Add rust-crypto#isCrossSigningReady implementation

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

@@ -168,4 +168,23 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("cross-signing (%s)", (backend: s
             });
         });
     });
+
+    describe("isCrossSigningReady()", () => {
+        it("should return false if cross-signing is not bootstrapped", async () => {
+            mockSetupCrossSigningRequests();
+
+            const isCrossSigningReady = await aliceClient.getCrypto()!.isCrossSigningReady();
+
+            expect(isCrossSigningReady).toBeFalsy();
+        });
+
+        it("should return true after bootstrapping cross-signing", async () => {
+            mockSetupCrossSigningRequests();
+            await bootstrapCrossSigning({ type: "test" });
+
+            const isCrossSigningReady = await aliceClient.getCrypto()!.isCrossSigningReady();
+
+            expect(isCrossSigningReady).toBeTruthy();
+        });
+    });
 });

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

@@ -93,11 +93,6 @@ describe("RustCrypto", () => {
         });
     });
 
-    it("isCrossSigningReady", async () => {
-        const rustCrypto = await makeTestRustCrypto();
-        await expect(rustCrypto.isCrossSigningReady()).resolves.toBe(false);
-    });
-
     it("getCrossSigningKeyId", async () => {
         const rustCrypto = await makeTestRustCrypto();
         await expect(rustCrypto.getCrossSigningKeyId()).resolves.toBe(null);

src/rust-crypto/rust-crypto.ts

@@ -326,7 +326,15 @@ export class RustCrypto implements CryptoBackend {
      * Implementation of {@link CryptoApi#isCrossSigningReady}
      */
     public async isCrossSigningReady(): Promise<boolean> {
-        return false;
+        const { publicKeysOnDevice, privateKeysInSecretStorage, privateKeysCachedLocally } =
+            await this.getCrossSigningStatus();
+        const hasKeysInCache =
+            Boolean(privateKeysCachedLocally.masterKey) &&
+            Boolean(privateKeysCachedLocally.selfSigningKey) &&
+            Boolean(privateKeysCachedLocally.userSigningKey);
+
+        // The cross signing is ready if the public and private keys are available
+        return publicKeysOnDevice && (hasKeysInCache || privateKeysInSecretStorage);
     }
 
     /**