/*
    * 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.crypto.hash;
  
  import org.apache.shiro.crypto.UnknownAlgorithmException;
  import org.apache.shiro.lang.codec.Base64;
  import org.apache.shiro.lang.codec.CodecException;
  import org.apache.shiro.lang.codec.CodecSupport;
  import org.apache.shiro.lang.codec.Hex;
  import org.apache.shiro.lang.util.ByteSource;
  import org.apache.shiro.lang.util.SimpleByteSource;
  import org.apache.shiro.lang.util.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.Serializable;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.Arrays;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A {@code Hash} implementation that allows any {@link java.security.MessageDigest MessageDigest} algorithm name to
   * be used.  This class is a less type-safe variant than the other {@code AbstractHash} subclasses
   * (e.g. {@link Sha512Hash}, etc.), but it does allow for any algorithm name to be specified in case the other subclass
   * implementations do not represent an algorithm that you may want to use.
   * <p/>
   * As of Shiro 1.1, this class effectively replaces the (now-deprecated) {@code AbstractHash} class.  It subclasses
   * {@code AbstractHash} only to retain backwards-compatibility.
   *
   * @since 1.1
   */
  public class SimpleHash extends CodecSupport implements Hash, Serializable {
  
      private static final int DEFAULT_ITERATIONS = 1;
      private static final long serialVersionUID = -6689895264902387303L;
  
      private static final Logger LOG = LoggerFactory.getLogger(SimpleHash.class);
  
      /**
       * The {@link java.security.MessageDigest MessageDigest} algorithm name to use when performing the hash.
       */
      private final String algorithmName;
  
      /**
       * The hashed data
       */
      private byte[] bytes;
  
      /**
       * Supplied salt, if any.
       */
      private ByteSource salt;
  
      /**
       * Number of hash iterations to perform.  Defaults to 1 in the constructor.
       */
      private int iterations;
  
      /**
       * Cached value of the {@link #toHex() toHex()} call so multiple calls won't incur repeated overhead.
       */
      private transient String hexEncoded;
  
      /**
       * Cached value of the {@link #toBase64() toBase64()} call so multiple calls won't incur repeated overhead.
       */
      private transient String base64Encoded;
  
      /**
       * Creates an new instance with only its {@code algorithmName} set - no hashing is performed.
       * <p/>
       * Because all other constructors in this class hash the {@code source} constructor argument, this
       * constructor is useful in scenarios when you have a byte array that you know is already hashed and
       * just want to set the bytes in their raw form directly on an instance.  After using this constructor,
       * you can then immediately call {@link #setBytes setBytes} to have a fully-initialized instance.
       * <p/>
       * <b>N.B.</b>The algorithm identified by the {@code algorithmName} parameter must be available on the JVM.  If it
       * is not, a {@link UnknownAlgorithmException} will be thrown when the hash is performed (not at instantiation).
       *
       * @param algorithmName the {@link java.security.MessageDigest MessageDigest} algorithm name to use when
       *                      performing the hash.
      * @see UnknownAlgorithmException
      */
     public SimpleHash(String algorithmName) {
         this.algorithmName = algorithmName;
         this.iterations = DEFAULT_ITERATIONS;
     }
 
     /**
      * Creates an {@code algorithmName}-specific hash of the specified {@code source} with no {@code salt} using a
      * single hash iteration.
      * <p/>
      * This is a convenience constructor that merely executes <code>this( algorithmName, source, null, 1);</code>.
      * <p/>
      * Please see the
      * {@link #SimpleHash(String algorithmName, Object source, Object salt, int numIterations)
      * SimpleHashHash(algorithmName, Object,Object,int)}
      * constructor for the types of Objects that may be passed into this constructor, as well as how to support further
      * types.
      *
      * @param algorithmName the {@link java.security.MessageDigest MessageDigest} algorithm name to use when
      *                      performing the hash.
      * @param source        the object to be hashed.
      * @throws org.apache.shiro.lang.codec.CodecException if the specified {@code source} cannot be converted
      *                                                    into a byte array (byte[]).
      * @throws UnknownAlgorithmException                  if the {@code algorithmName} is not available.
      */
     public SimpleHash(String algorithmName, Object source) throws CodecException, UnknownAlgorithmException {
         this(algorithmName, source, SimpleByteSource.empty(), DEFAULT_ITERATIONS);
     }
 
     /**
      * Creates an {@code algorithmName}-specific hash of the specified {@code source} using the given {@code salt}
      * using a single hash iteration.
      * <p/>
      * It is a convenience constructor that merely executes <code>this( algorithmName, source, salt, 1);</code>.
      * <p/>
      * Please see the
      * {@link #SimpleHash(String algorithmName, Object source, Object salt, int numIterations)
      * SimpleHashHash(algorithmName, Object,Object,int)}
      * constructor for the types of Objects that may be passed into this constructor, as well as how to support further
      * types.
      *
      * @param algorithmName the {@link java.security.MessageDigest MessageDigest} algorithm name to use when
      *                      performing the hash.
      * @param source        the source object to be hashed.
      * @param salt          the salt to use for the hash
      * @throws CodecException            if either constructor argument cannot be converted into a byte array.
      * @throws UnknownAlgorithmException if the {@code algorithmName} is not available.
      */
     public SimpleHash(String algorithmName, Object source, Object salt) throws CodecException, UnknownAlgorithmException {
         this(algorithmName, source, salt, DEFAULT_ITERATIONS);
     }
 
     /**
      * Creates an {@code algorithmName}-specific hash of the specified {@code source} using the given {@code salt}
      * using a single hash iteration.
      * <p/>
      * It is a convenience constructor that merely executes <code>this( algorithmName, source, salt, 1);</code>.
      * <p/>
      * Please see the
      * {@link #SimpleHash(String algorithmName, Object source, Object salt, int numIterations)
      * SimpleHashHash(algorithmName, Object,Object,int)}
      * constructor for the types of Objects that may be passed into this constructor, as well as how to support further
      * types.
      *
      * @param algorithmName  the {@link java.security.MessageDigest MessageDigest} algorithm name to use when
      *                       performing the hash.
      * @param source         the source object to be hashed.
      * @param hashIterations the number of times the {@code source} argument hashed for attack resiliency.
      * @throws CodecException            if either constructor argument cannot be converted into a byte array.
      * @throws UnknownAlgorithmException if the {@code algorithmName} is not available.
      */
     public SimpleHash(String algorithmName, Object source, int hashIterations) throws CodecException, UnknownAlgorithmException {
         this(algorithmName, source, SimpleByteSource.empty(), hashIterations);
     }
 
     /**
      * Creates an {@code algorithmName}-specific hash of the specified {@code source} using the given
      * {@code salt} a total of {@code hashIterations} times.
      * <p/>
      * By default, this class only supports Object method arguments of
      * type {@code byte[]}, {@code char[]}, {@link String}, {@link java.io.File File},
      * {@link java.io.InputStream InputStream} or {@link org.apache.shiro.lang.util.ByteSource ByteSource}.  If either
      * argument is anything other than these types a {@link org.apache.shiro.lang.codec.CodecException CodecException}
      * will be thrown.
      * <p/>
      * If you want to be able to hash other object types, or use other salt types, you need to override the
      * {@link #toBytes(Object) toBytes(Object)} method to support those specific types.  Your other option is to
      * convert your arguments to one of the default supported types first before passing them in to this
      * constructor}.
      *
      * @param algorithmName  the {@link java.security.MessageDigest MessageDigest} algorithm name to use when
      *                       performing the hash.
      * @param source         the source object to be hashed.
      * @param salt           the salt to use for the hash
      * @param hashIterations the number of times the {@code source} argument hashed for attack resiliency.
      * @throws CodecException            if either Object constructor argument cannot be converted into a byte array.
      * @throws UnknownAlgorithmException if the {@code algorithmName} is not available.
      */
     public SimpleHash(String algorithmName, Object source, Object salt, int hashIterations)
             throws CodecException, UnknownAlgorithmException {
         if (!StringUtils.hasText(algorithmName)) {
             throw new NullPointerException("algorithmName argument cannot be null or empty.");
         }
         this.algorithmName = algorithmName;
         this.iterations = Math.max(DEFAULT_ITERATIONS, hashIterations);
         ByteSource saltBytes = convertSaltToBytes(salt);
         this.salt = saltBytes;
         ByteSource sourceBytes = convertSourceToBytes(source);
         hash(sourceBytes, saltBytes, hashIterations);
     }
 
     /**
      * Acquires the specified {@code source} argument's bytes and returns them in the form of a {@code ByteSource} instance.
      * <p/>
      * This implementation merely delegates to the convenience {@link #toByteSource(Object)} method for generic
      * conversion.  Can be overridden by subclasses for source-specific conversion.
      *
      * @param source the source object to be hashed.
      * @return the source's bytes in the form of a {@code ByteSource} instance.
      * @since 1.2
      */
     protected ByteSource convertSourceToBytes(Object source) {
         return toByteSource(source);
     }
 
     /**
      * Acquires the specified {@code salt} argument's bytes and returns them in the form of a {@code ByteSource} instance.
      * <p/>
      * This implementation merely delegates to the convenience {@link #toByteSource(Object)} method for generic
      * conversion.  Can be overridden by subclasses for salt-specific conversion.
      *
      * @param salt the salt to be use for the hash.
      * @return the salt's bytes in the form of a {@code ByteSource} instance.
      * @since 1.2
      */
     protected ByteSource convertSaltToBytes(Object salt) {
         return toByteSource(salt);
     }
 
     /**
      * Converts a given object into a {@code ByteSource} instance.  Assumes the object can be converted to bytes.
      *
      * @param object the Object to convert into a {@code ByteSource} instance.
      * @return the {@code ByteSource} representation of the specified object's bytes.
      * @since 1.2
      */
     protected ByteSource toByteSource(Object object) {
         if (object instanceof ByteSource) {
             return (ByteSource) object;
         }
         byte[] bytes = toBytes(object);
         return ByteSource.Util.bytes(bytes);
     }
 
     private void hash(ByteSource source, ByteSource salt, int hashIterations) throws CodecException, UnknownAlgorithmException {
         byte[] saltBytes = requireNonNull(salt).getBytes();
         byte[] hashedBytes = hash(source.getBytes(), saltBytes, hashIterations);
         setBytes(hashedBytes);
     }
 
     /**
      * Returns the {@link java.security.MessageDigest MessageDigest} algorithm name to use when performing the hash.
      *
      * @return the {@link java.security.MessageDigest MessageDigest} algorithm name to use when performing the hash.
      */
     @Override
     public String getAlgorithmName() {
         return this.algorithmName;
     }
 
     @Override
     public ByteSource getSalt() {
         return this.salt;
     }
 
     @Override
     public int getIterations() {
         return this.iterations;
     }
 
     @Override
     public boolean matchesPassword(ByteSource plaintextBytes) {
         try {
             SimpleHash otherHash = new SimpleHash(this.getAlgorithmName(), plaintextBytes, this.getSalt(), this.getIterations());
             return this.equals(otherHash);
         } catch (IllegalArgumentException illegalArgumentException) {
             // cannot recreate hash. Do not log password.
             LOG.warn("Cannot recreate a hash using the same parameters.", illegalArgumentException);
             return false;
         }
     }
 
     @Override
     public byte[] getBytes() {
         return this.bytes;
     }
 
     /**
      * Sets the raw bytes stored by this hash instance.
      * <p/>
      * The bytes are kept in raw form - they will not be hashed/changed.  This is primarily a utility method for
      * constructing a Hash instance when the hashed value is already known.
      *
      * @param alreadyHashedBytes the raw already-hashed bytes to store in this instance.
      */
     public void setBytes(byte[] alreadyHashedBytes) {
         this.bytes = alreadyHashedBytes;
         this.hexEncoded = null;
         this.base64Encoded = null;
     }
 
     /**
      * Sets the iterations used to previously compute AN ALREADY GENERATED HASH.
      * <p/>
      * This is provided <em>ONLY</em> to reconstitute an already-created Hash instance.  It should ONLY ever be
      * invoked when re-constructing a hash instance from an already-hashed value.
      *
      * @param iterations the number of hash iterations used to previously create the hash/digest.
      * @since 1.2
      */
     public void setIterations(int iterations) {
         this.iterations = Math.max(DEFAULT_ITERATIONS, iterations);
     }
 
     /**
      * Sets the salt used to previously compute AN ALREADY GENERATED HASH.
      * <p/>
      * This is provided <em>ONLY</em> to reconstitute a Hash instance that has already been computed.  It should ONLY
      * ever be invoked when re-constructing a hash instance from an already-hashed value.
      *
      * @param salt the salt used to previously create the hash/digest.
      * @since 1.2
      */
     public void setSalt(ByteSource salt) {
         this.salt = salt;
     }
 
     /**
      * Returns the JDK MessageDigest instance to use for executing the hash.
      *
      * @param algorithmName the algorithm to use for the hash, provided by subclasses.
      * @return the MessageDigest object for the specified {@code algorithm}.
      * @throws UnknownAlgorithmException if the specified algorithm name is not available.
      */
     protected MessageDigest getDigest(String algorithmName) throws UnknownAlgorithmException {
         try {
             return MessageDigest.getInstance(algorithmName);
         } catch (NoSuchAlgorithmException e) {
             String msg = "No native '" + algorithmName + "' MessageDigest instance available on the current JVM.";
             throw new UnknownAlgorithmException(msg, e);
         }
     }
 
     /**
      * Hashes the specified byte array without a salt for a single iteration.
      *
      * @param bytes the bytes to hash.
      * @return the hashed bytes.
      * @throws UnknownAlgorithmException if the configured {@link #getAlgorithmName() algorithmName} is not available.
      */
     protected byte[] hash(byte[] bytes) throws UnknownAlgorithmException {
         return hash(bytes, new byte[0], DEFAULT_ITERATIONS);
     }
 
     /**
      * Hashes the specified byte array using the given {@code salt} for a single iteration.
      *
      * @param bytes the bytes to hash
      * @param salt  the salt to use for the initial hash
      * @return the hashed bytes
      * @throws UnknownAlgorithmException if the configured {@link #getAlgorithmName() algorithmName} is not available.
      */
     protected byte[] hash(byte[] bytes, byte[] salt) throws UnknownAlgorithmException {
         return hash(bytes, salt, DEFAULT_ITERATIONS);
     }
 
     /**
      * Hashes the specified byte array using the given {@code salt} for the specified number of iterations.
      *
      * @param bytes          the bytes to hash
      * @param salt           the salt to use for the initial hash
      * @param hashIterations the number of times the the {@code bytes} will be hashed (for attack resiliency).
      * @return the hashed bytes.
      * @throws UnknownAlgorithmException if the {@link #getAlgorithmName() algorithmName} is not available.
      */
     protected byte[] hash(byte[] bytes, byte[] salt, int hashIterations) throws UnknownAlgorithmException {
         MessageDigest digest = getDigest(getAlgorithmName());
         if (salt.length != 0) {
             digest.reset();
             digest.update(salt);
         }
         byte[] hashed = digest.digest(bytes);
         //already hashed once above
         int iterations = hashIterations - 1;
         //iterate remaining number:
         for (int i = 0; i < iterations; i++) {
             digest.reset();
             hashed = digest.digest(hashed);
         }
         return hashed;
     }
 
     @Override
     public boolean isEmpty() {
         return this.bytes == null || this.bytes.length == 0;
     }
 
     /**
      * Returns a hex-encoded string of the underlying {@link #getBytes byte array}.
      * <p/>
      * This implementation caches the resulting hex string so multiple calls to this method remain efficient.
      * However, calling {@link #setBytes setBytes} will null the cached value, forcing it to be recalculated the
      * next time this method is called.
      *
      * @return a hex-encoded string of the underlying {@link #getBytes byte array}.
      */
     @Override
     public String toHex() {
         if (this.hexEncoded == null) {
             this.hexEncoded = Hex.encodeToString(getBytes());
         }
         return this.hexEncoded;
     }
 
     /**
      * Returns a Base64-encoded string of the underlying {@link #getBytes byte array}.
      * <p/>
      * This implementation caches the resulting Base64 string so multiple calls to this method remain efficient.
      * However, calling {@link #setBytes setBytes} will null the cached value, forcing it to be recalculated the
      * next time this method is called.
      *
      * @return a Base64-encoded string of the underlying {@link #getBytes byte array}.
      */
     @Override
     public String toBase64() {
         if (this.base64Encoded == null) {
             //cache result in case this method is called multiple times.
             this.base64Encoded = Base64.encodeToString(getBytes());
         }
         return this.base64Encoded;
     }
 
     /**
      * Simple implementation that merely returns {@link #toHex() toHex()}.
      *
      * @return the {@link #toHex() toHex()} value.
      */
     @Override
     public String toString() {
         return toHex();
     }
 
     /**
      * Returns {@code true} if the specified object is a Hash and its {@link #getBytes byte array} is identical to
      * this Hash's byte array, {@code false} otherwise.
      *
      * @param o the object (Hash) to check for equality.
      * @return {@code true} if the specified object is a Hash and its {@link #getBytes byte array} is identical to
      * this Hash's byte array, {@code false} otherwise.
      */
     @Override
     public boolean equals(Object o) {
         if (o instanceof Hash) {
             Hash other = (Hash) o;
             return MessageDigest.isEqual(getBytes(), other.getBytes());
         }
         return false;
     }
 
     /**
      * Simply returns toHex().hashCode();
      *
      * @return toHex().hashCode()
      */
     @Override
     public int hashCode() {
         if (this.bytes == null || this.bytes.length == 0) {
             return 0;
         }
         return Arrays.hashCode(this.bytes);
     }
 }