services/core/java/com/android/server/RecoverySystemService.java

/*
 * Copyright (C) 2016 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.server;

import android.content.Context;
import android.net.LocalSocket;
import android.net.LocalSocketAddress;
import android.os.IRecoverySystem;
import android.os.IRecoverySystemProgressListener;
import android.os.RecoverySystem;
import android.os.RemoteException;
import android.os.SystemProperties;
import android.system.ErrnoException;
import android.system.Os;
import android.util.Slog;

import libcore.io.IoUtils;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

/**
 * The recovery system service is responsible for coordinating recovery related
 * functions on the device. It sets up (or clears) the bootloader control block
 * (BCB), which will be read by the bootloader and the recovery image. It also
 * triggers /system/bin/uncrypt via init to de-encrypt an OTA package on the
 * /data partition so that it can be accessed under the recovery image.
 */
public final class RecoverySystemService extends SystemService {
    private static final String TAG = "RecoverySystemService";
    private static final boolean DEBUG = false;

    // The socket at /dev/socket/uncrypt to communicate with uncrypt.
    private static final String UNCRYPT_SOCKET = "uncrypt";

    private static final int SOCKET_CONNECTION_MAX_RETRY = 30;

    private Context mContext;

    public RecoverySystemService(Context context) {
        super(context);
        mContext = context;
    }

    @Override
    public void onStart() {
        publishBinderService(Context.RECOVERY_SERVICE, new BinderService());
    }

    private final class BinderService extends IRecoverySystem.Stub {
        @Override // Binder call
        public boolean uncrypt(String filename, IRecoverySystemProgressListener listener) {
            if (DEBUG) Slog.d(TAG, "uncrypt: " + filename);

            mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);

            // Write the filename into UNCRYPT_PACKAGE_FILE to be read by
            // uncrypt.
            RecoverySystem.UNCRYPT_PACKAGE_FILE.delete();

            try (FileWriter uncryptFile = new FileWriter(RecoverySystem.UNCRYPT_PACKAGE_FILE)) {
                uncryptFile.write(filename + "\n");
            } catch (IOException e) {
                Slog.e(TAG, "IOException when writing \"" + RecoverySystem.UNCRYPT_PACKAGE_FILE +
                        "\": " + e.getMessage());
                return false;
            }

            // Trigger uncrypt via init.
            SystemProperties.set("ctl.start", "uncrypt");

            // Connect to the uncrypt service socket.
            LocalSocket socket = connectService();
            if (socket == null) {
                Slog.e(TAG, "Failed to connect to uncrypt socket");
                return false;
            }

            // Read the status from the socket.
            try (DataInputStream dis = new DataInputStream(socket.getInputStream());
                    DataOutputStream dos = new DataOutputStream(socket.getOutputStream())) {
                int lastStatus = Integer.MIN_VALUE;
                while (true) {
                    int status = dis.readInt();
                    // Avoid flooding the log with the same message.
                    if (status == lastStatus && lastStatus != Integer.MIN_VALUE) {
                        continue;
                    }
                    lastStatus = status;

                    if (status >= 0 && status <= 100) {
                        // Update status
                        Slog.i(TAG, "uncrypt read status: " + status);
                        if (listener != null) {
                            try {
                                listener.onProgress(status);
                            } catch (RemoteException unused) {
                                Slog.w(TAG, "RemoteException when posting progress");
                            }
                        }
                        if (status == 100) {
                            Slog.i(TAG, "uncrypt successfully finished.");
                            // Ack receipt of the final status code. uncrypt
                            // waits for the ack so the socket won't be
                            // destroyed before we receive the code.
                            dos.writeInt(0);
                            dos.flush();
                            break;
                        }
                    } else {
                        // Error in /system/bin/uncrypt.
                        Slog.e(TAG, "uncrypt failed with status: " + status);
                        // Ack receipt of the final status code. uncrypt waits
                        // for the ack so the socket won't be destroyed before
                        // we receive the code.
                        dos.writeInt(0);
                        dos.flush();
                        return false;
                    }
                }
            } catch (IOException e) {
                Slog.e(TAG, "IOException when reading status: " + e);
                return false;
            } finally {
                IoUtils.closeQuietly(socket);
            }

            return true;
        }

        @Override // Binder call
        public boolean clearBcb() {
            if (DEBUG) Slog.d(TAG, "clearBcb");
            return setupOrClearBcb(false, null);
        }

        @Override // Binder call
        public boolean setupBcb(String command) {
            if (DEBUG) Slog.d(TAG, "setupBcb: [" + command + "]");
            return setupOrClearBcb(true, command);
        }

        private LocalSocket connectService() {
            LocalSocket socket = new LocalSocket();
            boolean done = false;
            // The uncrypt socket will be created by init upon receiving the
            // service request. It may not be ready by this point. So we will
            // keep retrying until success or reaching timeout.
            for (int retry = 0; retry < SOCKET_CONNECTION_MAX_RETRY; retry++) {
                try {
                    socket.connect(new LocalSocketAddress(UNCRYPT_SOCKET,
                            LocalSocketAddress.Namespace.RESERVED));
                    done = true;
                    break;
                } catch (IOException unused) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        Slog.w(TAG, "Interrupted: " + e);
                    }
                }
            }
            if (!done) {
                Slog.e(TAG, "Timed out connecting to uncrypt socket");
                return null;
            }
            return socket;
        }

        private boolean setupOrClearBcb(boolean isSetup, String command) {
            mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);

            if (isSetup) {
                SystemProperties.set("ctl.start", "setup-bcb");
            } else {
                SystemProperties.set("ctl.start", "clear-bcb");
            }

            // Connect to the uncrypt service socket.
            LocalSocket socket = connectService();
            if (socket == null) {
                Slog.e(TAG, "Failed to connect to uncrypt socket");
                return false;
            }

            try (DataInputStream dis = new DataInputStream(socket.getInputStream());
                    DataOutputStream dos = new DataOutputStream(socket.getOutputStream())) {
                // Send the BCB commands if it's to setup BCB.
                if (isSetup) {
                    dos.writeInt(command.length());
                    dos.writeBytes(command);
                    dos.flush();
                }

                // Read the status from the socket.
                int status = dis.readInt();

                // Ack receipt of the status code. uncrypt waits for the ack so
                // the socket won't be destroyed before we receive the code.
                dos.writeInt(0);
                dos.flush();

                if (status == 100) {
                    Slog.i(TAG, "uncrypt " + (isSetup ? "setup" : "clear") +
                            " bcb successfully finished.");
                } else {
                    // Error in /system/bin/uncrypt.
                    Slog.e(TAG, "uncrypt failed with status: " + status);
                    return false;
                }
            } catch (IOException e) {
                Slog.e(TAG, "IOException when getting output stream: " + e);
                return false;
            } finally {
                IoUtils.closeQuietly(socket);
            }

            return true;
        }
    }
}