Merge "Improve documentation for keys requiring user auth." into mnc-dev

  keystore, they can be used for cryptographic operations with the key material

  remaining non-exportable. Moreover, it offers facilities to restrict when and

  how keys can be used, such as requiring user authentication for key use or

  restricting encryption keys to be used only in certain block modes. See

  restricting keys to be used only in certain cryptographic modes. See

  <a href="#SecurityFeatures">Security Features</a> section for more information.</p>

<p>The Keystore system is used by the {@link

mitigates unauthorized use of key material outside of the Android device by preventing extraction of

the key material from application processes and from the Android device as a whole. Secondly,

Android KeyStore mitigates unauthorized use of key material on the Android device by making apps

specify authorized uses of their keys and then enforcing these restrictions.

specify authorized uses of their keys and then enforcing these restrictions outside of the apps'

processes.

<h3 id="ExtractionPrevention">Extraction Prevention</h3>

To mitigate unauthorized use of keys on the Android device, Android Keystore lets apps specify

authorized uses of their keys when generating or importing the keys. Once a key is generated or

imported, its authorizations can not be changed. Authorizations are then enforced by the Android

Keystore whenever the key is used.

Keystore whenever the key is used. This is an advanced security feature which is generally useful

only if your requirements are that a compromise of your application process after key

generation/import (but not before or during) cannot lead to unauthorized uses of the key.

<p>Supported key use authorizations fall into the following categories:

<ul>

<li><em>cryptography</em>: authorized key algorithm, operations or purposes (encrypt, decrypt, sign,

  verify), padding schemes, block modes, digests with which the key can be used</li>

  verify), padding schemes, block modes, digests with which the key can be used;</li>

<li><em>temporal validity interval</em>: interval of time during which the key is authorized for

  use</li>

  use;</li>

<li><em>user authentication</em>: the key can only be used if the user has been authenticated

  recently enough. See <a href="#UserAuthentication">Requiring User Authentication For Key Use</a>.

  </li>

<h3 id="UserAuthentication">Requiring User Authentication For Key Use</h3>

<p>When generating or importing a key into the {@code AndroidKeyStore} you can specify that the key

can only be used if user has been authenticated. The user is authenticated using a subset of their

secure lock screen credentials. This is a security measure which makes it possible to generate

cryptographic assertions about the user having been authenticated.

is only authorized to be used if the user has been authenticated. The user is authenticated using a

subset of their secure lock screen credentials (pattern/PIN/password, fingerprint).

<p>When a key is configured to require user authentication, it is also configured to operate in one

of the two modes:

<p>This is an advanced security feature which is generally useful only if your requirements are that

a compromise of your application process after key generation/import (but not before or during)

cannot bypass the requirement for the user to be authenticated to use the key.

<p>When a key is authorized to be used only if the user has been authenticated, it is configured to

operate in one of the two modes:

<ul>

<li>User authentication is valid for a duration of time. All keys in this mode are authorized

  for use as soon as the user unlocks the secure lock screen or confirms their secure lock screen

  credentials using the {@link android.app.KeyguardManager#createConfirmDeviceCredentialIntent(CharSequence, CharSequence) KeyguardManager.createConfirmDeviceCredentialIntent}

  flow. Each key specifies for how long the authorization remains valid for that key. Such keys

  can only be generated or imported if the secure lock screen is enabled (see {@link android.app.KeyguardManager#isDeviceSecure() KeyguardManager.isDeviceSecure()}).

  These keys become permanently invalidated once the secure lock screen is disabled or forcibly

  reset (e.g. by a Device Admin).</li>

<li>User authentication is required for every use of the key. In this mode, a specific operation

  involving a specific key is authorized by the user. Currently, the only means of such

  authorization is fingerprint authentication: {@link android.hardware.fingerprint.FingerprintManager#authenticate(CryptoObject, CancellationSignal, int, AuthenticationCallback, Handler) FingerprintManager.authenticate}.

  Such keys can only be generated or imported if at least one fingerprint is enrolled (see {@link android.hardware.fingerprint.FingerprintManager#hasEnrolledFingerprints() FingerprintManager.hasEnrolledFingerprints}).

  These keys become permanently invalidated once all fingerprints are unenrolled.</li>

<li>User authentication authorizes the use of keys for a duration of time. All keys in this mode are

  authorized for use as soon as the user unlocks the secure lock screen or confirms their secure

  lock screen credential using the

  {@link android.app.KeyguardManager#createConfirmDeviceCredentialIntent(CharSequence, CharSequence) KeyguardManager.createConfirmDeviceCredentialIntent}

  flow. The duration for which the authorization remains valid is specific to each key, as specified

  using {@code setUserAuthenticationValidityDurationSeconds} during key generation or import. Such

  keys can only be generated or imported if the secure lock screen is enabled (see

  {@link android.app.KeyguardManager#isDeviceSecure() KeyguardManager.isDeviceSecure()}). These keys

  become permanently invalidated once the secure lock screen is disabled (reconfigured to None,

  Swipe or other mode which does not authenticate the user) or forcibly reset (e.g. by a Device

  Administrator).</li>

<li>User authentication authorizes a specific cryptographic operation associated with one key. In

  this mode, each operation involving such a key must be individually authorized by the user.

  Currently, the only means of such authorization is fingerprint authentication:

  {@link android.hardware.fingerprint.FingerprintManager#authenticate(CryptoObject, CancellationSignal, int, AuthenticationCallback, Handler) FingerprintManager.authenticate}.

  Such keys can only be generated or imported if at least one fingerprint is enrolled (see

  {@link android.hardware.fingerprint.FingerprintManager#hasEnrolledFingerprints() FingerprintManager.hasEnrolledFingerprints}).

  These keys become permanently invalidated once a new fingerprint is enrolled or all fingerprints

  are unenrolled.</li>

</ul>

 No newline at end of file

import android.annotation.IntRange;

import android.annotation.NonNull;

import android.annotation.Nullable;

import android.app.KeyguardManager;

import android.hardware.fingerprint.FingerprintManager;

import android.text.TextUtils;

import java.math.BigInteger;

import java.security.KeyPairGenerator;

import java.security.Signature;

import java.security.cert.Certificate;

import java.security.spec.AlgorithmParameterSpec;

import java.util.Date;

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.Mac;

import javax.security.auth.x500.X500Principal;

/**

 * <p>NOTE: If a private key is not authorized to sign the self-signed certificate, then the

 * certificate will be created with an invalid signature which will not verify. Such a certificate

 * is still useful because it provides access to the public key. To generate a valid

 * signature for the certificate the key needs to be authorized for

 * {@link KeyProperties#PURPOSE_SIGN}, a suitable digest or {@link KeyProperties#DIGEST_NONE}, and

 * {@link KeyProperties#SIGNATURE_PADDING_RSA_PKCS1} or

 * {@link KeyProperties#ENCRYPTION_PADDING_NONE}.

 * signature for the certificate the key needs to be authorized for all of the following:

 * <ul>

 * <li>{@link KeyProperties#PURPOSE_SIGN},</li>

 * <li>operation without requiring the user to be authenticated (see

 * {@link Builder#setUserAuthenticationRequired(boolean)}),</li>

 * <li>suitable digest or {@link KeyProperties#DIGEST_NONE},</li>

 * <li>(RSA keys only) padding scheme {@link KeyProperties#SIGNATURE_PADDING_RSA_PKCS1} or

 * {@link KeyProperties#ENCRYPTION_PADDING_NONE}.</li>

 * </ul>

 *

 * <p>NOTE: The key material of the generated symmetric and private keys is not accessible. The key

 * material of the public keys is accessible.

    }

    /**

     * Returns {@code true} if user authentication is required for this key to be used.

     * Returns {@code true} if the key is authorized to be used only if the user has been

     * authenticated.

     *

     * <p>This restriction applies only to private key operations. Public key operations are not

     * restricted.

     * <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 can be used after the user is

     * successfully authenticated. This has effect only if user authentication is required.

     * 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 restriction applies only to private key operations. Public key operations are not

     * restricted.

     * <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;

        }

        /**

         * Sets whether user authentication is required to use this key.

         * Sets whether this key is authorized to be used only if the user has been authenticated.

         *

         * <p>By default, the key can be used without user authentication.

         * <p>By default, the key is authorized to be used regardless of whether the user has been

         * authenticated.

         *

         * <p>When user authentication is required, the user authorizes the use of the key by

         * authenticating to this Android device using a subset of their secure lock screen

         * credentials. Different authentication methods are used depending on whether the every

         * use of the key must be authenticated (as specified by

         * {@link #setUserAuthenticationValidityDurationSeconds(int)}).

         * <p>When user authentication is required:

         * <ul>

         * <li>The key can only be generated 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 restriction applies only to private key operations. Public key operations are not

         * restricted.

         * <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) {

        }

        /**

         * Sets the duration of time (seconds) for which this key can be used after the user is

         * successfully authenticated. This has effect only if user authentication is required.

         * 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>By default, the user needs to authenticate for every use of the key.

         * <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 the user needs to authenticate for

         *        every use of the key.

         * @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(

    }

    /**

     * Returns {@code true} if user authentication is required for this key to be used.

     * 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 KeyGenParameterSpec.Builder#setUserAuthenticationRequired(boolean)

     * @see KeyProtection.Builder#setUserAuthenticationRequired(boolean)

     */

    public boolean isUserAuthenticationRequired() {

        return mUserAuthenticationRequired;

    }

    /**

     * Gets the duration of time (seconds) for which this key can be used after the user is

     * successfully authenticated. This has effect only if user authentication is required.

     * 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.

/**

 * Indicates that the key can no longer be used because it has been permanently invalidated.

 *

 * <p>This can currently occur only for keys that require user authentication. Such keys are

 * permanently invalidated once the secure lock screen is disabled (i.e., 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 Device Admin). Additionally, keys configured to require user

 * authentication for every use of the key are also permanently invalidated once a new fingerprint

 * is enrolled or once no more fingerprints are enrolled.

 * <p>This only occurs for keys which are authorized to be used only if the user has been

 * authenticated. Such keys are permanently and irreversibly invalidated once the secure lock screen

 * is disabled (i.e., 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 Device Admin). Additionally,

 * keys configured to require user authentication to take place for every of the keys, are also

 * permanently invalidated once a new fingerprint is enrolled or once no more fingerprints are

 * enrolled.

 */

public class KeyPermanentlyInvalidatedException extends InvalidKeyException {