypto.ts

@@ -41,6 +41,7 @@ import {
     ImportRoomKeyProgressData,
     ImportRoomKeysOpts,
     VerificationRequest,
+    CrossSigningKeyInfo,
 } from "../crypto-api";
 import { deviceKeysToDeviceMap, rustDeviceToJsDevice } from "./device-converter";
 import { IDownloadKeyResult, IQueryKeysRequest } from "../client";
@@ -417,8 +418,45 @@ export class RustCrypto extends TypedEventEmitter<RustCryptoEvents, RustCryptoEv
      * Implementation of {@link CryptoApi#getCrossSigningKeyId}
      */
     public async getCrossSigningKeyId(type: CrossSigningKey = CrossSigningKey.Master): Promise<string | null> {
-        // TODO
-        return null;
+        const userIdentity: RustSdkCryptoJs.OwnUserIdentity | undefined = await this.olmMachine.getIdentity(
+            new RustSdkCryptoJs.UserId(this.userId),
+        );
+
+        const crossSigningStatus: RustSdkCryptoJs.CrossSigningStatus = await this.olmMachine.crossSigningStatus();
+        const privateKeysOnDevice =
+            crossSigningStatus.hasMaster && crossSigningStatus.hasUserSigning && crossSigningStatus.hasSelfSigning;
+
+        if (!userIdentity || !privateKeysOnDevice) {
+            // The public or private keys are not available on this device
+            return null;
+        }
+
+        if (!userIdentity.isVerified()) {
+            // We have both public and private keys, but they don't match!
+            return null;
+        }
+
+        let key: string;
+        switch (type) {
+            case CrossSigningKey.Master:
+                key = userIdentity.masterKey;
+                break;
+            case CrossSigningKey.SelfSigning:
+                key = userIdentity.selfSigningKey;
+                break;
+            case CrossSigningKey.UserSigning:
+                key = userIdentity.userSigningKey;
+                break;
+            default:
+                // Unknown type
+                return null;
+        }
+
+        const parsedKey: CrossSigningKeyInfo = JSON.parse(key);
+        // `keys` is an object with { [`ed25519:${pubKey}`]: pubKey }
+        // We assume only a single key, and we want the bare form without type
+        // prefix, so we select the values.
+        return Object.values(parsedKey.keys)[0];
     }
 
     /**