shiro认证流程源码分析--练气初期

写在前面

在上一篇文章当中，我们通过一个简单的例子，简单地认识了一下shiro。在这篇文章当中，我们将通过阅读源码的方式了解shiro的认证流程。

建议大家边读文章边动手调试代码，这样效果会更好。

认证异常分析

shiro中的异常主要分为两类，一类是AuthenticationException认证异常，一类是AuthorizationException权限异常。分别对应http响应状态码中的401和403

认证异常AuthenticationException子类

权限异常AuthorizationException子类

当认证不通过时将根据具体情况抛出AuthenticationException的子类，当鉴权不通过时将会抛出AuthorizationException的子类。

我们通过检验shiro是否抛出异常，从而判断登录对象是否通过认证、是否具备相关保护资源的访问权限。

这也是我们在上一节的例子中，需要捕获相关异常的原因。

接下来，我们通过阅读源码的方式来分析一下shiro框架的认证流程。

认证流程分析

/**认证器
 * @author 赖柄沣 bingfengdev@aliyun.com
 * @version 1.0
 * @date 2020/9/21 0:50
 */
public class Authenticator {

    private DefaultSecurityManager securityManager;

    public Authenticator(){
        //1. 创建安全管理器
        this.securityManager = new DefaultSecurityManager();

        //2. 给安全管理器设置问题域
        //因为权限信息从ini文件中读取，所以是IniRealm
        this.securityManager.setRealm(new IniRealm("classpath:shiro.ini"));

        //3. 注入安全管理器，并使用SecurityUtils全局安全工具类完成认证
        SecurityUtils.setSecurityManager(securityManager);

    }

    /**认证
     * @author 赖柄沣 bingfengdev@aliyun.com
     * @date 2020-09-23 16:22:11
     * @param username 用户名
     * @param password 密码
     * @return void
     * @version 1.0
     */
    public void authenticate(String username,String password){
        //4. 获取当前主题
        Subject subject = SecurityUtils.getSubject();

        //5.根据登录对象身份凭证信息创建登录令牌
        UsernamePasswordToken token = new UsernamePasswordToken(username,password);

        //6.认证
        //如果认证通过，则不抛出异常，否则抛出AuthenticationExceptixon异常子类
        //正式项目建议直接抛出，统一异常处理
        try {
            subject.login(token);
        }catch (IncorrectCredentialsException e) {
            e.printStackTrace();
        }catch (ConcurrentAccessException e){
            e.printStackTrace();
        }catch (UnknownAccountException e){
            e.printStackTrace();
        }catch (ExcessiveAttemptsException e){
            e.printStackTrace();
        }catch (ExpiredCredentialsException e){
            e.printStackTrace();
        }catch (LockedAccountException e){
            e.printStackTrace();
        }

    }

}

这是上一个例子当中的认证器的代码。 我们在上述代码的44行，shiro认证的入口处打个断点，以便跟踪其认证流程。

然后在idea中以debug的形式启动程序。

DelegatingSubject

login()方法

我们发现我们进入了DelegatingSubject.login方法当中；

public class DelegatingSubject implements Subject {
    //省略了其他不影响理解的代码
      public void login(AuthenticationToken token) throws AuthenticationException {

        this.clearRunAsIdentitiesInternal();
          // 1. 真正做认证的还是securityManager对象
        Subject subject = this.securityManager.login(this, token);
        String host = null;
        PrincipalCollection principals;
        if (subject instanceof DelegatingSubject) {
            DelegatingSubject delegating = (DelegatingSubject)subject;
            principals = delegating.principals;
            host = delegating.host;
        } else {
            principals = subject.getPrincipals();
        }

        if (principals != null && !principals.isEmpty()) {
            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 = this.decorate(session);
            } else {
                this.session = null;
            }

        } else {
            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);
        }
    }

}

从上面的源码中我们发现，虽然我们调用了Subject对象的认证方法，但是，真正的认证操作还是由安全管理器对象securityManager执行。

DefaultSecurityManager

login() 方法

接着，我们进入到securityManager的login方法当中去。

public class DefaultSecurityManager extends SessionsSecurityManager {

    //省略了其他无关代码
    public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info;
        try {
            //调用认证方法
            info = this.authenticate(token);
        } catch (AuthenticationException var7) {
            AuthenticationException ae = var7;

            try {
                this.onFailedLogin(token, ae, subject);
            } catch (Exception var6) {
                if (log.isInfoEnabled()) {
                    log.info("onFailedLogin method threw an exception.  Logging and propagating original AuthenticationException.", var6);
                }
            }

            throw var7;
        }

        Subject loggedIn = this.createSubject(token, info, subject);
        this.onSuccessfulLogin(token, info, loggedIn);
        return loggedIn;
    }

}

AuthenticatingSecurityManager

authenticate()方法

当我们进入到authenticate方法中时，发现他是AuthenticatingSecurityManager的方法

public abstract class AuthenticatingSecurityManager extends RealmSecurityManager {
//省略了其他无关代码
public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
    return this.authenticator.authenticate(token);
    }
}

AbstractAuthenticator

authenticate()方法

接着，他又调用了authenticator对象的authenticate方法

public abstract class AbstractAuthenticator implements Authenticator, LogoutAware {
    //省略了其他无关方法
     public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
        if (token == null) {
            throw new IllegalArgumentException("Method argument (authentication token) cannot be null.");
        } else {
            log.trace("Authentication attempt received for token [{}]", token);

            AuthenticationInfo info;
            try {

                info = this.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 var8) {
                AuthenticationException ae = null;
                if (var8 instanceof AuthenticationException) {
                    ae = (AuthenticationException)var8;
                }

                if (ae == null) {
                    String msg = "Authentication failed for token submission [" + token + "].  Possible unexpected error? (Typical or expected login exceptions should extend from AuthenticationException).";
                    ae = new AuthenticationException(msg, var8);
                    if (log.isWarnEnabled()) {
                        log.warn(msg, var8);
                    }
                }

                try {
                    this.notifyFailure(token, ae);
                } catch (Throwable var7) {
                    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, var7);
                    }
                }

                throw ae;
            }

            log.debug("Authentication successful for token [{}].  Returned account [{}]", token, info);
            this.notifySuccess(token, info);
            return info;
        }
    }
}

ModularRealmAuthenticator

doAuthenticate()方法

紧接着进入到了ModularRealmAuthenticator认证器对象的doAuthenticate方法

public class ModularRealmAuthenticator extends AbstractAuthenticator {
    protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException {
        this.assertRealmsConfigured();
        Collection<Realm> realms = this.getRealms();
        return realms.size() == 1 ?
 /**终于到了真正的认证逻辑*/            	this.doSingleRealmAuthentication((Realm)realms.iterator().next(), authenticationToken) : this.doMultiRealmAuthentication(realms, authenticationToken);
    }
}

在这一步当中，在检验我们的Realms对象创建后，开始进入到doSingleRealmAuthentication方法当中进行认证操作

doSingleRealmAuthentication()方法

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);
        } else {
            //获取认证信息
            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);
            } else {
                return info;
            }
        }
    }

AuthenticatingRealm

getAuthenticationInfo()方法

在这一步当中开始根据我们传入的令牌获取认证信息

public abstract class AuthenticatingRealm extends CachingRealm implements Initializable {

    public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
        // 首先从缓存中获取
        AuthenticationInfo info = this.getCachedAuthenticationInfo(token);
        if (info == null) {
            //缓存中没有，则从持久化数据中获取
            info = this.doGetAuthenticationInfo(token);
            log.debug("Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo", info);
            if (token != null && info != null) {
                this.cacheAuthenticationInfoIfPossible(token, info);
            }
        } else {
            log.debug("Using cached authentication info [{}] to perform credentials matching.", info);
        }

        if (info != null) {
            this.assertCredentialsMatch(token, info);
        } else {
            log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
        }

        return info;
    }
}

SimpleAccountRealm

doGetAuthenticationInfo()方法

从持久化数据源中获取登录对象信息

public class SimpleAccountRealm extends AuthorizingRealm {
protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
    UsernamePasswordToken upToken = (UsernamePasswordToken)token;
    //根据用户名查询账户信息
    SimpleAccount account = this.getUser(upToken.getUsername());
    //如果查询到了账户信息
    if (account != null) {
        //开始判断账户状态
        if (account.isLocked()) {
            throw new LockedAccountException("Account [" + account + "] is locked.");
        }

        if (account.isCredentialsExpired()) {
            String msg = "The credentials for account [" + account + "] are expired";
            throw new ExpiredCredentialsException(msg);
        }
    }

    return account;
}
}

在这里，便完成了对用户名的校验。

AuthenticatingRealm

接下来，我们获取到了账户信息并返回到了AuthenticatingRealm的getAuthenticationInfo方法。

在这个方法中有如下几行代码，在第二行中，调用assertCredentialsMatch方法开始校验用户凭证

if (info != null) {
    this.assertCredentialsMatch(token, info);
} else {
    log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
}

assertCredentialsMatch()方法

protected void assertCredentialsMatch(AuthenticationToken token, AuthenticationInfo info) throws AuthenticationException {
    //获取凭证匹配器对象
    CredentialsMatcher cm = this.getCredentialsMatcher();
    if (cm != null) {
        if (!cm.doCredentialsMatch(token, info)) {
            String msg = "Submitted credentials for token [" + token + "] did not match the expected credentials.";
            throw new IncorrectCredentialsException(msg);
        }
    } else {
        throw new AuthenticationException("A CredentialsMatcher must be configured in order to verify credentials during authentication.  If you do not wish for credentials to be examined, you can configure an " + AllowAllCredentialsMatcher.class.getName() + " instance.");
    }
}

在这里完成对用户凭证的校验。真正的比较逻辑则在SimpleCredentialsMatcher的equals方法中完成。里面还会区分加密和不加密的情况，具体请查看源码。

分析到这一步我们可以发现，SimpleAccountRealm继承了AuthorizingRealm类实现doGetAuthenticationInfo方法完成账户信息查询并校验，并将结果返回给AuthorizingRealm。AuthorizingRealm帮SimpleAccountRealm完成对用户凭证的校验。

那么，如果我们需要从数据库当中获取账户信息，应该怎么将账户信息传给shiro进行验证呢？这个问题留给大家思考一下，我将在下一篇文章当中为大家解答。

写在最后

在这篇文章当中，我们通过断点调试，阅读源码的方式弄清楚了shiro的认证流程。我们拆开他的层层封装，发现在SimpleAccountRealm对象中的doGetAuthenticationInfo方法中完成账户验证，在AuthenticatingRealm的assertCredentialsMatch完成对用户凭证的校验。

在下一篇文章当中，我们将学习如何使用数据库信息完成认证和授权。