/*
* Copyright (C) 2014 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.Manifest;
import android.app.ActivityManager;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Binder;
import android.os.IBinder;
import android.os.RemoteException;
import android.os.SystemProperties;
import android.os.UserHandle;
import android.os.UserManager;
import android.service.persistentdata.IPersistentDataBlockService;
import android.service.persistentdata.PersistentDataBlockManager;
import android.util.Log;
import android.util.Slog;
import com.android.internal.R;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.util.Preconditions;
import libcore.io.IoUtils;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* Service for reading and writing blocks to a persistent partition.
* This data will live across factory resets not initiated via the Settings UI.
* When a device is factory reset through Settings this data is wiped.
*
* Allows writing one block at a time. Namely, each time {@link IPersistentDataBlockService#write}
* is called, it will overwrite the data that was previously written on the block.
*
* Clients can query the size of the currently written block via
* {@link IPersistentDataBlockService#getDataBlockSize}
*
* Clients can read any number of bytes from the currently written block up to its total size by
* invoking {@link IPersistentDataBlockService#read}
*/
public class PersistentDataBlockService extends SystemService {
private static final String TAG = PersistentDataBlockService.class.getSimpleName();
private static final String PERSISTENT_DATA_BLOCK_PROP = "ro.frp.pst";
private static final int HEADER_SIZE = 8;
// Magic number to mark block device as adhering to the format consumed by this service
private static final int PARTITION_TYPE_MARKER = 0x19901873;
/** Size of the block reserved for FPR credential, including 4 bytes for the size header. */
private static final int FRP_CREDENTIAL_RESERVED_SIZE = 1000;
/** Maximum size of the FRP credential handle that can be stored. */
private static final int MAX_FRP_CREDENTIAL_HANDLE_SIZE = FRP_CREDENTIAL_RESERVED_SIZE - 4;
// Limit to 100k as blocks larger than this might cause strain on Binder.
private static final int MAX_DATA_BLOCK_SIZE = 1024 * 100;
public static final int DIGEST_SIZE_BYTES = 32;
private static final String OEM_UNLOCK_PROP = "sys.oem_unlock_allowed";
private static final String FLASH_LOCK_PROP = "ro.boot.flash.locked";
private static final String FLASH_LOCK_LOCKED = "1";
private static final String FLASH_LOCK_UNLOCKED = "0";
private final Context mContext;
private final String mDataBlockFile;
private final Object mLock = new Object();
private final CountDownLatch mInitDoneSignal = new CountDownLatch(1);
private int mAllowedUid = -1;
private long mBlockDeviceSize;
@GuardedBy("mLock")
private boolean mIsWritable = true;
public PersistentDataBlockService(Context context) {
super(context);
mContext = context;
mDataBlockFile = SystemProperties.get(PERSISTENT_DATA_BLOCK_PROP);
mBlockDeviceSize = -1; // Load lazily
}
private int getAllowedUid(int userHandle) {
String allowedPackage = mContext.getResources()
.getString(R.string.config_persistentDataPackageName);
PackageManager pm = mContext.getPackageManager();
int allowedUid = -1;
try {
allowedUid = pm.getPackageUidAsUser(allowedPackage,
PackageManager.MATCH_SYSTEM_ONLY, userHandle);
} catch (PackageManager.NameNotFoundException e) {
// not expected
Slog.e(TAG, "not able to find package " + allowedPackage, e);
}
return allowedUid;
}
@Override
public void onStart() {
// Do init on a separate thread, will join in PHASE_ACTIVITY_MANAGER_READY
SystemServerInitThreadPool.get().submit(() -> {
mAllowedUid = getAllowedUid(UserHandle.USER_SYSTEM);
enforceChecksumValidity();
formatIfOemUnlockEnabled();
publishBinderService(Context.PERSISTENT_DATA_BLOCK_SERVICE, mService);
mInitDoneSignal.countDown();
}, TAG + ".onStart");
}
@Override
public void onBootPhase(int phase) {
// Wait for initialization in onStart to finish
if (phase == PHASE_SYSTEM_SERVICES_READY) {
try {
if (!mInitDoneSignal.await(10, TimeUnit.SECONDS)) {
throw new IllegalStateException("Service " + TAG + " init timeout");
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new IllegalStateException("Service " + TAG + " init interrupted", e);
}
LocalServices.addService(PersistentDataBlockManagerInternal.class, mInternalService);
}
super.onBootPhase(phase);
}
private void formatIfOemUnlockEnabled() {
boolean enabled = doGetOemUnlockEnabled();
if (enabled) {
synchronized (mLock) {
formatPartitionLocked(true);
}
}
SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0");
}
private void enforceOemUnlockReadPermission() {
if (mContext.checkCallingOrSelfPermission(Manifest.permission.READ_OEM_UNLOCK_STATE)
== PackageManager.PERMISSION_DENIED
&& mContext.checkCallingOrSelfPermission(Manifest.permission.OEM_UNLOCK_STATE)
== PackageManager.PERMISSION_DENIED) {
throw new SecurityException("Can't access OEM unlock state. Requires "
+ "READ_OEM_UNLOCK_STATE or OEM_UNLOCK_STATE permission.");
}
}
private void enforceOemUnlockWritePermission() {
mContext.enforceCallingOrSelfPermission(
Manifest.permission.OEM_UNLOCK_STATE,
"Can't modify OEM unlock state");
}
private void enforceUid(int callingUid) {
if (callingUid != mAllowedUid) {
throw new SecurityException("uid " + callingUid + " not allowed to access PST");
}
}
private void enforceIsAdmin() {
final int userId = UserHandle.getCallingUserId();
final boolean isAdmin = UserManager.get(mContext).isUserAdmin(userId);
if (!isAdmin) {
throw new SecurityException(
"Only the Admin user is allowed to change OEM unlock state");
}
}
private void enforceUserRestriction(String userRestriction) {
if (UserManager.get(mContext).hasUserRestriction(userRestriction)) {
throw new SecurityException(
"OEM unlock is disallowed by user restriction: " + userRestriction);
}
}
private int getTotalDataSizeLocked(DataInputStream inputStream) throws IOException {
// skip over checksum
inputStream.skipBytes(DIGEST_SIZE_BYTES);
int totalDataSize;
int blockId = inputStream.readInt();
if (blockId == PARTITION_TYPE_MARKER) {
totalDataSize = inputStream.readInt();
} else {
totalDataSize = 0;
}
return totalDataSize;
}
private long getBlockDeviceSize() {
synchronized (mLock) {
if (mBlockDeviceSize == -1) {
mBlockDeviceSize = nativeGetBlockDeviceSize(mDataBlockFile);
}
}
return mBlockDeviceSize;
}
private boolean enforceChecksumValidity() {
byte[] storedDigest = new byte[DIGEST_SIZE_BYTES];
synchronized (mLock) {
byte[] digest = computeDigestLocked(storedDigest);
if (digest == null || !Arrays.equals(storedDigest, digest)) {
Slog.i(TAG, "Formatting FRP partition...");
formatPartitionLocked(false);
return false;
}
}
return true;
}
private boolean computeAndWriteDigestLocked() {
byte[] digest = computeDigestLocked(null);
if (digest != null) {
DataOutputStream outputStream;
try {
outputStream = new DataOutputStream(
new FileOutputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available?", e);
return false;
}
try {
outputStream.write(digest, 0, DIGEST_SIZE_BYTES);
outputStream.flush();
} catch (IOException e) {
Slog.e(TAG, "failed to write block checksum", e);
return false;
} finally {
IoUtils.closeQuietly(outputStream);
}
return true;
} else {
return false;
}
}
private byte[] computeDigestLocked(byte[] storedDigest) {
DataInputStream inputStream;
try {
inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available?", e);
return null;
}
MessageDigest md;
try {
md = MessageDigest.getInstance("SHA-256");
} catch (NoSuchAlgorithmException e) {
// won't ever happen -- every implementation is required to support SHA-256
Slog.e(TAG, "SHA-256 not supported?", e);
IoUtils.closeQuietly(inputStream);
return null;
}
try {
if (storedDigest != null && storedDigest.length == DIGEST_SIZE_BYTES) {
inputStream.read(storedDigest);
} else {
inputStream.skipBytes(DIGEST_SIZE_BYTES);
}
int read;
byte[] data = new byte[1024];
md.update(data, 0, DIGEST_SIZE_BYTES); // include 0 checksum in digest
while ((read = inputStream.read(data)) != -1) {
md.update(data, 0, read);
}
} catch (IOException e) {
Slog.e(TAG, "failed to read partition", e);
return null;
} finally {
IoUtils.closeQuietly(inputStream);
}
return md.digest();
}
private void formatPartitionLocked(boolean setOemUnlockEnabled) {
DataOutputStream outputStream;
try {
outputStream = new DataOutputStream(new FileOutputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available?", e);
return;
}
byte[] data = new byte[DIGEST_SIZE_BYTES];
try {
outputStream.write(data, 0, DIGEST_SIZE_BYTES);
outputStream.writeInt(PARTITION_TYPE_MARKER);
outputStream.writeInt(0); // data size
outputStream.flush();
} catch (IOException e) {
Slog.e(TAG, "failed to format block", e);
return;
} finally {
IoUtils.closeQuietly(outputStream);
}
doSetOemUnlockEnabledLocked(setOemUnlockEnabled);
computeAndWriteDigestLocked();
}
private void doSetOemUnlockEnabledLocked(boolean enabled) {
FileOutputStream outputStream;
try {
outputStream = new FileOutputStream(new File(mDataBlockFile));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available", e);
return;
}
try {
FileChannel channel = outputStream.getChannel();
channel.position(getBlockDeviceSize() - 1);
ByteBuffer data = ByteBuffer.allocate(1);
data.put(enabled ? (byte) 1 : (byte) 0);
data.flip();
channel.write(data);
outputStream.flush();
} catch (IOException e) {
Slog.e(TAG, "unable to access persistent partition", e);
return;
} finally {
SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0");
IoUtils.closeQuietly(outputStream);
}
}
private boolean doGetOemUnlockEnabled() {
DataInputStream inputStream;
try {
inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available");
return false;
}
try {
synchronized (mLock) {
inputStream.skip(getBlockDeviceSize() - 1);
return inputStream.readByte() != 0;
}
} catch (IOException e) {
Slog.e(TAG, "unable to access persistent partition", e);
return false;
} finally {
IoUtils.closeQuietly(inputStream);
}
}
private long doGetMaximumDataBlockSize() {
long actualSize = getBlockDeviceSize() - HEADER_SIZE - DIGEST_SIZE_BYTES
- FRP_CREDENTIAL_RESERVED_SIZE - 1;
return actualSize <= MAX_DATA_BLOCK_SIZE ? actualSize : MAX_DATA_BLOCK_SIZE;
}
private native long nativeGetBlockDeviceSize(String path);
private native int nativeWipe(String path);
private final IBinder mService = new IPersistentDataBlockService.Stub() {
@Override
public int write(byte[] data) throws RemoteException {
enforceUid(Binder.getCallingUid());
// Need to ensure we don't write over the last byte
long maxBlockSize = doGetMaximumDataBlockSize();
if (data.length > maxBlockSize) {
// partition is ~500k so shouldn't be a problem to downcast
return (int) -maxBlockSize;
}
DataOutputStream outputStream;
try {
outputStream = new DataOutputStream(new FileOutputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available?", e);
return -1;
}
ByteBuffer headerAndData = ByteBuffer.allocate(data.length + HEADER_SIZE);
headerAndData.putInt(PARTITION_TYPE_MARKER);
headerAndData.putInt(data.length);
headerAndData.put(data);
synchronized (mLock) {
if (!mIsWritable) {
IoUtils.closeQuietly(outputStream);
return -1;
}
try {
byte[] checksum = new byte[DIGEST_SIZE_BYTES];
outputStream.write(checksum, 0, DIGEST_SIZE_BYTES);
outputStream.write(headerAndData.array());
outputStream.flush();
} catch (IOException e) {
Slog.e(TAG, "failed writing to the persistent data block", e);
return -1;
} finally {
IoUtils.closeQuietly(outputStream);
}
if (computeAndWriteDigestLocked()) {
return data.length;
} else {
return -1;
}
}
}
@Override
public byte[] read() {
enforceUid(Binder.getCallingUid());
if (!enforceChecksumValidity()) {
return new byte[0];
}
DataInputStream inputStream;
try {
inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available?", e);
return null;
}
try {
synchronized (mLock) {
int totalDataSize = getTotalDataSizeLocked(inputStream);
if (totalDataSize == 0) {
return new byte[0];
}
byte[] data = new byte[totalDataSize];
int read = inputStream.read(data, 0, totalDataSize);
if (read < totalDataSize) {
// something went wrong, not returning potentially corrupt data
Slog.e(TAG, "failed to read entire data block. bytes read: " +
read + "/" + totalDataSize);
return null;
}
return data;
}
} catch (IOException e) {
Slog.e(TAG, "failed to read data", e);
return null;
} finally {
try {
inputStream.close();
} catch (IOException e) {
Slog.e(TAG, "failed to close OutputStream");
}
}
}
@Override
public void wipe() {
enforceOemUnlockWritePermission();
synchronized (mLock) {
int ret = nativeWipe(mDataBlockFile);
if (ret < 0) {
Slog.e(TAG, "failed to wipe persistent partition");
} else {
mIsWritable = false;
Slog.i(TAG, "persistent partition now wiped and unwritable");
}
}
}
@Override
public void setOemUnlockEnabled(boolean enabled) throws SecurityException {
// do not allow monkey to flip the flag
if (ActivityManager.isUserAMonkey()) {
return;
}
enforceOemUnlockWritePermission();
enforceIsAdmin();
if (enabled) {
// Do not allow oem unlock to be enabled if it's disallowed by a user restriction.
enforceUserRestriction(UserManager.DISALLOW_OEM_UNLOCK);
enforceUserRestriction(UserManager.DISALLOW_FACTORY_RESET);
}
synchronized (mLock) {
doSetOemUnlockEnabledLocked(enabled);
computeAndWriteDigestLocked();
}
}
@Override
public boolean getOemUnlockEnabled() {
enforceOemUnlockReadPermission();
return doGetOemUnlockEnabled();
}
@Override
public int getFlashLockState() {
enforceOemUnlockReadPermission();
String locked = SystemProperties.get(FLASH_LOCK_PROP);
switch (locked) {
case FLASH_LOCK_LOCKED:
return PersistentDataBlockManager.FLASH_LOCK_LOCKED;
case FLASH_LOCK_UNLOCKED:
return PersistentDataBlockManager.FLASH_LOCK_UNLOCKED;
default:
return PersistentDataBlockManager.FLASH_LOCK_UNKNOWN;
}
}
@Override
public int getDataBlockSize() {
enforcePersistentDataBlockAccess();
DataInputStream inputStream;
try {
inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available");
return 0;
}
try {
synchronized (mLock) {
return getTotalDataSizeLocked(inputStream);
}
} catch (IOException e) {
Slog.e(TAG, "error reading data block size");
return 0;
} finally {
IoUtils.closeQuietly(inputStream);
}
}
private void enforcePersistentDataBlockAccess() {
if (mContext.checkCallingPermission(Manifest.permission.ACCESS_PDB_STATE)
!= PackageManager.PERMISSION_GRANTED) {
enforceUid(Binder.getCallingUid());
}
}
@Override
public long getMaximumDataBlockSize() {
enforceUid(Binder.getCallingUid());
return doGetMaximumDataBlockSize();
}
@Override
public boolean hasFrpCredentialHandle() {
enforcePersistentDataBlockAccess();
try {
return mInternalService.getFrpCredentialHandle() != null;
} catch (IllegalStateException e) {
Slog.e(TAG, "error reading frp handle", e);
throw new UnsupportedOperationException("cannot read frp credential");
}
}
};
private PersistentDataBlockManagerInternal mInternalService =
new PersistentDataBlockManagerInternal() {
@Override
public void setFrpCredentialHandle(byte[] handle) {
Preconditions.checkArgument(handle == null || handle.length > 0,
"handle must be null or non-empty");
Preconditions.checkArgument(handle == null
|| handle.length <= MAX_FRP_CREDENTIAL_HANDLE_SIZE,
"handle must not be longer than " + MAX_FRP_CREDENTIAL_HANDLE_SIZE);
FileOutputStream outputStream;
try {
outputStream = new FileOutputStream(new File(mDataBlockFile));
} catch (FileNotFoundException e) {
Slog.e(TAG, "partition not available", e);
return;
}
ByteBuffer data = ByteBuffer.allocate(FRP_CREDENTIAL_RESERVED_SIZE);
data.putInt(handle == null ? 0 : handle.length);
if (handle != null) {
data.put(handle);
}
data.flip();
synchronized (mLock) {
if (!mIsWritable) {
IoUtils.closeQuietly(outputStream);
return;
}
try {
FileChannel channel = outputStream.getChannel();
channel.position(getBlockDeviceSize() - 1 - FRP_CREDENTIAL_RESERVED_SIZE);
channel.write(data);
outputStream.flush();
} catch (IOException e) {
Slog.e(TAG, "unable to access persistent partition", e);
return;
} finally {
IoUtils.closeQuietly(outputStream);
}
computeAndWriteDigestLocked();
}
}
@Override
public byte[] getFrpCredentialHandle() {
if (!enforceChecksumValidity()) {
throw new IllegalStateException("invalid checksum");
}
DataInputStream inputStream;
try {
inputStream = new DataInputStream(
new FileInputStream(new File(mDataBlockFile)));
} catch (FileNotFoundException e) {
throw new IllegalStateException("frp partition not available");
}
try {
synchronized (mLock) {
inputStream.skip(getBlockDeviceSize() - 1 - FRP_CREDENTIAL_RESERVED_SIZE);
int length = inputStream.readInt();
if (length <= 0 || length > MAX_FRP_CREDENTIAL_HANDLE_SIZE) {
return null;
}
byte[] bytes = new byte[length];
inputStream.readFully(bytes);
return bytes;
}
} catch (IOException e) {
throw new IllegalStateException("frp handle not readable", e);
} finally {
IoUtils.closeQuietly(inputStream);
}
}
@Override
public void forceOemUnlockEnabled(boolean enabled) {
synchronized (mLock) {
doSetOemUnlockEnabledLocked(enabled);
computeAndWriteDigestLocked();
}
}
};
}