src/com/android/remoteprovisioner/service/GenerateRkpKeyService.java

/**
 * Copyright (C) 2020 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 com.android.remoteprovisioner.service;

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.security.IGenerateRkpKeyService;
import android.security.remoteprovisioning.AttestationPoolStatus;
import android.security.remoteprovisioning.ImplInfo;
import android.security.remoteprovisioning.IRemoteProvisioning;
import android.util.Log;

import com.android.remoteprovisioner.GeekResponse;
import com.android.remoteprovisioner.Provisioner;
import com.android.remoteprovisioner.ServerInterface;
import com.android.remoteprovisioner.SettingsManager;

/**
 * Provides the implementation for IGenerateKeyService.aidl
 */
public class GenerateRkpKeyService extends Service {
    private static final int KEY_GENERATION_PAUSE_MS = 1000;
    private static final String SERVICE = "android.security.remoteprovisioning";
    private static final String TAG = "RemoteProvisioningService";

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    private final IGenerateRkpKeyService.Stub mBinder = new IGenerateRkpKeyService.Stub() {
        @Override
        public void generateKey(int securityLevel) {
            try {
                IRemoteProvisioning binder =
                        IRemoteProvisioning.Stub.asInterface(ServiceManager.getService(SERVICE));
                checkAndFillPool(binder, securityLevel);
            } catch (RemoteException e) {
                Log.e(TAG, "Remote Exception: ", e);
            }
        }

        @Override
        public void notifyKeyGenerated(int securityLevel) {
            try {
                IRemoteProvisioning binder =
                        IRemoteProvisioning.Stub.asInterface(ServiceManager.getService(SERVICE));
                checkAndFillPool(binder, securityLevel);
            } catch (RemoteException e) {
                Log.e(TAG, "Remote Exception: ", e);
            }
        }

        private void checkAndFillPool(IRemoteProvisioning binder, int secLevel)
                throws RemoteException {
            AttestationPoolStatus pool =
                    binder.getPoolStatus(System.currentTimeMillis(), secLevel);
            ImplInfo[] implInfos = binder.getImplementationInfo();
            int curve = 0;
            for (int i = 0; i < implInfos.length; i++) {
                if (implInfos[i].secLevel == secLevel) {
                    curve = implInfos[i].supportedCurve;
                    break;
                }
            }
            // If there are no unassigned keys, go ahead and provision some. If there are no
            // attested keys at all on the system, this implies that it is a hybrid
            // rkp/factory-provisioned system that has turned off RKP. In that case, do
            // not provision.
            if (pool.unassigned == 0 && pool.attested != 0) {
                Log.i(TAG, "All signed keys are currently in use, provisioning more.");
                Context context = getApplicationContext();
                int keysToProvision = SettingsManager.getExtraSignedKeysAvailable(context);
                int existingUnsignedKeys = pool.total - pool.attested;
                int keysToGenerate = keysToProvision - existingUnsignedKeys;
                try {
                    for (int i = 0; i < keysToGenerate; i++) {
                        binder.generateKeyPair(false /* isTestMode */, secLevel);
                        Thread.sleep(KEY_GENERATION_PAUSE_MS);
                    }
                } catch (InterruptedException e) {
                    Log.i(TAG, "Thread interrupted", e);
                }
                GeekResponse resp = ServerInterface.fetchGeek(context);
                if (resp == null) {
                    Log.e(TAG, "Server unavailable");
                    return;
                }
                Provisioner.provisionCerts(keysToProvision, secLevel, resp.getGeekChain(curve),
                                           resp.getChallenge(), binder, context);
            }
        }
    };
}