Add an extra consistency check in bootstrapCrossSigning (#4629)

* Add an extra consistency check in `bootstrapCrossSigning`

check that `importCrossSigningKeys` has actually worked

* Update src/rust-crypto/CrossSigningIdentity.ts

* declare type in @types, instead of in source

Author: richvdh

src/@types/matrix-sdk-crypto-wasm.d.ts

@@ -20,6 +20,11 @@ declare module "@matrix-org/matrix-sdk-crypto-wasm" {
     interface OlmMachine {
         importSecretsBundle(bundle: RustSdkCryptoJs.SecretsBundle): Promise<void>;
         exportSecretsBundle(): Promise<RustSdkCryptoJs.SecretsBundle>;
+        importCrossSigningKeys(
+            master_key?: string,
+            self_signing_key?: string,
+            user_signing_key?: string,
+        ): Promise<RustSdkCryptoJs.CrossSigningStatus>;
     }
 
     interface SecretsBundle {

src/rust-crypto/CrossSigningIdentity.ts

@@ -87,12 +87,18 @@ export class CrossSigningIdentity {
                     "bootstrapCrossSigning: Cross-signing private keys not found locally, but they are available " +
                         "in secret storage, reading storage and caching locally",
                 );
-                await this.olmMachine.importCrossSigningKeys(
+                const status = await this.olmMachine.importCrossSigningKeys(
                     masterKeyFromSecretStorage,
                     selfSigningKeyFromSecretStorage,
                     userSigningKeyFromSecretStorage,
                 );
 
+                // Check that `importCrossSigningKeys` worked correctly (for example, it will fail silently if the
+                // public keys are not available).
+                if (!status.hasMaster || !status.hasSelfSigning || !status.hasUserSigning) {
+                    throw new Error("importCrossSigningKeys failed to import the keys");
+                }
+
                 // Get the current device
                 const device: RustSdkCryptoJs.Device = await this.olmMachine.getDevice(
                     this.olmMachine.userId,