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/*
* Copyright (C) 2021 The Android Open Source Project
*
* 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.
*/
package android.security;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* GenerateKey is a helper class to handle interactions between Keystore and the RemoteProvisioner
* app. There are two cases where Keystore should use this class.
*
* (1) : An app generates a new attested key pair, so Keystore calls notifyKeyGenerated to let the
* RemoteProvisioner app check if the state of the attestation key pool is getting low enough
* to warrant provisioning more attestation certificates early.
*
* (2) : An app attempts to generate a new key pair, but the keystore service discovers it is out of
* attestation key pairs and cannot provide one for the given application. Keystore can then
* make a blocking call on notifyEmpty to allow the RemoteProvisioner app to get another
* attestation certificate chain provisioned.
*
* In most cases, the proper usage of (1) should preclude the need for (2).
*
* @hide
*/
public class GenerateRkpKey {
private static final String TAG = "GenerateRkpKey";
private static final int NOTIFY_EMPTY = 0;
private static final int NOTIFY_KEY_GENERATED = 1;
private static final int TIMEOUT_MS = 1000;
private IGenerateRkpKeyService mBinder;
private Context mContext;
private CountDownLatch mCountDownLatch;
private ServiceConnection mConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName className, IBinder service) {
mBinder = IGenerateRkpKeyService.Stub.asInterface(service);
mCountDownLatch.countDown();
}
@Override public void onBindingDied(ComponentName className) {
mCountDownLatch.countDown();
}
@Override
public void onServiceDisconnected(ComponentName className) {
mBinder = null;
}
};
/**
* Constructor which takes a Context object.
*/
public GenerateRkpKey(Context context) {
mContext = context;
}
private void bindAndSendCommand(int command, int securityLevel) throws RemoteException {
Intent intent = new Intent(IGenerateRkpKeyService.class.getName());
ComponentName comp = intent.resolveSystemService(mContext.getPackageManager(), 0);
if (comp == null) {
// On a system that does not use RKP, the RemoteProvisioner app won't be installed.
return;
}
intent.setComponent(comp);
mCountDownLatch = new CountDownLatch(1);
if (!mContext.bindService(intent, mConnection, Context.BIND_AUTO_CREATE)) {
throw new RemoteException("Failed to bind to GenerateRkpKeyService");
}
try {
mCountDownLatch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
Log.e(TAG, "Interrupted: ", e);
}
if (mBinder != null) {
switch (command) {
case NOTIFY_EMPTY:
mBinder.generateKey(securityLevel);
break;
case NOTIFY_KEY_GENERATED:
mBinder.notifyKeyGenerated(securityLevel);
break;
default:
Log.e(TAG, "Invalid case for command");
}
} else {
Log.e(TAG, "Binder object is null; failed to bind to GenerateRkpKeyService.");
}
mContext.unbindService(mConnection);
}
/**
* Fulfills the use case of (2) described in the class documentation. Blocks until the
* RemoteProvisioner application can get new attestation keys signed by the server.
*/
public void notifyEmpty(int securityLevel) throws RemoteException {
bindAndSendCommand(NOTIFY_EMPTY, securityLevel);
}
/**
* Fulfills the use case of (1) described in the class documentation. Non blocking call.
*/
public void notifyKeyGenerated(int securityLevel) throws RemoteException {
bindAndSendCommand(NOTIFY_KEY_GENERATED, securityLevel);
}
}
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