/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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 org.apache.shiro.mgt;

 import org.apache.shiro.authc.AuthenticationException;

 import org.apache.shiro.authc.AuthenticationInfo;

 import org.apache.shiro.authc.AuthenticationToken;

 import org.apache.shiro.authc.RememberMeAuthenticationToken;

 import org.apache.shiro.codec.Base64;

 import org.apache.shiro.crypto.AesCipherService;

 import org.apache.shiro.crypto.CipherService;

 import org.apache.shiro.io.DefaultSerializer;

 import org.apache.shiro.io.Serializer;

 import org.apache.shiro.subject.PrincipalCollection;

 import org.apache.shiro.subject.Subject;

 import org.apache.shiro.subject.SubjectContext;

 import org.apache.shiro.util.ByteSource;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 /**

  * Abstract implementation of the {@code RememberMeManager} interface that handles

  * {@link #setSerializer(org.apache.shiro.io.Serializer) serialization} and

  * {@link #setCipherService encryption} of the remembered user identity.

  * <p/>

  * The remembered identity storage location and details are left to subclasses.

  * <h2>Default encryption key</h2>

  * This implementation uses an {@link AesCipherService AesCipherService} for strong encryption by default.  It also

  * uses a default generated symmetric key to both encrypt and decrypt data.  As AES is a symmetric cipher, the same

  * {@code key} is used to both encrypt and decrypt data, BUT NOTE:

  * <p/>

  * Because Shiro is an open-source project, if anyone knew that you were using Shiro's default

  * {@code key}, they could download/view the source, and with enough effort, reconstruct the {@code key}

  * and decode encrypted data at will.

  * <p/>

  * Of course, this key is only really used to encrypt the remembered {@code PrincipalCollection} which is typically

  * a user id or username.  So if you do not consider that sensitive information, and you think the default key still

  * makes things 'sufficiently difficult', then you can ignore this issue.

  * <p/>

  * However, if you do feel this constitutes sensitive information, it is recommended that you provide your own

  * {@code key} via the {@link #setCipherKey setCipherKey} method to a key known only to your application,

  * guaranteeing that no third party can decrypt your data.  You can generate your own key by calling the

  * {@code CipherService}'s {@link org.apache.shiro.crypto.AesCipherService#generateNewKey() generateNewKey} method

  * and using that result as the {@link #setCipherKey cipherKey} configuration attribute.

  *

  * @since 0.9

  */

 public abstract class AbstractRememberMeManager implements RememberMeManager {

     /**

      * private inner log instance.

      */

     private static final Logger log = LoggerFactory.getLogger(AbstractRememberMeManager.class);

     /**

      * The following Base64 string was generated by auto-generating an AES Key:

      * <pre>

      * AesCipherService aes = new AesCipherService();

      * byte[] key = aes.generateNewKey().getEncoded();

      * String base64 = Base64.encodeToString(key);

      * </pre>

      * The value of 'base64' was copied-n-pasted here:

      */

     private static final byte[] DEFAULT_CIPHER_KEY_BYTES = Base64.decode("kPH+bIxk5D2deZiIxcaaaA==");

     /**

      * Serializer to use for converting PrincipalCollection instances to/from byte arrays

      */

     private Serializer<PrincipalCollection> serializer;

     /**

      * Cipher to use for encrypting/decrypting serialized byte arrays for added security

      */

     private CipherService cipherService;

     /**

      * Cipher encryption key to use with the Cipher when encrypting data

      */

     private byte[] encryptionCipherKey;

     /**

      * Cipher decryption key to use with the Cipher when decrypting data

      */

     private byte[] decryptionCipherKey;

     /**

      * Default constructor that initializes a {@link DefaultSerializer} as the {@link #getSerializer() serializer} and

      * an {@link AesCipherService} as the {@link #getCipherService() cipherService}.

      */

     public AbstractRememberMeManager() {

         this.serializer = new DefaultSerializer<PrincipalCollection>();

         this.cipherService = new AesCipherService();

         setCipherKey(DEFAULT_CIPHER_KEY_BYTES);

     }

     /**

      * Returns the {@code Serializer} used to serialize and deserialize {@link PrincipalCollection} instances for

      * persistent remember me storage.

      * <p/>

      * Unless overridden by the {@link #setSerializer} method, the default instance is a

      * {@link org.apache.shiro.io.DefaultSerializer}.

      *

      * @return the {@code Serializer} used to serialize and deserialize {@link PrincipalCollection} instances for

      *         persistent remember me storage.

      */

     public Serializer<PrincipalCollection> getSerializer() {

         return serializer;

     }

     /**

      * Sets the {@code Serializer} used to serialize and deserialize {@link PrincipalCollection} instances for

      * persistent remember me storage.

      * <p/>

      * Unless overridden by this method, the default instance is a {@link DefaultSerializer}.

      *

      * @param serializer the {@code Serializer} used to serialize and deserialize {@link PrincipalCollection} instances

      *                   for persistent remember me storage.

      */

     public void setSerializer(Serializer<PrincipalCollection> serializer) {

         this.serializer = serializer;

     }

     /**

      * Returns the {@code CipherService} to use for encrypting and decrypting serialized identity data to prevent easy

      * inspection of Subject identity data.

      * <p/>

      * Unless overridden by the {@link #setCipherService} method, the default instance is an {@link AesCipherService}.

      *

      * @return the {@code Cipher} to use for encrypting and decrypting serialized identity data to prevent easy

      *         inspection of Subject identity data

      */

     public CipherService getCipherService() {

         return cipherService;

     }

     /**

      * Sets the {@code CipherService} to use for encrypting and decrypting serialized identity data to prevent easy

      * inspection of Subject identity data.

      * <p/>

      * If the CipherService is a symmetric CipherService (using the same key for both encryption and decryption), you

      * should set your key via the {@link #setCipherKey(byte[])} method.

      * <p/>

      * If the CipherService is an asymmetric CipherService (different keys for encryption and decryption, such as

      * public/private key pairs), you should set your encryption and decryption key via the respective

      * {@link #setEncryptionCipherKey(byte[])} and {@link #setDecryptionCipherKey(byte[])} methods.

      * <p/>

      * <b>N.B.</b> Unless overridden by this method, the default CipherService instance is an

      * {@link AesCipherService}.  This {@code RememberMeManager} implementation already has a configured symmetric key

      * to use for encryption and decryption, but it is recommended to provide your own for added security.  See the

      * class-level JavaDoc for more information and why it might be good to provide your own.

      *

      * @param cipherService the {@code CipherService} to use for encrypting and decrypting serialized identity data to

      *                      prevent easy inspection of Subject identity data.

      */

     public void setCipherService(CipherService cipherService) {

         this.cipherService = cipherService;

     }

     /**

      * Returns the cipher key to use for encryption operations.

      *

      * @return the cipher key to use for encryption operations.

      * @see #setCipherService for a description of the various {@code get/set*Key} methods.

      */

     public byte[] getEncryptionCipherKey() {

         return encryptionCipherKey;

     }

     /**

      * Sets the encryption key to use for encryption operations.

      *

      * @param encryptionCipherKey the encryption key to use for encryption operations.

      * @see #setCipherService for a description of the various {@code get/set*Key} methods.

      */

     public void setEncryptionCipherKey(byte[] encryptionCipherKey) {

         this.encryptionCipherKey = encryptionCipherKey;

     }

     /**

      * Returns the decryption cipher key to use for decryption operations.

      *

      * @return the cipher key to use for decryption operations.

      * @see #setCipherService for a description of the various {@code get/set*Key} methods.

      */

     public byte[] getDecryptionCipherKey() {

         return decryptionCipherKey;

     }

     /**

      * Sets the decryption key to use for decryption operations.

      *

      * @param decryptionCipherKey the decryption key to use for decryption operations.

      * @see #setCipherService for a description of the various {@code get/set*Key} methods.

      */

     public void setDecryptionCipherKey(byte[] decryptionCipherKey) {

         this.decryptionCipherKey = decryptionCipherKey;

     }

     /**

      * Convenience method that returns the cipher key to use for <em>both</em> encryption and decryption.

      * <p/>

      * <b>N.B.</b> This method can only be called if the underlying {@link #getCipherService() cipherService} is a symmetric

      * CipherService which by definition uses the same key for both encryption and decryption.  If using an asymmetric

      * CipherService public/private key pair, you cannot use this method, and should instead use the

      * {@link #getEncryptionCipherKey()} and {@link #getDecryptionCipherKey()} methods individually.

      * <p/>

      * The default {@link AesCipherService} instance is a symmetric cipher service, so this method can be used if you are

      * using the default.

      *

      * @return the symmetric cipher key used for both encryption and decryption.

      */

     public byte[] getCipherKey() {

         //Since this method should only be used with symmetric ciphers

         //(where the enc and dec keys are the same), either is fine, just return one of them:

         return getEncryptionCipherKey();

     }

     /**

      * Convenience method that sets the cipher key to use for <em>both</em> encryption and decryption.

      * <p/>

      * <b>N.B.</b> This method can only be called if the underlying {@link #getCipherService() cipherService} is a

      * symmetric CipherService?which by definition uses the same key for both encryption and decryption.  If using an

      * asymmetric CipherService?(such as a public/private key pair), you cannot use this method, and should instead use

      * the {@link #setEncryptionCipherKey(byte[])} and {@link #setDecryptionCipherKey(byte[])} methods individually.

      * <p/>

      * The default {@link AesCipherService} instance is a symmetric CipherService, so this method can be used if you

      * are using the default.

      *

      * @param cipherKey the symmetric cipher key to use for both encryption and decryption.

      */

     public void setCipherKey(byte[] cipherKey) {

         //Since this method should only be used in symmetric ciphers

         //(where the enc and dec keys are the same), set it on both:

         setEncryptionCipherKey(cipherKey);

         setDecryptionCipherKey(cipherKey);

     }

     /**

      * Forgets (removes) any remembered identity data for the specified {@link Subject} instance.

      *

      * @param subject the subject instance for which identity data should be forgotten from the underlying persistence

      *                mechanism.

      */

     protected abstract void forgetIdentity(Subject subject);

     /**

      * Determines whether or not remember me services should be performed for the specified token.  This method returns

      * {@code true} iff:

      * <ol>

      * <li>The token is not {@code null} and</li>

      * <li>The token is an {@code instanceof} {@link RememberMeAuthenticationToken} and</li>

      * <li>{@code token}.{@link org.apache.shiro.authc.RememberMeAuthenticationToken#isRememberMe() isRememberMe()} is

      * {@code true}</li>

      * </ol>

      *

      * @param token the authentication token submitted during the successful authentication attempt.

      * @return true if remember me services should be performed as a result of the successful authentication attempt.

      */

     protected boolean isRememberMe(AuthenticationToken token) {

         return token != null && (token instanceof RememberMeAuthenticationToken) &&

                 ((RememberMeAuthenticationToken) token).isRememberMe();

     }

     /**

      * Reacts to the successful login attempt by first always {@link #forgetIdentity(Subject) forgetting} any previously

      * stored identity.  Then if the {@code token}

      * {@link #isRememberMe(org.apache.shiro.authc.AuthenticationToken) is a RememberMe} token, the associated identity

      * will be {@link #rememberIdentity(org.apache.shiro.subject.Subject, org.apache.shiro.authc.AuthenticationToken, org.apache.shiro.authc.AuthenticationInfo) remembered}

      * for later retrieval during a new user session.

      *

      * @param subject the subject for which the principals are being remembered.

      * @param token   the token that resulted in a successful authentication attempt.

      * @param info    the authentication info resulting from the successful authentication attempt.

      */

     public void onSuccessfulLogin(Subject subject, AuthenticationToken token, AuthenticationInfo info) {

         //always clear any previous identity:

         forgetIdentity(subject);

         //now save the new identity:

         if (isRememberMe(token)) {

             rememberIdentity(subject, token, info);

         } else {

             if (log.isDebugEnabled()) {

                 log.debug("AuthenticationToken did not indicate RememberMe is requested.  " +

                         "RememberMe functionality will not be executed for corresponding account.");

             }

         }

     }

     /**

      * Remembers a subject-unique identity for retrieval later.  This implementation first

      * {@link #getIdentityToRemember resolves} the exact

      * {@link PrincipalCollection principals} to remember.  It then remembers the principals by calling

      * {@link #rememberIdentity(org.apache.shiro.subject.Subject, org.apache.shiro.subject.PrincipalCollection)}.

      * <p/>

      * This implementation ignores the {@link AuthenticationToken} argument, but it is available to subclasses if

      * necessary for custom logic.

      *

      * @param subject   the subject for which the principals are being remembered.

      * @param token     the token that resulted in a successful authentication attempt.

      * @param authcInfo the authentication info resulting from the successful authentication attempt.

      */

     public void rememberIdentity(Subject subject, AuthenticationToken token, AuthenticationInfo authcInfo) {

         PrincipalCollection principals = getIdentityToRemember(subject, authcInfo);

         rememberIdentity(subject, principals);

     }

     /**

      * Returns {@code info}.{@link org.apache.shiro.authc.AuthenticationInfo#getPrincipals() getPrincipals()} and

      * ignores the {@link Subject} argument.

      *

      * @param subject the subject for which the principals are being remembered.

      * @param info    the authentication info resulting from the successful authentication attempt.

      * @return the {@code PrincipalCollection} to remember.

      */

     protected PrincipalCollection getIdentityToRemember(Subject subject, AuthenticationInfo info) {

         return info.getPrincipals();

     }

     /**

      * Remembers the specified account principals by first

      * {@link #convertPrincipalsToBytes(org.apache.shiro.subject.PrincipalCollection) converting} them to a byte

      * array and then {@link #rememberSerializedIdentity(org.apache.shiro.subject.Subject, byte[]) remembers} that

      * byte array.

      *

      * @param subject           the subject for which the principals are being remembered.

      * @param accountPrincipals the principals to remember for retrieval later.

      */

     protected void rememberIdentity(Subject subject, PrincipalCollection accountPrincipals) {

         byte[] bytes = convertPrincipalsToBytes(accountPrincipals);

         rememberSerializedIdentity(subject, bytes);

     }

     /**

      * Converts the given principal collection the byte array that will be persisted to be 'remembered' later.

      * <p/>

      * This implementation first {@link #serialize(org.apache.shiro.subject.PrincipalCollection) serializes} the

      * principals to a byte array and then {@link #encrypt(byte[]) encrypts} that byte array.

      *

      * @param principals the {@code PrincipalCollection} to convert to a byte array

      * @return the representative byte array to be persisted for remember me functionality.

      */

     protected byte[] convertPrincipalsToBytes(PrincipalCollection principals) {

         byte[] bytes = serialize(principals);

         if (getCipherService() != null) {

             bytes = encrypt(bytes);

         }

         return bytes;

     }

     /**

      * Persists the identity bytes to a persistent store for retrieval later via the

      * {@link #getRememberedSerializedIdentity(SubjectContext)} method.

      *

      * @param subject    the Subject for which the identity is being serialized.

      * @param serialized the serialized bytes to be persisted.

      */

     protected abstract void rememberSerializedIdentity(Subject subject, byte[] serialized);

     /**

      * Implements the interface method by first {@link #getRememberedSerializedIdentity(SubjectContext) acquiring}

      * the remembered serialized byte array.  Then it {@link #convertBytesToPrincipals(byte[], SubjectContext) converts}

      * them and returns the re-constituted {@link PrincipalCollection}.  If no remembered principals could be

      * obtained, {@code null} is returned.

      * <p/>

      * If any exceptions are thrown, the {@link #onRememberedPrincipalFailure(RuntimeException, SubjectContext)} method

      * is called to allow any necessary post-processing (such as immediately removing any previously remembered

      * values for safety).

      *

      * @param subjectContext the contextual data, usually provided by a {@link Subject.Builder} implementation, that

      *                       is being used to construct a {@link Subject} instance.

      * @return the remembered principals or {@code null} if none could be acquired.

      */

     public PrincipalCollection getRememberedPrincipals(SubjectContext subjectContext) {

         PrincipalCollection principals = null;

         try {

             byte[] bytes = getRememberedSerializedIdentity(subjectContext);

             //SHIRO-138 - only call convertBytesToPrincipals if bytes exist:

             if (bytes != null && bytes.length > 0) {

                 principals = convertBytesToPrincipals(bytes, subjectContext);

             }

         } catch (RuntimeException re) {

             principals = onRememberedPrincipalFailure(re, subjectContext);

         }

         return principals;

     }

     /**

      * Based on the given subject context data, retrieves the previously persisted serialized identity, or

      * {@code null} if there is no available data.  The context map is usually populated by a {@link Subject.Builder}

      * implementation.  See the {@link SubjectFactory} class constants for Shiro's known map keys.

      *

      * @param subjectContext the contextual data, usually provided by a {@link Subject.Builder} implementation, that

      *                       is being used to construct a {@link Subject} instance.  To be used to assist with data

      *                       lookup.

      * @return the previously persisted serialized identity, or {@code null} if there is no available data for the

      *         Subject.

      */

     protected abstract byte[] getRememberedSerializedIdentity(SubjectContext subjectContext);

     /**

      * If a {@link #getCipherService() cipherService} is available, it will be used to first decrypt the byte array.

      * Then the bytes are then {@link #deserialize(byte[]) deserialized} and then returned.

      *

      * @param bytes          the bytes to decrypt if necessary and then deserialize.

      * @param subjectContext the contextual data, usually provided by a {@link Subject.Builder} implementation, that

      *                       is being used to construct a {@link Subject} instance.

      * @return the de-serialized and possibly decrypted principals

      */

     protected PrincipalCollection convertBytesToPrincipals(byte[] bytes, SubjectContext subjectContext) {

         if (getCipherService() != null) {

             bytes = decrypt(bytes);

         }

         return deserialize(bytes);

     }

     /**

      * Called when an exception is thrown while trying to retrieve principals.  The default implementation logs a

      * debug message and forgets ('unremembers') the problem identity by calling

      * {@link #forgetIdentity(SubjectContext) forgetIdentity(context)} and then immediately re-throws the

      * exception to allow the calling component to react accordingly.

      * <p/>

      * This method implementation never returns an

      * object - it always rethrows, but can be overridden by subclasses for custom handling behavior.

      * <p/>

      * This most commonly would be called when an encryption key is updated and old principals are retrieved that have

      * been encrypted with the previous key.

      *

      * @param e       the exception that was thrown.

      * @param context the contextual data, usually provided by a {@link Subject.Builder} implementation, that

      *                is being used to construct a {@link Subject} instance.

      * @return nothing - the original {@code RuntimeException} is propagated in all cases.

      */

     protected PrincipalCollection onRememberedPrincipalFailure(RuntimeException e, SubjectContext context) {

         if (log.isDebugEnabled()) {

             log.debug("There was a failure while trying to retrieve remembered principals.  This could be due to a " +

                     "configuration problem or corrupted principals.  This could also be due to a recently " +

                     "changed encryption key.  The remembered identity will be forgotten and not used for this " +

                     "request.", e);

         }

         forgetIdentity(context);

         //propagate - security manager implementation will handle and warn appropriately

         throw e;

     }

     /**

      * Encrypts the byte array by using the configured {@link #getCipherService() cipherService}.

      *

      * @param serialized the serialized object byte array to be encrypted

      * @return an encrypted byte array returned by the configured {@link #getCipherService () cipher}.

      */

     protected byte[] encrypt(byte[] serialized) {

         byte[] value = serialized;

         CipherService cipherService = getCipherService();

         if (cipherService != null) {

             ByteSource byteSource = cipherService.encrypt(serialized, getEncryptionCipherKey());

             value = byteSource.getBytes();

         }

         return value;

     }

     /**

      * Decrypts the byte array using the configured {@link #getCipherService() cipherService}.

      *

      * @param encrypted the encrypted byte array to decrypt

      * @return the decrypted byte array returned by the configured {@link #getCipherService () cipher}.

      */

     protected byte[] decrypt(byte[] encrypted) {

         byte[] serialized = encrypted;

         CipherService cipherService = getCipherService();

         if (cipherService != null) {

             ByteSource byteSource = cipherService.decrypt(encrypted, getDecryptionCipherKey());

             serialized = byteSource.getBytes();

         }

         return serialized;

     }

     /**

      * Serializes the given {@code principals} by serializing them to a byte array by using the

      * {@link #getSerializer() serializer}'s {@link Serializer#serialize(Object) serialize} method.

      *

      * @param principals the principal collection to serialize to a byte array

      * @return the serialized principal collection in the form of a byte array

      */

     protected byte[] serialize(PrincipalCollection principals) {

         return getSerializer().serialize(principals);

     }

     /**

      * De-serializes the given byte array by using the {@link #getSerializer() serializer}'s

      * {@link Serializer#deserialize deserialize} method.

      *

      * @param serializedIdentity the previously serialized {@code PrincipalCollection} as a byte array

      * @return the de-serialized (reconstituted) {@code PrincipalCollection}

      */

     protected PrincipalCollection deserialize(byte[] serializedIdentity) {

         return getSerializer().deserialize(serializedIdentity);

     }

     /**

      * Reacts to a failed login by immediately {@link #forgetIdentity(org.apache.shiro.subject.Subject) forgetting} any

      * previously remembered identity.  This is an additional security feature to prevent any remenant identity data

      * from being retained in case the authentication attempt is not being executed by the expected user.

      *

      * @param subject the subject which executed the failed login attempt

      * @param token   the authentication token resulting in a failed login attempt - ignored by this implementation

      * @param ae      the exception thrown as a result of the failed login attempt - ignored by this implementation

      */

     public void onFailedLogin(Subject subject, AuthenticationToken token, AuthenticationException ae) {

         forgetIdentity(subject);

     }

     /**

      * Reacts to a subject logging out of the application and immediately

      * {@link #forgetIdentity(org.apache.shiro.subject.Subject) forgets} any previously stored identity and returns.

      *

      * @param subject the subject logging out.

      */

     public void onLogout(Subject subject) {

         forgetIdentity(subject);

     }

 }