/*
    * 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);
  
      /**
       * 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>();
          AesCipherService cipherService = new AesCipherService();
          this.cipherService = cipherService;
          setCipherKey(cipherService.generateNewKey().getEncoded());
     }
 
     /**
      * 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
      * warning 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.isWarnEnabled()) {
             String message = "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, if you are using a shiro.ini file, this property would be " +
                     "'securityManager.rememberMeManager.cipherKey' see: http://shiro.apache.org/web.html#Web-RememberMeServices. " +
                     "The remembered identity will be forgotten and not used for this request.";
             log.warn(message);
         }
         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);
     }
 }