AndroidKeyStoreKeyPairGeneratorSpi.java revision 2e3aaa7dc1c40c0145e8d52422f2fb65799a3a60
1/* 2 * Copyright (C) 2012 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 android.security.keystore; 18 19import android.annotation.Nullable; 20import android.security.Credentials; 21import android.security.KeyPairGeneratorSpec; 22import android.security.KeyStore; 23import android.security.keymaster.KeyCharacteristics; 24import android.security.keymaster.KeymasterArguments; 25import android.security.keymaster.KeymasterDefs; 26 27import com.android.org.bouncycastle.asn1.ASN1EncodableVector; 28import com.android.org.bouncycastle.asn1.ASN1InputStream; 29import com.android.org.bouncycastle.asn1.ASN1Integer; 30import com.android.org.bouncycastle.asn1.ASN1ObjectIdentifier; 31import com.android.org.bouncycastle.asn1.DERBitString; 32import com.android.org.bouncycastle.asn1.DERInteger; 33import com.android.org.bouncycastle.asn1.DERNull; 34import com.android.org.bouncycastle.asn1.DERSequence; 35import com.android.org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers; 36import com.android.org.bouncycastle.asn1.x509.AlgorithmIdentifier; 37import com.android.org.bouncycastle.asn1.x509.Certificate; 38import com.android.org.bouncycastle.asn1.x509.SubjectPublicKeyInfo; 39import com.android.org.bouncycastle.asn1.x509.TBSCertificate; 40import com.android.org.bouncycastle.asn1.x509.Time; 41import com.android.org.bouncycastle.asn1.x509.V3TBSCertificateGenerator; 42import com.android.org.bouncycastle.asn1.x9.X9ObjectIdentifiers; 43import com.android.org.bouncycastle.jce.X509Principal; 44import com.android.org.bouncycastle.jce.provider.X509CertificateObject; 45import com.android.org.bouncycastle.x509.X509V3CertificateGenerator; 46 47import libcore.util.EmptyArray; 48 49import java.math.BigInteger; 50import java.security.InvalidAlgorithmParameterException; 51import java.security.KeyPair; 52import java.security.KeyPairGenerator; 53import java.security.KeyPairGeneratorSpi; 54import java.security.PrivateKey; 55import java.security.ProviderException; 56import java.security.PublicKey; 57import java.security.SecureRandom; 58import java.security.UnrecoverableKeyException; 59import java.security.cert.CertificateEncodingException; 60import java.security.cert.X509Certificate; 61import java.security.spec.AlgorithmParameterSpec; 62import java.security.spec.ECGenParameterSpec; 63import java.security.spec.RSAKeyGenParameterSpec; 64import java.util.ArrayList; 65import java.util.Collections; 66import java.util.Date; 67import java.util.HashMap; 68import java.util.HashSet; 69import java.util.List; 70import java.util.Locale; 71import java.util.Map; 72import java.util.Set; 73 74/** 75 * Provides a way to create instances of a KeyPair which will be placed in the 76 * Android keystore service usable only by the application that called it. This 77 * can be used in conjunction with 78 * {@link java.security.KeyStore#getInstance(String)} using the 79 * {@code "AndroidKeyStore"} type. 80 * <p> 81 * This class can not be directly instantiated and must instead be used via the 82 * {@link KeyPairGenerator#getInstance(String) 83 * KeyPairGenerator.getInstance("AndroidKeyStore")} API. 84 * 85 * @hide 86 */ 87public abstract class AndroidKeyStoreKeyPairGeneratorSpi extends KeyPairGeneratorSpi { 88 89 public static class RSA extends AndroidKeyStoreKeyPairGeneratorSpi { 90 public RSA() { 91 super(KeymasterDefs.KM_ALGORITHM_RSA); 92 } 93 } 94 95 public static class EC extends AndroidKeyStoreKeyPairGeneratorSpi { 96 public EC() { 97 super(KeymasterDefs.KM_ALGORITHM_EC); 98 } 99 } 100 101 /* 102 * These must be kept in sync with system/security/keystore/defaults.h 103 */ 104 105 /* EC */ 106 private static final int EC_DEFAULT_KEY_SIZE = 256; 107 108 /* RSA */ 109 private static final int RSA_DEFAULT_KEY_SIZE = 2048; 110 private static final int RSA_MIN_KEY_SIZE = 512; 111 private static final int RSA_MAX_KEY_SIZE = 8192; 112 113 private static final Map<String, Integer> SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE = 114 new HashMap<String, Integer>(); 115 private static final List<String> SUPPORTED_EC_NIST_CURVE_NAMES = new ArrayList<String>(); 116 private static final List<Integer> SUPPORTED_EC_NIST_CURVE_SIZES = new ArrayList<Integer>(); 117 static { 118 // Aliases for NIST P-224 119 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("p-224", 224); 120 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("secp224r1", 224); 121 122 123 // Aliases for NIST P-256 124 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("p-256", 256); 125 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("secp256r1", 256); 126 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("prime256v1", 256); 127 128 // Aliases for NIST P-384 129 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("p-384", 384); 130 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("secp384r1", 384); 131 132 // Aliases for NIST P-521 133 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("p-521", 521); 134 SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.put("secp521r1", 521); 135 136 SUPPORTED_EC_NIST_CURVE_NAMES.addAll(SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.keySet()); 137 Collections.sort(SUPPORTED_EC_NIST_CURVE_NAMES); 138 139 SUPPORTED_EC_NIST_CURVE_SIZES.addAll( 140 new HashSet<Integer>(SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.values())); 141 Collections.sort(SUPPORTED_EC_NIST_CURVE_SIZES); 142 } 143 144 private final int mOriginalKeymasterAlgorithm; 145 146 private KeyStore mKeyStore; 147 148 private KeyGenParameterSpec mSpec; 149 150 private String mEntryAlias; 151 private boolean mEncryptionAtRestRequired; 152 private @KeyProperties.KeyAlgorithmEnum String mJcaKeyAlgorithm; 153 private int mKeymasterAlgorithm = -1; 154 private int mKeySizeBits; 155 private SecureRandom mRng; 156 157 private int[] mKeymasterPurposes; 158 private int[] mKeymasterBlockModes; 159 private int[] mKeymasterEncryptionPaddings; 160 private int[] mKeymasterSignaturePaddings; 161 private int[] mKeymasterDigests; 162 163 private long mRSAPublicExponent; 164 165 protected AndroidKeyStoreKeyPairGeneratorSpi(int keymasterAlgorithm) { 166 mOriginalKeymasterAlgorithm = keymasterAlgorithm; 167 } 168 169 @Override 170 public void initialize(int keysize, SecureRandom random) { 171 throw new IllegalArgumentException( 172 KeyGenParameterSpec.class.getName() + " or " + KeyPairGeneratorSpec.class.getName() 173 + " required to initialize this KeyPairGenerator"); 174 } 175 176 @Override 177 public void initialize(AlgorithmParameterSpec params, SecureRandom random) 178 throws InvalidAlgorithmParameterException { 179 resetAll(); 180 181 boolean success = false; 182 try { 183 if (params == null) { 184 throw new InvalidAlgorithmParameterException( 185 "Must supply params of type " + KeyGenParameterSpec.class.getName() 186 + " or " + KeyPairGeneratorSpec.class.getName()); 187 } 188 189 KeyGenParameterSpec spec; 190 boolean encryptionAtRestRequired = false; 191 int keymasterAlgorithm = mOriginalKeymasterAlgorithm; 192 if (params instanceof KeyGenParameterSpec) { 193 spec = (KeyGenParameterSpec) params; 194 } else if (params instanceof KeyPairGeneratorSpec) { 195 // Legacy/deprecated spec 196 KeyPairGeneratorSpec legacySpec = (KeyPairGeneratorSpec) params; 197 try { 198 KeyGenParameterSpec.Builder specBuilder; 199 String specKeyAlgorithm = legacySpec.getKeyType(); 200 if (specKeyAlgorithm != null) { 201 // Spec overrides the generator's default key algorithm 202 try { 203 keymasterAlgorithm = 204 KeyProperties.KeyAlgorithm.toKeymasterAsymmetricKeyAlgorithm( 205 specKeyAlgorithm); 206 } catch (IllegalArgumentException e) { 207 throw new InvalidAlgorithmParameterException( 208 "Invalid key type in parameters", e); 209 } 210 } 211 switch (keymasterAlgorithm) { 212 case KeymasterDefs.KM_ALGORITHM_EC: 213 specBuilder = new KeyGenParameterSpec.Builder( 214 legacySpec.getKeystoreAlias(), 215 KeyProperties.PURPOSE_SIGN 216 | KeyProperties.PURPOSE_VERIFY); 217 // Authorized to be used with any digest (including no digest). 218 specBuilder.setDigests(KeyProperties.DIGEST_NONE); 219 break; 220 case KeymasterDefs.KM_ALGORITHM_RSA: 221 specBuilder = new KeyGenParameterSpec.Builder( 222 legacySpec.getKeystoreAlias(), 223 KeyProperties.PURPOSE_ENCRYPT 224 | KeyProperties.PURPOSE_DECRYPT 225 | KeyProperties.PURPOSE_SIGN 226 | KeyProperties.PURPOSE_VERIFY); 227 // Authorized to be used with any digest (including no digest). 228 specBuilder.setDigests(KeyProperties.DIGEST_NONE); 229 // Authorized to be used with any encryption and signature padding 230 // scheme (including no padding). 231 specBuilder.setEncryptionPaddings( 232 KeyProperties.ENCRYPTION_PADDING_NONE); 233 // Disable randomized encryption requirement to support encryption 234 // padding NONE above. 235 specBuilder.setRandomizedEncryptionRequired(false); 236 break; 237 default: 238 throw new ProviderException( 239 "Unsupported algorithm: " + mKeymasterAlgorithm); 240 } 241 242 if (legacySpec.getKeySize() != -1) { 243 specBuilder.setKeySize(legacySpec.getKeySize()); 244 } 245 if (legacySpec.getAlgorithmParameterSpec() != null) { 246 specBuilder.setAlgorithmParameterSpec( 247 legacySpec.getAlgorithmParameterSpec()); 248 } 249 specBuilder.setCertificateSubject(legacySpec.getSubjectDN()); 250 specBuilder.setCertificateSerialNumber(legacySpec.getSerialNumber()); 251 specBuilder.setCertificateNotBefore(legacySpec.getStartDate()); 252 specBuilder.setCertificateNotAfter(legacySpec.getEndDate()); 253 encryptionAtRestRequired = legacySpec.isEncryptionRequired(); 254 specBuilder.setUserAuthenticationRequired(false); 255 256 spec = specBuilder.build(); 257 } catch (NullPointerException | IllegalArgumentException e) { 258 throw new InvalidAlgorithmParameterException(e); 259 } 260 } else { 261 throw new InvalidAlgorithmParameterException( 262 "Unsupported params class: " + params.getClass().getName() 263 + ". Supported: " + KeyGenParameterSpec.class.getName() 264 + ", " + KeyPairGeneratorSpec.class.getName()); 265 } 266 267 mEntryAlias = spec.getKeystoreAlias(); 268 mSpec = spec; 269 mKeymasterAlgorithm = keymasterAlgorithm; 270 mEncryptionAtRestRequired = encryptionAtRestRequired; 271 mKeySizeBits = spec.getKeySize(); 272 initAlgorithmSpecificParameters(); 273 if (mKeySizeBits == -1) { 274 mKeySizeBits = getDefaultKeySize(keymasterAlgorithm); 275 } 276 checkValidKeySize(keymasterAlgorithm, mKeySizeBits); 277 278 if (spec.getKeystoreAlias() == null) { 279 throw new InvalidAlgorithmParameterException("KeyStore entry alias not provided"); 280 } 281 282 String jcaKeyAlgorithm; 283 try { 284 jcaKeyAlgorithm = KeyProperties.KeyAlgorithm.fromKeymasterAsymmetricKeyAlgorithm( 285 keymasterAlgorithm); 286 mKeymasterPurposes = KeyProperties.Purpose.allToKeymaster(spec.getPurposes()); 287 mKeymasterBlockModes = KeyProperties.BlockMode.allToKeymaster(spec.getBlockModes()); 288 mKeymasterEncryptionPaddings = KeyProperties.EncryptionPadding.allToKeymaster( 289 spec.getEncryptionPaddings()); 290 mKeymasterSignaturePaddings = KeyProperties.SignaturePadding.allToKeymaster( 291 spec.getSignaturePaddings()); 292 if (spec.isDigestsSpecified()) { 293 mKeymasterDigests = KeyProperties.Digest.allToKeymaster(spec.getDigests()); 294 } else { 295 mKeymasterDigests = EmptyArray.INT; 296 } 297 } catch (IllegalArgumentException e) { 298 throw new InvalidAlgorithmParameterException(e); 299 } 300 301 mJcaKeyAlgorithm = jcaKeyAlgorithm; 302 mRng = random; 303 mKeyStore = KeyStore.getInstance(); 304 success = true; 305 } finally { 306 if (!success) { 307 resetAll(); 308 } 309 } 310 } 311 312 private void resetAll() { 313 mEntryAlias = null; 314 mJcaKeyAlgorithm = null; 315 mKeymasterAlgorithm = -1; 316 mKeymasterPurposes = null; 317 mKeymasterBlockModes = null; 318 mKeymasterEncryptionPaddings = null; 319 mKeymasterSignaturePaddings = null; 320 mKeymasterDigests = null; 321 mKeySizeBits = 0; 322 mSpec = null; 323 mRSAPublicExponent = -1; 324 mEncryptionAtRestRequired = false; 325 mRng = null; 326 mKeyStore = null; 327 } 328 329 private void initAlgorithmSpecificParameters() throws InvalidAlgorithmParameterException { 330 AlgorithmParameterSpec algSpecificSpec = mSpec.getAlgorithmParameterSpec(); 331 switch (mKeymasterAlgorithm) { 332 case KeymasterDefs.KM_ALGORITHM_RSA: 333 { 334 BigInteger publicExponent = null; 335 if (algSpecificSpec instanceof RSAKeyGenParameterSpec) { 336 RSAKeyGenParameterSpec rsaSpec = (RSAKeyGenParameterSpec) algSpecificSpec; 337 if (mKeySizeBits == -1) { 338 mKeySizeBits = rsaSpec.getKeysize(); 339 } else if (mKeySizeBits != rsaSpec.getKeysize()) { 340 throw new InvalidAlgorithmParameterException("RSA key size must match " 341 + " between " + mSpec + " and " + algSpecificSpec 342 + ": " + mKeySizeBits + " vs " + rsaSpec.getKeysize()); 343 } 344 publicExponent = rsaSpec.getPublicExponent(); 345 } else if (algSpecificSpec != null) { 346 throw new InvalidAlgorithmParameterException( 347 "RSA may only use RSAKeyGenParameterSpec"); 348 } 349 if (publicExponent == null) { 350 publicExponent = RSAKeyGenParameterSpec.F4; 351 } 352 if (publicExponent.compareTo(BigInteger.ZERO) < 1) { 353 throw new InvalidAlgorithmParameterException( 354 "RSA public exponent must be positive: " + publicExponent); 355 } 356 if (publicExponent.compareTo(BigInteger.valueOf(Long.MAX_VALUE)) > 0) { 357 throw new InvalidAlgorithmParameterException( 358 "Unsupported RSA public exponent: " + publicExponent 359 + ". Only exponents <= " + Long.MAX_VALUE + " supported"); 360 } 361 mRSAPublicExponent = publicExponent.longValue(); 362 break; 363 } 364 case KeymasterDefs.KM_ALGORITHM_EC: 365 if (algSpecificSpec instanceof ECGenParameterSpec) { 366 ECGenParameterSpec ecSpec = (ECGenParameterSpec) algSpecificSpec; 367 String curveName = ecSpec.getName(); 368 Integer ecSpecKeySizeBits = SUPPORTED_EC_NIST_CURVE_NAME_TO_SIZE.get( 369 curveName.toLowerCase(Locale.US)); 370 if (ecSpecKeySizeBits == null) { 371 throw new InvalidAlgorithmParameterException( 372 "Unsupported EC curve name: " + curveName 373 + ". Supported: " + SUPPORTED_EC_NIST_CURVE_NAMES); 374 } 375 if (mKeySizeBits == -1) { 376 mKeySizeBits = ecSpecKeySizeBits; 377 } else if (mKeySizeBits != ecSpecKeySizeBits) { 378 throw new InvalidAlgorithmParameterException("EC key size must match " 379 + " between " + mSpec + " and " + algSpecificSpec 380 + ": " + mKeySizeBits + " vs " + ecSpecKeySizeBits); 381 } 382 } else if (algSpecificSpec != null) { 383 throw new InvalidAlgorithmParameterException( 384 "EC may only use ECGenParameterSpec"); 385 } 386 break; 387 default: 388 throw new ProviderException("Unsupported algorithm: " + mKeymasterAlgorithm); 389 } 390 } 391 392 @Override 393 public KeyPair generateKeyPair() { 394 if (mKeyStore == null || mSpec == null) { 395 throw new IllegalStateException("Not initialized"); 396 } 397 398 final int flags = (mEncryptionAtRestRequired) ? KeyStore.FLAG_ENCRYPTED : 0; 399 if (((flags & KeyStore.FLAG_ENCRYPTED) != 0) 400 && (mKeyStore.state() != KeyStore.State.UNLOCKED)) { 401 throw new IllegalStateException( 402 "Encryption at rest using secure lock screen credential requested for key pair" 403 + ", but the user has not yet entered the credential"); 404 } 405 406 KeymasterArguments args = new KeymasterArguments(); 407 args.addInt(KeymasterDefs.KM_TAG_KEY_SIZE, mKeySizeBits); 408 args.addInt(KeymasterDefs.KM_TAG_ALGORITHM, mKeymasterAlgorithm); 409 args.addInts(KeymasterDefs.KM_TAG_PURPOSE, mKeymasterPurposes); 410 args.addInts(KeymasterDefs.KM_TAG_BLOCK_MODE, mKeymasterBlockModes); 411 args.addInts(KeymasterDefs.KM_TAG_PADDING, mKeymasterEncryptionPaddings); 412 args.addInts(KeymasterDefs.KM_TAG_PADDING, mKeymasterSignaturePaddings); 413 args.addInts(KeymasterDefs.KM_TAG_DIGEST, mKeymasterDigests); 414 415 KeymasterUtils.addUserAuthArgs(args, 416 mSpec.isUserAuthenticationRequired(), 417 mSpec.getUserAuthenticationValidityDurationSeconds()); 418 args.addDate(KeymasterDefs.KM_TAG_ACTIVE_DATETIME, 419 (mSpec.getKeyValidityStart() != null) 420 ? mSpec.getKeyValidityStart() : new Date(0)); 421 args.addDate(KeymasterDefs.KM_TAG_ORIGINATION_EXPIRE_DATETIME, 422 (mSpec.getKeyValidityForOriginationEnd() != null) 423 ? mSpec.getKeyValidityForOriginationEnd() : new Date(Long.MAX_VALUE)); 424 args.addDate(KeymasterDefs.KM_TAG_USAGE_EXPIRE_DATETIME, 425 (mSpec.getKeyValidityForConsumptionEnd() != null) 426 ? mSpec.getKeyValidityForConsumptionEnd() : new Date(Long.MAX_VALUE)); 427 addAlgorithmSpecificParameters(args); 428 429 byte[] additionalEntropy = 430 KeyStoreCryptoOperationUtils.getRandomBytesToMixIntoKeystoreRng( 431 mRng, (mKeySizeBits + 7) / 8); 432 433 final String privateKeyAlias = Credentials.USER_PRIVATE_KEY + mEntryAlias; 434 boolean success = false; 435 try { 436 Credentials.deleteAllTypesForAlias(mKeyStore, mEntryAlias); 437 KeyCharacteristics resultingKeyCharacteristics = new KeyCharacteristics(); 438 int errorCode = mKeyStore.generateKey( 439 privateKeyAlias, 440 args, 441 additionalEntropy, 442 flags, 443 resultingKeyCharacteristics); 444 if (errorCode != KeyStore.NO_ERROR) { 445 throw new ProviderException( 446 "Failed to generate key pair", KeyStore.getKeyStoreException(errorCode)); 447 } 448 449 KeyPair result; 450 try { 451 result = AndroidKeyStoreProvider.loadAndroidKeyStoreKeyPairFromKeystore( 452 mKeyStore, privateKeyAlias); 453 } catch (UnrecoverableKeyException e) { 454 throw new ProviderException("Failed to load generated key pair from keystore", e); 455 } 456 457 if (!mJcaKeyAlgorithm.equalsIgnoreCase(result.getPrivate().getAlgorithm())) { 458 throw new ProviderException( 459 "Generated key pair algorithm does not match requested algorithm: " 460 + result.getPrivate().getAlgorithm() + " vs " + mJcaKeyAlgorithm); 461 } 462 463 final X509Certificate cert; 464 try { 465 cert = generateSelfSignedCertificate(result.getPrivate(), result.getPublic()); 466 } catch (Exception e) { 467 throw new ProviderException("Failed to generate self-signed certificate", e); 468 } 469 470 byte[] certBytes; 471 try { 472 certBytes = cert.getEncoded(); 473 } catch (CertificateEncodingException e) { 474 throw new ProviderException( 475 "Failed to obtain encoded form of self-signed certificate", e); 476 } 477 478 int insertErrorCode = mKeyStore.insert( 479 Credentials.USER_CERTIFICATE + mEntryAlias, 480 certBytes, 481 KeyStore.UID_SELF, 482 flags); 483 if (insertErrorCode != KeyStore.NO_ERROR) { 484 throw new ProviderException("Failed to store self-signed certificate", 485 KeyStore.getKeyStoreException(insertErrorCode)); 486 } 487 488 success = true; 489 return result; 490 } finally { 491 if (!success) { 492 Credentials.deleteAllTypesForAlias(mKeyStore, mEntryAlias); 493 } 494 } 495 } 496 497 private void addAlgorithmSpecificParameters(KeymasterArguments keymasterArgs) { 498 switch (mKeymasterAlgorithm) { 499 case KeymasterDefs.KM_ALGORITHM_RSA: 500 keymasterArgs.addLong(KeymasterDefs.KM_TAG_RSA_PUBLIC_EXPONENT, mRSAPublicExponent); 501 break; 502 case KeymasterDefs.KM_ALGORITHM_EC: 503 break; 504 default: 505 throw new ProviderException("Unsupported algorithm: " + mKeymasterAlgorithm); 506 } 507 } 508 509 private X509Certificate generateSelfSignedCertificate( 510 PrivateKey privateKey, PublicKey publicKey) throws Exception { 511 String signatureAlgorithm = 512 getCertificateSignatureAlgorithm(mKeymasterAlgorithm, mKeySizeBits, mSpec); 513 if (signatureAlgorithm == null) { 514 // Key cannot be used to sign a certificate 515 return generateSelfSignedCertificateWithFakeSignature(publicKey); 516 } else { 517 // Key can be used to sign a certificate 518 return generateSelfSignedCertificateWithValidSignature( 519 privateKey, publicKey, signatureAlgorithm); 520 } 521 } 522 523 @SuppressWarnings("deprecation") 524 private X509Certificate generateSelfSignedCertificateWithValidSignature( 525 PrivateKey privateKey, PublicKey publicKey, String signatureAlgorithm) 526 throws Exception { 527 final X509V3CertificateGenerator certGen = new X509V3CertificateGenerator(); 528 certGen.setPublicKey(publicKey); 529 certGen.setSerialNumber(mSpec.getCertificateSerialNumber()); 530 certGen.setSubjectDN(mSpec.getCertificateSubject()); 531 certGen.setIssuerDN(mSpec.getCertificateSubject()); 532 certGen.setNotBefore(mSpec.getCertificateNotBefore()); 533 certGen.setNotAfter(mSpec.getCertificateNotAfter()); 534 certGen.setSignatureAlgorithm(signatureAlgorithm); 535 return certGen.generate(privateKey); 536 } 537 538 @SuppressWarnings("deprecation") 539 private X509Certificate generateSelfSignedCertificateWithFakeSignature( 540 PublicKey publicKey) throws Exception { 541 V3TBSCertificateGenerator tbsGenerator = new V3TBSCertificateGenerator(); 542 ASN1ObjectIdentifier sigAlgOid; 543 AlgorithmIdentifier sigAlgId; 544 byte[] signature; 545 switch (mKeymasterAlgorithm) { 546 case KeymasterDefs.KM_ALGORITHM_EC: 547 sigAlgOid = X9ObjectIdentifiers.ecdsa_with_SHA256; 548 sigAlgId = new AlgorithmIdentifier(sigAlgOid); 549 ASN1EncodableVector v = new ASN1EncodableVector(); 550 v.add(new DERInteger(0)); 551 v.add(new DERInteger(0)); 552 signature = new DERSequence().getEncoded(); 553 break; 554 case KeymasterDefs.KM_ALGORITHM_RSA: 555 sigAlgOid = PKCSObjectIdentifiers.sha256WithRSAEncryption; 556 sigAlgId = new AlgorithmIdentifier(sigAlgOid, DERNull.INSTANCE); 557 signature = new byte[1]; 558 break; 559 default: 560 throw new ProviderException("Unsupported key algorithm: " + mKeymasterAlgorithm); 561 } 562 563 try (ASN1InputStream publicKeyInfoIn = new ASN1InputStream(publicKey.getEncoded())) { 564 tbsGenerator.setSubjectPublicKeyInfo( 565 SubjectPublicKeyInfo.getInstance(publicKeyInfoIn.readObject())); 566 } 567 tbsGenerator.setSerialNumber(new ASN1Integer(mSpec.getCertificateSerialNumber())); 568 X509Principal subject = 569 new X509Principal(mSpec.getCertificateSubject().getEncoded()); 570 tbsGenerator.setSubject(subject); 571 tbsGenerator.setIssuer(subject); 572 tbsGenerator.setStartDate(new Time(mSpec.getCertificateNotBefore())); 573 tbsGenerator.setEndDate(new Time(mSpec.getCertificateNotAfter())); 574 tbsGenerator.setSignature(sigAlgId); 575 TBSCertificate tbsCertificate = tbsGenerator.generateTBSCertificate(); 576 577 ASN1EncodableVector result = new ASN1EncodableVector(); 578 result.add(tbsCertificate); 579 result.add(sigAlgId); 580 result.add(new DERBitString(signature)); 581 return new X509CertificateObject(Certificate.getInstance(new DERSequence(result))); 582 } 583 584 private static int getDefaultKeySize(int keymasterAlgorithm) { 585 switch (keymasterAlgorithm) { 586 case KeymasterDefs.KM_ALGORITHM_EC: 587 return EC_DEFAULT_KEY_SIZE; 588 case KeymasterDefs.KM_ALGORITHM_RSA: 589 return RSA_DEFAULT_KEY_SIZE; 590 default: 591 throw new ProviderException("Unsupported algorithm: " + keymasterAlgorithm); 592 } 593 } 594 595 private static void checkValidKeySize(int keymasterAlgorithm, int keySize) 596 throws InvalidAlgorithmParameterException { 597 switch (keymasterAlgorithm) { 598 case KeymasterDefs.KM_ALGORITHM_EC: 599 if (!SUPPORTED_EC_NIST_CURVE_SIZES.contains(keySize)) { 600 throw new InvalidAlgorithmParameterException("Unsupported EC key size: " 601 + keySize + " bits. Supported: " + SUPPORTED_EC_NIST_CURVE_SIZES); 602 } 603 break; 604 case KeymasterDefs.KM_ALGORITHM_RSA: 605 if (keySize < RSA_MIN_KEY_SIZE || keySize > RSA_MAX_KEY_SIZE) { 606 throw new InvalidAlgorithmParameterException("RSA key size must be >= " 607 + RSA_MIN_KEY_SIZE + " and <= " + RSA_MAX_KEY_SIZE); 608 } 609 break; 610 default: 611 throw new ProviderException("Unsupported algorithm: " + keymasterAlgorithm); 612 } 613 } 614 615 /** 616 * Returns the {@code Signature} algorithm to be used for signing a certificate using the 617 * specified key or {@code null} if the key cannot be used for signing a certificate. 618 */ 619 @Nullable 620 private static String getCertificateSignatureAlgorithm( 621 int keymasterAlgorithm, 622 int keySizeBits, 623 KeyGenParameterSpec spec) { 624 // Constraints: 625 // 1. Key must be authorized for signing without user authentication. 626 // 2. Signature digest must be one of key's authorized digests. 627 // 3. For RSA keys, the digest output size must not exceed modulus size minus space needed 628 // for RSA PKCS#1 signature padding (about 29 bytes: minimum 10 bytes of padding + 15--19 629 // bytes overhead for encoding digest OID and digest value in DER). 630 // 4. For EC keys, the there is no point in using a digest whose output size is longer than 631 // key/field size because the digest will be truncated to that size. 632 633 if ((spec.getPurposes() & KeyProperties.PURPOSE_SIGN) == 0) { 634 // Key not authorized for signing 635 return null; 636 } 637 if (spec.isUserAuthenticationRequired()) { 638 // Key not authorized for use without user authentication 639 return null; 640 } 641 if (!spec.isDigestsSpecified()) { 642 // Key not authorized for any digests -- can't sign 643 return null; 644 } 645 switch (keymasterAlgorithm) { 646 case KeymasterDefs.KM_ALGORITHM_EC: 647 { 648 Set<Integer> availableKeymasterDigests = getAvailableKeymasterSignatureDigests( 649 spec.getDigests(), 650 AndroidKeyStoreBCWorkaroundProvider.getSupportedEcdsaSignatureDigests()); 651 652 int bestKeymasterDigest = -1; 653 int bestDigestOutputSizeBits = -1; 654 for (int keymasterDigest : availableKeymasterDigests) { 655 int outputSizeBits = KeymasterUtils.getDigestOutputSizeBits(keymasterDigest); 656 if (outputSizeBits == keySizeBits) { 657 // Perfect match -- use this digest 658 bestKeymasterDigest = keymasterDigest; 659 bestDigestOutputSizeBits = outputSizeBits; 660 break; 661 } 662 // Not a perfect match -- check against the best digest so far 663 if (bestKeymasterDigest == -1) { 664 // First digest tested -- definitely the best so far 665 bestKeymasterDigest = keymasterDigest; 666 bestDigestOutputSizeBits = outputSizeBits; 667 } else { 668 // Prefer output size to be as close to key size as possible, with output 669 // sizes larger than key size preferred to those smaller than key size. 670 if (bestDigestOutputSizeBits < keySizeBits) { 671 // Output size of the best digest so far is smaller than key size. 672 // Anything larger is a win. 673 if (outputSizeBits > bestDigestOutputSizeBits) { 674 bestKeymasterDigest = keymasterDigest; 675 bestDigestOutputSizeBits = outputSizeBits; 676 } 677 } else { 678 // Output size of the best digest so far is larger than key size. 679 // Anything smaller is a win, as long as it's not smaller than key size. 680 if ((outputSizeBits < bestDigestOutputSizeBits) 681 && (outputSizeBits >= keySizeBits)) { 682 bestKeymasterDigest = keymasterDigest; 683 bestDigestOutputSizeBits = outputSizeBits; 684 } 685 } 686 } 687 } 688 if (bestKeymasterDigest == -1) { 689 return null; 690 } 691 return KeyProperties.Digest.fromKeymasterToSignatureAlgorithmDigest( 692 bestKeymasterDigest) + "WithECDSA"; 693 } 694 case KeymasterDefs.KM_ALGORITHM_RSA: 695 { 696 // Check whether this key is authorized for PKCS#1 signature padding. 697 // We use Bouncy Castle to generate self-signed RSA certificates. Bouncy Castle 698 // only supports RSA certificates signed using PKCS#1 padding scheme. The key needs 699 // to be authorized for PKCS#1 padding or padding NONE which means any padding. 700 boolean pkcs1SignaturePaddingSupported = false; 701 for (int keymasterPadding : KeyProperties.SignaturePadding.allToKeymaster( 702 spec.getSignaturePaddings())) { 703 if ((keymasterPadding == KeymasterDefs.KM_PAD_RSA_PKCS1_1_5_SIGN) 704 || (keymasterPadding == KeymasterDefs.KM_PAD_NONE)) { 705 pkcs1SignaturePaddingSupported = true; 706 break; 707 } 708 } 709 if (!pkcs1SignaturePaddingSupported) { 710 // Keymaster doesn't distinguish between encryption padding NONE and signature 711 // padding NONE. In the Android Keystore API only encryption padding NONE is 712 // exposed. 713 for (int keymasterPadding : KeyProperties.EncryptionPadding.allToKeymaster( 714 spec.getEncryptionPaddings())) { 715 if (keymasterPadding == KeymasterDefs.KM_PAD_NONE) { 716 pkcs1SignaturePaddingSupported = true; 717 break; 718 } 719 } 720 } 721 if (!pkcs1SignaturePaddingSupported) { 722 // Key not authorized for PKCS#1 signature padding -- can't sign 723 return null; 724 } 725 726 Set<Integer> availableKeymasterDigests = getAvailableKeymasterSignatureDigests( 727 spec.getDigests(), 728 AndroidKeyStoreBCWorkaroundProvider.getSupportedEcdsaSignatureDigests()); 729 730 // The amount of space available for the digest is less than modulus size because 731 // padding must be at least 10 bytes long, and then there's also the 15--19 732 // bytes overhead for encoding digest OID and digest value in DER. 733 int maxDigestOutputSizeBits = keySizeBits - 29 * 8; 734 int bestKeymasterDigest = -1; 735 int bestDigestOutputSizeBits = -1; 736 for (int keymasterDigest : availableKeymasterDigests) { 737 int outputSizeBits = KeymasterUtils.getDigestOutputSizeBits(keymasterDigest); 738 if (outputSizeBits > maxDigestOutputSizeBits) { 739 // Digest too long (signature generation will fail) -- skip 740 continue; 741 } 742 if (bestKeymasterDigest == -1) { 743 // First digest tested -- definitely the best so far 744 bestKeymasterDigest = keymasterDigest; 745 bestDigestOutputSizeBits = outputSizeBits; 746 } else { 747 // The longer the better 748 if (outputSizeBits > bestDigestOutputSizeBits) { 749 bestKeymasterDigest = keymasterDigest; 750 bestDigestOutputSizeBits = outputSizeBits; 751 } 752 } 753 } 754 if (bestKeymasterDigest == -1) { 755 return null; 756 } 757 return KeyProperties.Digest.fromKeymasterToSignatureAlgorithmDigest( 758 bestKeymasterDigest) + "WithRSA"; 759 } 760 default: 761 throw new ProviderException("Unsupported algorithm: " + keymasterAlgorithm); 762 } 763 } 764 765 private static Set<Integer> getAvailableKeymasterSignatureDigests( 766 @KeyProperties.DigestEnum String[] authorizedKeyDigests, 767 @KeyProperties.DigestEnum String[] supportedSignatureDigests) { 768 Set<Integer> authorizedKeymasterKeyDigests = new HashSet<Integer>(); 769 for (int keymasterDigest : KeyProperties.Digest.allToKeymaster(authorizedKeyDigests)) { 770 authorizedKeymasterKeyDigests.add(keymasterDigest); 771 } 772 Set<Integer> supportedKeymasterSignatureDigests = new HashSet<Integer>(); 773 for (int keymasterDigest 774 : KeyProperties.Digest.allToKeymaster(supportedSignatureDigests)) { 775 supportedKeymasterSignatureDigests.add(keymasterDigest); 776 } 777 if (authorizedKeymasterKeyDigests.contains(KeymasterDefs.KM_DIGEST_NONE)) { 778 // Key is authorized to be used with any digest 779 return supportedKeymasterSignatureDigests; 780 } else { 781 // Key is authorized to be used only with specific digests. 782 Set<Integer> result = new HashSet<Integer>(supportedKeymasterSignatureDigests); 783 result.retainAll(authorizedKeymasterKeyDigests); 784 return result; 785 } 786 } 787} 788