PersistentDataBlockService.java revision 6aa436bef287c71d569b4855e6874fd5a5b7fd0e
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.android.server; 18 19import android.Manifest; 20import android.app.ActivityManager; 21import android.content.Context; 22import android.content.pm.PackageManager; 23import android.os.Binder; 24import android.os.IBinder; 25import android.os.RemoteException; 26import android.os.SystemProperties; 27import android.os.UserHandle; 28import android.service.persistentdata.IPersistentDataBlockService; 29import android.util.Slog; 30 31import com.android.internal.R; 32import com.android.internal.annotations.GuardedBy; 33 34import libcore.io.IoUtils; 35 36import java.io.DataInputStream; 37import java.io.DataOutputStream; 38import java.io.File; 39import java.io.FileInputStream; 40import java.io.FileNotFoundException; 41import java.io.FileOutputStream; 42import java.io.IOException; 43import java.nio.ByteBuffer; 44import java.nio.channels.FileChannel; 45import java.security.MessageDigest; 46import java.security.NoSuchAlgorithmException; 47import java.util.Arrays; 48 49/** 50 * Service for reading and writing blocks to a persistent partition. 51 * This data will live across factory resets not initiated via the Settings UI. 52 * When a device is factory reset through Settings this data is wiped. 53 * 54 * Allows writing one block at a time. Namely, each time {@link IPersistentDataBlockService#write} 55 * is called, it will overwrite the data that was previously written on the block. 56 * 57 * Clients can query the size of the currently written block via 58 * {@link IPersistentDataBlockService#getDataBlockSize} 59 * 60 * Clients can read any number of bytes from the currently written block up to its total size by 61 * invoking {@link IPersistentDataBlockService#read} 62 */ 63public class PersistentDataBlockService extends SystemService { 64 private static final String TAG = PersistentDataBlockService.class.getSimpleName(); 65 66 private static final String PERSISTENT_DATA_BLOCK_PROP = "ro.frp.pst"; 67 private static final int HEADER_SIZE = 8; 68 // Magic number to mark block device as adhering to the format consumed by this service 69 private static final int PARTITION_TYPE_MARKER = 0x19901873; 70 // Limit to 100k as blocks larger than this might cause strain on Binder. 71 private static final int MAX_DATA_BLOCK_SIZE = 1024 * 100; 72 public static final int DIGEST_SIZE_BYTES = 32; 73 private static final String OEM_UNLOCK_PROP = "sys.oem_unlock_allowed"; 74 75 private final Context mContext; 76 private final String mDataBlockFile; 77 private final Object mLock = new Object(); 78 79 private int mAllowedUid = -1; 80 private long mBlockDeviceSize; 81 82 @GuardedBy("mLock") 83 private boolean mIsWritable = true; 84 85 public PersistentDataBlockService(Context context) { 86 super(context); 87 mContext = context; 88 mDataBlockFile = SystemProperties.get(PERSISTENT_DATA_BLOCK_PROP); 89 mBlockDeviceSize = -1; // Load lazily 90 mAllowedUid = getAllowedUid(UserHandle.USER_OWNER); 91 } 92 93 private int getAllowedUid(int userHandle) { 94 String allowedPackage = mContext.getResources() 95 .getString(R.string.config_persistentDataPackageName); 96 PackageManager pm = mContext.getPackageManager(); 97 int allowedUid = -1; 98 try { 99 allowedUid = pm.getPackageUid(allowedPackage, userHandle); 100 } catch (PackageManager.NameNotFoundException e) { 101 // not expected 102 Slog.e(TAG, "not able to find package " + allowedPackage, e); 103 } 104 return allowedUid; 105 } 106 107 @Override 108 public void onStart() { 109 enforceChecksumValidity(); 110 formatIfOemUnlockEnabled(); 111 publishBinderService(Context.PERSISTENT_DATA_BLOCK_SERVICE, mService); 112 } 113 114 private void formatIfOemUnlockEnabled() { 115 boolean enabled = doGetOemUnlockEnabled(); 116 if (enabled) { 117 synchronized (mLock) { 118 formatPartitionLocked(true); 119 } 120 } 121 122 SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0"); 123 } 124 125 private void enforceOemUnlockPermission() { 126 mContext.enforceCallingOrSelfPermission( 127 Manifest.permission.OEM_UNLOCK_STATE, 128 "Can't access OEM unlock state"); 129 } 130 131 private void enforceUid(int callingUid) { 132 if (callingUid != mAllowedUid) { 133 throw new SecurityException("uid " + callingUid + " not allowed to access PST"); 134 } 135 } 136 137 private void enforceIsOwner() { 138 if (!Binder.getCallingUserHandle().isOwner()) { 139 throw new SecurityException("Only the Owner is allowed to change OEM unlock state"); 140 } 141 } 142 private int getTotalDataSizeLocked(DataInputStream inputStream) throws IOException { 143 // skip over checksum 144 inputStream.skipBytes(DIGEST_SIZE_BYTES); 145 146 int totalDataSize; 147 int blockId = inputStream.readInt(); 148 if (blockId == PARTITION_TYPE_MARKER) { 149 totalDataSize = inputStream.readInt(); 150 } else { 151 totalDataSize = 0; 152 } 153 return totalDataSize; 154 } 155 156 private long getBlockDeviceSize() { 157 synchronized (mLock) { 158 if (mBlockDeviceSize == -1) { 159 mBlockDeviceSize = nativeGetBlockDeviceSize(mDataBlockFile); 160 } 161 } 162 163 return mBlockDeviceSize; 164 } 165 166 private boolean enforceChecksumValidity() { 167 byte[] storedDigest = new byte[DIGEST_SIZE_BYTES]; 168 169 synchronized (mLock) { 170 byte[] digest = computeDigestLocked(storedDigest); 171 if (digest == null || !Arrays.equals(storedDigest, digest)) { 172 Slog.i(TAG, "Formatting FRP partition..."); 173 formatPartitionLocked(false); 174 return false; 175 } 176 } 177 178 return true; 179 } 180 181 private boolean computeAndWriteDigestLocked() { 182 byte[] digest = computeDigestLocked(null); 183 if (digest != null) { 184 DataOutputStream outputStream; 185 try { 186 outputStream = new DataOutputStream( 187 new FileOutputStream(new File(mDataBlockFile))); 188 } catch (FileNotFoundException e) { 189 Slog.e(TAG, "partition not available?", e); 190 return false; 191 } 192 193 try { 194 outputStream.write(digest, 0, DIGEST_SIZE_BYTES); 195 outputStream.flush(); 196 } catch (IOException e) { 197 Slog.e(TAG, "failed to write block checksum", e); 198 return false; 199 } finally { 200 IoUtils.closeQuietly(outputStream); 201 } 202 return true; 203 } else { 204 return false; 205 } 206 } 207 208 private byte[] computeDigestLocked(byte[] storedDigest) { 209 DataInputStream inputStream; 210 try { 211 inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile))); 212 } catch (FileNotFoundException e) { 213 Slog.e(TAG, "partition not available?", e); 214 return null; 215 } 216 217 MessageDigest md; 218 try { 219 md = MessageDigest.getInstance("SHA-256"); 220 } catch (NoSuchAlgorithmException e) { 221 // won't ever happen -- every implementation is required to support SHA-256 222 Slog.e(TAG, "SHA-256 not supported?", e); 223 IoUtils.closeQuietly(inputStream); 224 return null; 225 } 226 227 try { 228 if (storedDigest != null && storedDigest.length == DIGEST_SIZE_BYTES) { 229 inputStream.read(storedDigest); 230 } else { 231 inputStream.skipBytes(DIGEST_SIZE_BYTES); 232 } 233 234 int read; 235 byte[] data = new byte[1024]; 236 md.update(data, 0, DIGEST_SIZE_BYTES); // include 0 checksum in digest 237 while ((read = inputStream.read(data)) != -1) { 238 md.update(data, 0, read); 239 } 240 } catch (IOException e) { 241 Slog.e(TAG, "failed to read partition", e); 242 return null; 243 } finally { 244 IoUtils.closeQuietly(inputStream); 245 } 246 247 return md.digest(); 248 } 249 250 private void formatPartitionLocked(boolean setOemUnlockEnabled) { 251 DataOutputStream outputStream; 252 try { 253 outputStream = new DataOutputStream(new FileOutputStream(new File(mDataBlockFile))); 254 } catch (FileNotFoundException e) { 255 Slog.e(TAG, "partition not available?", e); 256 return; 257 } 258 259 byte[] data = new byte[DIGEST_SIZE_BYTES]; 260 try { 261 outputStream.write(data, 0, DIGEST_SIZE_BYTES); 262 outputStream.writeInt(PARTITION_TYPE_MARKER); 263 outputStream.writeInt(0); // data size 264 outputStream.flush(); 265 } catch (IOException e) { 266 Slog.e(TAG, "failed to format block", e); 267 return; 268 } finally { 269 IoUtils.closeQuietly(outputStream); 270 } 271 272 doSetOemUnlockEnabledLocked(setOemUnlockEnabled); 273 computeAndWriteDigestLocked(); 274 } 275 276 private void doSetOemUnlockEnabledLocked(boolean enabled) { 277 FileOutputStream outputStream; 278 try { 279 outputStream = new FileOutputStream(new File(mDataBlockFile)); 280 } catch (FileNotFoundException e) { 281 Slog.e(TAG, "partition not available", e); 282 return; 283 } 284 285 try { 286 FileChannel channel = outputStream.getChannel(); 287 288 channel.position(getBlockDeviceSize() - 1); 289 290 ByteBuffer data = ByteBuffer.allocate(1); 291 data.put(enabled ? (byte) 1 : (byte) 0); 292 data.flip(); 293 channel.write(data); 294 outputStream.flush(); 295 } catch (IOException e) { 296 Slog.e(TAG, "unable to access persistent partition", e); 297 return; 298 } finally { 299 SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0"); 300 IoUtils.closeQuietly(outputStream); 301 } 302 } 303 304 private boolean doGetOemUnlockEnabled() { 305 DataInputStream inputStream; 306 try { 307 inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile))); 308 } catch (FileNotFoundException e) { 309 Slog.e(TAG, "partition not available"); 310 return false; 311 } 312 313 try { 314 synchronized (mLock) { 315 inputStream.skip(getBlockDeviceSize() - 1); 316 return inputStream.readByte() != 0; 317 } 318 } catch (IOException e) { 319 Slog.e(TAG, "unable to access persistent partition", e); 320 return false; 321 } finally { 322 IoUtils.closeQuietly(inputStream); 323 } 324 } 325 326 private native long nativeGetBlockDeviceSize(String path); 327 private native int nativeWipe(String path); 328 329 private final IBinder mService = new IPersistentDataBlockService.Stub() { 330 @Override 331 public int write(byte[] data) throws RemoteException { 332 enforceUid(Binder.getCallingUid()); 333 334 // Need to ensure we don't write over the last byte 335 long maxBlockSize = getBlockDeviceSize() - HEADER_SIZE - 1; 336 if (data.length > maxBlockSize) { 337 // partition is ~500k so shouldn't be a problem to downcast 338 return (int) -maxBlockSize; 339 } 340 341 DataOutputStream outputStream; 342 try { 343 outputStream = new DataOutputStream(new FileOutputStream(new File(mDataBlockFile))); 344 } catch (FileNotFoundException e) { 345 Slog.e(TAG, "partition not available?", e); 346 return -1; 347 } 348 349 ByteBuffer headerAndData = ByteBuffer.allocate(data.length + HEADER_SIZE); 350 headerAndData.putInt(PARTITION_TYPE_MARKER); 351 headerAndData.putInt(data.length); 352 headerAndData.put(data); 353 354 synchronized (mLock) { 355 if (!mIsWritable) { 356 IoUtils.closeQuietly(outputStream); 357 return -1; 358 } 359 360 try { 361 byte[] checksum = new byte[DIGEST_SIZE_BYTES]; 362 outputStream.write(checksum, 0, DIGEST_SIZE_BYTES); 363 outputStream.write(headerAndData.array()); 364 outputStream.flush(); 365 } catch (IOException e) { 366 Slog.e(TAG, "failed writing to the persistent data block", e); 367 return -1; 368 } finally { 369 IoUtils.closeQuietly(outputStream); 370 } 371 372 if (computeAndWriteDigestLocked()) { 373 return data.length; 374 } else { 375 return -1; 376 } 377 } 378 } 379 380 @Override 381 public byte[] read() { 382 enforceUid(Binder.getCallingUid()); 383 if (!enforceChecksumValidity()) { 384 return new byte[0]; 385 } 386 387 DataInputStream inputStream; 388 try { 389 inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile))); 390 } catch (FileNotFoundException e) { 391 Slog.e(TAG, "partition not available?", e); 392 return null; 393 } 394 395 try { 396 synchronized (mLock) { 397 int totalDataSize = getTotalDataSizeLocked(inputStream); 398 399 if (totalDataSize == 0) { 400 return new byte[0]; 401 } 402 403 byte[] data = new byte[totalDataSize]; 404 int read = inputStream.read(data, 0, totalDataSize); 405 if (read < totalDataSize) { 406 // something went wrong, not returning potentially corrupt data 407 Slog.e(TAG, "failed to read entire data block. bytes read: " + 408 read + "/" + totalDataSize); 409 return null; 410 } 411 return data; 412 } 413 } catch (IOException e) { 414 Slog.e(TAG, "failed to read data", e); 415 return null; 416 } finally { 417 try { 418 inputStream.close(); 419 } catch (IOException e) { 420 Slog.e(TAG, "failed to close OutputStream"); 421 } 422 } 423 } 424 425 @Override 426 public void wipe() { 427 enforceOemUnlockPermission(); 428 429 synchronized (mLock) { 430 int ret = nativeWipe(mDataBlockFile); 431 432 if (ret < 0) { 433 Slog.e(TAG, "failed to wipe persistent partition"); 434 } else { 435 mIsWritable = false; 436 Slog.i(TAG, "persistent partition now wiped and unwritable"); 437 } 438 } 439 } 440 441 @Override 442 public void setOemUnlockEnabled(boolean enabled) { 443 // do not allow monkey to flip the flag 444 if (ActivityManager.isUserAMonkey()) { 445 return; 446 } 447 enforceOemUnlockPermission(); 448 enforceIsOwner(); 449 450 synchronized (mLock) { 451 doSetOemUnlockEnabledLocked(enabled); 452 computeAndWriteDigestLocked(); 453 } 454 } 455 456 @Override 457 public boolean getOemUnlockEnabled() { 458 enforceOemUnlockPermission(); 459 return doGetOemUnlockEnabled(); 460 } 461 462 @Override 463 public int getDataBlockSize() { 464 enforcePersistentDataBlockAccess(); 465 466 DataInputStream inputStream; 467 try { 468 inputStream = new DataInputStream(new FileInputStream(new File(mDataBlockFile))); 469 } catch (FileNotFoundException e) { 470 Slog.e(TAG, "partition not available"); 471 return 0; 472 } 473 474 try { 475 synchronized (mLock) { 476 return getTotalDataSizeLocked(inputStream); 477 } 478 } catch (IOException e) { 479 Slog.e(TAG, "error reading data block size"); 480 return 0; 481 } finally { 482 IoUtils.closeQuietly(inputStream); 483 } 484 } 485 486 private void enforcePersistentDataBlockAccess() { 487 if (mContext.checkCallingPermission(Manifest.permission.ACCESS_PDB_STATE) 488 != PackageManager.PERMISSION_GRANTED) { 489 enforceUid(Binder.getCallingUid()); 490 } 491 } 492 493 @Override 494 public long getMaximumDataBlockSize() { 495 long actualSize = getBlockDeviceSize() - HEADER_SIZE - 1; 496 return actualSize <= MAX_DATA_BLOCK_SIZE ? actualSize : MAX_DATA_BLOCK_SIZE; 497 } 498 }; 499} 500