Basic Authentication

This section provides details on how Spring Security provides support for Basic HTTP Authentication for servlet-based applications.

This section describes how HTTP Basic Authentication works within Spring Security. First, we see the WWW-Authenticate header is sent back to an unauthenticated client:

basicauthenticationentrypoint
Figure 1. Sending WWW-Authenticate Header

The preceding figure builds off our SecurityFilterChain diagram.

number 1 First, a user makes an unauthenticated request to the resource /private for which it is not authorized.

number 2 Spring Security’s FilterSecurityInterceptor indicates that the unauthenticated request is Denied by throwing an AccessDeniedException.

number 3 Since the user is not authenticated, ExceptionTranslationFilter initiates Start Authentication. The configured AuthenticationEntryPoint is an instance of BasicAuthenticationEntryPoint, which sends a WWW-Authenticate header. The RequestCache is typically a NullRequestCache that does not save the request since the client is capable of replaying the requests it originally requested.

When a client receives the WWW-Authenticate header, it knows it should retry with a username and password. The following image shows the flow for the username and password being processed:

basicauthenticationfilter
Figure 2. Authenticating Username and Password

The preceding figure builds off our SecurityFilterChain diagram.

number 1 When the user submits their username and password, the BasicAuthenticationFilter creates a UsernamePasswordAuthenticationToken, which is a type of Authentication by extracting the username and password from the HttpServletRequest.

number 2 Next, the UsernamePasswordAuthenticationToken is passed into the AuthenticationManager to be authenticated. The details of what AuthenticationManager looks like depend on how the user information is stored.

number 3 If authentication fails, then Failure.

  1. The SecurityContextHolder is cleared out.

  2. RememberMeServices.loginFail is invoked. If remember me is not configured, this is a no-op. See the RememberMeServices interface in the Javadoc.

  3. AuthenticationEntryPoint is invoked to trigger the WWW-Authenticate to be sent again. See the AuthenticationEntryPoint interface in the Javadoc.

number 4 If authentication is successful, then Success.

  1. The Authentication is set on the SecurityContextHolder.

  2. RememberMeServices.loginSuccess is invoked. If remember me is not configured, this is a no-op. See the RememberMeServices interface in the Javadoc.

  3. The BasicAuthenticationFilter invokes FilterChain.doFilter(request,response) to continue with the rest of the application logic. See the BasicAuthenticationFilter Class in the Javadoc

By default, Spring Security’s HTTP Basic Authentication support is enabled. However, as soon as any servlet based configuration is provided, HTTP Basic must be explicitly provided.

The following example shows a minimal, explicit configuration:

Example 1. Explicit HTTP Basic Configuration
Java
@Bean
public SecurityFilterChain filterChain(HttpSecurity http) {
	http
		// ...
		.httpBasic(withDefaults());
	return http.build();
}
XML
<http>
	<!-- ... -->
	<http-basic />
</http>
Kotlin
@Bean
open fun filterChain(http: HttpSecurity): SecurityFilterChain {
	http {
		// ...
		httpBasic { }
	}
	return http.build()
}