1 /* 2 * Copyright (C) 2011 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 package android.security; 17 18 import android.annotation.NonNull; 19 import android.annotation.Nullable; 20 import android.annotation.SdkConstant; 21 import android.annotation.SdkConstant.SdkConstantType; 22 import android.annotation.WorkerThread; 23 import android.app.Activity; 24 import android.app.PendingIntent; 25 import android.app.Service; 26 import android.content.ComponentName; 27 import android.content.Context; 28 import android.content.Intent; 29 import android.content.ServiceConnection; 30 import android.net.Uri; 31 import android.os.Binder; 32 import android.os.IBinder; 33 import android.os.Looper; 34 import android.os.Process; 35 import android.os.RemoteException; 36 import android.os.UserHandle; 37 import android.security.keystore.AndroidKeyStoreProvider; 38 import android.security.keystore.KeyPermanentlyInvalidatedException; 39 import android.security.keystore.KeyProperties; 40 41 import com.android.org.conscrypt.TrustedCertificateStore; 42 43 import java.io.ByteArrayInputStream; 44 import java.io.Closeable; 45 import java.io.Serializable; 46 import java.security.KeyPair; 47 import java.security.Principal; 48 import java.security.PrivateKey; 49 import java.security.UnrecoverableKeyException; 50 import java.security.cert.Certificate; 51 import java.security.cert.CertificateException; 52 import java.security.cert.CertificateFactory; 53 import java.security.cert.X509Certificate; 54 import java.util.ArrayList; 55 import java.util.Collection; 56 import java.util.List; 57 import java.util.Locale; 58 import java.util.concurrent.BlockingQueue; 59 import java.util.concurrent.LinkedBlockingQueue; 60 61 import javax.security.auth.x500.X500Principal; 62 63 /** 64 * The {@code KeyChain} class provides access to private keys and 65 * their corresponding certificate chains in credential storage. 66 * 67 * <p>Applications accessing the {@code KeyChain} normally go through 68 * these steps: 69 * 70 * <ol> 71 * 72 * <li>Receive a callback from an {@link javax.net.ssl.X509KeyManager 73 * X509KeyManager} that a private key is requested. 74 * 75 * <li>Call {@link #choosePrivateKeyAlias 76 * choosePrivateKeyAlias} to allow the user to select from a 77 * list of currently available private keys and corresponding 78 * certificate chains. The chosen alias will be returned by the 79 * callback {@link KeyChainAliasCallback#alias}, or null if no private 80 * key is available or the user cancels the request. 81 * 82 * <li>Call {@link #getPrivateKey} and {@link #getCertificateChain} to 83 * retrieve the credentials to return to the corresponding {@link 84 * javax.net.ssl.X509KeyManager} callbacks. 85 * 86 * </ol> 87 * 88 * <p>An application may remember the value of a selected alias to 89 * avoid prompting the user with {@link #choosePrivateKeyAlias 90 * choosePrivateKeyAlias} on subsequent connections. If the alias is 91 * no longer valid, null will be returned on lookups using that value 92 * 93 * <p>An application can request the installation of private keys and 94 * certificates via the {@code Intent} provided by {@link 95 * #createInstallIntent}. Private keys installed via this {@code 96 * Intent} will be accessible via {@link #choosePrivateKeyAlias} while 97 * Certificate Authority (CA) certificates will be trusted by all 98 * applications through the default {@code X509TrustManager}. 99 */ 100 // TODO reference intent for credential installation when public 101 public final class KeyChain { 102 103 /** 104 * @hide Also used by KeyChainService implementation 105 */ 106 public static final String ACCOUNT_TYPE = "com.android.keychain"; 107 108 /** 109 * Package name for KeyChain chooser. 110 */ 111 private static final String KEYCHAIN_PACKAGE = "com.android.keychain"; 112 113 /** 114 * Action to bring up the KeyChainActivity 115 */ 116 private static final String ACTION_CHOOSER = "com.android.keychain.CHOOSER"; 117 118 /** 119 * Package name for the Certificate Installer. 120 */ 121 private static final String CERT_INSTALLER_PACKAGE = "com.android.certinstaller"; 122 123 /** 124 * Extra for use with {@link #ACTION_CHOOSER} 125 * @hide Also used by KeyChainActivity implementation 126 */ 127 public static final String EXTRA_RESPONSE = "response"; 128 129 /** 130 * Extra for use with {@link #ACTION_CHOOSER} 131 * @hide Also used by KeyChainActivity implementation 132 */ 133 public static final String EXTRA_URI = "uri"; 134 135 /** 136 * Extra for use with {@link #ACTION_CHOOSER} 137 * @hide Also used by KeyChainActivity implementation 138 */ 139 public static final String EXTRA_ALIAS = "alias"; 140 141 /** 142 * Extra for use with {@link #ACTION_CHOOSER} 143 * @hide Also used by KeyChainActivity implementation 144 */ 145 public static final String EXTRA_SENDER = "sender"; 146 147 /** 148 * Extra for use with {@link #ACTION_CHOOSER} 149 * @hide Also used by KeyChainActivity implementation 150 */ 151 public static final String EXTRA_KEY_TYPES = "key_types"; 152 153 /** 154 * Extra for use with {@link #ACTION_CHOOSER} 155 * @hide Also used by KeyChainActivity implementation 156 */ 157 public static final String EXTRA_ISSUERS = "issuers"; 158 159 /** 160 * Action to bring up the CertInstaller. 161 */ 162 private static final String ACTION_INSTALL = "android.credentials.INSTALL"; 163 164 /** 165 * Optional extra to specify a {@code String} credential name on 166 * the {@code Intent} returned by {@link #createInstallIntent}. 167 */ 168 // Compatible with old com.android.certinstaller.CredentialHelper.CERT_NAME_KEY 169 public static final String EXTRA_NAME = "name"; 170 171 /** 172 * Optional extra to specify an X.509 certificate to install on 173 * the {@code Intent} returned by {@link #createInstallIntent}. 174 * The extra value should be a PEM or ASN.1 DER encoded {@code 175 * byte[]}. An {@link X509Certificate} can be converted to DER 176 * encoded bytes with {@link X509Certificate#getEncoded}. 177 * 178 * <p>{@link #EXTRA_NAME} may be used to provide a default alias 179 * name for the installed certificate. 180 */ 181 // Compatible with old android.security.Credentials.CERTIFICATE 182 public static final String EXTRA_CERTIFICATE = "CERT"; 183 184 /** 185 * Optional extra for use with the {@code Intent} returned by 186 * {@link #createInstallIntent} to specify a PKCS#12 key store to 187 * install. The extra value should be a {@code byte[]}. The bytes 188 * may come from an external source or be generated with {@link 189 * java.security.KeyStore#store} on a "PKCS12" instance. 190 * 191 * <p>The user will be prompted for the password to load the key store. 192 * 193 * <p>The key store will be scanned for {@link 194 * java.security.KeyStore.PrivateKeyEntry} entries and both the 195 * private key and associated certificate chain will be installed. 196 * 197 * <p>{@link #EXTRA_NAME} may be used to provide a default alias 198 * name for the installed credentials. 199 */ 200 // Compatible with old android.security.Credentials.PKCS12 201 public static final String EXTRA_PKCS12 = "PKCS12"; 202 203 /** 204 * Broadcast Action: Indicates the trusted storage has changed. Sent when 205 * one of this happens: 206 * 207 * <ul> 208 * <li>a new CA is added, 209 * <li>an existing CA is removed or disabled, 210 * <li>a disabled CA is enabled, 211 * <li>trusted storage is reset (all user certs are cleared), 212 * <li>when permission to access a private key is changed. 213 * </ul> 214 * 215 * @deprecated Use {@link #ACTION_KEYCHAIN_CHANGED}, {@link #ACTION_TRUST_STORE_CHANGED} or 216 * {@link #ACTION_KEY_ACCESS_CHANGED}. Apps that target a version higher than 217 * {@link android.os.Build.VERSION_CODES#N_MR1} will only receive this broadcast if they 218 * register for it at runtime. 219 */ 220 @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION) 221 public static final String ACTION_STORAGE_CHANGED = "android.security.STORAGE_CHANGED"; 222 223 /** 224 * Broadcast Action: Indicates the contents of the keychain has changed. Sent when a KeyChain 225 * entry is added, modified or removed. 226 */ 227 @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION) 228 public static final String ACTION_KEYCHAIN_CHANGED = "android.security.action.KEYCHAIN_CHANGED"; 229 230 /** 231 * Broadcast Action: Indicates the contents of the trusted certificate store has changed. Sent 232 * when one the following occurs: 233 * 234 * <ul> 235 * <li>A pre-installed CA is disabled or re-enabled</li> 236 * <li>A CA is added or removed from the trust store</li> 237 * </ul> 238 */ 239 @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION) 240 public static final String ACTION_TRUST_STORE_CHANGED = 241 "android.security.action.TRUST_STORE_CHANGED"; 242 243 /** 244 * Broadcast Action: Indicates that the access permissions for a private key have changed. 245 * 246 */ 247 @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION) 248 public static final String ACTION_KEY_ACCESS_CHANGED = 249 "android.security.action.KEY_ACCESS_CHANGED"; 250 251 /** 252 * Used as a String extra field in {@link #ACTION_KEY_ACCESS_CHANGED} to supply the alias of 253 * the key. 254 */ 255 public static final String EXTRA_KEY_ALIAS = "android.security.extra.KEY_ALIAS"; 256 257 /** 258 * Used as a boolean extra field in {@link #ACTION_KEY_ACCESS_CHANGED} to supply if the key is 259 * accessible to the application. 260 */ 261 public static final String EXTRA_KEY_ACCESSIBLE = "android.security.extra.KEY_ACCESSIBLE"; 262 263 /** 264 * Indicates that a call to {@link #generateKeyPair} was successful. 265 * @hide 266 */ 267 public static final int KEY_GEN_SUCCESS = 0; 268 269 /** 270 * An alias was missing from the key specifications when calling {@link #generateKeyPair}. 271 * @hide 272 */ 273 public static final int KEY_GEN_MISSING_ALIAS = 1; 274 275 /** 276 * A key attestation challenge was provided to {@link #generateKeyPair}, but it shouldn't 277 * have been provided. 278 * @hide 279 */ 280 public static final int KEY_GEN_SUPERFLUOUS_ATTESTATION_CHALLENGE = 2; 281 282 /** 283 * Algorithm not supported by {@link #generateKeyPair} 284 * @hide 285 */ 286 public static final int KEY_GEN_NO_SUCH_ALGORITHM = 3; 287 288 /** 289 * Invalid algorithm parameters when calling {@link #generateKeyPair} 290 * @hide 291 */ 292 public static final int KEY_GEN_INVALID_ALGORITHM_PARAMETERS = 4; 293 294 /** 295 * Keystore is not available when calling {@link #generateKeyPair} 296 * @hide 297 */ 298 public static final int KEY_GEN_NO_KEYSTORE_PROVIDER = 5; 299 300 /** 301 * StrongBox unavailable when calling {@link #generateKeyPair} 302 * @hide 303 */ 304 public static final int KEY_GEN_STRONGBOX_UNAVAILABLE = 6; 305 306 /** 307 * General failure while calling {@link #generateKeyPair} 308 * @hide 309 */ 310 public static final int KEY_GEN_FAILURE = 7; 311 312 /** 313 * Successful call to {@link #attestKey} 314 * @hide 315 */ 316 public static final int KEY_ATTESTATION_SUCCESS = 0; 317 318 /** 319 * Attestation challenge missing when calling {@link #attestKey} 320 * @hide 321 */ 322 public static final int KEY_ATTESTATION_MISSING_CHALLENGE = 1; 323 324 /** 325 * The caller requested Device ID attestation when calling {@link #attestKey}, but has no 326 * permissions to get device identifiers. 327 * @hide 328 */ 329 public static final int KEY_ATTESTATION_CANNOT_COLLECT_DATA = 2; 330 331 /** 332 * The underlying hardware does not support Device ID attestation or cannot attest to the 333 * identifiers that are stored on the device. This indicates permanent inability 334 * to get attestation records on the device. 335 * @hide 336 */ 337 public static final int KEY_ATTESTATION_CANNOT_ATTEST_IDS = 3; 338 339 /** 340 * General failure when calling {@link #attestKey} 341 * @hide 342 */ 343 public static final int KEY_ATTESTATION_FAILURE = 4; 344 345 /** 346 * Returns an {@code Intent} that can be used for credential 347 * installation. The intent may be used without any extras, in 348 * which case the user will be able to install credentials from 349 * their own source. 350 * 351 * <p>Alternatively, {@link #EXTRA_CERTIFICATE} or {@link 352 * #EXTRA_PKCS12} maybe used to specify the bytes of an X.509 353 * certificate or a PKCS#12 key store for installation. These 354 * extras may be combined with {@link #EXTRA_NAME} to provide a 355 * default alias name for credentials being installed. 356 * 357 * <p>When used with {@link Activity#startActivityForResult}, 358 * {@link Activity#RESULT_OK} will be returned if a credential was 359 * successfully installed, otherwise {@link 360 * Activity#RESULT_CANCELED} will be returned. 361 */ 362 @NonNull 363 public static Intent createInstallIntent() { 364 Intent intent = new Intent(ACTION_INSTALL); 365 intent.setClassName(CERT_INSTALLER_PACKAGE, 366 "com.android.certinstaller.CertInstallerMain"); 367 return intent; 368 } 369 370 /** 371 * Launches an {@code Activity} for the user to select the alias 372 * for a private key and certificate pair for authentication. The 373 * selected alias or null will be returned via the 374 * KeyChainAliasCallback callback. 375 * 376 * <p>A device policy controller (as a device or profile owner) can 377 * intercept the request before the activity is shown, to pick a 378 * specific private key alias by implementing 379 * {@link android.app.admin.DeviceAdminReceiver#onChoosePrivateKeyAlias 380 * onChoosePrivateKeyAlias}. 381 * 382 * <p>{@code keyTypes} and {@code issuers} may be used to 383 * narrow down suggested choices to the user. If either {@code keyTypes} 384 * or {@code issuers} is specified and non-empty, and there are no 385 * matching certificates in the KeyChain, then the certificate 386 * selection prompt would be suppressed entirely. 387 * 388 * <p>{@code host} and {@code port} may be used to give the user 389 * more context about the server requesting the credentials. 390 * 391 * <p>{@code alias} allows the caller to preselect an existing 392 * alias which will still be subject to user confirmation. 393 * 394 * @param activity The {@link Activity} context to use for 395 * launching the new sub-Activity to prompt the user to select 396 * a private key; used only to call startActivity(); must not 397 * be null. 398 * @param response Callback to invoke when the request completes; 399 * must not be null. 400 * @param keyTypes The acceptable types of asymmetric keys such as 401 * "RSA", "EC" or null. 402 * @param issuers The acceptable certificate issuers for the 403 * certificate matching the private key, or null. 404 * @param host The host name of the server requesting the 405 * certificate, or null if unavailable. 406 * @param port The port number of the server requesting the 407 * certificate, or -1 if unavailable. 408 * @param alias The alias to preselect if available, or null if 409 * unavailable. 410 */ 411 public static void choosePrivateKeyAlias(@NonNull Activity activity, 412 @NonNull KeyChainAliasCallback response, 413 @Nullable @KeyProperties.KeyAlgorithmEnum String[] keyTypes, 414 @Nullable Principal[] issuers, 415 @Nullable String host, int port, @Nullable String alias) { 416 Uri uri = null; 417 if (host != null) { 418 uri = new Uri.Builder() 419 .authority(host + (port != -1 ? ":" + port : "")) 420 .build(); 421 } 422 choosePrivateKeyAlias(activity, response, keyTypes, issuers, uri, alias); 423 } 424 425 /** 426 * Launches an {@code Activity} for the user to select the alias 427 * for a private key and certificate pair for authentication. The 428 * selected alias or null will be returned via the 429 * KeyChainAliasCallback callback. 430 * 431 * <p>A device policy controller (as a device or profile owner) can 432 * intercept the request before the activity is shown, to pick a 433 * specific private key alias by implementing 434 * {@link android.app.admin.DeviceAdminReceiver#onChoosePrivateKeyAlias 435 * onChoosePrivateKeyAlias}. 436 * 437 * <p>{@code keyTypes} and {@code issuers} may be used to 438 * narrow down suggested choices to the user. If either {@code keyTypes} 439 * or {@code issuers} is specified and non-empty, and there are no 440 * matching certificates in the KeyChain, then the certificate 441 * selection prompt would be suppressed entirely. 442 * 443 * <p>{@code uri} may be used to give the user more context about 444 * the server requesting the credentials. 445 * 446 * <p>{@code alias} allows the caller to preselect an existing 447 * alias which will still be subject to user confirmation. 448 * 449 * @param activity The {@link Activity} context to use for 450 * launching the new sub-Activity to prompt the user to select 451 * a private key; used only to call startActivity(); must not 452 * be null. 453 * @param response Callback to invoke when the request completes; 454 * must not be null. 455 * @param keyTypes The acceptable types of asymmetric keys such as 456 * "RSA", "EC" or null. 457 * @param issuers The acceptable certificate issuers for the 458 * certificate matching the private key, or null. 459 * @param uri The full URI the server is requesting the certificate 460 * for, or null if unavailable. 461 * @param alias The alias to preselect if available, or null if 462 * unavailable. 463 * @throws IllegalArgumentException if the specified issuers are not 464 * of type {@code X500Principal}. 465 */ 466 public static void choosePrivateKeyAlias(@NonNull Activity activity, 467 @NonNull KeyChainAliasCallback response, 468 @Nullable @KeyProperties.KeyAlgorithmEnum String[] keyTypes, 469 @Nullable Principal[] issuers, 470 @Nullable Uri uri, @Nullable String alias) { 471 /* 472 * Specifying keyTypes excludes certificates with different key types 473 * from the list of certificates presented to the user. 474 * In practice today, most servers would require RSA or EC 475 * certificates. 476 * 477 * Specifying issuers narrows down the list by filtering out 478 * certificates with issuers which are not matching the provided ones. 479 * This has been reported to Chrome several times (crbug.com/731769). 480 * There's no concrete description on what to do when the client has no 481 * certificates that match the provided issuers. 482 * To be conservative, Android will not present the user with any 483 * certificates to choose from. 484 * If the list of issuers is empty then the client may send any 485 * certificate, see: 486 * https://tools.ietf.org/html/rfc5246#section-7.4.4 487 */ 488 if (activity == null) { 489 throw new NullPointerException("activity == null"); 490 } 491 if (response == null) { 492 throw new NullPointerException("response == null"); 493 } 494 Intent intent = new Intent(ACTION_CHOOSER); 495 intent.setPackage(KEYCHAIN_PACKAGE); 496 intent.putExtra(EXTRA_RESPONSE, new AliasResponse(response)); 497 intent.putExtra(EXTRA_URI, uri); 498 intent.putExtra(EXTRA_ALIAS, alias); 499 intent.putExtra(EXTRA_KEY_TYPES, keyTypes); 500 ArrayList<byte[]> issuersList = new ArrayList(); 501 if (issuers != null) { 502 for (Principal issuer: issuers) { 503 // In a TLS client context (like Chrome), issuers would only 504 // be specified as X500Principals. No other use cases for 505 // specifying principals have been brought up. Under these 506 // circumstances, only allow issuers specified as 507 // X500Principals. 508 if (!(issuer instanceof X500Principal)) { 509 throw new IllegalArgumentException(String.format( 510 "Issuer %s is of type %s, not X500Principal", 511 issuer.toString(), issuer.getClass())); 512 } 513 // Pass the DER-encoded issuer as that's the most accurate 514 // representation and what is sent over the wire. 515 issuersList.add(((X500Principal) issuer).getEncoded()); 516 } 517 } 518 intent.putExtra(EXTRA_ISSUERS, (Serializable) issuersList); 519 // the PendingIntent is used to get calling package name 520 intent.putExtra(EXTRA_SENDER, PendingIntent.getActivity(activity, 0, new Intent(), 0)); 521 activity.startActivity(intent); 522 } 523 524 private static class AliasResponse extends IKeyChainAliasCallback.Stub { 525 private final KeyChainAliasCallback keyChainAliasResponse; 526 private AliasResponse(KeyChainAliasCallback keyChainAliasResponse) { 527 this.keyChainAliasResponse = keyChainAliasResponse; 528 } 529 @Override public void alias(String alias) { 530 keyChainAliasResponse.alias(alias); 531 } 532 } 533 534 /** 535 * Returns the {@code PrivateKey} for the requested alias, or null if the alias does not exist 536 * or the caller has no permission to access it (see note on exceptions below). 537 * 538 * <p> This method may block while waiting for a connection to another process, and must never 539 * be called from the main thread. 540 * <p> As {@link Activity} and {@link Service} contexts are short-lived and can be destroyed 541 * at any time from the main thread, it is safer to rely on a long-lived context such as one 542 * returned from {@link Context#getApplicationContext()}. 543 * 544 * <p> If the caller provides a valid alias to which it was not granted access, then the 545 * caller must invoke {@link #choosePrivateKeyAlias} again to get another valid alias 546 * or a grant to access the same alias. 547 * <p>On Android versions prior to Q, when a key associated with the specified alias is 548 * unavailable, the method will throw a {@code KeyChainException} rather than return null. 549 * If the exception's cause (as obtained by calling {@code KeyChainException.getCause()}) 550 * is a throwable of type {@code IllegalStateException} then the caller lacks a grant 551 * to access the key and certificates associated with this alias. 552 * 553 * @param alias The alias of the desired private key, typically returned via 554 * {@link KeyChainAliasCallback#alias}. 555 * @throws KeyChainException if the alias was valid but there was some problem accessing it. 556 * @throws IllegalStateException if called from the main thread. 557 */ 558 @Nullable @WorkerThread 559 public static PrivateKey getPrivateKey(@NonNull Context context, @NonNull String alias) 560 throws KeyChainException, InterruptedException { 561 KeyPair keyPair = getKeyPair(context, alias); 562 if (keyPair != null) { 563 return keyPair.getPrivate(); 564 } 565 566 return null; 567 } 568 569 /** @hide */ 570 @Nullable @WorkerThread 571 public static KeyPair getKeyPair(@NonNull Context context, @NonNull String alias) 572 throws KeyChainException, InterruptedException { 573 if (alias == null) { 574 throw new NullPointerException("alias == null"); 575 } 576 if (context == null) { 577 throw new NullPointerException("context == null"); 578 } 579 580 final String keyId; 581 try (KeyChainConnection keyChainConnection = bind(context.getApplicationContext())) { 582 keyId = keyChainConnection.getService().requestPrivateKey(alias); 583 } catch (RemoteException e) { 584 throw new KeyChainException(e); 585 } catch (RuntimeException e) { 586 // only certain RuntimeExceptions can be propagated across the IKeyChainService call 587 throw new KeyChainException(e); 588 } 589 590 if (keyId == null) { 591 return null; 592 } else { 593 try { 594 return AndroidKeyStoreProvider.loadAndroidKeyStoreKeyPairFromKeystore( 595 KeyStore.getInstance(), keyId, KeyStore.UID_SELF); 596 } catch (RuntimeException | UnrecoverableKeyException | KeyPermanentlyInvalidatedException e) { 597 throw new KeyChainException(e); 598 } 599 } 600 } 601 602 /** 603 * Returns the {@code X509Certificate} chain for the requested alias, or null if the alias 604 * does not exist or the caller has no permission to access it (see note on exceptions 605 * in {@link #getPrivateKey}). 606 * 607 * <p> 608 * <strong>Note:</strong> If a certificate chain was explicitly specified when the alias was 609 * installed, this method will return that chain. If only the client certificate was specified 610 * at the installation time, this method will try to build a certificate chain using all 611 * available trust anchors (preinstalled and user-added). 612 * 613 * <p> This method may block while waiting for a connection to another process, and must never 614 * be called from the main thread. 615 * <p> As {@link Activity} and {@link Service} contexts are short-lived and can be destroyed 616 * at any time from the main thread, it is safer to rely on a long-lived context such as one 617 * returned from {@link Context#getApplicationContext()}. 618 * <p> In case the caller specifies an alias for which it lacks a grant, it must call 619 * {@link #choosePrivateKeyAlias} again. See {@link #getPrivateKey} for more details on 620 * coping with this scenario. 621 * 622 * @param alias The alias of the desired certificate chain, typically 623 * returned via {@link KeyChainAliasCallback#alias}. 624 * @throws KeyChainException if the alias was valid but there was some problem accessing it. 625 * @throws IllegalStateException if called from the main thread. 626 */ 627 @Nullable @WorkerThread 628 public static X509Certificate[] getCertificateChain(@NonNull Context context, 629 @NonNull String alias) throws KeyChainException, InterruptedException { 630 if (alias == null) { 631 throw new NullPointerException("alias == null"); 632 } 633 634 final byte[] certificateBytes; 635 final byte[] certChainBytes; 636 try (KeyChainConnection keyChainConnection = bind(context.getApplicationContext())) { 637 IKeyChainService keyChainService = keyChainConnection.getService(); 638 certificateBytes = keyChainService.getCertificate(alias); 639 if (certificateBytes == null) { 640 return null; 641 } 642 certChainBytes = keyChainService.getCaCertificates(alias); 643 } catch (RemoteException e) { 644 throw new KeyChainException(e); 645 } catch (RuntimeException e) { 646 // only certain RuntimeExceptions can be propagated across the IKeyChainService call 647 throw new KeyChainException(e); 648 } 649 650 try { 651 X509Certificate leafCert = toCertificate(certificateBytes); 652 // If the keypair is installed with a certificate chain by either 653 // DevicePolicyManager.installKeyPair or CertInstaller, return that chain. 654 if (certChainBytes != null && certChainBytes.length != 0) { 655 Collection<X509Certificate> chain = toCertificates(certChainBytes); 656 ArrayList<X509Certificate> fullChain = new ArrayList<>(chain.size() + 1); 657 fullChain.add(leafCert); 658 fullChain.addAll(chain); 659 return fullChain.toArray(new X509Certificate[fullChain.size()]); 660 } else { 661 // If there isn't a certificate chain, either due to a pre-existing keypair 662 // installed before N, or no chain is explicitly installed under the new logic, 663 // fall back to old behavior of constructing the chain from trusted credentials. 664 // 665 // This logic exists to maintain old behaviour for already installed keypair, at 666 // the cost of potentially returning extra certificate chain for new clients who 667 // explicitly installed only the client certificate without a chain. The latter 668 // case is actually no different from pre-N behaviour of getCertificateChain(), 669 // in that sense this change introduces no regression. Besides the returned chain 670 // is still valid so the consumer of the chain should have no problem verifying it. 671 TrustedCertificateStore store = new TrustedCertificateStore(); 672 List<X509Certificate> chain = store.getCertificateChain(leafCert); 673 return chain.toArray(new X509Certificate[chain.size()]); 674 } 675 } catch (CertificateException | RuntimeException e) { 676 throw new KeyChainException(e); 677 } 678 } 679 680 /** 681 * Returns {@code true} if the current device's {@code KeyChain} supports a 682 * specific {@code PrivateKey} type indicated by {@code algorithm} (e.g., 683 * "RSA"). 684 */ 685 public static boolean isKeyAlgorithmSupported( 686 @NonNull @KeyProperties.KeyAlgorithmEnum String algorithm) { 687 final String algUpper = algorithm.toUpperCase(Locale.US); 688 return KeyProperties.KEY_ALGORITHM_EC.equals(algUpper) 689 || KeyProperties.KEY_ALGORITHM_RSA.equals(algUpper); 690 } 691 692 /** 693 * Returns {@code true} if the current device's {@code KeyChain} binds any 694 * {@code PrivateKey} of the given {@code algorithm} to the device once 695 * imported or generated. This can be used to tell if there is special 696 * hardware support that can be used to bind keys to the device in a way 697 * that makes it non-exportable. 698 * 699 * @deprecated Whether the key is bound to the secure hardware is known only 700 * once the key has been imported. To find out, use: 701 * <pre>{@code 702 * PrivateKey key = ...; // private key from KeyChain 703 * 704 * KeyFactory keyFactory = 705 * KeyFactory.getInstance(key.getAlgorithm(), "AndroidKeyStore"); 706 * KeyInfo keyInfo = keyFactory.getKeySpec(key, KeyInfo.class); 707 * if (keyInfo.isInsideSecureHardware()) { 708 * // The key is bound to the secure hardware of this Android 709 * }}</pre> 710 */ 711 @Deprecated 712 public static boolean isBoundKeyAlgorithm( 713 @NonNull @KeyProperties.KeyAlgorithmEnum String algorithm) { 714 if (!isKeyAlgorithmSupported(algorithm)) { 715 return false; 716 } 717 718 return KeyStore.getInstance().isHardwareBacked(algorithm); 719 } 720 721 /** @hide */ 722 @NonNull 723 public static X509Certificate toCertificate(@NonNull byte[] bytes) { 724 if (bytes == null) { 725 throw new IllegalArgumentException("bytes == null"); 726 } 727 try { 728 CertificateFactory certFactory = CertificateFactory.getInstance("X.509"); 729 Certificate cert = certFactory.generateCertificate(new ByteArrayInputStream(bytes)); 730 return (X509Certificate) cert; 731 } catch (CertificateException e) { 732 throw new AssertionError(e); 733 } 734 } 735 736 /** @hide */ 737 @NonNull 738 public static Collection<X509Certificate> toCertificates(@NonNull byte[] bytes) { 739 if (bytes == null) { 740 throw new IllegalArgumentException("bytes == null"); 741 } 742 try { 743 CertificateFactory certFactory = CertificateFactory.getInstance("X.509"); 744 return (Collection<X509Certificate>) certFactory.generateCertificates( 745 new ByteArrayInputStream(bytes)); 746 } catch (CertificateException e) { 747 throw new AssertionError(e); 748 } 749 } 750 751 /** 752 * @hide for reuse by CertInstaller and Settings. 753 * @see KeyChain#bind 754 */ 755 public static class KeyChainConnection implements Closeable { 756 private final Context context; 757 private final ServiceConnection serviceConnection; 758 private final IKeyChainService service; 759 protected KeyChainConnection(Context context, 760 ServiceConnection serviceConnection, 761 IKeyChainService service) { 762 this.context = context; 763 this.serviceConnection = serviceConnection; 764 this.service = service; 765 } 766 @Override public void close() { 767 context.unbindService(serviceConnection); 768 } 769 public IKeyChainService getService() { 770 return service; 771 } 772 } 773 774 /** 775 * @hide for reuse by CertInstaller and Settings. 776 * 777 * Caller should call unbindService on the result when finished. 778 */ 779 @WorkerThread 780 public static KeyChainConnection bind(@NonNull Context context) throws InterruptedException { 781 return bindAsUser(context, Process.myUserHandle()); 782 } 783 784 /** 785 * @hide 786 */ 787 @WorkerThread 788 public static KeyChainConnection bindAsUser(@NonNull Context context, UserHandle user) 789 throws InterruptedException { 790 if (context == null) { 791 throw new NullPointerException("context == null"); 792 } 793 ensureNotOnMainThread(context); 794 final BlockingQueue<IKeyChainService> q = new LinkedBlockingQueue<IKeyChainService>(1); 795 ServiceConnection keyChainServiceConnection = new ServiceConnection() { 796 volatile boolean mConnectedAtLeastOnce = false; 797 @Override public void onServiceConnected(ComponentName name, IBinder service) { 798 if (!mConnectedAtLeastOnce) { 799 mConnectedAtLeastOnce = true; 800 try { 801 q.put(IKeyChainService.Stub.asInterface(Binder.allowBlocking(service))); 802 } catch (InterruptedException e) { 803 // will never happen, since the queue starts with one available slot 804 } 805 } 806 } 807 @Override public void onServiceDisconnected(ComponentName name) {} 808 }; 809 Intent intent = new Intent(IKeyChainService.class.getName()); 810 ComponentName comp = intent.resolveSystemService(context.getPackageManager(), 0); 811 intent.setComponent(comp); 812 if (comp == null || !context.bindServiceAsUser( 813 intent, keyChainServiceConnection, Context.BIND_AUTO_CREATE, user)) { 814 throw new AssertionError("could not bind to KeyChainService"); 815 } 816 return new KeyChainConnection(context, keyChainServiceConnection, q.take()); 817 } 818 819 private static void ensureNotOnMainThread(@NonNull Context context) { 820 Looper looper = Looper.myLooper(); 821 if (looper != null && looper == context.getMainLooper()) { 822 throw new IllegalStateException( 823 "calling this from your main thread can lead to deadlock"); 824 } 825 } 826 } 827
