/*
* 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.IntRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.app.KeyguardManager;
import android.hardware.fingerprint.FingerprintManager;
import java.security.Key;
import java.security.Signature;
import java.security.KeyStore.ProtectionParameter;
import java.security.cert.Certificate;
import java.util.Date;
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)
* and with what parameters (e.g., only with a particular padding scheme or digest), the key's and
* 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>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 public key is unrestricted, thus permitting signature verification using any
* 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 = ...; // 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 public key is unrestricted, thus permitting signature
* verification using any padding schemes and digests, and without user authentication. 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 {
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 @KeyProperties.BlockModeEnum String[] mBlockModes;
private final boolean mRandomizedEncryptionRequired;
private final boolean mUserAuthenticationRequired;
private final int mUserAuthenticationValidityDurationSeconds;
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.BlockModeEnum String[] blockModes,
boolean randomizedEncryptionRequired,
boolean userAuthenticationRequired,
int userAuthenticationValidityDurationSeconds) {
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);
mBlockModes = ArrayUtils.cloneIfNotEmpty(ArrayUtils.nullToEmpty(blockModes));
mRandomizedEncryptionRequired = randomizedEncryptionRequired;
mUserAuthenticationRequired = userAuthenticationRequired;
mUserAuthenticationValidityDurationSeconds = userAuthenticationValidityDurationSeconds;
}
/**
* 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;
}
/**
* 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;
}
/**
* 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;
}
/**
* 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 @KeyProperties.BlockModeEnum String[] mBlockModes;
private boolean mRandomizedEncryptionRequired = true;
private boolean mUserAuthenticationRequired;
private int mUserAuthenticationValidityDurationSeconds = -1;
/**
* 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 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 fingerprint
* must be enrolled (see {@link FingerprintManager#hasEnrolledFingerprints()}).</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 fingerprint.
* <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 fingerprint is enrolled or once\
* no more fingerprints are enrolled. 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 FingerprintManager#hasEnrolledFingerprints()
*/
@NonNull
public Builder setUserAuthenticationRequired(boolean required) {
mUserAuthenticationRequired = 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 fingerprint authentication. This is achieved by
* initializing a cryptographic operation ({@link Signature}, {@link Cipher}, {@link Mac})
* with the key, wrapping it into a {@link FingerprintManager.CryptoObject}, invoking
* {@code FingerprintManager.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 FingerprintManager
* @see FingerprintManager.CryptoObject
* @see KeyguardManager
*/
@NonNull
public Builder setUserAuthenticationValidityDurationSeconds(
@IntRange(from = -1) int seconds) {
if (seconds < -1) {
throw new IllegalArgumentException("seconds must be -1 or larger");
}
mUserAuthenticationValidityDurationSeconds = seconds;
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,
mBlockModes,
mRandomizedEncryptionRequired,
mUserAuthenticationRequired,
mUserAuthenticationValidityDurationSeconds);
}
}
}