protected void configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
            .anyRequest().authenticated()
            .and()
        .requestCache()
            .requestCache(new NullRequestCache())
            .and()
        .httpBasic();
}

import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.authority.AuthorityUtils;

public class RestAuthenticationProvider implements AuthenticationProvider {

    public Authentication authenticate(Authentication authentication)
            throws AuthenticationException {
        UsernamePasswordAuthenticationToken token = (UsernamePasswordAuthenticationToken) authentication;

        String username = token.getName();
        String password = (String) token.getCredentials();

        // validate making REST call
        boolean success = true;
        // likely your REST call will return the roles for the user
        String[] roles = new String[] { "ROLE_USER" };

        if(!success) {
            throw new BadCredentialsException("Bad credentials");
        }

        return new UsernamePasswordAuthenticationToken(username, null, AuthorityUtils.createAuthorityList(roles));
    }

    public boolean supports(Class<?> authentication) {
        return (UsernamePasswordAuthenticationToken.class
                .isAssignableFrom(authentication));
    }

}

@EnableWebSecurity
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    ...

    @Bean
    public RestAuthenticationProvider restAuthenticationProvider() {
        return new RestAuthenticationProvider();
    }

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth, AuthenticationProvider provider) throws Exception {
        auth
            .authenticationProvider(provider);
    }
}

http.formLogin().failureHandler(authenticationFailureHandler()).permitAll();

private AuthenticationFailureHandler authenticationFailureHandler() {
    return new AuthenticationFailureHandler();
}

public class AuthenticationFailureHandler
    extends SimpleUrlAuthenticationFailureHandler {
}