Spring Security架构以及源码详析

前言

现在流行的通用授权框架有apache的shiro和Spring家族的Spring Security,在涉及今天的微服务鉴权时,需要利用我们的授权框架搭建自己的鉴权服务,今天总理了Spring Security。

Spring Security 主要实现了Authentication（认证，解决who are you? ） 和 Access Control（访问控制，也就是what are you allowed to do？，也称为Authorization）。Spring Security在架构上将认证与授权分离，并提供了扩展点。

核心对象

主要代码在spring-security-core包下面。要了解Spring Security，需要先关注里面的核心对象。

SecurityContextHolder, SecurityContext 和 Authentication

SecurityContextHolder 是 SecurityContext的存放容器，默认使用ThreadLocal 存储，意味SecurityContext在相同线程中的方法都可用。

SecurityContext主要是存储应用的principal信息，在Spring Security中用Authentication 来表示。

获取principal：

Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal();

if (principal instanceof UserDetails) {
String username = ((UserDetails)principal).getUsername();
} else {
String username = principal.toString();
}

在Spring Security中，可以看一下Authentication定义：

public interface Authentication extends Principal, Serializable {
 Collection<? extends GrantedAuthority> getAuthorities();
 /**
 * 通常是密码
 */
 Object getCredentials();
 /**
 * Stores additional details about the authentication request. These might be an IP
 * address, certificate serial number etc.
 */
 Object getDetails();

 /**
 * 用来标识是否已认证，如果使用用户名和密码登录,通常是用户名
 */
 Object getPrincipal();
 /**
 * 是否已认证
 */
 boolean isAuthenticated();
 void setAuthenticated(boolean isAuthenticated) throws IllegalArgumentException;
}

在实际应用中，通常使用UsernamePasswordAuthenticationToken：

public abstract class AbstractAuthenticationToken implements Authentication,
 CredentialsContainer {
 }
public class UsernamePasswordAuthenticationToken extends AbstractAuthenticationToken {
}

一个常见的认证过程通常是这样的，创建一个UsernamePasswordAuthenticationToken，然后交给authenticationManager认证（后面详细说明），认证通过则通过SecurityContextHolder存放Authentication信息。

 UsernamePasswordAuthenticationToken authenticationToken =
 new UsernamePasswordAuthenticationToken(loginVM.getUsername(), loginVM.getPassword());

Authentication authentication = this.authenticationManager.authenticate(authenticationToken);
SecurityContextHolder.getContext().setAuthentication(authentication);

UserDetails与UserDetailsService

UserDetails 是Spring Security里的一个关键接口，他用来表示一个principal。

public interface UserDetails extends Serializable {
 /**
 * 用户的授权信息，可以理解为角色
 */
 Collection<? extends GrantedAuthority> getAuthorities();
 /**
 * 用户密码
 *
 * @return the password
 */
 String getPassword();
 /**
 * 用户名
 * */
 String getUsername();
 boolean isAccountNonExpired();
 boolean isAccountNonLocked();
 boolean isCredentialsNonExpired();
 boolean isEnabled();
}

UserDetails提供了认证所需的必要信息，在实际使用里，可以自己实现UserDetails，并增加额外的信息，比如email、mobile等信息。

在Authentication中的principal通常是用户名，我们可以通过UserDetailsService来通过principal获取UserDetails：

public interface UserDetailsService {
 UserDetails loadUserByUsername(String username) throws UsernameNotFoundException;
}

GrantedAuthority

在UserDetails里说了，GrantedAuthority可以理解为角色，例如 ROLE_ADMINISTRATOR or ROLE_HR_SUPERVISOR。

小结

• SecurityContextHolder, 用来访问 SecurityContext.
• SecurityContext, 用来存储Authentication .
• Authentication, 代表凭证.
• GrantedAuthority, 代表权限.
• UserDetails, 用户信息.
• UserDetailsService,获取用户信息.

Authentication认证

AuthenticationManager

实现认证主要是通过AuthenticationManager接口，它只包含了一个方法：

public interface AuthenticationManager {
 Authentication authenticate(Authentication authentication)
 throws AuthenticationException;
}

authenticate()方法主要做三件事：

• 如果验证通过，返回Authentication（通常带上authenticated=true）。
• 认证失败抛出AuthenticationException
• 如果无法确定，则返回null

AuthenticationException是运行时异常,它通常由应用程序按通用方式处理，用户代码通常不用特意被捕获和处理这个异常。

AuthenticationManager的默认实现是ProviderManager，它委托一组AuthenticationProvider实例来实现认证。
AuthenticationProvider和AuthenticationManager类似，都包含authenticate，但它有一个额外的方法supports，以允许查询调用方是否支持给定Authentication类型：

public interface AuthenticationProvider {
 Authentication authenticate(Authentication authentication)
 throws AuthenticationException;
 boolean supports(Class<?> authentication);
}

ProviderManager包含一组AuthenticationProvider，执行authenticate时，遍历Providers，然后调用supports，如果支持，则执行遍历当前provider的authenticate方法，如果一个provider认证成功，则break。

public Authentication authenticate(Authentication authentication)
 throws AuthenticationException {
 Class<? extends Authentication> toTest = authentication.getClass();
 AuthenticationException lastException = null;
 Authentication result = null;
 boolean debug = logger.isDebugEnabled();

 for (AuthenticationProvider provider : getProviders()) {
 if (!provider.supports(toTest)) {
 continue;
 }

 if (debug) {
 logger.debug("Authentication attempt using "
  + provider.getClass().getName());
 }

 try {
 result = provider.authenticate(authentication);

 if (result != null) {
  copyDetails(authentication, result);
  break;
 }
 }
 catch (AccountStatusException e) {
 prepareException(e, authentication);
 // SEC-546: Avoid polling additional providers if auth failure is due to
 // invalid account status
 throw e;
 }
 catch (InternalAuthenticationServiceException e) {
 prepareException(e, authentication);
 throw e;
 }
 catch (AuthenticationException e) {
 lastException = e;
 }
 }

 if (result == null && parent != null) {
 // Allow the parent to try.
 try {
 result = parent.authenticate(authentication);
 }
 catch (ProviderNotFoundException e) {
 // ignore as we will throw below if no other exception occurred prior to
 // calling parent and the parent
 // may throw ProviderNotFound even though a provider in the child already
 // handled the request
 }
 catch (AuthenticationException e) {
 lastException = e;
 }
 }

 if (result != null) {
 if (eraseCredentialsAfterAuthentication
  && (result instanceof CredentialsContainer)) {
 // Authentication is complete. Remove credentials and other secret data
 // from authentication
 ((CredentialsContainer) result).eraseCredentials();
 }
 eventPublisher.publishAuthenticationSuccess(result);
 return result;
 }

 // Parent was null, or didn't authenticate (or throw an exception).
 if (lastException == null) {
 lastException = new ProviderNotFoundException(messages.getMessage(
  "ProviderManager.providerNotFound",
  new Object[] { toTest.getName() },
  "No AuthenticationProvider found for {0}"));
 }
 prepareException(lastException, authentication);
 throw lastException;
 }

从上面的代码可以看出， ProviderManager有一个可选parent，如果parent不为空，则调用parent.authenticate(authentication)

AuthenticationProvider

AuthenticationProvider有多种实现，大家最关注的通常是DaoAuthenticationProvider，继承于AbstractUserDetailsAuthenticationProvider，核心是通过UserDetails来实现认证,DaoAuthenticationProvider默认会自动加载，不用手动配。

先来看AbstractUserDetailsAuthenticationProvider，看最核心的authenticate：

public Authentication authenticate(Authentication authentication)
 throws AuthenticationException {
 // 必须是UsernamePasswordAuthenticationToken
 Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,
 messages.getMessage(
  "AbstractUserDetailsAuthenticationProvider.onlySupports",
  "Only UsernamePasswordAuthenticationToken is supported"));

 // 获取用户名
 String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED"
 : authentication.getName();

 boolean cacheWasUsed = true;
 // 从缓存获取
 UserDetails user = this.userCache.getUserFromCache(username);

 if (user == null) {
 cacheWasUsed = false;

 try {
 // retrieveUser 抽象方法，获取用户
 user = retrieveUser(username,
  (UsernamePasswordAuthenticationToken) authentication);
 }
 catch (UsernameNotFoundException notFound) {
 logger.debug("User '" + username + "' not found");

 if (hideUserNotFoundExceptions) {
  throw new BadCredentialsException(messages.getMessage(
  "AbstractUserDetailsAuthenticationProvider.badCredentials",
  "Bad credentials"));
 }
 else {
  throw notFound;
 }
 }

 Assert.notNull(user,
  "retrieveUser returned null - a violation of the interface contract");
 }

 try {
 // 预先检查，DefaultPreAuthenticationChecks，检查用户是否被lock或者账号是否可用
 preAuthenticationChecks.check(user);

 // 抽象方法，自定义检验
 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;
 }
 }

 // 后置检查 DefaultPostAuthenticationChecks，检查isCredentialsNonExpired
 postAuthenticationChecks.check(user);
 if (!cacheWasUsed) {
 this.userCache.putUserInCache(user);
 }

 Object principalToReturn = user;
 if (forcePrincipalAsString) {
 principalToReturn = user.getUsername();
 }

 return createSuccessAuthentication(principalToReturn, authentication, user);
 }

上面的检验主要基于UserDetails实现，其中获取用户和检验逻辑由具体的类去实现，默认实现是DaoAuthenticationProvider，这个类的核心是让开发者提供UserDetailsService来获取UserDetails以及 PasswordEncoder来检验密码是否有效：

private UserDetailsService userDetailsService;
private PasswordEncoder passwordEncoder;

看具体的实现，retrieveUser,直接调用userDetailsService获取用户：

protected final UserDetails retrieveUser(String username,
 UsernamePasswordAuthenticationToken authentication)
 throws AuthenticationException {
 UserDetails loadedUser;

 try {
 loadedUser = this.getUserDetailsService().loadUserByUsername(username);
 }
 catch (UsernameNotFoundException notFound) {
 if (authentication.getCredentials() != null) {
 String presentedPassword = authentication.getCredentials().toString();
 passwordEncoder.isPasswordValid(userNotFoundEncodedPassword,
  presentedPassword, null);
 }
 throw notFound;
 }
 catch (Exception repositoryProblem) {
 throw new InternalAuthenticationServiceException(
  repositoryProblem.getMessage(), repositoryProblem);
 }

 if (loadedUser == null) {
 throw new InternalAuthenticationServiceException(
  "UserDetailsService returned null, which is an interface contract violation");
 }
 return loadedUser;
 }

再来看验证：

protected void additionalAuthenticationChecks(UserDetails userDetails,
 UsernamePasswordAuthenticationToken authentication)
 throws AuthenticationException {
 Object salt = null;

 if (this.saltSource != null) {
 salt = this.saltSource.getSalt(userDetails);
 }

 if (authentication.getCredentials() == null) {
 logger.debug("Authentication failed: no credentials provided");

 throw new BadCredentialsException(messages.getMessage(
  "AbstractUserDetailsAuthenticationProvider.badCredentials",
  "Bad credentials"));
 }
 // 获取用户密码
 String presentedPassword = authentication.getCredentials().toString();
 // 比较passwordEncoder后的密码是否和userdetails的密码一致
 if (!passwordEncoder.isPasswordValid(userDetails.getPassword(),
 presentedPassword, salt)) {
 logger.debug("Authentication failed: password does not match stored value");

 throw new BadCredentialsException(messages.getMessage(
  "AbstractUserDetailsAuthenticationProvider.badCredentials",
  "Bad credentials"));
 }
 }

小结：要自定义认证，使用DaoAuthenticationProvider，只需要为其提供PasswordEncoder和UserDetailsService就可以了。

定制 Authentication Managers

Spring Security提供了一个Builder类AuthenticationManagerBuilder，借助它可以快速实现自定义认证。

看官方源码说明：

SecurityBuilder used to create an AuthenticationManager . Allows for easily building in memory authentication, LDAP authentication, JDBC based authentication, adding UserDetailsService , and adding AuthenticationProvider's.

AuthenticationManagerBuilder可以用来Build一个AuthenticationManager，可以创建基于内存的认证、LDAP认证、 JDBC认证，以及添加UserDetailsService和AuthenticationProvider。

简单使用：

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true)
public class ApplicationSecurity extends WebSecurityConfigurerAdapter {
 public SecurityConfiguration(AuthenticationManagerBuilder authenticationManagerBuilder, UserDetailsService userDetailsService,TokenProvider tokenProvider,CorsFilter corsFilter, SecurityProblemSupport problemSupport) {
 this.authenticationManagerBuilder = authenticationManagerBuilder;
 this.userDetailsService = userDetailsService;
 this.tokenProvider = tokenProvider;
 this.corsFilter = corsFilter;
 this.problemSupport = problemSupport;
 }

 @PostConstruct
 public void init() {
 try {
 authenticationManagerBuilder
 .userDetailsService(userDetailsService)
 .passwordEncoder(passwordEncoder());
 } catch (Exception e) {
 throw new BeanInitializationException("Security configuration failed", e);
 }
 }

 @Override
 protected void configure(HttpSecurity http) throws Exception {
 http
 .addFilterBefore(corsFilter, UsernamePasswordAuthenticationFilter.class)
 .exceptionHandling()
 .authenticationEntryPoint(problemSupport)
 .accessDeniedHandler(problemSupport)
 .and()
 .csrf()
 .disable()
 .headers()
 .frameOptions()
 .disable()
 .and()
 .sessionManagement()
 .sessionCreationPolicy(SessionCreationPolicy.STATELESS)
 .and()
 .authorizeRequests()
 .antMatchers("/api/register").permitAll()
 .antMatchers("/api/activate").permitAll()
 .antMatchers("/api/authenticate").permitAll()
 .antMatchers("/api/account/reset-password/init").permitAll()
 .antMatchers("/api/account/reset-password/finish").permitAll()
 .antMatchers("/api/profile-info").permitAll()
 .antMatchers("/api/**").authenticated()
 .antMatchers("/management/health").permitAll()
 .antMatchers("/management/**").hasAuthority(AuthoritiesConstants.ADMIN)
 .antMatchers("/v2/api-docs/**").permitAll()
 .antMatchers("/swagger-resources/configuration/ui").permitAll()
 .antMatchers("/swagger-ui/index.html").hasAuthority(AuthoritiesConstants.ADMIN)
 .and()
 .apply(securityConfigurerAdapter());
 }
}

授权与访问控制

一旦认证成功，我们可以继续进行授权，授权是通过AccessDecisionManager来实现的。框架有三种实现，默认是AffirmativeBased，通过AccessDecisionVoter决策，有点像ProviderManager委托给AuthenticationProviders来认证。

public void decide(Authentication authentication, Object object,
 Collection<ConfigAttribute> configAttributes) throws AccessDeniedException {
 int deny = 0;
 // 遍历DecisionVoter
 for (AccessDecisionVoter voter : getDecisionVoters()) {
 // 投票
 int result = voter.vote(authentication, object, configAttributes);

 if (logger.isDebugEnabled()) {
 logger.debug("Voter: " + voter + ", returned: " + result);
 }

 switch (result) {
 case AccessDecisionVoter.ACCESS_GRANTED:
 return;

 case AccessDecisionVoter.ACCESS_DENIED:
 deny++;

 break;

 default:
 break;
 }
 }

 // 一票否决
 if (deny > 0) {
 throw new AccessDeniedException(messages.getMessage(
  "AbstractAccessDecisionManager.accessDenied", "Access is denied"));
 }

 // To get this far, every AccessDecisionVoter abstained
 checkAllowIfAllAbstainDecisions();
 }

来看AccessDecisionVoter：

boolean supports(ConfigAttribute attribute);
boolean supports(Class<?> clazz);
int vote(Authentication authentication, S object,
 Collection<ConfigAttribute> attributes);

object是用户要访问的资源，ConfigAttribute则是访问object要满足的条件，通常payload是字符串，比如ROLE_ADMIN 。所以我们来看下RoleVoter的实现，其核心就是从authentication提取出GrantedAuthority，然后和ConfigAttribute比较是否满足条件。

public boolean supports(ConfigAttribute attribute) {
 if ((attribute.getAttribute() != null)
 && attribute.getAttribute().startsWith(getRolePrefix())) {
 return true;
 }
 else {
 return false;
 }
 }

public boolean supports(Class<?> clazz) {
 return true;
 }

public int vote(Authentication authentication, Object object,
 Collection<ConfigAttribute> attributes) {
 if(authentication == null) {
 return ACCESS_DENIED;
 }
 int result = ACCESS_ABSTAIN;

 // 获取GrantedAuthority信息
 Collection<? extends GrantedAuthority> authorities = extractAuthorities(authentication);

 for (ConfigAttribute attribute : attributes) {
 if (this.supports(attribute)) {
 // 默认拒绝访问
 result = ACCESS_DENIED;

 // Attempt to find a matching granted authority
 for (GrantedAuthority authority : authorities) {
  // 判断是否有匹配的 authority
  if (attribute.getAttribute().equals(authority.getAuthority())) {
  // 可访问
  return ACCESS_GRANTED;
  }
 }
 }
 }
 return result;
 }

这里要疑问，ConfigAttribute哪来的？其实就是上面ApplicationSecurity的configure里的。

web security 如何实现

Web层中的Spring Security（用于UI和HTTP后端）基于Servlet Filters，下图显示了单个HTTP请求的处理程序的典型分层。

Spring Security通过FilterChainProxy作为单一的Filter注册到web层，Proxy内部的Filter。

FilterChainProxy相当于一个filter的容器，通过VirtualFilterChain来依次调用各个内部filter

public void doFilter(ServletRequest request, ServletResponse response,
  FilterChain chain) throws IOException, ServletException {
 boolean clearContext = request.getAttribute(FILTER_APPLIED) == null;
 if (clearContext) {
  try {
  request.setAttribute(FILTER_APPLIED, Boolean.TRUE);
  doFilterInternal(request, response, chain);
  }
  finally {
  SecurityContextHolder.clearContext();
  request.removeAttribute(FILTER_APPLIED);
  }
 }
 else {
  doFilterInternal(request, response, chain);
 }
 }

 private void doFilterInternal(ServletRequest request, ServletResponse response,
  FilterChain chain) throws IOException, ServletException {

 FirewalledRequest fwRequest = firewall
  .getFirewalledRequest((HttpServletRequest) request);
 HttpServletResponse fwResponse = firewall
  .getFirewalledResponse((HttpServletResponse) response);

 List<Filter> filters = getFilters(fwRequest);

 if (filters == null || filters.size() == 0) {
  if (logger.isDebugEnabled()) {
  logger.debug(UrlUtils.buildRequestUrl(fwRequest)
   + (filters == null ? " has no matching filters"
    : " has an empty filter list"));
  }

  fwRequest.reset();

  chain.doFilter(fwRequest, fwResponse);

  return;
 }

 VirtualFilterChain vfc = new VirtualFilterChain(fwRequest, chain, filters);
 vfc.doFilter(fwRequest, fwResponse);
 }

 private static class VirtualFilterChain implements FilterChain {
 private final FilterChain originalChain;
 private final List<Filter> additionalFilters;
 private final FirewalledRequest firewalledRequest;
 private final int size;
 private int currentPosition = 0;

 private VirtualFilterChain(FirewalledRequest firewalledRequest,
  FilterChain chain, List<Filter> additionalFilters) {
  this.originalChain = chain;
  this.additionalFilters = additionalFilters;
  this.size = additionalFilters.size();
  this.firewalledRequest = firewalledRequest;
 }

 public void doFilter(ServletRequest request, ServletResponse response)
  throws IOException, ServletException {
  if (currentPosition == size) {
  if (logger.isDebugEnabled()) {
   logger.debug(UrlUtils.buildRequestUrl(firewalledRequest)
    + " reached end of additional filter chain; proceeding with original chain");
  }

  // Deactivate path stripping as we exit the security filter chain
  this.firewalledRequest.reset();

  originalChain.doFilter(request, response);
  }
  else {
  currentPosition++;

  Filter nextFilter = additionalFilters.get(currentPosition - 1);

  if (logger.isDebugEnabled()) {
   logger.debug(UrlUtils.buildRequestUrl(firewalledRequest)
    + " at position " + currentPosition + " of " + size
    + " in additional filter chain; firing Filter: '"
    + nextFilter.getClass().getSimpleName() + "'");
  }

  nextFilter.doFilter(request, response, this);
  }
 }
 }

参考

https://spring.io/guides/topicals/spring-security-architecture/

https://docs.spring.io/spring-security/site/docs/5.0.5.RELEASE/reference/htmlsingle/#overall-architecture

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对我们的支持。