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這篇文章主要介紹Spring Security原理是什么，文中介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們一定要看完！
知彼知己方能百戰百勝，用 Spring Security 來滿足我們的需求最好了解其原理，這樣才能隨意拓展，本篇文章主要記錄 Spring Security 的基本運行流程。
過濾器
Spring Security 基本都是通過過濾器來完成配置的身份認證、權限認證以及登出。
Spring Security 在 Servlet 的過濾鏈（filter chain）中注冊了一個過濾器 FilterChainProxy，它會把請求代理到 Spring Security 自己維護的多個過濾鏈，每個過濾鏈會匹配一些 URL，如果匹配則執行對應的過濾器。過濾鏈是有順序的，一個請求只會執行第一條匹配的過濾鏈。Spring Security 的配置本質上就是新增、刪除、修改過濾器。
默認情況下系統幫我們注入的這 15 個過濾器，分別對應配置不同的需求。接下來我們重點是分析下 UsernamePasswordAuthenticationFilter 這個過濾器，他是用來使用用戶名和密碼登錄認證的過濾器，但是很多情況下我們的登錄不止是簡單的用戶名和密碼，又可能是用到第三方授權登錄，這個時候我們就需要使用自定義過濾器，當然這里不做詳細說明，只是說下自定義過濾器怎么注入。
@Override
protected void configure(HttpSecurity http) throws Exception {
http.addFilterAfter(...);
...
}在開始身份認證流程之前我們需要了解下幾個基本概念
SecurityContextHolder 存儲 SecurityContext 對象。SecurityContextHolder 是一個存儲代理，有三種存儲模式分別是：
SecurityContextHolder 默認使用 MODE_THREADLOCAL 模式，SecurityContext 存儲在當前線程中。調用 SecurityContextHolder 時不需要顯示的參數傳遞，在當前線程中可以直接獲取到 SecurityContextHolder 對象。
SecurityContext context = SecurityContextHolder.getContext(); Authentication authentication = context.getAuthentication();
Authentication 即驗證，表明當前用戶是誰。什么是驗證，比如一組用戶名和密碼就是驗證，當然錯誤的用戶名和密碼也是驗證，只不過 Spring Security 會校驗失敗。
Authentication 接口
public interface Authentication extends Principal, Serializable {
//獲取用戶權限，一般情況下獲取到的是用戶的角色信息
Collection<? extends GrantedAuthority> getAuthorities();
//獲取證明用戶認證的信息，通常情況下獲取到的是密碼等信息，不過登錄成功就會被移除
Object getCredentials();
//獲取用戶的額外信息，比如 IP 地址、經緯度等
Object getDetails();
//獲取用戶身份信息，在未認證的情況下獲取到的是用戶名，在已認證的情況下獲取到的是 UserDetails (暫時理解為，當前應用用戶對象的擴展)
Object getPrincipal();
//獲取當前 Authentication 是否已認證
boolean isAuthenticated();
//設置當前 Authentication 是否已認證
void setAuthenticated(boolean isAuthenticated);
}其實這三者很好區分，AuthenticationManager 主要就是為了完成身份認證流程，ProviderManager 是 AuthenticationManager 接口的具體實現類，ProviderManager 里面有個記錄 AuthenticationProvider 對象的集合屬性 providers，AuthenticationProvider 接口類里有兩個方法
public interface AuthenticationProvider {
//實現具體的身份認證邏輯，認證失敗拋出對應的異常
Authentication authenticate(Authentication authentication)
throws AuthenticationException;
//該認證類是否支持該 Authentication 的認證
boolean supports(Class<?> authentication);
}接下來就是遍歷 ProviderManager 里面的 providers 集合，找到和合適的 AuthenticationProvider 完成身份認證。
4.UserDetailsService UserDetails
在 UserDetailsService 接口中只有一個簡單的方法
public interface UserDetailsService {
//根據用戶名查到對應的 UserDetails 對象
UserDetails loadUserByUsername(String username) throws UsernameNotFoundException;
}對于上面概念有什么不明白的地方，在們在接下來的流程中慢慢分析
在運行到 UsernamePasswordAuthenticationFilter 過濾器的時候首先是進入其父類AbstractAuthenticationProcessingFilter的 doFilter() 方法中
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
throws IOException, ServletException {
...
//首先配對是不是配置的身份認證的URI,是則執行下面的認證,不是則跳過
if (!requiresAuthentication(request, response)) {
chain.doFilter(request, response);
return;
}
...
Authentication authResult;
try {
//關鍵方法, 實現認證邏輯并返回 Authentication, 由其子類 UsernamePasswordAuthenticationFilter 實現, 由下面 5.3 詳解
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) {
//認證失敗調用...由下面 5.1 詳解
unsuccessfulAuthentication(request, response, failed);
return;
}
catch (AuthenticationException failed) {
//認證失敗調用...由下面 5.1 詳解
unsuccessfulAuthentication(request, response, failed);
return;
}
// Authentication success
if (continueChainBeforeSuccessfulAuthentication) {
chain.doFilter(request, response);
}
//認證成功調用...由下面 5.2 詳解
successfulAuthentication(request, response, chain, authResult);
}protected void unsuccessfulAuthentication(HttpServletRequest request,
HttpServletResponse response, AuthenticationException failed)
throws IOException, ServletException {
SecurityContextHolder.clearContext();
...
rememberMeServices.loginFail(request, response);
//該 handler 處理失敗界面跳轉和響應邏輯
failureHandler.onAuthenticationFailure(request, response, failed);
}這里默認配置的失敗處理 handler 是 SimpleUrlAuthenticationFailureHandler，可自定義。
public class SimpleUrlAuthenticationFailureHandler implements
AuthenticationFailureHandler {
...
public void onAuthenticationFailure(HttpServletRequest request,
HttpServletResponse response, AuthenticationException exception)
throws IOException, ServletException {
//沒有配置失敗跳轉的URL則直接響應錯誤
if (defaultFailureUrl == null) {
logger.debug("No failure URL set, sending 401 Unauthorized error");
response.sendError(HttpStatus.UNAUTHORIZED.value(),
HttpStatus.UNAUTHORIZED.getReasonPhrase());
}
else {
//否則
//緩存異常
saveException(request, exception);
//根據配置的異常頁面是重定向還是轉發進行不同方式跳轉
if (forwardToDestination) {
logger.debug("Forwarding to " + defaultFailureUrl);
request.getRequestDispatcher(defaultFailureUrl)
.forward(request, response);
}
else {
logger.debug("Redirecting to " + defaultFailureUrl);
redirectStrategy.sendRedirect(request, response, defaultFailureUrl);
}
}
}
//緩存異常,轉發則保存在request里面,重定向則保存在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);
}
}
}
}這里做下小拓展：用系統的錯誤處理handler，指定認證失敗跳轉的URL，在MVC里面對應的URL方法里面可以通過key從request或session里面拿到錯誤信息，反饋給前端
protected void successfulAuthentication(HttpServletRequest request,
HttpServletResponse response, FilterChain chain, Authentication authResult)
throws IOException, ServletException {
...
//這里要注意很重要，將認證完成返回的 Authentication 保存到線程對應的 `SecurityContext` 中
SecurityContextHolder.getContext().setAuthentication(authResult);
rememberMeServices.loginSuccess(request, response, authResult);
// Fire event
if (this.eventPublisher != null) {
eventPublisher.publishEvent(new InteractiveAuthenticationSuccessEvent(
authResult, this.getClass()));
}
//該 handler 就是為了完成頁面跳轉
successHandler.onAuthenticationSuccess(request, response, authResult);
}這里默認配置的成功處理 handler 是 SavedRequestAwareAuthenticationSuccessHandler，里面的代碼就不做具體展開了，反正是跳轉到指定的認證成功之后的界面，可自定義。
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;
...
//開始身份認證邏輯
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();
//先用前端提交過來的 username 和 password 封裝一個簡易的 AuthenticationToken
UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
username, password);
// Allow subclasses to set the "details" property
setDetails(request, authRequest);
//具體的認證邏輯還是交給 AuthenticationManager 對象的 authenticate(..) 方法完成,接著往下看
return this.getAuthenticationManager().authenticate(authRequest);
}
}由源碼斷點跟蹤得知，最終解析是由 AuthenticationManager 接口實現類 ProviderManager 來完成
public class ProviderManager implements AuthenticationManager, MessageSourceAware,
InitializingBean {
...
private List<AuthenticationProvider> providers = Collections.emptyList();
...
public Authentication authenticate(Authentication authentication)
throws AuthenticationException {
....
//遍歷所有的 AuthenticationProvider, 找到合適的完成身份驗證
for (AuthenticationProvider provider : getProviders()) {
if (!provider.supports(toTest)) {
continue;
}
...
try {
//進行具體的身份驗證邏輯, 這里使用到的是 DaoAuthenticationProvider, 具體邏輯記著往下看
result = provider.authenticate(authentication);
if (result != null) {
copyDetails(authentication, result);
break;
}
}
catch
...
}
...
throw lastException;
}
}DaoAuthenticationProvider 繼承自 AbstractUserDetailsAuthenticationProvider 實現了 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 {
...
// 獲得提交過來的用戶名
String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED"
: authentication.getName();
//根據用戶名從緩存中查找 UserDetails
boolean cacheWasUsed = true;
UserDetails user = this.userCache.getUserFromCache(username);
if (user == null) {
cacheWasUsed = false;
try {
//緩存中沒有則通過 retrieveUser(..) 方法查找 (看下面 DaoAuthenticationProvider 的實現)
user = retrieveUser(username,
(UsernamePasswordAuthenticationToken) authentication);
}
catch
...
}
try {
//比對前的檢查,例如賬戶以一些狀態信息(是否鎖定, 過期...)
preAuthenticationChecks.check(user);
//子類實現比對規則 (看下面 DaoAuthenticationProvider 的實現)
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();
}
//根據最終user的一些信息重新生成具體詳細的 Authentication 對象并返回
return createSuccessAuthentication(principalToReturn, authentication, user);
}
//具體生成還是看子類實現
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;
}
}接下來我們來看下 DaoAuthenticationProvider 里面的三個重要的方法，比對方式、獲取需要比對的 UserDetails 對象以及生產最終返回 Authentication 的方法。
public class DaoAuthenticationProvider extends AbstractUserDetailsAuthenticationProvider {
...
//密碼比對
@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();
//通過 PasswordEncoder 進行密碼比對, 注: 可自定義
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"));
}
}
//通過 UserDetailsService 獲取 UserDetails
protected final UserDetails retrieveUser(String username,
UsernamePasswordAuthenticationToken authentication)
throws AuthenticationException {
prepareTimingAttackProtection();
try {
//通過 UserDetailsService 獲取 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);
}
}
//生成身份認證通過后最終返回的 Authentication, 記錄認證的身份信息
@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);
}
}以上是Spring Security原理是什么的所有內容，感謝各位的閱讀！希望分享的內容對大家有幫助，更多相關知識，歡迎關注億速云行業資訊頻道！
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