源码分析shiro认证授权流程（shiro框架的认证和授权流程）

1. shiro介绍

Apache Shiro是一个强大易用的Java安全框架，提供了认证、授权、加密和会话管理等功能：

• 认证 – 用户身份识别，常被称为用户“登录”；
• 授权 – 访问控制；
• 密码加密 – 保护或隐藏数据防止被偷窥；
• 会话管理 – 每用户相关的时间敏感的状态。

对于任何一个应用程序，Shiro都可以提供全面的安全管理服务。并且相对于其他安全框架，Shiro要简单的多。

2. shiro源码概况

先要了解shiro的基本框架(见http://www.cnblogs.com/davidwang456/p/4425145.html)。

然后看一下各个组件之间的关系：

一下内容参考：http://kdboy.iteye.com/blog/1154644

subject：即“当前操作用户”。但是，在Shiro中，Subject这一概念并不仅仅指人，也可以是第三方进程、后台帐户（Daemon Account）或其他类似事物。它仅仅意味着“当前跟软件交互的东西”。但考虑到大多数目的和用途，你可以把它认为是Shiro的“用户”概念。

Subject代表了当前用户的安全操作，SecurityManager则管理所有用户的安全操作。

SecurityManager：它是Shiro框架的核心，典型的Facade模式，Shiro通过SecurityManager来管理内部组件实例，并通过它来提供安全管理的各种服务。

Realm： Realm充当了Shiro与应用安全数据间的“桥梁”或者“连接器”。也就是说，当对用户执行认证（登录）和授权（访问控制）验证时，Shiro会从应用配置的Realm中查找用户及其权限信息。

从这个意义上讲，Realm实质上是一个安全相关的DAO：它封装了数据源的连接细节，并在需要时将相关数据提供给Shiro。当配置Shiro时，你必须至少指定一个Realm，用于认证和（或）授权。配置多个Realm是可以的，但是至少需要一个。

Shiro内置了可以连接大量安全数据源（又名目录）的Realm，如LDAP、关系数据库（JDBC）、类似INI的文本配置资源以及属性文件等。如果缺省的Realm不能满足需求，你还可以插入代表自定义数据源的自己的Realm实现。

Shiro主要组件还包括：

Authenticator ：认证就是核实用户身份的过程。这个过程的常见例子是大家都熟悉的“用户/密码”组合。多数用户在登录软件系统时，通常提供自己的用户名（当事人）和支持他们的密码（证书）。如果存储在系统中的密码（或密码表示）与用户提供的匹配，他们就被认为通过认证。

Authorizer ：授权实质上就是访问控制 – 控制用户能够访问应用中的哪些内容，比如资源、Web页面等等。

sessionManager ：在安全框架领域，Apache Shiro提供了一些独特的东西：可在任何应用或架构层一致地使用Session API。即，Shiro为任何应用提供了一个会话编程范式 – 从小型后台独立应用到大型集群Web应用。这意味着，那些希望使用会话的应用开发者，不必被迫使用Servlet或EJB容器了。或者，如果正在使用这些容器，开发者现在也可以选择使用在任何层统一一致的会话API，取代Servlet或EJB机制。

CacheManager :对Shiro的其他组件提供缓存支持。

3. 做一个demo，跑shiro的源码，从login开始：

第一步：用户根据表单信息填写用户名和密码，然后调用登陆按钮。内部执行如下：

usernamePasswordToken token = new UsernamePasswordToken(loginForm.getUsername(), loginForm.getPassphrase()); token.setRememberMe(true); Subject currentUser = SecurityUtils.getSubject(); currentUser.login(token);

第二步：代理DelegatingSubject继承Subject执行login

public void login(AuthenticationToken token) throws AuthenticationException { clearRunAsIdentitiesInternal(); Subject subject = securityManager.login(this, token); PrincipalCollection principals; String host = null; if (subject instanceof DelegatingSubject) { DelegatingSubject delegating = (DelegatingSubject) subject; //we have to do this in case there are assumed identities – we don\’t want to lose the \’real\’ principals: principals = delegating.principals; host = delegating.host; } else { principals = subject.getPrincipals(); } if (principals == null || principals.isEmpty()) { String msg = \”Principals returned from securityManager.login( token ) returned a null or \” \”empty value. This value must be non null and populated with one or more elements.\”; throw new IllegalStateException(msg); } this.principals = principals; this.authenticated = true; if (token instanceof HostAuthenticationToken) { host = ((HostAuthenticationToken) token).getHost(); } if (host != null) { this.host = host; } Session session = subject.getSession(false); if (session != null) { this.session = decorate(session); } else { this.session = null; } }

第三步：调用DefaultSecurityManager继承SessionsSecurityManager执行login方法

public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException { AuthenticationInfo info; try { info = authenticate(token); } catch (AuthenticationException ae) { try { onFailedLogin(token, ae, subject); } catch (Exception e) { if (log.isInfoEnabled()) { log.info(\”onFailedLogin method threw an \” \”exception. Logging and propagating original AuthenticationException.\”, e); } } throw ae; //propagate } Subject loggedIn = createSubject(token, info, subject); onSuccessfulLogin(token, info, loggedIn); return loggedIn; }

第四步：认证管理器AuthenticatingSecurityManager继承RealmSecurityManager执行authenticate方法：

/** * Delegates to the wrapped {@link org.apache.shiro.authc.Authenticator Authenticator} for authentication. */ public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException { return this.authenticator.authenticate(token); }

第五步：抽象认证管理器AbstractAuthenticator继承Authenticator, LogoutAware 执行authenticate方法：

public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException { if (token == null) { throw new IllegalArgumentException(\”Method argumet (authentication token) cannot be null.\”); } log.trace(\”Authentication attempt received for token [{}]\”, token); AuthenticationInfo info; try { info = doAuthenticate(token); if (info == null) { String msg = \”No account information found for authentication token [\” token \”] by this \” \”Authenticator instance. Please check that it is configured correctly.\”; throw new AuthenticationException(msg); } } catch (Throwable t) { AuthenticationException ae = null; if (t instanceof AuthenticationException) { ae = (AuthenticationException) t; } if (ae == null) { //Exception thrown was not an expected AuthenticationException. Therefore it is probably a little more //severe or unexpected. So, wrap in an AuthenticationException, log to warn, and propagate: String msg = \”Authentication failed for token submission [\” token \”]. Possible unexpected \” \”error? (Typical or expected login exceptions should extend from AuthenticationException).\”; ae = new AuthenticationException(msg, t); } try { notifyFailure(token, ae); } catch (Throwable t2) { if (log.isWarnEnabled()) { String msg = \”Unable to send notification for failed authentication attempt – listener error?. \” \”Please check your AuthenticationListener implementation(s). Logging sending exception \” \”and propagating original AuthenticationException instead…\”; log.warn(msg, t2); } } throw ae; } log.debug(\”Authentication successful for token [{}]. Returned account [{}]\”, token, info); notifySuccess(token, info); return info; }

第六步：ModularRealmAuthenticator继承AbstractAuthenticator执行doAuthenticate方法

protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException { assertRealmsConfigured(); Collection<Realm> realms = getRealms(); if (realms.size() == 1) { return doSingleRealmAuthentication(realms.iterator().next(), authenticationToken); } else { return doMultiRealmAuthentication(realms, authenticationToken); } }

接着调用：

/** * Performs the authentication attempt by interacting with the single configured realm, which is significantly * simpler than performing multi-realm logic. * * @param realm the realm to consult for AuthenticationInfo. * @param token the submitted AuthenticationToken representing the subject\’s (user\’s) log-in principals and credentials. * @return the AuthenticationInfo associated with the user account corresponding to the specified {@code token} */ protected AuthenticationInfo doSingleRealmAuthentication(Realm realm, AuthenticationToken token) { if (!realm.supports(token)) { String msg = \”Realm [\” realm \”] does not support authentication token [\” token \”]. Please ensure that the appropriate Realm implementation is \” \”configured correctly or that the realm accepts AuthenticationTokens of this type.\”; throw new UnsupportedTokenException(msg); } AuthenticationInfo info = realm.getAuthenticationInfo(token); if (info == null) { String msg = \”Realm [\” realm \”] was unable to find account data for the \” \”submitted AuthenticationToken [\” token \”].\”; throw new UnknownAccountException(msg); } return info; }

第七步：AuthenticatingRealm继承CachingRealm执行getAuthenticationInfo方法

public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException { AuthenticationInfo info = getCachedAuthenticationInfo(token); //从缓存中读取 if (info == null) { //otherwise not cached, perform the lookup: info = doGetAuthenticationInfo(token); //缓存中读不到，则到数据库或者ldap或者jndi等去读 log.debug(\”Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo\”, info); if (token != null && info != null) { cacheAuthenticationInfoIfPossible(token, info); } } else { log.debug(\”Using cached authentication info [{}] to perform credentials matching.\”, info); } if (info != null) { assertCredentialsMatch(token, info); } else { log.debug(\”No AuthenticationInfo found for submitted AuthenticationToken [{}]. Returning null.\”, token); } return info; }

1. 从缓存中读取的方法：

/** * Checks to see if the authenticationCache class attribute is null, and if so, attempts to acquire one from * any configured {@link #getCacheManager() cacheManager}. If one is acquired, it is set as the class attribute. * The class attribute is then returned. * * @return an available cache instance to be used for authentication caching or {@code null} if one is not available. * @since 1.2 */ private Cache<Object, AuthenticationInfo> getAuthenticationCacheLazy() { if (this.authenticationCache == null) { log.trace(\”No authenticationCache instance set. Checking for a cacheManager…\”); CacheManager cacheManager = getCacheManager(); if (cacheManager != null) { String cacheName = getAuthenticationCacheName(); log.debug(\”CacheManager [{}] configured. Building authentication cache \'{}\’\”, cacheManager, cacheName); this.authenticationCache = cacheManager.getCache(cacheName); } } return this.authenticationCache; }

2. 从数据库中读取的方法：

JdbcRealm继承 AuthorizingRealm执行doGetAuthenticationInfo方法

protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token) throws AuthenticationException { UsernamePasswordToken upToken = (UsernamePasswordToken) token; String username = upToken.getUsername(); // Null username is invalid if (username == null) { throw new AccountException(\”Null usernames are not allowed by this realm.\”); } Connection conn = null; SimpleAuthenticationInfo info = null; try { conn = dataSource.getConnection(); String password = null; String salt = null; switch (saltStyle) { case NO_SALT: password = getPasswordForUser(conn, username)[0]; break; case CRYPT: // TODO: separate password and hash from getPasswordForUser[0] throw new ConfigurationException(\”Not implemented yet\”); //break; case COLUMN: String[] queryResults = getPasswordForUser(conn, username); password = queryResults[0]; salt = queryResults[1]; break; case EXTERNAL: password = getPasswordForUser(conn, username)[0]; salt = getSaltForUser(username); } if (password == null) { throw new UnknownAccountException(\”No account found for user [\” username \”]\”); } info = new SimpleAuthenticationInfo(username, password.toCharArray(), getName()); if (salt != null) { info.setCredentialsSalt(ByteSource.Util.bytes(salt)); } } catch (SQLException e) { final String message = \”There was a SQL error while authenticating user [\” username \”]\”; if (log.isErrorEnabled()) { log.error(message, e); } // Rethrow any SQL errors as an authentication exception throw new AuthenticationException(message, e); } finally { JdbcUtils.closeConnection(conn); } return info; }

接着调用sql语句：

private String[] getPasswordForUser(Connection conn, String username) throws SQLException { String[] result; boolean returningSeparatedSalt = false; switch (saltStyle) { case NO_SALT: case CRYPT: case EXTERNAL: result = new String[1]; break; default: result = new String[2]; returningSeparatedSalt = true; } PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(authenticationQuery); ps.setString(1, username); // Execute query rs = ps.executeQuery(); // Loop over results – although we are only expecting one result, since usernames should be unique boolean foundResult = false; while (rs.next()) { // Check to ensure only one row is processed if (foundResult) { throw new AuthenticationException(\”More than one user row found for user [\” username \”]. Usernames must be unique.\”); } result[0] = rs.getString(1); if (returningSeparatedSalt) { result[1] = rs.getString(2); } foundResult = true; } } finally { JdbcUtils.closeResultSet(rs); JdbcUtils.closeStatement(ps); } return result; }

其中authenticationQuery定义如下：

protected String authenticationQuery = DEFAULT_AUTHENTICATION_QUERY; protected static final String DEFAULT_AUTHENTICATION_QUERY = \”select password from users where username = ?\”;

4. 小结

Apache Shiro 是功能强大并且容易集成的开源权限框架，它能够完成认证、授权、加密、会话管理等功能。认证和授权为权限控制的核心，简单来说，“认证”就是证明你是谁？ Web 应用程序一般做法通过表单提交用户名及密码达到认证目的。“授权”即是否允许已认证用户访问受保护资源。

参考文献：

http://kdboy.iteye.com/blog/1154644

http://www.ibm.com/developerworks/cn/java/j-lo-shiro/