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			96 lines
		
	
	
		
			4.7 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
[[servlet-authentication-basic]]
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= Basic Authentication
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:figures: servlet/authentication/unpwd
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This section provides details on how Spring Security provides support for https://tools.ietf.org/html/rfc7617[Basic HTTP Authentication] for servlet based applications.
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// FIXME: describe authenticationentrypoint, authenticationfailurehandler, authenticationsuccesshandler
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Let's take a look at how HTTP Basic Authentication works within Spring Security.
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First, we see the https://tools.ietf.org/html/rfc7235#section-4.1[WWW-Authenticate] header is sent back to an unauthenticated client.
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.Sending WWW-Authenticate Header
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image::{figures}/basicauthenticationentrypoint.png[]
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The figure builds off our xref:servlet/architecture.adoc#servlet-securityfilterchain[`SecurityFilterChain`] diagram.
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image:{icondir}/number_1.png[] First, a user makes an unauthenticated request to the resource `/private` for which it is not authorized.
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image:{icondir}/number_2.png[] Spring Security's xref:servlet/authorization/authorize-requests.adoc#servlet-authorization-filtersecurityinterceptor[`FilterSecurityInterceptor`] indicates that the unauthenticated request is __Denied__ by throwing an `AccessDeniedException`.
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image:{icondir}/number_3.png[] Since the user is not authenticated, xref:servlet/architecture.adoc#servlet-exceptiontranslationfilter[`ExceptionTranslationFilter`] initiates __Start Authentication__.
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The configured xref:servlet/authentication/architecture.adoc#servlet-authentication-authenticationentrypoint[`AuthenticationEntryPoint`] is an instance of {security-api-url}org/springframework/security/web/authentication/www/BasicAuthenticationEntryPoint.html[`BasicAuthenticationEntryPoint`] which sends a WWW-Authenticate header.
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The `RequestCache` is typically a `NullRequestCache` that does not save the request since the client is capable of replaying the requests it originally requested.
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When a client receives the WWW-Authenticate header it knows it should retry with a username and password.
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Below is the flow for the username and password being processed.
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[[servlet-authentication-basicauthenticationfilter]]
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.Authenticating Username and Password
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image::{figures}/basicauthenticationfilter.png[]
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The figure builds off our xref:servlet/architecture.adoc#servlet-securityfilterchain[`SecurityFilterChain`] diagram.
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image:{icondir}/number_1.png[] When the user submits their username and password, the `BasicAuthenticationFilter` creates a `UsernamePasswordAuthenticationToken` which is a type of xref:servlet/authentication/architecture.adoc#servlet-authentication-authentication[`Authentication`] by extracting the username and password from the `HttpServletRequest`.
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image:{icondir}/number_2.png[] Next, the `UsernamePasswordAuthenticationToken` is passed into the `AuthenticationManager` to be authenticated.
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The details of what `AuthenticationManager` looks like depend on how the xref:servlet/authentication/passwords/index.adoc#servlet-authentication-unpwd-storage[user information is stored].
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image:{icondir}/number_3.png[] If authentication fails, then __Failure__
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* The xref:servlet/authentication/architecture.adoc#servlet-authentication-securitycontextholder[SecurityContextHolder] is cleared out.
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* `RememberMeServices.loginFail` is invoked.
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If remember me is not configured, this is a no-op.
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// FIXME: link to rememberme
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* `AuthenticationEntryPoint` is invoked to trigger the WWW-Authenticate to be sent again.
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image:{icondir}/number_4.png[] If authentication is successful, then __Success__.
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* The xref:servlet/authentication/architecture.adoc#servlet-authentication-authentication[Authentication] is set on the xref:servlet/authentication/architecture.adoc#servlet-authentication-securitycontextholder[SecurityContextHolder].
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* `RememberMeServices.loginSuccess` is invoked.
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If remember me is not configured, this is a no-op.
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// FIXME: link to rememberme
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* The `BasicAuthenticationFilter` invokes `FilterChain.doFilter(request,response)` to continue with the rest of the application logic.
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Spring Security's HTTP Basic Authentication support in is enabled by default.
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However, as soon as any servlet based configuration is provided, HTTP Basic must be explicitly provided.
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A minimal, explicit configuration can be found below:
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.Explicit HTTP Basic Configuration
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====
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[source,java,role="primary"]
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.Java
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----
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@Bean
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public SecurityFilterChain filterChain(HttpSecurity http) {
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	http
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		// ...
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		.httpBasic(withDefaults());
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	return http.build();
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}
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----
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[source,xml,role="secondary"]
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.XML
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----
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<http>
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	<!-- ... -->
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	<http-basic />
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</http>
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----
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[source,kotlin,role="secondary"]
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.Kotlin
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----
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@Bean
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open fun filterChain(http: HttpSecurity): SecurityFilterChain {
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	http {
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		// ...
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		httpBasic { }
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	}
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	return http.build()
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}
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----
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====
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