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  package org.apache.shiro.authc.credential;
  
  import org.apache.shiro.authc.AuthenticationInfo;
  import org.apache.shiro.authc.AuthenticationToken;
  import org.apache.shiro.authc.SaltedAuthenticationInfo;
  import org.apache.shiro.crypto.hash.Hash;
  import org.apache.shiro.crypto.hash.SimpleHash;
  import org.apache.shiro.lang.codec.Base64;
  import org.apache.shiro.lang.codec.Hex;
  import org.apache.shiro.lang.util.SimpleByteSource;
  import org.apache.shiro.lang.util.StringUtils;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A {@code HashedCredentialMatcher} provides support for hashing of supplied {@code AuthenticationToken} credentials
   * before being compared to those in the {@code AuthenticationInfo} from the data store.
   * <p/>
   * Credential hashing is one of the most common security techniques when safeguarding a user's private credentials
   * (passwords, keys, etc.).  Most developers never want to store their users' credentials in plain form, viewable by
   * anyone, so they often hash the users' credentials before they are saved in the data store.
   * <p/>
   * This class (and its subclasses) function as follows:
   * <ol>
   * <li>Hash the {@code AuthenticationToken} credentials supplied by the user during their login.</li>
   * <li>Compare this hashed value directly with the {@code AuthenticationInfo} credentials stored in the system
   * (the stored account credentials are expected to already be in hashed form).</li>
   * <li>If these two values are {@link #equals(Object, Object) equal}, the submitted credentials match, otherwise
   * they do not.</li>
   * </ol>
   * <h2>Salting and Multiple Hash Iterations</h2>
   * Because simple hashing is usually not good enough for secure applications, this class also supports 'salting'
   * and multiple hash iterations.  Please read this excellent
   * <a href="http://www.owasp.org/index.php/Hashing_Java" _target="blank">Hashing Java article</a> to learn about
   * salting and multiple iterations and why you might want to use them. (Note of sections 5
   * &quot;Why add salt?&quot; and 6 "Hardening against the attacker's attack").</p>
   * <h4>Real World Case Study</h4>
   * In April 2010, some public Atlassian Jira and Confluence
   * installations (Apache Software Foundation, Codehaus, etc.) were the target of account attacks and user accounts
   * were compromised.  The reason?  Jira and Confluence at the time did not salt user passwords and attackers were
   * able to use dictionary attacks to compromise user accounts (Atlassian has since
   * <a href="http://blogs.atlassian.com/news/2010/04/oh_man_what_a_day_an_update_on_our_security_breach.html">
   * fixed the problem</a> of course).
   * <p/>
   * The lesson?
   * <p/>
   * <b>ALWAYS, ALWAYS, ALWAYS SALT USER PASSWORDS!</b>
   * <p/>
   * <h3>Salting</h3>
   * Prior to Shiro 1.1, salts could be obtained based on the end-user submitted
   * {@link AuthenticationToken AuthenticationToken} via the now-deprecated
   * {@link #getSalt(org.apache.shiro.authc.AuthenticationToken) getSalt(AuthenticationToken)} method.  This however
   * could constitute a security hole since ideally salts should never be obtained based on what a user can submit.
   * User-submitted salt mechanisms are <em>much</em> more susceptible to dictionary attacks and <b>SHOULD NOT</b> be
   * used in secure systems.  Instead, salts should ideally be a secure randomly-generated number that is generated when
   * the user account is created.  The secure number should never be disseminated to the user and always kept private
   * by the application.
   * <h4>Shiro 1.1</h4>
   * As of Shiro 1.1, it is expected that any salt used to hash the submitted credentials will be obtained from the
   * stored account information (represented as an {@link AuthenticationInfo AuthenticationInfo} instance).  This is much
   * more secure because the salt value remains private to the application (Shiro will never store this value).
   * <p/>
   * To enable this, {@code Realm}s should return {@link SaltedAuthenticationInfo SaltedAuthenticationInfo} instances
   * during authentication.  {@code HashedCredentialsMatcher} implementations will then use the provided
   * {@link org.apache.shiro.authc.SaltedAuthenticationInfo#getCredentialsSalt credentialsSalt} for hashing.  To avoid
   * security risks,
   * <b>it is highly recommended that any existing {@code Realm} implementations that support hashed credentials are
   * updated to return {@link SaltedAuthenticationInfo SaltedAuthenticationInfo} instances as soon as possible</b>.
   * <h4>Shiro 1.0 Backwards Compatibility</h4>
   * Because of the identified security risk, {@code Realm} implementations that support credentials hashing should
   * be updated to return {@link SaltedAuthenticationInfo SaltedAuthenticationInfo} instances as
   * soon as possible.
   * <p/>
   * If this is not possible for some reason, this class will retain 1.0 backwards-compatible behavior of obtaining
   * the salt via the now-deprecated {@link #getSalt(AuthenticationToken) getSalt(AuthenticationToken)} method.  This
   * method will only be invoked if a {@code Realm} <em>does not</em> return
   * {@link SaltedAuthenticationInfo SaltedAuthenticationInfo} instances and {@link #isHashSalted() hashSalted} is
   * {@code true}.
   * But please note that the {@link #isHashSalted() hashSalted} property and the
   * {@link #getSalt(AuthenticationToken) getSalt(AuthenticationToken)} methods will be removed before the Shiro 2.0
   * release.
  * <h3>Multiple Hash Iterations</h3>
  * If you hash your users' credentials multiple times before persisting to the data store, you will also need to
  * set this class's {@link #setHashIterations(int) hashIterations} property.  See the
  * <a href="http://www.owasp.org/index.php/Hashing_Java" _target="blank">Hashing Java article</a>'s
  * <a href="http://www.owasp.org/index.php/Hashing_Java#Hardening_against_the_attacker.27s_attack">
  * &quot;Hardening against the attacker's attack&quot;</a> section to learn more about why you might want to use
  * multiple hash iterations.
  * <h2>MD5 &amp; SHA-1 Notice</h2>
  * <a href="http://en.wikipedia.org/wiki/MD5">MD5</a> and
  * <a href="http://en.wikipedia.org/wiki/SHA_hash_functions">SHA-1</a> algorithms are now known to be vulnerable to
  * compromise and/or collisions (read the linked pages for more).  While most applications are ok with either of these
  * two, if your application mandates high security, use the SHA-256 (or higher) hashing algorithms and their
  * supporting {@code CredentialsMatcher} implementations.
  *
  * @see org.apache.shiro.crypto.hash.Sha256Hash
  * @see org.apache.shiro.crypto.hash.Sha384Hash
  * @see org.apache.shiro.crypto.hash.Sha256Hash
  * @since 0.9
  */
 public class HashedCredentialsMatcher extends SimpleCredentialsMatcher {
 
     /**
      * @since 1.1
      */
     private String hashAlgorithm;
     private int hashIterations;
     private boolean hashSalted;
     private boolean storedCredentialsHexEncoded;
 
     /**
      * JavaBeans-compatible no-arg constructor intended for use in IoC/Dependency Injection environments.  If you
      * use this constructor, you <em>MUST</em> also additionally set the
      * {@link #setHashAlgorithmName(String) hashAlgorithmName} property.
      */
     public HashedCredentialsMatcher() {
         this.hashAlgorithm = null;
         this.hashSalted = false;
         this.hashIterations = 1;
         //false means Base64-encoded
         this.storedCredentialsHexEncoded = true;
     }
 
     /**
      * Creates an instance using the specified {@link #getHashAlgorithmName() hashAlgorithmName} to hash submitted
      * credentials.
      *
      * @param hashAlgorithmName the {@code Hash} {@link org.apache.shiro.crypto.hash.Hash#getAlgorithmName() algorithmName}
      *                          to use when performing hashes for credentials matching.
      * @since 1.1
      */
     public HashedCredentialsMatcher(String hashAlgorithmName) {
         this();
         if (!StringUtils.hasText(hashAlgorithmName)) {
             throw new IllegalArgumentException("hashAlgorithmName cannot be null or empty.");
         }
         this.hashAlgorithm = hashAlgorithmName;
     }
 
     /**
      * Returns the {@code Hash} {@link org.apache.shiro.crypto.hash.Hash#getAlgorithmName() algorithmName} to use
      * when performing hashes for credentials matching.
      *
      * @return the {@code Hash} {@link org.apache.shiro.crypto.hash.Hash#getAlgorithmName() algorithmName} to use
      * when performing hashes for credentials matching.
      * @since 1.1
      */
     public String getHashAlgorithmName() {
         return hashAlgorithm;
     }
 
     /**
      * Sets the {@code Hash} {@link org.apache.shiro.crypto.hash.Hash#getAlgorithmName() algorithmName} to use
      * when performing hashes for credentials matching.
      *
      * @param hashAlgorithmName the {@code Hash} {@link org.apache.shiro.crypto.hash.Hash#getAlgorithmName() algorithmName}
      *                          to use when performing hashes for credentials matching.
      * @since 1.1
      */
     public void setHashAlgorithmName(String hashAlgorithmName) {
         this.hashAlgorithm = hashAlgorithmName;
     }
 
     /**
      * Returns {@code true} if the system's stored credential hash is Hex encoded, {@code false} if it
      * is Base64 encoded.
      * <p/>
      * Default value is {@code true} for convenience - all of Shiro's {@link Hash Hash#toString()}
      * implementations return Hex encoded values by default, making this class's use with those implementations
      * easier.
      *
      * @return {@code true} if the system's stored credential hash is Hex encoded, {@code false} if it
      * is Base64 encoded.  Default is {@code true}
      */
     public boolean isStoredCredentialsHexEncoded() {
         return storedCredentialsHexEncoded;
     }
 
     /**
      * Sets the indicator if this system's stored credential hash is Hex encoded or not.
      * <p/>
      * A value of {@code true} will cause this class to decode the system credential from Hex, a
      * value of {@code false} will cause this class to decode the system credential from Base64.
      * <p/>
      * Unless overridden via this method, the default value is {@code true} for convenience - all of Shiro's
      * {@link Hash Hash#toString()} implementations return Hex encoded values by default, making this class's use with
      * those implementations easier.
      *
      * @param storedCredentialsHexEncoded the indicator if this system's stored credential hash is Hex
      *                                    encoded or not ('not' automatically implying it is Base64 encoded).
      */
     public void setStoredCredentialsHexEncoded(boolean storedCredentialsHexEncoded) {
         this.storedCredentialsHexEncoded = storedCredentialsHexEncoded;
     }
 
     /**
      * Returns {@code true} if a submitted {@code AuthenticationToken}'s credentials should be salted when hashing,
      * {@code false} if it should not be salted.
      * <p/>
      * If enabled, the salt used will be obtained via the {@link #getSalt(AuthenticationToken) getSalt} method.
      * <p/>
      * The default value is {@code false}.
      *
      * @return {@code true} if a submitted {@code AuthenticationToken}'s credentials should be salted when hashing,
      * {@code false} if it should not be salted.
      * @deprecated since Shiro 1.1.  Hash salting is now expected to be based on if the {@link AuthenticationInfo}
      * returned from the {@code Realm} is a {@link SaltedAuthenticationInfo} instance and its
      * {@link org.apache.shiro.authc.SaltedAuthenticationInfo#getCredentialsSalt() getCredentialsSalt()} method
      * returns a non-null value.
      * This method and the 1.0 behavior still exists for backwards compatibility if the {@code Realm} does not return
      * {@code SaltedAuthenticationInfo} instances, but <b>it is highly recommended that {@code Realm} implementations
      * that support hashed credentials start returning {@link SaltedAuthenticationInfo SaltedAuthenticationInfo}
      * instances as soon as possible</b>.
      * <p/>
      * This is because salts should always be obtained from the stored account information and
      * never be interpreted based on user/Subject-entered data.  User-entered data is easier to compromise for
      * attackers, whereas account-unique (and secure randomly-generated) salts never disseminated to the end-user
      * are almost impossible to break.  This method will be removed in Shiro 2.0.
      */
     @Deprecated
     public boolean isHashSalted() {
         return hashSalted;
     }
 
     /**
      * Sets whether to salt a submitted {@code AuthenticationToken}'s credentials when hashing.
      * <p/>
      * If enabled, the salt used will be obtained via the
      * {@link #getSalt(org.apache.shiro.authc.AuthenticationToken) getCredentialsSalt} method.
      * </p>
      * The default value is {@code false}.
      *
      * @param hashSalted whether to salt a submitted {@code AuthenticationToken}'s credentials when hashing.
      * @deprecated since Shiro 1.1.  Hash salting is now expected to be based on if the {@link AuthenticationInfo}
      * returned from the {@code Realm} is a {@link SaltedAuthenticationInfo} instance and its
      * {@link org.apache.shiro.authc.SaltedAuthenticationInfo#getCredentialsSalt() getCredentialsSalt()}
      * method returns a non-null value.
      * This method and the 1.0 behavior still exists for backwards compatibility if the {@code Realm} does not return
      * {@code SaltedAuthenticationInfo} instances, but <b>it is highly recommended that {@code Realm} implementations
      * that support hashed credentials start returning {@link SaltedAuthenticationInfo SaltedAuthenticationInfo}
      * instances as soon as possible</b>.
      * <p/>
      * This is because salts should always be obtained from the stored account information and
      * never be interpreted based on user/Subject-entered data.  User-entered data is easier to compromise for
      * attackers, whereas account-unique (and secure randomly-generated) salts never disseminated to the end-user
      * are almost impossible to break.  This method will be removed in Shiro 2.0.
      */
     @Deprecated
     public void setHashSalted(boolean hashSalted) {
         this.hashSalted = hashSalted;
     }
 
     /**
      * Returns the number of times a submitted {@code AuthenticationToken}'s credentials will be hashed before
      * comparing to the credentials stored in the system.
      * <p/>
      * Unless overridden, the default value is {@code 1}, meaning a normal hash execution will occur.
      *
      * @return the number of times a submitted {@code AuthenticationToken}'s credentials will be hashed before
      * comparing to the credentials stored in the system.
      */
     public int getHashIterations() {
         return hashIterations;
     }
 
     /**
      * Sets the number of times a submitted {@code AuthenticationToken}'s credentials will be hashed before comparing
      * to the credentials stored in the system.
      * <p/>
      * Unless overridden, the default value is {@code 1}, meaning a normal single hash execution will occur.
      * <p/>
      * If this argument is less than 1 (i.e. 0 or negative), the default value of 1 is applied.  There must always be
      * at least 1 hash iteration (otherwise there would be no hash).
      *
      * @param hashIterations the number of times to hash a submitted {@code AuthenticationToken}'s credentials.
      */
     public void setHashIterations(int hashIterations) {
         this.hashIterations = Math.max(hashIterations, 1);
     }
 
     /**
      * Returns a salt value used to hash the token's credentials.
      * <p/>
      * This default implementation merely returns {@code token.getPrincipal()}, effectively using the user's
      * identity (username, user id, etc.) as the salt, a most common technique.  If you wish to provide the
      * authentication token's salt another way, you may override this method.
      *
      * @param token the AuthenticationToken submitted during the authentication attempt.
      * @return a salt value to use to hash the authentication token's credentials.
      * @deprecated since Shiro 1.1.  Hash salting is now expected to be based on if the {@link AuthenticationInfo}
      * returned from the {@code Realm} is a {@link SaltedAuthenticationInfo} instance and its
      * {@link org.apache.shiro.authc.SaltedAuthenticationInfo#getCredentialsSalt() getCredentialsSalt()} method
      * returns a non-null value.
      * This method and the 1.0 behavior still exists for backwards compatibility if the {@code Realm} does not return
      * {@code SaltedAuthenticationInfo} instances, but <b>it is highly recommended that {@code Realm} implementations
      * that support hashed credentials start returning {@link SaltedAuthenticationInfo SaltedAuthenticationInfo}
      * instances as soon as possible</b>.<p/>
      * This is because salts should always be obtained from the stored account information and
      * never be interpreted based on user/Subject-entered data.  User-entered data is easier to compromise for
      * attackers, whereas account-unique (and secure randomly-generated) salts never disseminated to the end-user
      * are almost impossible to break.  This method will be removed in Shiro 2.0.
      */
     @Deprecated
     protected Object getSalt(AuthenticationToken token) {
         return token.getPrincipal();
     }
 
     /**
      * Returns a {@link Hash Hash} instance representing the already-hashed AuthenticationInfo credentials stored in the system.
      * <p/>
      * This method reconstructs a {@link Hash Hash} instance based on a {@code info.getCredentials} call,
      * but it does <em>not</em> hash that value - it is expected that method call will return an already-hashed value.
      * <p/>
      * This implementation's reconstruction effort functions as follows:
      * <ol>
      * <li>Convert {@code account.getCredentials()} to a byte array via the {@link #toBytes toBytes} method.
      * <li>If {@code account.getCredentials()} was originally a String or char[] before {@code toBytes} was
      * called, check for encoding:
      * <li>If {@link #storedCredentialsHexEncoded storedCredentialsHexEncoded}, Hex decode that byte array, otherwise
      * Base64 decode the byte array</li>
      * <li>Set the byte[] array directly on the {@code Hash} implementation and return it.</li>
      * </ol>
      *
      * @param info the AuthenticationInfo from which to retrieve the credentials which assumed to be in already-hashed form.
      * @return a {@link Hash Hash} instance representing the given AuthenticationInfo's stored credentials.
      */
     @Override
     protected Object getCredentials(AuthenticationInfo info) {
         Object credentials = info.getCredentials();
 
         byte[] storedBytes = toBytes(credentials);
 
         if (credentials instanceof String || credentials instanceof char[]) {
             //account.credentials were a char[] or String, so
             //we need to do text decoding first:
             if (isStoredCredentialsHexEncoded()) {
                 storedBytes = Hex.decode(storedBytes);
             } else {
                 storedBytes = Base64.decode(storedBytes);
             }
         }
         SimpleHash hash = newHashInstance();
         hash.setBytes(storedBytes);
         return hash;
     }
 
     /**
      * This implementation first hashes the {@code token}'s credentials, potentially using a
      * {@code salt} if the {@code info} argument is a
      * {@link org.apache.shiro.authc.SaltedAuthenticationInfo SaltedAuthenticationInfo}.  It then compares the hash
      * against the {@code AuthenticationInfo}'s
      * {@link #getCredentials(org.apache.shiro.authc.AuthenticationInfo) already-hashed credentials}.  This method
      * returns {@code true} if those two values are {@link #equals(Object, Object) equal}, {@code false} otherwise.
      *
      * @param token the {@code AuthenticationToken} submitted during the authentication attempt.
      * @param info  the {@code AuthenticationInfo} stored in the system matching the token principal
      * @return {@code true} if the provided token credentials hash match to the stored account credentials hash,
      * {@code false} otherwise
      * @since 1.1
      */
     @Override
     public boolean doCredentialsMatch(AuthenticationToken token, AuthenticationInfo info) {
         Object tokenHashedCredentials = hashProvidedCredentials(token, info);
         Object accountCredentials = getCredentials(info);
         return equals(tokenHashedCredentials, accountCredentials);
     }
 
     /**
      * Hash the provided {@code token}'s credentials using the salt stored with the account if the
      * {@code info} instance is an {@code instanceof} {@link SaltedAuthenticationInfo SaltedAuthenticationInfo} (see
      * the class-level JavaDoc for why this is the preferred approach).
      * <p/>
      * If the {@code info} instance is <em>not</em>
      * an {@code instanceof} {@code SaltedAuthenticationInfo}, the logic will fall back to Shiro 1.0
      * backwards-compatible logic:  it will first check to see {@link #isHashSalted() isHashSalted} and if so, will try
      * to acquire the salt from {@link #getSalt(AuthenticationToken) getSalt(AuthenticationToken)}.  See the class-level
      * JavaDoc for why this is not recommended.  This 'fallback' logic exists only for backwards-compatibility.
      * {@code Realm}s should be updated as soon as possible to return {@code SaltedAuthenticationInfo} instances
      * if account credentials salting is enabled (highly recommended for password-based systems).
      *
      * @param token the submitted authentication token from which its credentials will be hashed
      * @param info  the stored account data, potentially used to acquire a salt
      * @return the token credentials hash
      * @since 1.1
      */
     protected Object hashProvidedCredentials(AuthenticationToken token, AuthenticationInfo info) {
         final Object salt;
         if (info instanceof SaltedAuthenticationInfo) {
             salt = ((SaltedAuthenticationInfo) info).getCredentialsSalt();
         } else if (isHashSalted()) {
             //retain 1.0 backwards compatibility:
             salt = getSalt(token);
         } else {
             salt = SimpleByteSource.empty();
         }
         return hashProvidedCredentials(token.getCredentials(), salt, getHashIterations());
     }
 
     /**
      * Returns the {@link #getHashAlgorithmName() hashAlgorithmName} property, but will throw an
      * {@link IllegalStateException} if it has not been set.
      *
      * @return the required {@link #getHashAlgorithmName() hashAlgorithmName} property
      * @throws IllegalStateException if the property has not been set prior to calling this method.
      * @since 1.1
      */
     private String assertHashAlgorithmName() throws IllegalStateException {
         String hashAlgorithmName = getHashAlgorithmName();
         if (hashAlgorithmName == null) {
             String msg = "Required 'hashAlgorithmName' property has not been set.  This is required to execute "
                     + "the hashing algorithm.";
             throw new IllegalStateException(msg);
         }
         return hashAlgorithmName;
     }
 
     /**
      * Hashes the provided credentials a total of {@code hashIterations} times, using the given salt.  The hash
      * implementation/algorithm used is based on the {@link #getHashAlgorithmName() hashAlgorithmName} property.
      *
      * @param credentials    the submitted authentication token's credentials to hash
      * @param salt           the value to salt the hash. Cannot be {@code null}, but an empty ByteSource.
      * @param hashIterations the number of times to hash the credentials.  At least one hash will always occur though,
      *                       even if this argument is 0 or negative.
      * @return the hashed value of the provided credentials, according to the specified salt and hash iterations.
      * @throws NullPointerException if salt is {@code null}.
      */
     protected Hash hashProvidedCredentials(Object credentials, Object salt, int hashIterations) {
         String hashAlgorithmName = assertHashAlgorithmName();
         return new SimpleHash(hashAlgorithmName, credentials, requireNonNull(salt, "salt cannot be null."), hashIterations);
     }
 
     /**
      * Returns a new, <em>uninitialized</em> instance, without its byte array set.  Used as a utility method in the
      * {@link SimpleCredentialsMatcher#getCredentials(org.apache.shiro.authc.AuthenticationInfo)
      * getCredentials(AuthenticationInfo)} implementation.
      *
      * @return a new, <em>uninitialized</em> instance, without its byte array set.
      */
     protected SimpleHash newHashInstance() {
         String hashAlgorithmName = assertHashAlgorithmName();
         return new SimpleHash(hashAlgorithmName);
     }
 
 }