docs: add Spring Security request process analysis (#93)

* 提交SpringSecurity模块
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* Update SpringSecurity请求全过程解析.md
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- [SpringBoot 日志系统](/docs/SpringBoot/SpringBoot-LogSystem.md)
- [SpringBoot ConditionalOnBean](/docs/SpringBoot/SpringBoot-ConditionalOnBean.md)
### SpringSecurity
- [SpringSecurity请求全过程解析](/docs/SpringSecurity/SpringSecurity请求全过程解析.md)
## MyBatis
### 基础支持层

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# Spring Security请求全过程解析
Spring Security是一款基于Spring的安全框架主要包含认证和授权两大安全模块和另外一款流行的安全框架Apache Shiro相比它拥有更为强大的功能。Spring Security也可以轻松的自定义扩展以满足各种需求并且对常见的Web安全攻击提供了防护支持。如果你的Web框架选择的是Spring那么在安全方面Spring Security会是一个不错的选择。
这里我们使用Spring Boot来集成Spring SecuritySpring Boot版本为***2.5.3***Spring Security版本为***5.5.1***。
## 开启Spring Security
使用IDEA创建一个Spring Boot项目然后引入***spring-boot-starter-security***
```java
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-security'
implementation 'org.springframework.boot:spring-boot-starter-web'
implementation 'org.projectlombok:lombok:1.18.8'
annotationProcessor 'org.projectlombok:lombok:1.18.8'
providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
testImplementation 'org.springframework.boot:spring-boot-starter-test'
testImplementation 'org.springframework.security:spring-security-test'
}
```
接下来我们创建一个***HelloController***,对外提供一个<strong><i>/hello</i></strong>服务:
```java
@RestController
public class HelloController {
@GetMapping("hello")
public String hello() {
return "hello world";
}
}
```
这时候我们直接启动项目,访问<strong><i>http://localhost:8080/hello</i></strong>,可以看到页面跳转到一个登陆页面:
![image-20210811091508157](../../images/SpringSecurity/image-20210811091508157.png)
默认的用户名为user密码由Sping Security自动生成回到IDEA的控制台可以找到密码信息
```java
Using generated security password: 4f06ba04-37e9-4bdd-a085-3305260da0d6
```
输入用户名user密码4f06ba04-37e9-4bdd-a085-3305260da0d6后我们便可以成功访问<strong><i>/hello</i></strong>接口。
## 基本原理
Spring Security默认为我们开启了一个简单的安全配置下面让我们来了解其原理。
当Spring Boot项目配置了Spring Security后Spring Security的整个加载过程如下图所示
![image-20210811091633434](../../images/SpringSecurity/image-20210811091633434.png)
而当我们访问<strong><i>http://localhost:8080/hello</i></strong>时,代码的整个执行过程如下图所示:
![image-20210811091659121](../../images/SpringSecurity/image-20210811091659121.png)
如上图所示Spring Security包含了众多的过滤器这些过滤器形成了一条链所有请求都必须通过这些过滤器后才能成功访问到资源。
下面我们通过debug来验证这个过程
首先,通过前面可以知道,当有请求来到时,最先由***DelegatingFilterProxy***负责接收,因此在***DelegatingFilterProxy***的<strong><i>doFilter()</i></strong>的首行打上断点:
![image-20210811091719470](../../images/SpringSecurity/image-20210811091719470.png)
接着***DelegatingFilterProxy***会将请求委派给***FilterChainProxy***进行处理,在***FilterChainProxy***的首行打上断点:
![img](../../images/SpringSecurity/56ac5128-eab7-4b92-912f-ff50bac68a4f.png)
***FilterChainProxy***会在<strong><i>doFilterInternal()</i></strong>中生成一个内部类***VirtualFilterChain***的实例以此来调用Spring Security的整条过滤器链在***VirtualFilterChain***的<strong><i>doFilter()</i></strong>首行打上断点:
![image-20210811091755498](../../images/SpringSecurity/image-20210811091755498.png)
接下来***VirtualFilterChain***会通过***currentPosition***依次调用存在***additionalFilters***中的过滤器,其中比较重要的几个过滤器有:***UsernamePasswordAuthenticationFilter***、***DefaultLoginPageGeneratingFilter***、***AnonymousAuthenticationFilter***、***ExceptionTranslationFilter***、***FilterSecurityInterceptor***,我们依次在这些过滤器的<strong><i>doFilter()</i></strong>的首行打上断点:
![image-20210811091815473](../../images/SpringSecurity/image-20210811091815473.png)
准备完毕后,我们启动项目,然后访问<strong><i>http://localhost:8080/hello</i></strong>,程序首先跳转到***DelegatingFilterProxy***的断点上:
![image-20210811091833065](../../images/SpringSecurity/image-20210811091833065.png)
此时***delegate***还是null的接下来依次执行代码可以看到***delegate***最终被赋值一个***FilterChainProxy***的实例:
![img](../../images/SpringSecurity/f045b025-bd97-4222-8a02-51634be6745b.png)
接下来程序依次跳转到***FilterChainProxy***的<strong><i>doFilter()</i></strong>和***VirtualFilterChain***的<strong><i>doFilter()</i></strong>中:
![img](../../images/SpringSecurity/90d3e369-510f-45cb-982d-241d2eedb55c.png)
![image-20210811092048784](../../images/SpringSecurity/image-20210811092048784.png)
接着程序跳转到***AbstractAuthenticationProcessingFilter******UsernamePasswordAuthenticationFilter***的父类)的<strong><i>doFilter()</i></strong>中,通过<strong><i>requiresAuthentication()</i></strong>判定为false是否是POST请求
![img](../../images/SpringSecurity/2e5440bc-9488-4213-a030-0d25153bb2ea.png)
接着程序跳转到***DefaultLoginPageGeneratingFilter***的<strong><i>doFilter()</i></strong>中,通过<strong><i>isLoginUrlRequest()</i></strong>判定为false请求路径是否是<strong><i>/login</i></strong>
![img](../../images/SpringSecurity/47a7bca4-d858-4cb1-b126-347805b74053.png)
接着程序跳转到***AnonymousAuthenticationFilter***的<strong><i>doFilter()</i></strong>中,由于是首次请求,此时<strong><i>SecurityContextHolder.getContext().getAuthentication()</i></strong>为null因此会生成一个***AnonymousAuthenticationToken***的实例:
![img](../../images/SpringSecurity/6b1aded6-5229-47ba-b192-78a7c2622b8c.png)
接着程序跳转到***ExceptionTranslationFilter***的<strong><i>doFilter()</i></strong>中,***ExceptionTranslationFilter***负责处理***FilterSecurityInterceptor***抛出的异常我们在catch代码块的首行打上断点
**![img](../../images/SpringSecurity/8efa0b1c-2b32-4d5b-9655-985374326e10.png)**
接着程序跳转到***FilterSecurityInterceptor***的<strong><i>doFilter()</i></strong>中,依次执行代码后程序停留在其父类(***AbstractSecurityInterceptor***)的<strong><i>attemptAuthorization()</i></strong>中:
![img](../../images/SpringSecurity/d6e99143-6207-43a5-8d04-f0c81baa11b4.png)
***accessDecisionManager***是***AccessDecisionManager***(访问决策器)的实例,***AccessDecisionManager***主要有3个实现类***AffirmativeBased***(一票通过)**ConsensusBased**(少数服从多数)、UnanimousBased(一票否决),此时***AccessDecisionManager***的的实现类是***AffirmativeBased***,我们可以看到程序进入***AffirmativeBased***的<strong><i>decide()</i></strong>中:
![img](../../images/SpringSecurity/6724647c-34ee-4a57-8cfa-b46f57400d14.png)
从上图可以看出,决策的关键在<strong><i>voter.vote(authentication, object, configAttributes)</i></strong>这句代码上,通过跟踪调试,程序最终进入***AuthenticationTrustResolverImpl***的<strong><i>isAnonymous()</i></strong>中:
![img](../../images/SpringSecurity/4beaa02f-a93d-4d95-9ad1-0d7213cb0e46.png)
<strong><i>isAssignableFrom()</i></strong>判断前者是否是后者的父类,而***anonymousClass***被固定为***AnonymousAuthenticationToken.class***,参数***authentication***由前面***AnonymousAuthenticationFilter***可以知道是***AnonymousAuthenticationToken***的实例,因此<strong><i>isAnonymous()</i></strong>返回true***FilterSecurityInterceptor***抛出***AccessDeniedException***异常,程序返回***ExceptionTranslationFilter***的catch块中
![img](../../images/SpringSecurity/8e1ac9db-5987-484d-abf4-4c6535c60cc6.png)
接着程序会依次进入***DelegatingAuthenticationEntryPoint***、***LoginUrlAuthenticationEntryPoint***中,最后由***LoginUrlAuthenticationEntryPoint***的<strong><i>commence()</i></strong>决定重定向到<strong><i>/login</i></strong>
![img](../../images/SpringSecurity/1b03bdd4-6773-4b39-a664-fdf65d104403.png)
后续对<strong><i>/login</i></strong>的请求同样会经过之前的执行流程,在***DefaultLoginPageGeneratingFilter***的<strong><i>doFilter()</i></strong>中,通过<strong><i>isLoginUrlRequest()</i></strong>判定为true请求路径是否是<strong><i>/login</i></strong>,直接返回***login.html***,也就是我们开头看到的登录页面。
当我们输入用户名和密码,点击***Sign in***,程序来到***AbstractAuthenticationProcessingFilter***的<strong><i>doFilter()</i></strong>中,通过<strong><i>requiresAuthentication()</i></strong>判定为true是否是POST请求,因此交给其子类***UsernamePasswordAuthenticationFilter***进行处理,***UsernamePasswordAuthenticationFilter***会将用户名和密码封装成一个***UsernamePasswordAuthenticationToken***的实例并进行校验,当校验通过后会将请求重定向到我们一开始请求的路径:<strong><i>/hello</i></strong>
后续对<strong><i>/hello</i></strong>的请求经过过滤器链时就可以一路开绿灯直到最终交由***HelloController***返回"Hello World"。
## 参考
1. [Spring Security Reference](https://docs.spring.io/spring-security/site/docs/current/reference/html5/)
2. [Spring Boot中开启Spring Security](https://mrbird.cc/Spring-Boot&Spring-Security.html)

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