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，谢谢大家对的支持。