Spring Security에 JWT를 적용하는 방법을 알아보자.

JWT 인증 처리 필터

• JwtAuthenticationFilter : 로그인 진행 및 JWT 생성

@Slf4j(topic = "로그인 및 JWT 생성")
public class JwtAuthenticationFilter extends UsernamePasswordAuthenticationFilter {
    private final JwtUtil jwtUtil;

    public JwtAuthenticationFilter(JwtUtil jwtUtil) {
        this.jwtUtil = jwtUtil;
        setFilterProcessesUrl("/api/user/login"); // 로그인 시 이 필터를 거치도록
    }

    @Override
    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        log.info("로그인 시도");
        try {
            LoginRequestDto requestDto = new ObjectMapper().readValue(request.getInputStream(), LoginRequestDto.class);

            return getAuthenticationManager().authenticate(
                    new UsernamePasswordAuthenticationToken(
                            requestDto.getUsername(),
                            requestDto.getPassword(),
                            null
                    )
            ); // 인증 관리자에게 인증 객체 전달
        } catch (IOException e) {
            log.error(e.getMessage());
            throw new RuntimeException(e.getMessage());
        }
    }

    @Override
    protected void successfulAuthentication(HttpServletRequest request, HttpServletResponse response, FilterChain chain, Authentication authResult) throws IOException, ServletException {
        log.info("로그인 성공 및 JWT 생성");
        // Authentication의 Principal에서 UserDeatil 가져오기
        String username = ((UserDetailsImpl) authResult.getPrincipal()).getUsername();
        UserRoleEnum role = ((UserDetailsImpl) authResult.getPrincipal()).getUser().getRole();
        // 해당 정보를 기반으로 JWT 토큰 생성
        String token = jwtUtil.createToken(username, role);
        // JWT 토큰을 쿠키에 추가
        jwtUtil.addJwtToCookie(token, response);
    }

    @Override
    protected void unsuccessfulAuthentication(HttpServletRequest request, HttpServletResponse response, AuthenticationException failed) throws IOException, ServletException {
        log.info("로그인 실패");
        response.setStatus(401); // 인증이 되지 않음
    }
}

JWT 인가 처리 필터

• JwtAuthorizationFilter : API에 전달되는 JWT 유효성 검증 및 인가 처리

@Slf4j(topic = "JWT 검증 및 인가")
public class JwtAuthorizationFilter extends OncePerRequestFilter { // 얘를 상속받으면 HttpServlet객체를 가져올 수 있음

    private final JwtUtil jwtUtil;
    private final UserDetailsServiceImpl userDetailsService;

    public JwtAuthorizationFilter(JwtUtil jwtUtil, UserDetailsServiceImpl userDetailsService) {
        this.jwtUtil = jwtUtil;
        this.userDetailsService = userDetailsService;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest req, HttpServletResponse res, FilterChain filterChain) throws ServletException, IOException {

        String tokenValue = jwtUtil.getTokenFromRequest(req);

        if (StringUtils.hasText(tokenValue)) {
            // JWT 토큰 substring
            tokenValue = jwtUtil.substringToken(tokenValue);
            log.info(tokenValue);
            
            // JWT 토큰 검증
            if (!jwtUtil.validateToken(tokenValue)) {
                log.error("Token Error");
                return;
            }
            
            Claims info = jwtUtil.getUserInfoFromToken(tokenValue);

            try {
                 setAuthentication(info.getSubject());
            } catch (Exception e) {
                log.error(e.getMessage());
                return;
            }
        }

        filterChain.doFilter(req, res);
    }

    // 인증 처리
    public void setAuthentication(String username) {
        SecurityContext context = SecurityContextHolder.createEmptyContext();
        Authentication authentication = createAuthentication(username);
        context.setAuthentication(authentication);

        SecurityContextHolder.setContext(context);
    }

    // 인증 객체 생성
    private Authentication createAuthentication(String username) {
        UserDetails userDetails = userDetailsService.loadUserByUsername(username);
        return new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
    }
}

WebSecurityConfig: 필터 등록

@Configuration
@EnableWebSecurity // Spring Security 지원을 가능하게 함
public class WebSecurityConfig {

    private final JwtUtil jwtUtil;
    private final UserDetailsServiceImpl userDetailsService;
    private final AuthenticationConfiguration authenticationConfiguration; // Authentication Manager 생성을 위해 필요

    public WebSecurityConfig(JwtUtil jwtUtil, UserDetailsServiceImpl userDetailsService, AuthenticationConfiguration authenticationConfiguration) {
        this.jwtUtil = jwtUtil;
        this.userDetailsService = userDetailsService;
        this.authenticationConfiguration = authenticationConfiguration;
    }

    @Bean
    public AuthenticationManager authenticationManager(AuthenticationConfiguration configuration) throws Exception {
        return configuration.getAuthenticationManager();
    }

    @Bean
    public JwtAuthenticationFilter jwtAuthenticationFilter() throws Exception {
        JwtAuthenticationFilter filter = new JwtAuthenticationFilter(jwtUtil);
        filter.setAuthenticationManager(authenticationManager(authenticationConfiguration));
        return filter;
    }

    @Bean
    public JwtAuthorizationFilter jwtAuthorizationFilter() {
        return new JwtAuthorizationFilter(jwtUtil, userDetailsService);
    }

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        // CSRF 설정
        http.csrf((csrf) -> csrf.disable());

        // 기본 설정인 Session 방식은 사용하지 않고 JWT 방식을 사용하기 위한 설정
        http.sessionManagement((sessionManagement) ->
                sessionManagement.sessionCreationPolicy(SessionCreationPolicy.STATELESS)
        );

        http.authorizeHttpRequests((authorizeHttpRequests) ->
                authorizeHttpRequests
                        .requestMatchers(PathRequest.toStaticResources().atCommonLocations()).permitAll() // resources 접근 허용 설정
                        .requestMatchers("/api/user/**").permitAll() // '/api/user/'로 시작하는 요청 모두 접근 허가
                        .anyRequest().authenticated() // 그 외 모든 요청 인증처리
        );

        http.formLogin((formLogin) ->
                formLogin
                        .loginPage("/api/user/login-page").permitAll()
        );

        // 필터 관리
        http.addFilterBefore(jwtAuthorizationFilter(), JwtAuthenticationFilter.class); // 두번째인자 필터 전에 첫번째 인자를 필터로 등록
        http.addFilterBefore(jwtAuthenticationFilter(), UsernamePasswordAuthenticationFilter.class);

        return http.build();
    }
}