前提介绍
本篇文章给大家带来的内容是关于Spring Security原理的介绍，对实际业务开发会有一定的参考价值，希望对你有所帮助。所谓知彼知己方能百战百胜，用Spring Security来满足我们的需求最好了解其原理，这样才能随意拓展，本篇文章主要记录 Spring Security 的基本运行流程。
过滤器的原理机制
Spring Security基本都是通过过滤器来完成配置的身份认证、权限认证以及登出。
Spring Security在Servlet的过滤链（filter chain）中注册了一个过滤器 FilterChainProxy，它会把请求代理到Spring Security自己维护的多个过滤链，每个过滤链会匹配一些URL，如果匹配则执行对应的过滤器，过滤链是有顺序的，一个请求只会执行第一条匹配的过滤链。
Spring Security 的配置本质上就是新增、删除、修改过滤器。
默认情况下系统帮我们注入的这15个过滤器，分别对应配置不同的需求。
认证控制过滤器UsernamePasswordAuthenticationFilter
接下来我们重点是分析下 UsernamePasswordAuthenticationFilter 这个过滤器，他是用来使用用户名和密码登录认证的过滤器，但是很多情况下我们的登录不止是简单的用户名和密码，又可能是用到第三方授权登录，这个时候我们就需要使用自定义过滤器，当然这里不做详细说明，只是说下自定义过滤器怎么注入。
@Override
protected void configure(HttpSecurity http) throws Exception {
http.addFilterAfter(...);
...
}身份认证流程
在开始身份认证流程之前我们需要了解下几个基本概念：
SecurityContextHolder
SecurityContextHolder存储SecurityContext对象。SecurityContextHolder是一个存储代理，有三种存储模式分别是：
MODE_THREADLOCAL：SecurityContext 存储在线程中。
MODE_INHERITABLETHREADLOCAL：SecurityContext 存储在线程中，但子线程可以获取到父线程中的 SecurityContext。
MODE_GLOBAL：SecurityContext 在所有线程中都相同。
SecurityContextHolder默认使用MODE_THREADLOCAL模式，SecurityContext 存储在当前线程中。
调用SecurityContextHolder时不需要显示的参数传递，在当前线程中可以直接获取到SecurityContextHolder对象。
SecurityContext context = SecurityContextHolder.getContext(); Authentication authentication = context.getAuthentication();
Authentication
Authentication即验证，表明当前用户是谁。什么是验证，比如，一组用户名和密码就是验证，当然错误的用户名和密码也是验证，只不过 Spring Security会校验失败。
Authentication接口
public interface Authentication extends Principal, Serializable {
Collection getAuthorities();
Object getCredentials();
Object getDetails();
Object getPrincipal();
boolean isAuthenticated();
void setAuthenticated(boolean isAuthenticated);
}getAuthorities()：获取用户权限，一般情况下获取到的是用户的角色信息。
getCredentials()：获取证明用户认证的信息，通常情况下获取到的是密码等信息，不过登录成功就会被移除。
getDetails()：获取用户的额外信息，比如 IP 地址、经纬度等
getPrincipal()：获取用户身份信息，在未认证的情况下获取到的是用户名，在已认证的情况下获取到的是 UserDetails (暂时理解为，当前应用用户对象的扩展)
isAuthenticated()：获取当前 Authentication 是否已认证
setAuthenticated：设置当前 Authentication 是否已认证
AuthenticationManager ProviderManager AuthenticationProvider
其实这三者很好区分：
AuthenticationManager：主要就是为了完成身份认证流程。
ProviderManager：AuthenticationManager 接口的具体实现类
ProviderManager 里面有个记录AuthenticationProvider对象的集合属性 providers
AuthenticationProvider接口类里有两个方法
public interface AuthenticationProvider {
//实现具体的身份认证逻辑，认证失败抛出对应的异常
Authentication authenticate(Authentication authentication)
throws AuthenticationException;
//该认证类是否支持该 Authentication 的认证
boolean supports(Class authentication);
}接下来就是遍历 ProviderManager 里面的 providers 集合，找到和合适的 AuthenticationProvider 完成身份认证。
UserDetailsService UserDetails
在 UserDetailsService 接口中只有一个简单的方法
public interface UserDetailsService {
//根据用户名查到对应的 UserDetails 对象
UserDetails loadUserByUsername(String username) throws UsernameNotFoundException;
}执行认证流程
慢慢分析在运行到 UsernamePasswordAuthenticationFilter过滤器的时候。
首先是进入其父类AbstractAuthenticationProcessingFilter的doFilter()方法中
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)throws IOException, ServletException {
...
//首先配对是不是配置的身份认证的URI,是则执行下面的认证,不是则跳过
if (!requiresAuthentication(request, response)) {
chain.doFilter(request, response);
return;
}
...
Authentication authResult;
try {
//关键方法, 实现认证逻辑并返回 Authentication, 由其子类 UsernamePasswordAuthenticationFilter 实现
authResult = attemptAuthentication(request, response);
if (authResult == null) {
// return immediately as subclass has indicated that it hasn't completed
// authentication
return;
}
sessionStrategy.onAuthentication(authResult, request, response);
}
catch (InternalAuthenticationServiceException failed) {
//认证失败调用
unsuccessfulAuthentication(request, response, failed);
return;
}catch (AuthenticationException failed) {
//认证失败调用
unsuccessfulAuthentication(request, response, failed);
return;
}
// Authentication success
if (continueChainBeforeSuccessfulAuthentication) {
chain.doFilter(request, response);
}
//认证成功调
successfulAuthentication(request, response, chain, authResult);
}认证失败处理逻辑
protected void unsuccessfulAuthentication(HttpServletRequest request,HttpServletResponse response, AuthenticationException failed)throws IOException, ServletException {
SecurityContextHolder.clearContext();
...
rememberMeServices.loginFail(request, response);
//该 handler 处理失败界面跳转和响应逻辑
failureHandler.onAuthenticationFailure(request, response, failed);
}默认配置的失败处理 handler是 SimpleUrlAuthenticationFailureHandler，可自定义。
public class SimpleUrlAuthenticationFailureHandler implements
AuthenticationFailureHandler {
...
public void onAuthenticationFailure(HttpServletRequest request,
HttpServletResponse response, AuthenticationException exception)throws IOException, ServletException {
//没有配置失败跳转的URL则直接响应错误
if (defaultFailureUrl == null) {
logger.debug("No failure URL set, sending 401 Unauthorized error");
response.sendError(HttpStatus.UNAUTHORIZED.value(),
HttpStatus.UNAUTHORIZED.getReasonPhrase());
}else {
//否则
//缓存异常
saveException(request, exception);
//根据配置的异常页面是重定向还是转发进行不同方式跳转
if (forwardToDestination) {
logger.debug("Forwarding to " + defaultFailureUrl);
request.getRequestDispatcher(defaultFailureUrl)
.forward(request, response);
}else {
logger.debug("Redirecting to " + defaultFailureUrl);
redirectStrategy.sendRedirect(request, response, defaultFailureUrl);
}
}
}
//缓存异常,转发则保存在request里面,重定向则保存在session里面
protected final void saveException(HttpServletRequest request,
AuthenticationException exception) {
if (forwardToDestination) {
request.setAttribute(WebAttributes.AUTHENTICATION_EXCEPTION, exception);
}else {
HttpSession session = request.getSession(false);
if (session != null || allowSessionCreation) {
request.getSession().setAttribute(WebAttributes.AUTHENTICATION_EXCEPTION,exception);
}
}
}
}这里做下小拓展：用系统的错误处理handler，指定认证失败跳转的URL，在MVC里面对应的URL方法里面可以通过key从request或session里面拿到错误信息，反馈给前端。
认证成功处理逻辑
protected void successfulAuthentication(HttpServletRequest request,
HttpServletResponse response, FilterChain chain, Authentication authResult)
throws IOException, ServletException {
...
//这里要注意很重要，将认证完成返回的Authentication保存到线程对应的 `SecurityContext` 中
SecurityContextHolder.getContext().setAuthentication(authResult);
rememberMeServices.loginSuccess(request, response, authResult);
// Fire event
if (this.eventPublisher != null) {
eventPublisher.publishEvent(new InteractiveAuthenticationSuccessEvent(authResult, this.getClass()));
}
//该 handler 就是为了完成页面跳转
successHandler.onAuthenticationSuccess(request, response, authResult);
}这里默认配置的成功处理 handler 是 SavedRequestAwareAuthenticationSuccessHandler，里面的代码就不做具体展开了，反正是跳转到指定的认证成功之后的界面，可自定义。
身份认证详情
public class UsernamePasswordAuthenticationFilter extends
AbstractAuthenticationProcessingFilter {
...
public static final String SPRING_SECURITY_FORM_USERNAME_KEY = "username";
public static final String SPRING_SECURITY_FORM_PASSWORD_KEY = "password";
private String usernameParameter = SPRING_SECURITY_FORM_USERNAME_KEY;
private String passwordParameter = SPRING_SECURITY_FORM_PASSWORD_KEY;
private boolean postOnly = true;
...
//开始身份认证逻辑
public Authentication attemptAuthentication(HttpServletRequest request,
HttpServletResponse response) throws AuthenticationException {
if (postOnly && !request.getMethod().equals("POST")) {
throw new AuthenticationServiceException(
"Authentication method not supported: " + request.getMethod());
}
String username = obtainUsername(request);
String password = obtainPassword(request);
if (username == null) {
username = "";
}
if (password == null) {
password = "";
}
username = username.trim();
//先用前端提交过来的 username 和 password 封装一个简易的 AuthenticationToken
UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
username, password);
// Allow subclasses to set the "details" property
setDetails(request, authRequest);
//具体的认证逻辑还是交给 AuthenticationManager 对象的 authenticate(..) 方法完成,接着往下看
return this.getAuthenticationManager().authenticate(authRequest);
}
}由源码断点跟踪得知，最终解析是由 AuthenticationManager 接口实现类 ProviderManager 来完成
public class ProviderManager implements AuthenticationManager, MessageSourceAware,InitializingBean {
...
private List providers = Collections.emptyList();
...
public Authentication authenticate(Authentication authentication)
throws AuthenticationException {
....
//遍历所有的 AuthenticationProvider, 找到合适的完成身份验证
for (AuthenticationProvider provider : getProviders()) {
if (!provider.supports(toTest)) {
continue;
}
...
try {
//进行具体的身份验证逻辑, 这里使用到的是 DaoAuthenticationProvider, 具体逻辑记着往下看
result = provider.authenticate(authentication);
if (result != null) {
copyDetails(authentication, result);
break;
}
}catch
...
}
...
throw lastException;
}
}DaoAuthenticationProvider
DaoAuthenticationProvider继承自 AbstractUserDetailsAuthenticationProvider实现AuthenticationProvider接口
public abstract class AbstractUserDetailsAuthenticationProvider implements
AuthenticationProvider, InitializingBean, MessageSourceAware {
...
private UserDetailsChecker preAuthenticationChecks = new DefaultPreAuthenticationChecks();
private UserDetailsChecker postAuthenticationChecks = new DefaultPostAuthenticationChecks();
...
public Authentication authenticate(Authentication authentication)
throws AuthenticationException {
...
// 获得提交过来的用户名
String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED" : authentication.getName();
//根据用户名从缓存中查找 UserDetails
boolean cacheWasUsed = true;
UserDetails user = this.userCache.getUserFromCache(username);
if (user == null) {
cacheWasUsed = false;
try {
//缓存中没有则通过 retrieveUser(..) 方法查找 (看下面 DaoAuthenticationProvider 的实现)
user = retrieveUser(username,
(UsernamePasswordAuthenticationToken) authentication);
}catch
...
}
try {
//比对前的检查,例如账户以一些状态信息(是否锁定, 过期...)
preAuthenticationChecks.check(user);
//子类实现比对规则 (看下面 DaoAuthenticationProvider 的实现)
additionalAuthenticationChecks(user,
(UsernamePasswordAuthenticationToken) authentication);
}catch (AuthenticationException exception) {
if (cacheWasUsed) {
// There was a problem, so try again after checking
// we're using latest data (i.e. not from the cache)
cacheWasUsed = false;
user = retrieveUser(username,
(UsernamePasswordAuthenticationToken) authentication);
preAuthenticationChecks.check(user);
additionalAuthenticationChecks(user,
(UsernamePasswordAuthenticationToken) authentication);
}else {
throw exception;
}
}
postAuthenticationChecks.check(user);
if (!cacheWasUsed) {
this.userCache.putUserInCache(user);
}
Object principalToReturn = user;
if (forcePrincipalAsString) {
principalToReturn = user.getUsername();
}
//根据最终user的一些信息重新生成具体详细的 Authentication 对象并返回
return createSuccessAuthentication(principalToReturn, authentication, user);
}
//具体生成还是看子类实现
protected Authentication createSuccessAuthentication(Object principal,Authentication authentication, UserDetails user) {
// Ensure we return the original credentials the user supplied,
// so subsequent attempts are successful even with encoded passwords.
// Also ensure we return the original getDetails(), so that future
// authentication events after cache expiry contain the details
UsernamePasswordAuthenticationToken result = new UsernamePasswordAuthenticationToken(
principal, authentication.getCredentials(),
authoritiesMapper.mapAuthorities(user.getAuthorities()));
result.setDetails(authentication.getDetails());
return result;
}
}接下来我们来看下 DaoAuthenticationProvider 里面的三个重要的方法，比对方式、获取需要比对的 UserDetails 对象以及生产最终返回 Authentication 的方法。
public class DaoAuthenticationProvider extends AbstractUserDetailsAuthenticationProvider {
...
//密码比对
@SuppressWarnings("deprecation")
protected void additionalAuthenticationChecks(UserDetails userDetails,UsernamePasswordAuthenticationToken authentication)
throws AuthenticationException {
if (authentication.getCredentials() == null) {
logger.debug("Authentication failed: no credentials provided");
throw new BadCredentialsException(messages.getMessage(
"AbstractUserDetailsAuthenticationProvider.badCredentials",
"Bad credentials"));
}
String presentedPassword = authentication.getCredentials().toString();
//通过 PasswordEncoder 进行密码比对, 注: 可自定义
if (!passwordEncoder.matches(presentedPassword, userDetails.getPassword())) {
logger.debug("Authentication failed: password does not match stored value");
throw new BadCredentialsException(messages.getMessage(
"AbstractUserDetailsAuthenticationProvider.badCredentials",
"Bad credentials"));
}
}
//通过 UserDetailsService 获取 UserDetails
protected final UserDetails retrieveUser(String username,
UsernamePasswordAuthenticationToken authentication)
throws AuthenticationException {
prepareTimingAttackProtection();
try {
//通过 UserDetailsService 获取 UserDetails
UserDetails loadedUser = this.getUserDetailsService().loadUserByUsername(username);
if (loadedUser == null) {
throw new InternalAuthenticationServiceException(
"UserDetailsService returned null, which is an interface contract violation");
}
return loadedUser;
}
catch (UsernameNotFoundException ex) {
mitigateAgainstTimingAttack(authentication);
throw ex;
}
catch (InternalAuthenticationServiceException ex) {
throw ex;
}
catch (Exception ex) {
throw new InternalAuthenticationServiceException(ex.getMessage(), ex);
}
}
//生成身份认证通过后最终返回的 Authentication, 记录认证的身份信息
@Override
protected Authentication createSuccessAuthentication(Object principal,Authentication authentication, UserDetails user) {
boolean upgradeEncoding = this.userDetailsPasswordService != null && this.passwordEncoder.upgradeEncoding(user.getPassword());
if (upgradeEncoding) {
String presentedPassword = authentication.getCredentials().toString();
String newPassword = this.passwordEncoder.encode(presentedPassword);
user = this.userDetailsPasswordService.updatePassword(user, newPassword);
}
return super.createSuccessAuthentication(principal, authentication, user);
}
}
