To import a key or key pair into the Android Keystore, create an instance of this class using * the {@link Builder} and pass the instance into {@link java.security.KeyStore#setEntry(String, java.security.KeyStore.Entry, ProtectionParameter) KeyStore.setEntry} * with the key or key pair being imported. * *
To obtain the secret/symmetric or private key from the Android Keystore use * {@link java.security.KeyStore#getKey(String, char[]) KeyStore.getKey(String, null)} or * {@link java.security.KeyStore#getEntry(String, java.security.KeyStore.ProtectionParameter) KeyStore.getEntry(String, null)}. * To obtain the public key from the Android Keystore use * {@link java.security.KeyStore#getCertificate(String)} and then * {@link Certificate#getPublicKey()}. * *
To help obtain algorithm-specific public parameters of key pairs stored in the Android * Keystore, its private keys implement {@link java.security.interfaces.ECKey} or * {@link java.security.interfaces.RSAKey} interfaces whereas its public keys implement * {@link java.security.interfaces.ECPublicKey} or {@link java.security.interfaces.RSAPublicKey} * interfaces. * *
NOTE: The key material of keys stored in the Android Keystore is not accessible. * *
Instances of this class are immutable. * *
{@code
* PublicKey unrestrictedPublicKey =
* KeyFactory.getInstance(publicKey.getAlgorithm()).generatePublic(
* new X509EncodedKeySpec(publicKey.getEncoded()));
* }
*
* {@code
* SecretKey key = ...; // AES key
*
* KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
* keyStore.load(null);
* keyStore.setEntry(
* "key1",
* new KeyStore.SecretKeyEntry(key),
* new KeyProtection.Builder(KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
* .setBlockMode(KeyProperties.BLOCK_MODE_GCM)
* .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
* .build());
* // Key imported, obtain a reference to it.
* SecretKey keyStoreKey = (SecretKey) keyStore.getKey("key1", null);
* // The original key can now be discarded.
*
* Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
* cipher.init(Cipher.ENCRYPT_MODE, keyStoreKey);
* ...
* }
*
* {@code
* SecretKey key = ...; // HMAC key of algorithm "HmacSHA512".
*
* KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
* keyStore.load(null);
* keyStore.setEntry(
* "key1",
* new KeyStore.SecretKeyEntry(key),
* new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN).build());
* // Key imported, obtain a reference to it.
* SecretKey keyStoreKey = (SecretKey) keyStore.getKey("key1", null);
* // The original key can now be discarded.
*
* Mac mac = Mac.getInstance("HmacSHA512");
* mac.init(keyStoreKey);
* ...
* }
*
* {@code
* PrivateKey privateKey = ...; // EC private key
* Certificate[] certChain = ...; // Certificate chain with the first certificate
* // containing the corresponding EC public key.
*
* KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
* keyStore.load(null);
* keyStore.setEntry(
* "key2",
* new KeyStore.PrivateKeyEntry(privateKey, certChain),
* new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN)
* .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
* .build());
* // Key pair imported, obtain a reference to it.
* PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
* PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
* // The original private key can now be discarded.
*
* Signature signature = Signature.getInstance("SHA256withECDSA");
* signature.initSign(keyStorePrivateKey);
* ...
* }
*
* {@code
* PrivateKey privateKey = ...; // RSA private key
* Certificate[] certChain = ...; // Certificate chain with the first certificate
* // containing the corresponding RSA public key.
*
* KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
* keyStore.load(null);
* keyStore.setEntry(
* "key2",
* new KeyStore.PrivateKeyEntry(privateKey, certChain),
* new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN)
* .setDigests(KeyProperties.DIGEST_SHA256)
* .setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
* // Only permit this key to be used if the user
* // authenticated within the last ten minutes.
* .setUserAuthenticationRequired(true)
* .setUserAuthenticationValidityDurationSeconds(10 * 60)
* .build());
* // Key pair imported, obtain a reference to it.
* PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
* PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
* // The original private key can now be discarded.
*
* Signature signature = Signature.getInstance("SHA256withRSA");
* signature.initSign(keyStorePrivateKey);
* ...
* }
*
* {@code
* PrivateKey privateKey = ...; // RSA private key
* Certificate[] certChain = ...; // Certificate chain with the first certificate
* // containing the corresponding RSA public key.
*
* KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
* keyStore.load(null);
* keyStore.setEntry(
* "key2",
* new KeyStore.PrivateKeyEntry(privateKey, certChain),
* new KeyProtection.Builder(KeyProperties.PURPOSE_DECRYPT)
* .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
* .build());
* // Key pair imported, obtain a reference to it.
* PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
* PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
* // The original private key can now be discarded.
*
* Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
* cipher.init(Cipher.DECRYPT_MODE, keyStorePrivateKey);
* ...
* }
*/
public final class KeyProtection implements ProtectionParameter, UserAuthArgs {
private final Date mKeyValidityStart;
private final Date mKeyValidityForOriginationEnd;
private final Date mKeyValidityForConsumptionEnd;
private final @KeyProperties.PurposeEnum int mPurposes;
private final @KeyProperties.EncryptionPaddingEnum String[] mEncryptionPaddings;
private final @KeyProperties.SignaturePaddingEnum String[] mSignaturePaddings;
private final @KeyProperties.DigestEnum String[] mDigests;
private final @NonNull @KeyProperties.DigestEnum SetSee {@link KeyProperties}.{@code PURPOSE} flags. */ public @KeyProperties.PurposeEnum int getPurposes() { return mPurposes; } /** * Gets the set of padding schemes (e.g., {@code PKCS7Padding}, {@code PKCS1Padding}, * {@code NoPadding}) with which the key can be used when encrypting/decrypting. Attempts to use * the key with any other padding scheme will be rejected. * *
See {@link KeyProperties}.{@code ENCRYPTION_PADDING} constants. */ @NonNull public @KeyProperties.EncryptionPaddingEnum String[] getEncryptionPaddings() { return ArrayUtils.cloneIfNotEmpty(mEncryptionPaddings); } /** * Gets the set of padding schemes (e.g., {@code PSS}, {@code PKCS#1}) with which the key * can be used when signing/verifying. Attempts to use the key with any other padding scheme * will be rejected. * *
See {@link KeyProperties}.{@code SIGNATURE_PADDING} constants. */ @NonNull public @KeyProperties.SignaturePaddingEnum String[] getSignaturePaddings() { return ArrayUtils.cloneIfNotEmpty(mSignaturePaddings); } /** * Gets the set of digest algorithms (e.g., {@code SHA-256}, {@code SHA-384}) with which the key * can be used. * *
See {@link KeyProperties}.{@code DIGEST} constants. * * @throws IllegalStateException if this set has not been specified. * * @see #isDigestsSpecified() */ @NonNull public @KeyProperties.DigestEnum String[] getDigests() { if (mDigests == null) { throw new IllegalStateException("Digests not specified"); } return ArrayUtils.cloneIfNotEmpty(mDigests); } /** * Returns {@code true} if the set of digest algorithms with which the key can be used has been * specified. * * @see #getDigests() */ public boolean isDigestsSpecified() { return mDigests != null; } /** * Returns the set of digests that can be used by the MGF1 mask generation function * (e.g., {@code SHA-256}, {@code SHA-384}) with the key. Useful with the {@code RSA-OAEP} * scheme. * If not explicitly specified during key generation, the default {@code SHA-1} digest is * used and may be specified. * *
See {@link KeyProperties}.{@code DIGEST} constants.
*
* @throws IllegalStateException if this set has not been specified.
*
* @see #isMgf1DigestsSpecified()
*/
@NonNull
@FlaggedApi(android.security.Flags.FLAG_MGF1_DIGEST_SETTER_V2)
public @KeyProperties.DigestEnum Set See {@link KeyProperties}.{@code BLOCK_MODE} constants.
*/
@NonNull
public @KeyProperties.BlockModeEnum String[] getBlockModes() {
return ArrayUtils.cloneIfNotEmpty(mBlockModes);
}
/**
* Returns {@code true} if encryption using this key must be sufficiently randomized to produce
* different ciphertexts for the same plaintext every time. The formal cryptographic property
* being required is indistinguishability under chosen-plaintext attack ({@code
* IND-CPA}). This property is important because it mitigates several classes of
* weaknesses due to which ciphertext may leak information about plaintext. For example, if a
* given plaintext always produces the same ciphertext, an attacker may see the repeated
* ciphertexts and be able to deduce something about the plaintext.
*/
public boolean isRandomizedEncryptionRequired() {
return mRandomizedEncryptionRequired;
}
/**
* Returns {@code true} if the key is authorized to be used only if the user has been
* authenticated.
*
* This authorization applies only to secret key and private key operations. Public key
* operations are not restricted.
*
* @see #getUserAuthenticationValidityDurationSeconds()
* @see Builder#setUserAuthenticationRequired(boolean)
*/
public boolean isUserAuthenticationRequired() {
return mUserAuthenticationRequired;
}
/**
* Returns {@code true} if the key is authorized to be used only for messages confirmed by the
* user.
*
* Confirmation is separate from user authentication (see
* {@link #isUserAuthenticationRequired()}). Keys can be created that require confirmation but
* not user authentication, or user authentication but not confirmation, or both. Confirmation
* verifies that some user with physical possession of the device has approved a displayed
* message. User authentication verifies that the correct user is present and has
* authenticated.
*
* This authorization applies only to secret key and private key operations. Public key
* operations are not restricted.
*
* @see Builder#setUserConfirmationRequired(boolean)
*/
public boolean isUserConfirmationRequired() {
return mUserConfirmationRequired;
}
public @KeyProperties.AuthEnum int getUserAuthenticationType() {
return mUserAuthenticationType;
}
/**
* Gets the duration of time (seconds) for which this key is authorized to be used after the
* user is successfully authenticated. This has effect only if user authentication is required
* (see {@link #isUserAuthenticationRequired()}).
*
* This authorization applies only to secret key and private key operations. Public key
* operations are not restricted.
*
* @return duration in seconds or {@code -1} if authentication is required for every use of the
* key.
*
* @see #isUserAuthenticationRequired()
* @see Builder#setUserAuthenticationValidityDurationSeconds(int)
*/
public int getUserAuthenticationValidityDurationSeconds() {
return mUserAuthenticationValidityDurationSeconds;
}
/**
* Returns {@code true} if the key is authorized to be used only if a test of user presence has
* been performed between the {@code Signature.initSign()} and {@code Signature.sign()} calls.
* It requires that the KeyStore implementation have a direct way to validate the user presence
* for example a KeyStore hardware backed strongbox can use a button press that is observable
* in hardware. A test for user presence is tangential to authentication. The test can be part
* of an authentication step as long as this step can be validated by the hardware protecting
* the key and cannot be spoofed. For example, a physical button press can be used as a test of
* user presence if the other pins connected to the button are not able to simulate a button
* press. There must be no way for the primary processor to fake a button press, or that
* button must not be used as a test of user presence.
*/
public boolean isUserPresenceRequired() {
return mUserPresenceRequred;
}
/**
* Returns {@code true} if the key will be de-authorized when the device is removed from the
* user's body. This option has no effect on keys that don't have an authentication validity
* duration, and has no effect if the device lacks an on-body sensor.
*
* Authorization applies only to secret key and private key operations. Public key operations
* are not restricted.
*
* @see #isUserAuthenticationRequired()
* @see #getUserAuthenticationValidityDurationSeconds()
* @see Builder#setUserAuthenticationValidWhileOnBody(boolean)
*/
public boolean isUserAuthenticationValidWhileOnBody() {
return mUserAuthenticationValidWhileOnBody;
}
/**
* Returns {@code true} if the key is irreversibly invalidated when a new biometric is
* enrolled or all enrolled biometrics are removed. This has effect only for keys that
* require biometric user authentication for every use.
*
* @see #isUserAuthenticationRequired()
* @see #getUserAuthenticationValidityDurationSeconds()
* @see Builder#setInvalidatedByBiometricEnrollment(boolean)
*/
public boolean isInvalidatedByBiometricEnrollment() {
return mInvalidatedByBiometricEnrollment;
}
/**
* Return the secure user id that this key should be bound to.
*
* Normally an authentication-bound key is tied to the secure user id of the current user
* (either the root SID from GateKeeper for auth-bound keys with a timeout, or the authenticator
* id of the current biometric set for keys requiring explicit biometric authorization).
* If this parameter is set (this method returning non-zero value), the key should be tied to
* the specified secure user id, overriding the logic above.
*
* This is only applicable when {@link #isUserAuthenticationRequired} is {@code true}
*
* @see KeymasterUtils#addUserAuthArgs
* @hide
*/
@TestApi
public long getBoundToSpecificSecureUserId() {
return mBoundToSecureUserId;
}
/**
* Return whether this key is critical to the device encryption flow.
*
* @see Builder#setCriticalToDeviceEncryption(boolean)
* @hide
*/
public boolean isCriticalToDeviceEncryption() {
return mCriticalToDeviceEncryption;
}
/**
* Returns {@code true} if the key is authorized to be used only while the device is unlocked.
*
* @see Builder#setUnlockedDeviceRequired(boolean)
*/
public boolean isUnlockedDeviceRequired() {
return mUnlockedDeviceRequired;
}
/**
* Returns {@code true} if the key is protected by a Strongbox security chip.
* @hide
*/
public boolean isStrongBoxBacked() {
return mIsStrongBoxBacked;
}
/**
* Returns the maximum number of times the limited use key is allowed to be used or
* {@link KeyProperties#UNRESTRICTED_USAGE_COUNT} if there’s no restriction on the number of
* times the key can be used.
*
* @see Builder#setMaxUsageCount(int)
*/
public int getMaxUsageCount() {
return mMaxUsageCount;
}
/**
* Returns {@code true} if the key is rollback-resistant, meaning that when deleted it is
* guaranteed to be permanently deleted and unusable.
*
* @see Builder#setRollbackResistant(boolean)
* @hide
*/
public boolean isRollbackResistant() {
return mRollbackResistant;
}
/**
* Builder of {@link KeyProtection} instances.
*/
public final static class Builder {
private @KeyProperties.PurposeEnum int mPurposes;
private Date mKeyValidityStart;
private Date mKeyValidityForOriginationEnd;
private Date mKeyValidityForConsumptionEnd;
private @KeyProperties.EncryptionPaddingEnum String[] mEncryptionPaddings;
private @KeyProperties.SignaturePaddingEnum String[] mSignaturePaddings;
private @KeyProperties.DigestEnum String[] mDigests;
private @NonNull @KeyProperties.DigestEnum Set See {@link KeyProperties}.{@code PURPOSE} flags.
*/
public Builder(@KeyProperties.PurposeEnum int purposes) {
mPurposes = purposes;
}
/**
* Sets the time instant before which the key is not yet valid.
*
* By default, the key is valid at any instant.
*
* @see #setKeyValidityEnd(Date)
*/
@NonNull
public Builder setKeyValidityStart(Date startDate) {
mKeyValidityStart = Utils.cloneIfNotNull(startDate);
return this;
}
/**
* Sets the time instant after which the key is no longer valid.
*
* By default, the key is valid at any instant.
*
* @see #setKeyValidityStart(Date)
* @see #setKeyValidityForConsumptionEnd(Date)
* @see #setKeyValidityForOriginationEnd(Date)
*/
@NonNull
public Builder setKeyValidityEnd(Date endDate) {
setKeyValidityForOriginationEnd(endDate);
setKeyValidityForConsumptionEnd(endDate);
return this;
}
/**
* Sets the time instant after which the key is no longer valid for encryption and signing.
*
* By default, the key is valid at any instant.
*
* @see #setKeyValidityForConsumptionEnd(Date)
*/
@NonNull
public Builder setKeyValidityForOriginationEnd(Date endDate) {
mKeyValidityForOriginationEnd = Utils.cloneIfNotNull(endDate);
return this;
}
/**
* Sets the time instant after which the key is no longer valid for decryption and
* verification.
*
* By default, the key is valid at any instant.
*
* @see #setKeyValidityForOriginationEnd(Date)
*/
@NonNull
public Builder setKeyValidityForConsumptionEnd(Date endDate) {
mKeyValidityForConsumptionEnd = Utils.cloneIfNotNull(endDate);
return this;
}
/**
* Sets the set of padding schemes (e.g., {@code OAEPPadding}, {@code PKCS7Padding},
* {@code NoPadding}) with which the key can be used when encrypting/decrypting. Attempts to
* use the key with any other padding scheme will be rejected.
*
* This must be specified for keys which are used for encryption/decryption.
*
* For RSA private keys used by TLS/SSL servers to authenticate themselves to clients it
* is usually necessary to authorize the use of no/any padding
* ({@link KeyProperties#ENCRYPTION_PADDING_NONE}) and/or PKCS#1 encryption padding
* ({@link KeyProperties#ENCRYPTION_PADDING_RSA_PKCS1}). This is because RSA decryption is
* required by some cipher suites, and some stacks request decryption using no padding
* whereas others request PKCS#1 padding.
*
* See {@link KeyProperties}.{@code ENCRYPTION_PADDING} constants.
*/
@NonNull
public Builder setEncryptionPaddings(
@KeyProperties.EncryptionPaddingEnum String... paddings) {
mEncryptionPaddings = ArrayUtils.cloneIfNotEmpty(paddings);
return this;
}
/**
* Sets the set of padding schemes (e.g., {@code PSS}, {@code PKCS#1}) with which the key
* can be used when signing/verifying. Attempts to use the key with any other padding scheme
* will be rejected.
*
* This must be specified for RSA keys which are used for signing/verification.
*
* See {@link KeyProperties}.{@code SIGNATURE_PADDING} constants.
*/
@NonNull
public Builder setSignaturePaddings(
@KeyProperties.SignaturePaddingEnum String... paddings) {
mSignaturePaddings = ArrayUtils.cloneIfNotEmpty(paddings);
return this;
}
/**
* Sets the set of digest algorithms (e.g., {@code SHA-256}, {@code SHA-384}) with which the
* key can be used. Attempts to use the key with any other digest algorithm will be
* rejected.
*
* This must be specified for signing/verification keys and RSA encryption/decryption
* keys used with RSA OAEP padding scheme because these operations involve a digest. For
* HMAC keys, the default is the digest specified in {@link Key#getAlgorithm()} (e.g.,
* {@code SHA-256} for key algorithm {@code HmacSHA256}). HMAC keys cannot be authorized
* for more than one digest.
*
* For private keys used for TLS/SSL client or server authentication it is usually
* necessary to authorize the use of no digest ({@link KeyProperties#DIGEST_NONE}). This is
* because TLS/SSL stacks typically generate the necessary digest(s) themselves and then use
* a private key to sign it.
*
* See {@link KeyProperties}.{@code DIGEST} constants.
*/
@NonNull
public Builder setDigests(@KeyProperties.DigestEnum String... digests) {
mDigests = ArrayUtils.cloneIfNotEmpty(digests);
return this;
}
/**
* Sets the set of hash functions (e.g., {@code SHA-256}, {@code SHA-384}) which could be
* used by the mask generation function MGF1 (which is used for certain operations with
* the key). Attempts to use the key with any other digest for the mask generation
* function will be rejected.
*
* This can only be specified for signing/verification keys and RSA encryption/decryption
* keys used with RSA OAEP padding scheme because these operations involve a mask generation
* function (MGF1) with a digest.
* The default digest for MGF1 is {@code SHA-1}, which will be specified during key import
* time if no digests have been explicitly provided.
* When using the key, the caller may not specify any digests that were not provided during
* key import time. The caller may specify the default digest, {@code SHA-1}, if no
* digests were explicitly provided during key import (but it is not necessary to do so).
*
* See {@link KeyProperties}.{@code DIGEST} constants.
*/
@NonNull
@FlaggedApi(android.security.Flags.FLAG_MGF1_DIGEST_SETTER_V2)
public Builder setMgf1Digests(@Nullable @KeyProperties.DigestEnum String... mgf1Digests) {
mMgf1Digests = Set.of(mgf1Digests);
return this;
}
/**
* Sets the set of block modes (e.g., {@code GCM}, {@code CBC}) with which the key can be
* used when encrypting/decrypting. Attempts to use the key with any other block modes will
* be rejected.
*
* This must be specified for symmetric encryption/decryption keys.
*
* See {@link KeyProperties}.{@code BLOCK_MODE} constants.
*/
@NonNull
public Builder setBlockModes(@KeyProperties.BlockModeEnum String... blockModes) {
mBlockModes = ArrayUtils.cloneIfNotEmpty(blockModes);
return this;
}
/**
* Sets whether encryption using this key must be sufficiently randomized to produce
* different ciphertexts for the same plaintext every time. The formal cryptographic
* property being required is indistinguishability under chosen-plaintext attack
* ({@code IND-CPA}). This property is important because it mitigates several classes
* of weaknesses due to which ciphertext may leak information about plaintext. For example,
* if a given plaintext always produces the same ciphertext, an attacker may see the
* repeated ciphertexts and be able to deduce something about the plaintext.
*
* By default, {@code IND-CPA} is required.
*
* When {@code IND-CPA} is required:
* Before disabling this requirement, consider the following approaches instead:
* By default, the key is authorized to be used regardless of whether the user has been
* authenticated.
*
* When user authentication is required:
* This authorization applies only to secret key and private key operations. Public key
* operations are not restricted.
*
* @see #setUserAuthenticationValidityDurationSeconds(int)
* @see KeyguardManager#isDeviceSecure()
* @see BiometricManager#canAuthenticate()
*/
@NonNull
public Builder setUserAuthenticationRequired(boolean required) {
mUserAuthenticationRequired = required;
return this;
}
/**
* Sets whether this key is authorized to be used only for messages confirmed by the
* user.
*
* Confirmation is separate from user authentication (see
* {@link #setUserAuthenticationRequired(boolean)}). Keys can be created that require
* confirmation but not user authentication, or user authentication but not confirmation,
* or both. Confirmation verifies that some user with physical possession of the device has
* approved a displayed message. User authentication verifies that the correct user is
* present and has authenticated.
*
* This authorization applies only to secret key and private key operations. Public key
* operations are not restricted.
*
* See {@link android.security.ConfirmationPrompt} class for
* more details about user confirmations.
*/
@NonNull
public Builder setUserConfirmationRequired(boolean required) {
mUserConfirmationRequired = required;
return this;
}
/**
* Sets the duration of time (seconds) for which this key is authorized to be used after the
* user is successfully authenticated. This has effect if the key requires user
* authentication for its use (see {@link #setUserAuthenticationRequired(boolean)}).
*
* By default, if user authentication is required, it must take place for every use of
* the key.
*
* Cryptographic operations involving keys which require user authentication to take
* place for every operation can only use biometric authentication. This is achieved by
* initializing a cryptographic operation ({@link Signature}, {@link Cipher}, {@link Mac})
* with the key, wrapping it into a {@link BiometricPrompt.CryptoObject}, invoking
* {@code BiometricPrompt.authenticate} with {@code CryptoObject}, and proceeding with
* the cryptographic operation only if the authentication flow succeeds.
*
* Cryptographic operations involving keys which are authorized to be used for a duration
* of time after a successful user authentication event can only use secure lock screen
* authentication. These cryptographic operations will throw
* {@link UserNotAuthenticatedException} during initialization if the user needs to be
* authenticated to proceed. This situation can be resolved by the user unlocking the secure
* lock screen of the Android or by going through the confirm credential flow initiated by
* {@link KeyguardManager#createConfirmDeviceCredentialIntent(CharSequence, CharSequence)}.
* Once resolved, initializing a new cryptographic operation using this key (or any other
* key which is authorized to be used for a fixed duration of time after user
* authentication) should succeed provided the user authentication flow completed
* successfully.
*
* @param seconds duration in seconds or {@code -1} if user authentication must take place
* for every use of the key.
*
* @see #setUserAuthenticationRequired(boolean)
* @see BiometricPrompt
* @see BiometricPrompt.CryptoObject
* @see KeyguardManager
* @deprecated See {@link #setUserAuthenticationParameters(int, int)}
*/
@Deprecated
@NonNull
public Builder setUserAuthenticationValidityDurationSeconds(
@IntRange(from = -1) int seconds) {
if (seconds < -1) {
throw new IllegalArgumentException("seconds must be -1 or larger");
}
if (seconds == -1) {
return setUserAuthenticationParameters(0, KeyProperties.AUTH_BIOMETRIC_STRONG);
}
return setUserAuthenticationParameters(seconds, KeyProperties.AUTH_DEVICE_CREDENTIAL
| KeyProperties.AUTH_BIOMETRIC_STRONG);
}
/**
* Sets the duration of time (seconds) and authorization type for which this key is
* authorized to be used after the user is successfully authenticated. This has effect if
* the key requires user authentication for its use (see
* {@link #setUserAuthenticationRequired(boolean)}).
*
* By default, if user authentication is required, it must take place for every use of
* the key.
*
* These cryptographic operations will throw {@link UserNotAuthenticatedException} during
* initialization if the user needs to be authenticated to proceed. This situation can be
* resolved by the user authenticating with the appropriate biometric or credential as
* required by the key. See {@link BiometricPrompt.Builder#setAllowedAuthenticators(int)}
* and {@link BiometricManager.Authenticators}.
*
* Once resolved, initializing a new cryptographic operation using this key (or any other
* key which is authorized to be used for a fixed duration of time after user
* authentication) should succeed provided the user authentication flow completed
* successfully.
*
* @param timeout duration in seconds or {@code 0} if user authentication must take place
* for every use of the key.
* @param type set of authentication types which can authorize use of the key. See
* {@link KeyProperties}.{@code AUTH} flags.
*
* @see #setUserAuthenticationRequired(boolean)
* @see BiometricPrompt
* @see BiometricPrompt.CryptoObject
* @see KeyguardManager
*/
@NonNull
public Builder setUserAuthenticationParameters(@IntRange(from = 0) int timeout,
@KeyProperties.AuthEnum int type) {
if (timeout < 0) {
throw new IllegalArgumentException("timeout must be 0 or larger");
}
mUserAuthenticationValidityDurationSeconds = timeout;
mUserAuthenticationType = type;
return this;
}
/**
* Sets whether a test of user presence is required to be performed between the
* {@code Signature.initSign()} and {@code Signature.sign()} method calls. It requires that
* the KeyStore implementation have a direct way to validate the user presence for example
* a KeyStore hardware backed strongbox can use a button press that is observable in
* hardware. A test for user presence is tangential to authentication. The test can be part
* of an authentication step as long as this step can be validated by the hardware
* protecting the key and cannot be spoofed. For example, a physical button press can be
* used as a test of user presence if the other pins connected to the button are not able
* to simulate a button press. There must be no way for the primary processor to fake a
* button press, or that button must not be used as a test of user presence.
*/
@NonNull
public Builder setUserPresenceRequired(boolean required) {
mUserPresenceRequired = required;
return this;
}
/**
* Sets whether the key will remain authorized only until the device is removed from the
* user's body up to the limit of the authentication validity period (see
* {@link #setUserAuthenticationValidityDurationSeconds} and
* {@link #setUserAuthenticationRequired}). Once the device has been removed from the
* user's body, the key will be considered unauthorized and the user will need to
* re-authenticate to use it. If the device does not have an on-body sensor or the key does
* not have an authentication validity period, this parameter has no effect.
*
* Since Android 12 (API level 31), this parameter has no effect even on devices that have
* an on-body sensor. A future version of Android may restore enforcement of this parameter.
* Meanwhile, it is recommended to not use it.
*
* @param remainsValid if {@code true}, and if the device supports enforcement of this
* parameter, the key will be invalidated when the device is removed from the user's body or
* when the authentication validity expires, whichever occurs first.
*/
@NonNull
public Builder setUserAuthenticationValidWhileOnBody(boolean remainsValid) {
mUserAuthenticationValidWhileOnBody = remainsValid;
return this;
}
/**
* Sets whether this key should be invalidated on biometric enrollment. This
* applies only to keys which require user authentication (see {@link
* #setUserAuthenticationRequired(boolean)}) and if no positive validity duration has been
* set (see {@link #setUserAuthenticationValidityDurationSeconds(int)}, meaning the key is
* valid for biometric authentication only.
*
* By default, {@code invalidateKey} is {@code true}, so keys that are valid for
* biometric authentication only are irreversibly invalidated when a new
* biometric is enrolled, or when all existing biometrics are deleted. That may be
* changed by calling this method with {@code invalidateKey} set to {@code false}.
*
* Invalidating keys on enrollment of a new biometric or unenrollment of all biometrics
* improves security by ensuring that an unauthorized person who obtains the password can't
* gain the use of biometric-authenticated keys by enrolling their own biometric. However,
* invalidating keys makes key-dependent operations impossible, requiring some fallback
* procedure to authenticate the user and set up a new key.
*/
@NonNull
public Builder setInvalidatedByBiometricEnrollment(boolean invalidateKey) {
mInvalidatedByBiometricEnrollment = invalidateKey;
return this;
}
/**
* Set the secure user id that this key should be bound to.
*
* Normally an authentication-bound key is tied to the secure user id of the current user
* (either the root SID from GateKeeper for auth-bound keys with a timeout, or the
* authenticator id of the current biometric set for keys requiring explicit biometric
* authorization). If this parameter is set (this method returning non-zero value), the key
* should be tied to the specified secure user id, overriding the logic above.
*
* This is only applicable when {@link #setUserAuthenticationRequired} is set to
* {@code true}
*
* @see KeyProtection#getBoundToSpecificSecureUserId()
* @hide
*/
@TestApi
public Builder setBoundToSpecificSecureUserId(long secureUserId) {
mBoundToSecureUserId = secureUserId;
return this;
}
/**
* Set whether this key is critical to the device encryption flow
*
* This is a special flag only available to system servers to indicate the current key
* is part of the device encryption flow. Setting this flag causes the key to not
* be cryptographically bound to the LSKF even if the key is otherwise authentication
* bound.
*
* @hide
*/
public Builder setCriticalToDeviceEncryption(boolean critical) {
mCriticalToDeviceEncryption = critical;
return this;
}
/**
* Sets whether this key is authorized to be used only while the device is unlocked.
*
* The device is considered to be locked for a user when the user's apps are currently
* inaccessible and some form of lock screen authentication is required to regain access to
* them. For the full definition, see {@link KeyguardManager#isDeviceLocked()}.
*
* Public key operations aren't restricted by {@code setUnlockedDeviceRequired(true)} and
* may be performed even while the device is locked. In Android 11 (API level 30) and lower,
* encryption and verification operations with symmetric keys weren't restricted either.
*
* Keys that use {@code setUnlockedDeviceRequired(true)} can be imported and generated even
* while the device is locked, as long as the device has been unlocked at least once since
* the last reboot. However, such keys cannot be used (except for the unrestricted
* operations mentioned above) until the device is unlocked. Apps that need to encrypt data
* while the device is locked such that it can only be decrypted while the device is
* unlocked can generate a key and encrypt the data in software, import the key into
* Keystore using {@code setUnlockedDeviceRequired(true)}, and zeroize the original key.
*
* {@code setUnlockedDeviceRequired(true)} is related to but distinct from
* {@link #setUserAuthenticationRequired(boolean) setUserAuthenticationRequired(true)}.
* {@code setUnlockedDeviceRequired(true)} requires that the device be unlocked, whereas
* {@code setUserAuthenticationRequired(true)} requires that a specific type of strong
* authentication has happened within a specific time period. They may be used together or
* separately; there are cases in which one requirement can be satisfied but not the other.
*
* Warning: Be careful using {@code setUnlockedDeviceRequired(true)} on Android 14
* (API level 34) and lower, since the following bugs existed in Android 12 through 14:
* By default, there is no restriction on the usage of key.
*
* Some secure hardware may not support this feature at all, in which case it will
* be enforced in software, some secure hardware may support it but only with
* maxUsageCount = 1, and some secure hardware may support it with larger value
* of maxUsageCount.
*
* The PackageManger feature flags:
* {@link android.content.pm.PackageManager#FEATURE_KEYSTORE_SINGLE_USE_KEY} and
* {@link android.content.pm.PackageManager#FEATURE_KEYSTORE_LIMITED_USE_KEY} can be used
* to check whether the secure hardware cannot enforce this feature, can only enforce it
* with maxUsageCount = 1, or can enforce it with larger value of maxUsageCount.
*
* @param maxUsageCount maximum number of times the key is allowed to be used or
* {@link KeyProperties#UNRESTRICTED_USAGE_COUNT} if there is no restriction on the
* usage.
*/
@NonNull
public Builder setMaxUsageCount(int maxUsageCount) {
if (maxUsageCount == KeyProperties.UNRESTRICTED_USAGE_COUNT || maxUsageCount > 0) {
mMaxUsageCount = maxUsageCount;
return this;
}
throw new IllegalArgumentException("maxUsageCount is not valid");
}
/**
* Sets whether the key should be rollback-resistant, meaning that when deleted it is
* guaranteed to be permanently deleted and unusable. Not all implementations support
* rollback-resistant keys. This method is hidden because implementations only support a
* limited number of rollback-resistant keys; currently the available space is reserved for
* critical system keys.
*
* @hide
*/
@NonNull
public Builder setRollbackResistant(boolean rollbackResistant) {
mRollbackResistant = rollbackResistant;
return this;
}
/**
* Builds an instance of {@link KeyProtection}.
*
* @throws IllegalArgumentException if a required field is missing
*/
@NonNull
public KeyProtection build() {
return new KeyProtection(
mKeyValidityStart,
mKeyValidityForOriginationEnd,
mKeyValidityForConsumptionEnd,
mPurposes,
mEncryptionPaddings,
mSignaturePaddings,
mDigests,
mMgf1Digests,
mBlockModes,
mRandomizedEncryptionRequired,
mUserAuthenticationRequired,
mUserAuthenticationType,
mUserAuthenticationValidityDurationSeconds,
mUserPresenceRequired,
mUserAuthenticationValidWhileOnBody,
mInvalidatedByBiometricEnrollment,
mBoundToSecureUserId,
mCriticalToDeviceEncryption,
mUserConfirmationRequired,
mUnlockedDeviceRequired,
mIsStrongBoxBacked,
mMaxUsageCount,
mRollbackResistant);
}
}
}
*
*
*/
@NonNull
public Builder setRandomizedEncryptionRequired(boolean required) {
mRandomizedEncryptionRequired = required;
return this;
}
/**
* Sets whether this key is authorized to be used only if the user has been authenticated.
*
*
*
*
*
*
* These issues are fixed in Android 15, so apps can avoid them by using
* {@code setUnlockedDeviceRequired(true)} only on Android 15 and higher.
* Apps that use both {@code setUnlockedDeviceRequired(true)} and
* {@link #setUserAuthenticationRequired(boolean) setUserAuthenticationRequired(true)}
* are unaffected by the first two issues, since the first two issues describe expected
* behavior for {@code setUserAuthenticationRequired(true)}.
*/
@NonNull
public Builder setUnlockedDeviceRequired(boolean unlockedDeviceRequired) {
mUnlockedDeviceRequired = unlockedDeviceRequired;
return this;
}
/**
* Sets whether this key should be protected by a StrongBox security chip.
*/
@NonNull
public Builder setIsStrongBoxBacked(boolean isStrongBoxBacked) {
mIsStrongBoxBacked = isStrongBoxBacked;
return this;
}
/**
* Sets the maximum number of times the key is allowed to be used. After every use of the
* key, the use counter will decrease. This authorization applies only to secret key and
* private key operations. Public key operations are not restricted. For example, after
* successfully encrypting and decrypting data using methods such as
* {@link Cipher#doFinal()}, the use counter of the secret key will decrease. After
* successfully signing data using methods such as {@link Signature#sign()}, the use
* counter of the private key will decrease.
*
* When the use counter is depleted, the key will be marked for deletion by Android
* Keystore and any subsequent attempt to use the key will throw
* {@link KeyPermanentlyInvalidatedException}. There is no key to be loaded from the
* Android Keystore once the exhausted key is permanently deleted, as if the key never
* existed before.
*
*