Shiro认证流程

2019-07-29

上一节中我们分析了Shiro过滤器的原理，Shiro是通过访问资源的URL进行权限管控，分析了其不同的URL对应的过滤器链不同，可自己配置实现过滤器，也可以使用系统默认的过滤器。本节我们分析其认证的过程，FormAuthenticationFilter默认的认证过滤器。

我们上节分析其过滤器的继承关系图，我们再回顾一下。

每一类过滤器都继承自OncePerRequestFilter，我们直接看doFilter()源码

public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
        throws ServletException, IOException {
    String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();
    if ( request.getAttribute(alreadyFilteredAttributeName) != null ) {
        log.trace("Filter '{}' already executed.  Proceeding without invoking this filter.", getName());
        filterChain.doFilter(request, response);
    } else //noinspection deprecation
        if (/* added in 1.2: */ !isEnabled(request, response) ||
            /* retain backwards compatibility: */ shouldNotFilter(request) ) {
        log.debug("Filter '{}' is not enabled for the current request.  Proceeding without invoking this filter.",
                getName());
        filterChain.doFilter(request, response);
    } else {
        // Do invoke this filter...
        log.trace("Filter '{}' not yet executed.  Executing now.", getName());
        request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);

        try {
            doFilterInternal(request, response, filterChain);
        } finally {
            // Once the request has finished, we're done and we don't
            // need to mark as 'already filtered' any more.
            request.removeAttribute(alreadyFilteredAttributeName);
        }
    }
}

我们发现这个方法被final修饰，说明子类不能重写其方法，每一种的过滤器都需要执行这个方法。我们分析下核心方法doFilterInternal()

public void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain)
        throws ServletException, IOException {
    Exception exception = null;
    try {
    	//前置方法,判断是否需要执行执行器链
        boolean continueChain = preHandle(request, response);
        if (log.isTraceEnabled()) {
            log.trace("Invoked preHandle method.  Continuing chain?: [" + continueChain + "]");
        }
        if (continueChain) {
            executeChain(request, response, chain);
        }
        //后置方法
        postHandle(request, response);
        if (log.isTraceEnabled()) {
            log.trace("Successfully invoked postHandle method");
        }
    } catch (Exception e) {
        exception = e;
    } finally {
        cleanup(request, response, exception);
    }
}

其实现类PathMatchingFilter.preHandle()调用

protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
    if (this.appliedPaths == null || this.appliedPaths.isEmpty()) {
        if (log.isTraceEnabled()) {
            log.trace("appliedPaths property is null or empty.  This Filter will passthrough immediately.");
        }
        return true;
    }
    //appliedPaths 就是初始化时候的URL对应的执行器链的MAP
    for (String path : this.appliedPaths.keySet()) {
        //如果请求的地址匹配上appliedPaths中的path则执行
        if (pathsMatch(path, request)) {
            log.trace("Current requestURI matches pattern '{}'.  Determining filter chain execution...", path);
            Object config = this.appliedPaths.get(path);
            return isFilterChainContinued(request, response, path, config);
        }
    }
    return true;
}

核心方法PathMatchingFilter.isFilterChainContinued();

private boolean isFilterChainContinued(ServletRequest request, ServletResponse response,
                                       String path, Object pathConfig) throws Exception {
    if (isEnabled(request, response, path, pathConfig)) { //isEnabled check added in 1.2
        if (log.isTraceEnabled()) {
            log.trace("Filter '{}' is enabled for the current request under path '{}' with config [{}].  " +
                    "Delegating to subclass implementation for 'onPreHandle' check.",
                    new Object[]{getName(), path, pathConfig});
        }
        return onPreHandle(request, response, pathConfig);
    }

    if (log.isTraceEnabled()) {
        log.trace("Filter '{}' is disabled for the current request under path '{}' with config [{}].  " +
                "The next element in the FilterChain will be called immediately.",
                new Object[]{getName(), path, pathConfig});
    } 
    return true;
}

核心方法是onPreHandle(),其子类的实现是AccessControlFilter.onPreHandle()

查看源码

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public boolean onPreHandle(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception {
    return isAccessAllowed(request, response, mappedValue) || onAccessDenied(request, response, mappedValue);
}

AccessControlFilter. onPreHandle()方法中的isAccessAllowed一定是false,因为没有做登陆认证所以就会执行FormAuthenticationFilter的实现onAccessDenied()的实现。做登陆操作。

protected boolean onLoginSuccess(AuthenticationToken token, Subject subject,
                                 ServletRequest request, ServletResponse response) throws Exception {
    //登录成功跳转到登录成功页面，我们配置的successUrl的路径
	issueSuccessRedirect(request, response);
    return false;
}

登录成功直接重定向到成功页面返回false不再执行过滤器链后面的操作

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

调用父类AbstractAuthenticator.authenticate()方法

public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
    if (token == null) {
        throw new IllegalArgumentException("Method argument (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) {
            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);
            if (log.isWarnEnabled())
                log.warn(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;
}

核心方法doAuthenticate(),调用子类的ModularRealmAuthenticator.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);
    }
}

我们继续分析单个Realm的情况

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;
}