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script-astra/Android/Sdk/sources/android-35/android/security/keystore/KeyProtection.java

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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.security.keystore;
import android.annotation.FlaggedApi;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.TestApi;
import android.app.KeyguardManager;
import android.hardware.biometrics.BiometricManager;
import android.hardware.biometrics.BiometricPrompt;
import android.security.GateKeeper;
import android.security.keystore2.KeymasterUtils;
import java.security.Key;
import java.security.KeyStore.ProtectionParameter;
import java.security.Signature;
import java.security.cert.Certificate;
import java.util.Collections;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
import javax.crypto.Cipher;
import javax.crypto.Mac;
/**
* Specification of how a key or key pair is secured when imported into the
* <a href="{@docRoot}training/articles/keystore.html">Android Keystore system</a>. This class
* specifies authorized uses of the imported key, such as whether user authentication is required
* for using the key, what operations the key is authorized for (e.g., decryption, but not signing)
* with what parameters (e.g., only with a particular padding scheme or digest), and the key's
* validity start and end dates. Key use authorizations expressed in this class apply only to secret
* keys and private keys -- public keys can be used for any supported operations.
*
* <p>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.
*
* <p>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()}.
*
* <p>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.
*
* <p>NOTE: The key material of keys stored in the Android Keystore is not accessible.
*
* <p>Instances of this class are immutable.
*
* <p><h3>Known issues</h3>
* A known bug in Android 6.0 (API Level 23) causes user authentication-related authorizations to be
* enforced even for public keys. To work around this issue extract the public key material to use
* outside of Android Keystore. For example:
* <pre> {@code
* PublicKey unrestrictedPublicKey =
* KeyFactory.getInstance(publicKey.getAlgorithm()).generatePublic(
* new X509EncodedKeySpec(publicKey.getEncoded()));
* }</pre>
*
* <p><h3>Example: AES key for encryption/decryption in GCM mode</h3>
* This example illustrates how to import an AES key into the Android KeyStore under alias
* {@code key1} authorized to be used only for encryption/decryption in GCM mode with no padding.
* The key must export its key material via {@link Key#getEncoded()} in {@code RAW} format.
* <pre> {@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);
* ...
* }</pre>
*
* <p><h3>Example: HMAC key for generating MACs using SHA-512</h3>
* This example illustrates how to import an HMAC key into the Android KeyStore under alias
* {@code key1} authorized to be used only for generating MACs using SHA-512 digest. The key must
* export its key material via {@link Key#getEncoded()} in {@code RAW} format.
* <pre> {@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);
* ...
* }</pre>
*
* <p><h3>Example: EC key pair for signing/verification using ECDSA</h3>
* This example illustrates how to import an EC key pair into the Android KeyStore under alias
* {@code key2} with the private key authorized to be used only for signing with SHA-256 or SHA-512
* digests. The use of the public key is unrestricted. Both the private and the public key must
* export their key material via {@link Key#getEncoded()} in {@code PKCS#8} and {@code X.509} format
* respectively.
* <pre> {@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);
* ...
* }</pre>
*
* <p><h3>Example: RSA key pair for signing/verification using PKCS#1 padding</h3>
* This example illustrates how to import an RSA key pair into the Android KeyStore under alias
* {@code key2} with the private key authorized to be used only for signing using the PKCS#1
* signature padding scheme with SHA-256 digest and only if the user has been authenticated within
* the last ten minutes. The use of the public key is unrestricted (see Known Issues). Both the
* private and the public key must export their key material via {@link Key#getEncoded()} in
* {@code PKCS#8} and {@code X.509} format respectively.
* <pre> {@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);
* ...
* }</pre>
*
* <p><h3>Example: RSA key pair for encryption/decryption using PKCS#1 padding</h3>
* This example illustrates how to import an RSA key pair into the Android KeyStore under alias
* {@code key2} with the private key authorized to be used only for decryption using the PKCS#1
* encryption padding scheme. The use of public key is unrestricted, thus permitting encryption
* using any padding schemes and digests. Both the private and the public key must export their key
* material via {@link Key#getEncoded()} in {@code PKCS#8} and {@code X.509} format respectively.
* <pre> {@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);
* ...
* }</pre>
*/
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 Set<String> mMgf1Digests;
private final @KeyProperties.BlockModeEnum String[] mBlockModes;
private final boolean mRandomizedEncryptionRequired;
private final boolean mUserAuthenticationRequired;
private final @KeyProperties.AuthEnum int mUserAuthenticationType;
private final int mUserAuthenticationValidityDurationSeconds;
private final boolean mUserPresenceRequred;
private final boolean mUserAuthenticationValidWhileOnBody;
private final boolean mInvalidatedByBiometricEnrollment;
private final long mBoundToSecureUserId;
private final boolean mCriticalToDeviceEncryption;
private final boolean mUserConfirmationRequired;
private final boolean mUnlockedDeviceRequired;
private final boolean mIsStrongBoxBacked;
private final int mMaxUsageCount;
private final boolean mRollbackResistant;
private KeyProtection(
Date keyValidityStart,
Date keyValidityForOriginationEnd,
Date keyValidityForConsumptionEnd,
@KeyProperties.PurposeEnum int purposes,
@KeyProperties.EncryptionPaddingEnum String[] encryptionPaddings,
@KeyProperties.SignaturePaddingEnum String[] signaturePaddings,
@KeyProperties.DigestEnum String[] digests,
@KeyProperties.DigestEnum Set<String> mgf1Digests,
@KeyProperties.BlockModeEnum String[] blockModes,
boolean randomizedEncryptionRequired,
boolean userAuthenticationRequired,
@KeyProperties.AuthEnum int userAuthenticationType,
int userAuthenticationValidityDurationSeconds,
boolean userPresenceRequred,
boolean userAuthenticationValidWhileOnBody,
boolean invalidatedByBiometricEnrollment,
long boundToSecureUserId,
boolean criticalToDeviceEncryption,
boolean userConfirmationRequired,
boolean unlockedDeviceRequired,
boolean isStrongBoxBacked,
int maxUsageCount,
boolean rollbackResistant) {
mKeyValidityStart = Utils.cloneIfNotNull(keyValidityStart);
mKeyValidityForOriginationEnd = Utils.cloneIfNotNull(keyValidityForOriginationEnd);
mKeyValidityForConsumptionEnd = Utils.cloneIfNotNull(keyValidityForConsumptionEnd);
mPurposes = purposes;
mEncryptionPaddings =
ArrayUtils.cloneIfNotEmpty(ArrayUtils.nullToEmpty(encryptionPaddings));
mSignaturePaddings =
ArrayUtils.cloneIfNotEmpty(ArrayUtils.nullToEmpty(signaturePaddings));
mDigests = ArrayUtils.cloneIfNotEmpty(digests);
mMgf1Digests = mgf1Digests;
mBlockModes = ArrayUtils.cloneIfNotEmpty(ArrayUtils.nullToEmpty(blockModes));
mRandomizedEncryptionRequired = randomizedEncryptionRequired;
mUserAuthenticationRequired = userAuthenticationRequired;
mUserAuthenticationType = userAuthenticationType;
mUserAuthenticationValidityDurationSeconds = userAuthenticationValidityDurationSeconds;
mUserPresenceRequred = userPresenceRequred;
mUserAuthenticationValidWhileOnBody = userAuthenticationValidWhileOnBody;
mInvalidatedByBiometricEnrollment = invalidatedByBiometricEnrollment;
mBoundToSecureUserId = boundToSecureUserId;
mCriticalToDeviceEncryption = criticalToDeviceEncryption;
mUserConfirmationRequired = userConfirmationRequired;
mUnlockedDeviceRequired = unlockedDeviceRequired;
mIsStrongBoxBacked = isStrongBoxBacked;
mMaxUsageCount = maxUsageCount;
mRollbackResistant = rollbackResistant;
}
/**
* Gets the time instant before which the key is not yet valid.
*
* @return instant or {@code null} if not restricted.
*/
@Nullable
public Date getKeyValidityStart() {
return Utils.cloneIfNotNull(mKeyValidityStart);
}
/**
* Gets the time instant after which the key is no long valid for decryption and verification.
*
* @return instant or {@code null} if not restricted.
*/
@Nullable
public Date getKeyValidityForConsumptionEnd() {
return Utils.cloneIfNotNull(mKeyValidityForConsumptionEnd);
}
/**
* Gets the time instant after which the key is no long valid for encryption and signing.
*
* @return instant or {@code null} if not restricted.
*/
@Nullable
public Date getKeyValidityForOriginationEnd() {
return Utils.cloneIfNotNull(mKeyValidityForOriginationEnd);
}
/**
* Gets the set of purposes (e.g., encrypt, decrypt, sign) for which the key can be used.
* Attempts to use the key for any other purpose will be rejected.
*
* <p>See {@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.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>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<String> getMgf1Digests() {
if (mMgf1Digests.isEmpty()) {
throw new IllegalStateException("Mask generation function (MGF) not specified");
}
return new HashSet(mMgf1Digests);
}
/**
* Returns {@code true} if the set of digests for the MGF1 mask generation function,
* with which the key can be used, has been specified. Useful with the {@code RSA-OAEP} scheme.
*
* @see #getMgf1Digests()
*/
@NonNull
@FlaggedApi(android.security.Flags.FLAG_MGF1_DIGEST_SETTER_V2)
public boolean isMgf1DigestsSpecified() {
return !mMgf1Digests.isEmpty();
}
/**
* Gets 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.
*
* <p>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 <em>indistinguishability under chosen-plaintext attack ({@code
* IND-CPA})</em>. 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.
*
* <p>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.
*
* <p>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()}).
*
* <p>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.
*
* <p>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<String> mMgf1Digests =
Collections.emptySet();
private @KeyProperties.BlockModeEnum String[] mBlockModes;
private boolean mRandomizedEncryptionRequired = true;
private boolean mUserAuthenticationRequired;
private int mUserAuthenticationValidityDurationSeconds = 0;
private @KeyProperties.AuthEnum int mUserAuthenticationType =
KeyProperties.AUTH_BIOMETRIC_STRONG;
private boolean mUserPresenceRequired = false;
private boolean mUserAuthenticationValidWhileOnBody;
private boolean mInvalidatedByBiometricEnrollment = true;
private boolean mUserConfirmationRequired;
private boolean mUnlockedDeviceRequired = false;
private long mBoundToSecureUserId = GateKeeper.INVALID_SECURE_USER_ID;
private boolean mCriticalToDeviceEncryption = false;
private boolean mIsStrongBoxBacked = false;
private int mMaxUsageCount = KeyProperties.UNRESTRICTED_USAGE_COUNT;
private String mAttestKeyAlias = null;
private boolean mRollbackResistant = false;
/**
* Creates a new instance of the {@code Builder}.
*
* @param purposes set of purposes (e.g., encrypt, decrypt, sign) for which the key can be
* used. Attempts to use the key for any other purpose will be rejected.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>This must be specified for keys which are used for encryption/decryption.
*
* <p>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.
*
* <p>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.
*
* <p>This must be specified for RSA keys which are used for signing/verification.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>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).
*
* <p>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.
*
* <p>This must be specified for symmetric encryption/decryption keys.
*
* <p>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 <em>indistinguishability under chosen-plaintext attack
* ({@code IND-CPA})</em>. 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.
*
* <p>By default, {@code IND-CPA} is required.
*
* <p>When {@code IND-CPA} is required:
* <ul>
* <li>transformation which do not offer {@code IND-CPA}, such as symmetric ciphers using
* {@code ECB} mode or RSA encryption without padding, are prohibited;</li>
* <li>in transformations which use an IV, such as symmetric ciphers in {@code GCM},
* {@code CBC}, and {@code CTR} block modes, caller-provided IVs are rejected when
* encrypting, to ensure that only random IVs are used.</li>
*
* <p>Before disabling this requirement, consider the following approaches instead:
* <ul>
* <li>If you are generating a random IV for encryption and then initializing a {@code}
* Cipher using the IV, the solution is to let the {@code Cipher} generate a random IV
* instead. This will occur if the {@code Cipher} is initialized for encryption without an
* IV. The IV can then be queried via {@link Cipher#getIV()}.</li>
* <li>If you are generating a non-random IV (e.g., an IV derived from something not fully
* random, such as the name of the file being encrypted, or transaction ID, or password,
* or a device identifier), consider changing your design to use a random IV which will then
* be provided in addition to the ciphertext to the entities which need to decrypt the
* ciphertext.</li>
* <li>If you are using RSA encryption without padding, consider switching to padding
* schemes which offer {@code IND-CPA}, such as PKCS#1 or OAEP.</li>
* </ul>
*/
@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.
*
* <p>By default, the key is authorized to be used regardless of whether the user has been
* authenticated.
*
* <p>When user authentication is required:
* <ul>
* <li>The key can only be import if secure lock screen is set up (see
* {@link KeyguardManager#isDeviceSecure()}). Additionally, if the key requires that user
* authentication takes place for every use of the key (see
* {@link #setUserAuthenticationValidityDurationSeconds(int)}), at least one biometric
* must be enrolled (see {@link BiometricManager#canAuthenticate()}).</li>
* <li>The use of the key must be authorized by the user by authenticating to this Android
* device using a subset of their secure lock screen credentials such as
* password/PIN/pattern or biometric.
* <a href="{@docRoot}training/articles/keystore.html#UserAuthentication">More
* information</a>.
* <li>The key will become <em>irreversibly invalidated</em> once the secure lock screen is
* disabled (reconfigured to None, Swipe or other mode which does not authenticate the user)
* or when the secure lock screen is forcibly reset (e.g., by a Device Administrator).
* Additionally, if the key requires that user authentication takes place for every use of
* the key, it is also irreversibly invalidated once a new biometric is enrolled or once\
* no more biometrics are enrolled, unless {@link
* #setInvalidatedByBiometricEnrollment(boolean)} is used to allow validity after
* enrollment. Attempts to initialize cryptographic operations using such keys will throw
* {@link KeyPermanentlyInvalidatedException}.</li> </ul>
*
* <p>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.
*
* <p>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)}).
*
* <p>By default, if user authentication is required, it must take place for every use of
* the key.
*
* <p>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.
*
* <p>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)}).
*
* <p>By default, if user authentication is required, it must take place for every use of
* the key.
*
* <p>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}.
*
* <p>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.
* <p>
* 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.
*
* <p>By default, {@code invalidateKey} is {@code true}, so keys that are valid for
* biometric authentication only are <em>irreversibly invalidated</em> 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}.
*
* <p>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.
* <p>
* 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()}.
* <p>
* 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.
* <p>
* 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.
* <p>
* {@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.
* <p>
* <b>Warning:</b> Be careful using {@code setUnlockedDeviceRequired(true)} on Android 14
* (API level 34) and lower, since the following bugs existed in Android 12 through 14:
* <ul>
* <li>When the user didn't have a secure lock screen, unlocked-device-required keys
* couldn't be generated, imported, or used.</li>
* <li>When the user's secure lock screen was removed, all of that user's
* unlocked-device-required keys were automatically deleted.</li>
* <li>Unlocking the device with a non-strong biometric, such as face on many devices,
* didn't re-authorize the use of unlocked-device-required keys.</li>
* <li>Unlocking the device with a biometric didn't re-authorize the use of
* unlocked-device-required keys in profiles that share their parent user's lock.</li>
* </ul>
* 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.
*
* <p>By default, there is no restriction on the usage of key.
*
* <p>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.
*
* <p>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);
}
}
}
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