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Shiro源码分析----登录流程

作者:互联网

在Shiro中,登录操作是由Subject的login()方法完成的,Subject是个接口,在Web环境中,实现类为WebDelegatingSubjectlogin方法从DeletatingSubject继承而来:

public void login(AuthenticationToken token) throws AuthenticationException {
    clearRunAsIdentitiesInternal();
    Subject subject = securityManager.login(this, token);

    // 省略一些代码...
}

由上可见,Subject.login()方法委托给了SecurityManager对象,在Web环境中,SecurityManager实现类为DefaultWebSecurityManager,其login方法从DefaultSecurityManager继承而来:

public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
    AuthenticationInfo info;
    try {
        // 对提交的AuthenticationToken进行认证
        info = authenticate(token);
    } catch (AuthenticationException ae) {
        try {
            // 如果认证失败
            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,如果认证失败,使异常继续向上传播,从而返回至登录页面(见上篇)
    }

    // 如果认证成功则重新创建Subject对象
    Subject loggedIn = createSubject(token, info, subject);

    // 登录成功,主要处理RememberMe操作,即将登录信息存储在cookie中
    onSuccessfulLogin(token, info, loggedIn);

    return loggedIn;
}

最关键的authenticate方法:

public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
    return this.authenticator.authenticate(token);
}

SecurityManager把认证方法委托给认证器Authenticatorauthenticate方法,Authenticator的实现类为:ModularRealmAuthenticator,其可以实现多认证信息源综合认证。ModularRealmAuthenticator实现使用了模版方法设计模式,随后执行doAuthenticate方法:

protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException {
    assertRealmsConfigured();
    // Realm集合在为SecurityManager设置Realm时就会设置给Authenticator
    // 至于Realm代表什么,请参看:http://jinnianshilongnian.iteye.com/blog/2018936
    Collection<Realm> realms = getRealms();
    if (realms.size() == 1) {
        // 如果Realm只有一个
        return doSingleRealmAuthentication(realms.iterator().next(), authenticationToken);
    } else {
        // 如果Realm有多个
        return doMultiRealmAuthentication(realms, authenticationToken);
    }
}

单一Realm认证:

protected AuthenticationInfo doSingleRealmAuthentication(Realm realm, AuthenticationToken token) {
    // 该Realm是否支持此种Token,因为并不是任何一种Realm与AuthenticationToken都是相互匹配的
    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);
    }
    // 根据AuthenticationToken获取认证信息
    // Realm一般是由自己实现的,虽然说Shiro有一些自己的实现,但是在实际项目中,Shiro的实现直接就能使用的情况很少
    // 比较将认证信息(用户名密码等)存在数据库,则该getAuthenticationInfo方法就是根据Token中的信息去数据库中查找、
    // 匹配,如果匹配上了则返回相应认证后的认证信息
    AuthenticationInfo info = realm.getAuthenticationInfo(token);
    // 如果没有获取到则认证失败
    if (info == null) {
        String msg = "Realm [" + realm + "] was unable to find account data for the " +
                "submitted AuthenticationToken [" + token + "].";
        throw new UnknownAccountException(msg);
    }
    return info;
}

一般来说,自定义实现的Realm会继承自AuthenticatingRealm,所以会执行至:

public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {

    // 先去缓存中查找,如果你使用了缓存,则不用每次都去文件或数据库中查找
    AuthenticationInfo info = getCachedAuthenticationInfo(token);
    if (info == null) {
        //otherwise not cached, perform the lookup:
        // 使用模版方法模式,进行直正的认证信息查找
        info = doGetAuthenticationInfo(token);
        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) {
        // 断言AuthenticationToken与AuthenticationInfo是匹配的,简单点来说就是判断密码是否正确,不正确则抛异常
        // doGetAuthenticationInfo方法主要判断账户是否存在
        assertCredentialsMatch(token, info);
    } else {
        log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
    }

    return info;
}

单一Realm认证时,只需要判断一个Realm认证是否成功即可,但是当存在多个Realm时情况就有点复杂了。因为有可能有些Realm认证成功了,有些Realm又认证失败了,这时到底算是认证成功还是失败呢?所以这时Shiro使用了策略模式,用具体的策略类来处理这个问题。多个Realm认证时的doMultiRealmAuthentication方法如下:

protected AuthenticationInfo doMultiRealmAuthentication(Collection<Realm> realms, AuthenticationToken token) {
    // 首先就得获取认证策略,Shiro实现了三种:
    //1. AllSuccessfulStrategy: 必须所有Realm认证成功了才算是认证成功
    //2. AtLeastOneSuccessfulStrategy: 至少有一个Realm认证成功了就算是认证成功
    //3. FirstSuccessfulStrategy: 第一个Realm认证成功了就算是认证成功
    // 默认实现为AtLeastOneSuccessfulStrategy
    AuthenticationStrategy strategy = getAuthenticationStrategy();

    // 假设我们现在使用的就是AtLeastOneSuccessfulStrategy
    // 返回SimpleAuthenticationInfo,这是一个空认证信息,并不含有principal与credentials
    AuthenticationInfo aggregate = strategy.beforeAllAttempts(realms, token);

    if (log.isTraceEnabled()) {
        log.trace("Iterating through {} realms for PAM authentication", realms.size());
    }

    for (Realm realm : realms) {
        // 直接返回aggregate
        aggregate = strategy.beforeAttempt(realm, token, aggregate);

        if (realm.supports(token)) {

            log.trace("Attempting to authenticate token [{}] using realm [{}]", token, realm);

            AuthenticationInfo info = null;
            Throwable t = null;
            try {
                info = realm.getAuthenticationInfo(token);
            } catch (Throwable throwable) {
                t = throwable;
                if (log.isDebugEnabled()) {
                    String msg = "Realm [" + realm + "] threw an exception during a multi-realm authentication attempt:";
                    log.debug(msg, t);
                }
            }
            //如果认证成功则info不为null,且包含有principal与credentials
            //afterAttempt方法会将info与aggregate合并,也就是将AuthenticationInfo的principal与credentials
            //分别用一集合存储
            aggregate = strategy.afterAttempt(realm, token, info, aggregate, t);

        } else {
            log.debug("Realm [{}] does not support token {}.  Skipping realm.", realm, token);
        }
    }

    // 检测合并后的AuthenticationInfo中是否含用principal,如果有则返回aggregate
    // 没有则抛出异常认证失败,由此可见只要有一个Realm认证成功则算是认证成功
    aggregate = strategy.afterAllAttempts(token, aggregate);

    return aggregate;
}

上面只分析了AtLeastOneSuccessfulStrategy策略,其它两个请自行查看源码。

假设现在认证成功了,接下来执行DefaultSecurityManager.createSubject方法:

protected Subject createSubject(AuthenticationToken token, AuthenticationInfo info, Subject existing) {
    // 创建SubjectContext对象
    SubjectContext context = createSubjectContext();
    // 设置为已认证
    context.setAuthenticated(true);
    // 设置Token
    context.setAuthenticationToken(token);
    // 设置认证通过后的认证信息
    context.setAuthenticationInfo(info);
    if (existing != null) {
        // 设置先前存在的Subject
        context.setSubject(existing);
    }
    return createSubject(context);
}

public Subject createSubject(SubjectContext subjectContext) {
    // 复制SubjectContext,原SubjectContext信息得以保留
    SubjectContext context = copy(subjectContext);

    // 确保SubjectContext与SecurityManager关联
    context = ensureSecurityManager(context);

    // 解析会话,有可能使用Servlet中的Session实现,也可能使用Shiro自己实现的Session
    context = resolveSession(context);

    context = resolvePrincipals(context);

    // 交由DefaultWebSubjectFactory.createSubject重新创建Subject
    Subject subject = doCreateSubject(context);

    // 将Subject中的principal与credentials存储在Session中
    save(subject);

    return subject;
}

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标签:info,Realm,认证,----,token,源码,realm,AuthenticationInfo,Shiro
来源: https://blog.51cto.com/xtayfjpk/2661288