src/com/android/remoteprovisioner/BootReceiver.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;

import static java.lang.Math.max;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.security.remoteprovisioning.AttestationPoolStatus;
import android.security.remoteprovisioning.ImplInfo;
import android.security.remoteprovisioning.IRemoteProvisioning;
import android.util.Log;

import androidx.work.Constraints;
import androidx.work.ExistingPeriodicWorkPolicy;
import androidx.work.NetworkType;
import androidx.work.OneTimeWorkRequest;
import androidx.work.PeriodicWorkRequest;
import androidx.work.WorkManager;

import java.time.Duration;
import java.util.concurrent.TimeUnit;

/**
 * A receiver class that listens for boot to be completed and then starts a recurring job that will
 * monitor the status of the attestation key pool on device, purging old certificates and requesting
 * new ones as needed.
 */
public class BootReceiver extends BroadcastReceiver {
    private static final String TAG = "RemoteProvisioningBootReceiver";
    private static final String SERVICE = "android.security.remoteprovisioning";

    private static final Duration SCHEDULER_PERIOD = Duration.ofDays(1);

    private static final int ESTIMATED_DOWNLOAD_BYTES_STATIC = 2300;
    private static final int ESTIMATED_X509_CERT_BYTES = 540;
    private static final int ESTIMATED_UPLOAD_BYTES_STATIC = 600;
    private static final int ESTIMATED_CSR_KEY_BYTES = 44;

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i(TAG, "Caught boot intent, waking up.");
        SettingsManager.generateAndSetId(context);
        // An average call transmits about 500 bytes total. These calculations are for the
        // once a month wake-up where provisioning occurs, where the expected bytes sent is closer
        // to 8-10KB.
        int numKeysNeeded = max(SettingsManager.getExtraSignedKeysAvailable(context),
                                calcNumPotentialKeysToDownload());
        int estimatedDlBytes =
                ESTIMATED_DOWNLOAD_BYTES_STATIC + (ESTIMATED_X509_CERT_BYTES * numKeysNeeded);
        int estimatedUploadBytes =
                ESTIMATED_UPLOAD_BYTES_STATIC + (ESTIMATED_CSR_KEY_BYTES * numKeysNeeded);

        Constraints constraints = new Constraints.Builder()
               .setRequiredNetworkType(NetworkType.CONNECTED)
               .build();
        PeriodicWorkRequest workRequest =
                new PeriodicWorkRequest.Builder(PeriodicProvisioner.class, 1, TimeUnit.DAYS)
                        .setConstraints(constraints)
                        .build();
        WorkManager
                .getInstance(context)
                .enqueueUniquePeriodicWork("ProvisioningJob",
                                       ExistingPeriodicWorkPolicy.REPLACE, // Replace on reboot.
                                       workRequest);
        if (WidevineProvisioner.isWidevineProvisioningNeeded()) {
            Log.i(TAG, "WV provisioning needed. Queueing a one-time provisioning job.");
            OneTimeWorkRequest wvRequest =
                    new OneTimeWorkRequest.Builder(WidevineProvisioner.class)
                            .setConstraints(constraints)
                            .build();
            WorkManager.getInstance(context).enqueue(wvRequest);
        }
    }



    private int calcNumPotentialKeysToDownload() {
        try {
            IRemoteProvisioning binder =
                IRemoteProvisioning.Stub.asInterface(ServiceManager.getService(SERVICE));
            int totalKeysAssigned = 0;
            if (binder == null) {
                Log.e(TAG, "Binder returned null pointer to RemoteProvisioning service.");
                return totalKeysAssigned;
            }
            ImplInfo[] implInfos = binder.getImplementationInfo();
            if (implInfos == null) {
                Log.e(TAG, "No instances of IRemotelyProvisionedComponent registered in "
                           + SERVICE);
                return totalKeysAssigned;
            }
            for (int i = 0; i < implInfos.length; i++) {
                AttestationPoolStatus pool = binder.getPoolStatus(0, implInfos[i].secLevel);
                if (pool != null) {
                    totalKeysAssigned += pool.attested - pool.unassigned;
                }
            }
            return totalKeysAssigned;
        } catch (RemoteException e) {
            Log.e(TAG, "Failure on the RemoteProvisioning backend.", e);
            return 0;
        }
    }
}