KeySyncTask.java revision 14d993dc2c0bbdee6a6ae0c270a92107c9f57a84
1/* 2 * Copyright (C) 2017 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.locksettings.recoverablekeystore; 18 19import static android.security.keystore.recovery.KeyChainProtectionParams.TYPE_LOCKSCREEN; 20 21import android.annotation.Nullable; 22import android.content.Context; 23import android.security.keystore.recovery.KeyDerivationParams; 24import android.security.keystore.recovery.KeyChainProtectionParams; 25import android.security.keystore.recovery.KeyChainSnapshot; 26import android.security.keystore.recovery.WrappedApplicationKey; 27import android.util.Log; 28 29import com.android.internal.annotations.VisibleForTesting; 30import com.android.internal.util.ArrayUtils; 31import com.android.internal.widget.LockPatternUtils; 32import com.android.server.locksettings.recoverablekeystore.storage.RecoverableKeyStoreDb; 33import com.android.server.locksettings.recoverablekeystore.storage.RecoverySnapshotStorage; 34 35import java.nio.ByteBuffer; 36import java.nio.ByteOrder; 37import java.nio.charset.StandardCharsets; 38import java.security.GeneralSecurityException; 39import java.security.InvalidAlgorithmParameterException; 40import java.security.InvalidKeyException; 41import java.security.KeyStoreException; 42import java.security.MessageDigest; 43import java.security.NoSuchAlgorithmException; 44import java.security.PublicKey; 45import java.security.SecureRandom; 46import java.security.UnrecoverableKeyException; 47import java.security.cert.CertPath; 48import java.util.ArrayList; 49import java.util.List; 50import java.util.Map; 51 52import javax.crypto.KeyGenerator; 53import javax.crypto.NoSuchPaddingException; 54import javax.crypto.SecretKey; 55 56/** 57 * Task to sync application keys to a remote vault service. 58 * 59 * @hide 60 */ 61public class KeySyncTask implements Runnable { 62 private static final String TAG = "KeySyncTask"; 63 64 private static final String RECOVERY_KEY_ALGORITHM = "AES"; 65 private static final int RECOVERY_KEY_SIZE_BITS = 256; 66 private static final int SALT_LENGTH_BYTES = 16; 67 private static final int LENGTH_PREFIX_BYTES = Integer.BYTES; 68 private static final String LOCK_SCREEN_HASH_ALGORITHM = "SHA-256"; 69 private static final int TRUSTED_HARDWARE_MAX_ATTEMPTS = 10; 70 71 private final RecoverableKeyStoreDb mRecoverableKeyStoreDb; 72 private final int mUserId; 73 private final int mCredentialType; 74 private final String mCredential; 75 private final boolean mCredentialUpdated; 76 private final PlatformKeyManager mPlatformKeyManager; 77 private final RecoverySnapshotStorage mRecoverySnapshotStorage; 78 private final RecoverySnapshotListenersStorage mSnapshotListenersStorage; 79 80 public static KeySyncTask newInstance( 81 Context context, 82 RecoverableKeyStoreDb recoverableKeyStoreDb, 83 RecoverySnapshotStorage snapshotStorage, 84 RecoverySnapshotListenersStorage recoverySnapshotListenersStorage, 85 int userId, 86 int credentialType, 87 String credential, 88 boolean credentialUpdated 89 ) throws NoSuchAlgorithmException, KeyStoreException, InsecureUserException { 90 return new KeySyncTask( 91 recoverableKeyStoreDb, 92 snapshotStorage, 93 recoverySnapshotListenersStorage, 94 userId, 95 credentialType, 96 credential, 97 credentialUpdated, 98 PlatformKeyManager.getInstance(context, recoverableKeyStoreDb)); 99 } 100 101 /** 102 * A new task. 103 * 104 * @param recoverableKeyStoreDb Database where the keys are stored. 105 * @param userId The uid of the user whose profile has been unlocked. 106 * @param credentialType The type of credential as defined in {@code LockPatternUtils} 107 * @param credential The credential, encoded as a {@link String}. 108 * @param credentialUpdated signals weather credentials were updated. 109 * @param platformKeyManager platform key manager 110 */ 111 @VisibleForTesting 112 KeySyncTask( 113 RecoverableKeyStoreDb recoverableKeyStoreDb, 114 RecoverySnapshotStorage snapshotStorage, 115 RecoverySnapshotListenersStorage recoverySnapshotListenersStorage, 116 int userId, 117 int credentialType, 118 String credential, 119 boolean credentialUpdated, 120 PlatformKeyManager platformKeyManager) { 121 mSnapshotListenersStorage = recoverySnapshotListenersStorage; 122 mRecoverableKeyStoreDb = recoverableKeyStoreDb; 123 mUserId = userId; 124 mCredentialType = credentialType; 125 mCredential = credential; 126 mCredentialUpdated = credentialUpdated; 127 mPlatformKeyManager = platformKeyManager; 128 mRecoverySnapshotStorage = snapshotStorage; 129 } 130 131 @Override 132 public void run() { 133 try { 134 // Only one task is active If user unlocks phone many times in a short time interval. 135 synchronized(KeySyncTask.class) { 136 syncKeys(); 137 } 138 } catch (Exception e) { 139 Log.e(TAG, "Unexpected exception thrown during KeySyncTask", e); 140 } 141 } 142 143 private void syncKeys() { 144 if (mCredentialType == LockPatternUtils.CREDENTIAL_TYPE_NONE) { 145 // Application keys for the user will not be available for sync. 146 Log.w(TAG, "Credentials are not set for user " + mUserId); 147 int generation = mPlatformKeyManager.getGenerationId(mUserId); 148 mPlatformKeyManager.invalidatePlatformKey(mUserId, generation); 149 return; 150 } 151 152 List<Integer> recoveryAgents = mRecoverableKeyStoreDb.getRecoveryAgents(mUserId); 153 for (int uid : recoveryAgents) { 154 syncKeysForAgent(uid); 155 } 156 if (recoveryAgents.isEmpty()) { 157 Log.w(TAG, "No recovery agent initialized for user " + mUserId); 158 } 159 } 160 161 private void syncKeysForAgent(int recoveryAgentUid) { 162 boolean recreateCurrentVersion = false; 163 if (!shoudCreateSnapshot(recoveryAgentUid)) { 164 recreateCurrentVersion = 165 (mRecoverableKeyStoreDb.getSnapshotVersion(mUserId, recoveryAgentUid) != null) 166 && (mRecoverySnapshotStorage.get(recoveryAgentUid) == null); 167 if (recreateCurrentVersion) { 168 Log.d(TAG, "Recreating most recent snapshot"); 169 } else { 170 Log.d(TAG, "Key sync not needed."); 171 return; 172 } 173 } 174 175 if (!mSnapshotListenersStorage.hasListener(recoveryAgentUid)) { 176 Log.w(TAG, "No pending intent registered for recovery agent " + recoveryAgentUid); 177 return; 178 } 179 180 PublicKey publicKey; 181 CertPath certPath = mRecoverableKeyStoreDb.getRecoveryServiceCertPath(mUserId, 182 recoveryAgentUid); 183 if (certPath != null) { 184 Log.d(TAG, "Using the public key in stored CertPath for syncing"); 185 publicKey = certPath.getCertificates().get(0).getPublicKey(); 186 } else { 187 Log.d(TAG, "Using the stored raw public key for syncing"); 188 publicKey = mRecoverableKeyStoreDb.getRecoveryServicePublicKey(mUserId, 189 recoveryAgentUid); 190 } 191 if (publicKey == null) { 192 Log.w(TAG, "Not initialized for KeySync: no public key set. Cancelling task."); 193 return; 194 } 195 196 byte[] vaultHandle = mRecoverableKeyStoreDb.getServerParams(mUserId, recoveryAgentUid); 197 if (vaultHandle == null) { 198 Log.w(TAG, "No device ID set for user " + mUserId); 199 return; 200 } 201 202 byte[] salt = generateSalt(); 203 byte[] localLskfHash = hashCredentials(salt, mCredential); 204 205 Map<String, SecretKey> rawKeys; 206 try { 207 rawKeys = getKeysToSync(recoveryAgentUid); 208 } catch (GeneralSecurityException e) { 209 Log.e(TAG, "Failed to load recoverable keys for sync", e); 210 return; 211 } catch (InsecureUserException e) { 212 Log.wtf(TAG, "A screen unlock triggered the key sync flow, so user must have " 213 + "lock screen. This should be impossible.", e); 214 return; 215 } catch (BadPlatformKeyException e) { 216 Log.wtf(TAG, "Loaded keys for same generation ID as platform key, so " 217 + "BadPlatformKeyException should be impossible.", e); 218 return; 219 } 220 221 SecretKey recoveryKey; 222 try { 223 recoveryKey = generateRecoveryKey(); 224 } catch (NoSuchAlgorithmException e) { 225 Log.wtf("AES should never be unavailable", e); 226 return; 227 } 228 229 Map<String, byte[]> encryptedApplicationKeys; 230 try { 231 encryptedApplicationKeys = KeySyncUtils.encryptKeysWithRecoveryKey( 232 recoveryKey, rawKeys); 233 } catch (InvalidKeyException | NoSuchAlgorithmException e) { 234 Log.wtf(TAG, 235 "Should be impossible: could not encrypt application keys with random key", 236 e); 237 return; 238 } 239 240 Long counterId; 241 // counter id is generated exactly once for each credentials value. 242 if (mCredentialUpdated) { 243 counterId = generateAndStoreCounterId(recoveryAgentUid); 244 } else { 245 counterId = mRecoverableKeyStoreDb.getCounterId(mUserId, recoveryAgentUid); 246 if (counterId == null) { 247 counterId = generateAndStoreCounterId(recoveryAgentUid); 248 } 249 } 250 251 // TODO: make sure the same counter id is used during recovery and remove temporary fix. 252 counterId = 1L; 253 254 byte[] vaultParams = KeySyncUtils.packVaultParams( 255 publicKey, 256 counterId, 257 TRUSTED_HARDWARE_MAX_ATTEMPTS, 258 vaultHandle); 259 260 byte[] encryptedRecoveryKey; 261 try { 262 encryptedRecoveryKey = KeySyncUtils.thmEncryptRecoveryKey( 263 publicKey, 264 localLskfHash, 265 vaultParams, 266 recoveryKey); 267 } catch (NoSuchAlgorithmException e) { 268 Log.wtf(TAG, "SecureBox encrypt algorithms unavailable", e); 269 return; 270 } catch (InvalidKeyException e) { 271 Log.e(TAG,"Could not encrypt with recovery key", e); 272 return; 273 } 274 KeyChainProtectionParams metadata = new KeyChainProtectionParams.Builder() 275 .setUserSecretType(TYPE_LOCKSCREEN) 276 .setLockScreenUiFormat(getUiFormat(mCredentialType, mCredential)) 277 .setKeyDerivationParams(KeyDerivationParams.createSha256Params(salt)) 278 .setSecret(new byte[0]) 279 .build(); 280 281 ArrayList<KeyChainProtectionParams> metadataList = new ArrayList<>(); 282 metadataList.add(metadata); 283 284 // If application keys are not updated, snapshot will not be created on next unlock. 285 mRecoverableKeyStoreDb.setShouldCreateSnapshot(mUserId, recoveryAgentUid, false); 286 287 mRecoverySnapshotStorage.put(recoveryAgentUid, new KeyChainSnapshot.Builder() 288 .setSnapshotVersion(getSnapshotVersion(recoveryAgentUid, recreateCurrentVersion)) 289 .setMaxAttempts(TRUSTED_HARDWARE_MAX_ATTEMPTS) 290 .setCounterId(counterId) 291 .setTrustedHardwarePublicKey(SecureBox.encodePublicKey(publicKey)) 292 .setServerParams(vaultHandle) 293 .setKeyChainProtectionParams(metadataList) 294 .setWrappedApplicationKeys(createApplicationKeyEntries(encryptedApplicationKeys)) 295 .setEncryptedRecoveryKeyBlob(encryptedRecoveryKey) 296 .build()); 297 298 mSnapshotListenersStorage.recoverySnapshotAvailable(recoveryAgentUid); 299 } 300 301 @VisibleForTesting 302 int getSnapshotVersion(int recoveryAgentUid, boolean recreateCurrentVersion) { 303 Long snapshotVersion = mRecoverableKeyStoreDb.getSnapshotVersion(mUserId, recoveryAgentUid); 304 if (recreateCurrentVersion) { 305 // version shouldn't be null at this moment. 306 snapshotVersion = snapshotVersion == null ? 1 : snapshotVersion; 307 } else { 308 snapshotVersion = snapshotVersion == null ? 1 : snapshotVersion + 1; 309 } 310 mRecoverableKeyStoreDb.setSnapshotVersion(mUserId, recoveryAgentUid, snapshotVersion); 311 312 return snapshotVersion.intValue(); 313 } 314 315 private long generateAndStoreCounterId(int recoveryAgentUid) { 316 long counter = new SecureRandom().nextLong(); 317 mRecoverableKeyStoreDb.setCounterId(mUserId, recoveryAgentUid, counter); 318 return counter; 319 } 320 321 /** 322 * Returns all of the recoverable keys for the user. 323 */ 324 private Map<String, SecretKey> getKeysToSync(int recoveryAgentUid) 325 throws InsecureUserException, KeyStoreException, UnrecoverableKeyException, 326 NoSuchAlgorithmException, NoSuchPaddingException, BadPlatformKeyException, 327 InvalidKeyException, InvalidAlgorithmParameterException { 328 PlatformDecryptionKey decryptKey = mPlatformKeyManager.getDecryptKey(mUserId);; 329 Map<String, WrappedKey> wrappedKeys = mRecoverableKeyStoreDb.getAllKeys( 330 mUserId, recoveryAgentUid, decryptKey.getGenerationId()); 331 return WrappedKey.unwrapKeys(decryptKey, wrappedKeys); 332 } 333 334 /** 335 * Returns {@code true} if a sync is pending. 336 * @param recoveryAgentUid uid of the recovery agent. 337 */ 338 private boolean shoudCreateSnapshot(int recoveryAgentUid) { 339 int[] types = mRecoverableKeyStoreDb.getRecoverySecretTypes(mUserId, recoveryAgentUid); 340 if (!ArrayUtils.contains(types, KeyChainProtectionParams.TYPE_LOCKSCREEN)) { 341 // Only lockscreen type is supported. 342 // We will need to pass extra argument to KeySyncTask to support custom pass phrase. 343 return false; 344 } 345 if (mCredentialUpdated) { 346 // Sync credential if at least one snapshot was created. 347 if (mRecoverableKeyStoreDb.getSnapshotVersion(mUserId, recoveryAgentUid) != null) { 348 mRecoverableKeyStoreDb.setShouldCreateSnapshot(mUserId, recoveryAgentUid, true); 349 return true; 350 } 351 } 352 353 return mRecoverableKeyStoreDb.getShouldCreateSnapshot(mUserId, recoveryAgentUid); 354 } 355 356 /** 357 * The UI best suited to entering the given lock screen. This is synced with the vault so the 358 * user can be shown the same UI when recovering the vault on another device. 359 * 360 * @return The format - either pattern, pin, or password. 361 */ 362 @VisibleForTesting 363 @KeyChainProtectionParams.LockScreenUiFormat static int getUiFormat( 364 int credentialType, String credential) { 365 if (credentialType == LockPatternUtils.CREDENTIAL_TYPE_PATTERN) { 366 return KeyChainProtectionParams.UI_FORMAT_PATTERN; 367 } else if (isPin(credential)) { 368 return KeyChainProtectionParams.UI_FORMAT_PIN; 369 } else { 370 return KeyChainProtectionParams.UI_FORMAT_PASSWORD; 371 } 372 } 373 374 /** 375 * Generates a salt to include with the lock screen hash. 376 * 377 * @return The salt. 378 */ 379 private byte[] generateSalt() { 380 byte[] salt = new byte[SALT_LENGTH_BYTES]; 381 new SecureRandom().nextBytes(salt); 382 return salt; 383 } 384 385 /** 386 * Returns {@code true} if {@code credential} looks like a pin. 387 */ 388 @VisibleForTesting 389 static boolean isPin(@Nullable String credential) { 390 if (credential == null) { 391 return false; 392 } 393 int length = credential.length(); 394 for (int i = 0; i < length; i++) { 395 if (!Character.isDigit(credential.charAt(i))) { 396 return false; 397 } 398 } 399 return true; 400 } 401 402 /** 403 * Hashes {@code credentials} with the given {@code salt}. 404 * 405 * @return The SHA-256 hash. 406 */ 407 @VisibleForTesting 408 static byte[] hashCredentials(byte[] salt, String credentials) { 409 byte[] credentialsBytes = credentials.getBytes(StandardCharsets.UTF_8); 410 ByteBuffer byteBuffer = ByteBuffer.allocate( 411 salt.length + credentialsBytes.length + LENGTH_PREFIX_BYTES * 2); 412 byteBuffer.order(ByteOrder.LITTLE_ENDIAN); 413 byteBuffer.putInt(salt.length); 414 byteBuffer.put(salt); 415 byteBuffer.putInt(credentialsBytes.length); 416 byteBuffer.put(credentialsBytes); 417 byte[] bytes = byteBuffer.array(); 418 419 try { 420 return MessageDigest.getInstance(LOCK_SCREEN_HASH_ALGORITHM).digest(bytes); 421 } catch (NoSuchAlgorithmException e) { 422 // Impossible, SHA-256 must be supported on Android. 423 throw new RuntimeException(e); 424 } 425 } 426 427 private static SecretKey generateRecoveryKey() throws NoSuchAlgorithmException { 428 KeyGenerator keyGenerator = KeyGenerator.getInstance(RECOVERY_KEY_ALGORITHM); 429 keyGenerator.init(RECOVERY_KEY_SIZE_BITS); 430 return keyGenerator.generateKey(); 431 } 432 433 private static List<WrappedApplicationKey> createApplicationKeyEntries( 434 Map<String, byte[]> encryptedApplicationKeys) { 435 ArrayList<WrappedApplicationKey> keyEntries = new ArrayList<>(); 436 for (String alias : encryptedApplicationKeys.keySet()) { 437 keyEntries.add(new WrappedApplicationKey.Builder() 438 .setAlias(alias) 439 .setEncryptedKeyMaterial(encryptedApplicationKeys.get(alias)) 440 .build()); 441 } 442 return keyEntries; 443 } 444} 445