/*
* 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.authc.credential;
import org.apache.shiro.authc.AuthenticationInfo;
import org.apache.shiro.authc.AuthenticationToken;
import org.apache.shiro.codec.Base64;
import org.apache.shiro.codec.Hex;
import org.apache.shiro.crypto.hash.AbstractHash;
import org.apache.shiro.crypto.hash.Hash;
/**
* 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:
* <p/>
* It first hashes the {@code AuthenticationToken} credentials supplied by the user during their login. It then
* compares 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. If these two values are equal, the submitted credentials
* match.
* <h3>Salting and Multiple Hash Iterations</h3>
* Because simple hashing is sometimes not good enough for many 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
* "Why add salt?" and 6 "Hardening against the attacker's attack").
* <p/>
* We should also note here that all of Shiro's Hash implementations (for example,
* {@link org.apache.shiro.crypto.hash.Md5Hash Md5Hash}, {@link org.apache.shiro.crypto.hash.Sha1Hash Sha1Hash}, etc)
* support salting and multiple hash iterations via overloaded constructors.
* <h4>Salting</h4>
* Salting of the authentication token's credentials hash is disabled by default, but you may enable it by setting
* {@link #setHashSalted hashSalted} to
* {@code true}. If you do enable it, the value used to salt the hash will be
* obtained from {@link #getSalt(org.apache.shiro.authc.AuthenticationToken) getSalt(authenticationToken)}.
* <p/>
* The default {@code getSalt} implementation merely returns
* {@code token.getPrincipal()}, effectively using the user's identity as the salt, a most common
* technique. If you wish to provide the authentication token's salt another way, you may override this
* {@code getSalt} method.
* <h4>Multiple Hash Iterations</h4>
* 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.
* <p/>
* <b>Note:</b> <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.
*
* @author Les Hazlewood
* @see org.apache.shiro.crypto.hash.Md5Hash
* @see org.apache.shiro.crypto.hash.Sha1Hash
* @see org.apache.shiro.crypto.hash.Sha256Hash
* @since 0.9
*/
public abstract class HashedCredentialsMatcher extends SimpleCredentialsMatcher {
private boolean storedCredentialsHexEncoded = true; //false means base64 encoded
private boolean hashSalted = false;
private int hashIterations = 1;
/**
* 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.
*/
public boolean isHashSalted() {
return hashSalted;
}
/**
* Sets whether or not 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) getSalt} method.
* </p>
* The default value is {@code false}.
*
* @param hashSalted whether or not to salt a submitted {@code AuthenticationToken}'s credentials when hashing.
*/
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) {
if (hashIterations < 1) {
this.hashIterations = 1;
} else {
this.hashIterations = hashIterations;
}
}
/**
* 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.
*/
protected Object getSalt(AuthenticationToken token) {
return token.getPrincipal();
}
/**
* As this is a HashedCredentialMatcher, this method overrides the parent method by returning a hashed value
* of the submitted token's credentials.
* <p/>
* Based on this class's configuration, the return value may be salted and/or
* hashed multiple times (see the class-level JavaDoc for more information on salting and
* multiple hash iterations).
*
* @param token the authentication token submitted during the authentication attempt.
* @return the hashed value of the authentication token's credentials.
*/
protected Object getCredentials(AuthenticationToken token) {
Object credentials = token.getCredentials();
Object salt = isHashSalted() ? getSalt(token) : null;
return hashProvidedCredentials(credentials, salt, getHashIterations());
}
/**
* 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.
*/
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);
}
}
AbstractHash hash = newHashInstance();
hash.setBytes(storedBytes);
return hash;
}
/**
* Hashes the provided credentials a total of {@code hashIterations} times, using the given salt. The hash
* implementation/algorithm used is left to subclasses.
*
* @param credentials the submitted authentication token's credentials to hash
* @param salt the value to salt the hash, or {@code null} if a salt will not be used.
* @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.
*/
protected abstract Hash hashProvidedCredentials(Object credentials, Object salt, int 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 abstract AbstractHash newHashInstance();
}
|