InternalServiceAuthenticationFilter.java

package com.ecommerce.identity.infrastructure.security;

import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.List;

@Component
public class InternalServiceAuthenticationFilter extends OncePerRequestFilter {

    private final InternalServiceProperties properties;

    public InternalServiceAuthenticationFilter(InternalServiceProperties properties) {
        this.properties = properties;
    }

    @Override
    protected boolean shouldNotFilter(HttpServletRequest request) {
        return !request.getRequestURI().startsWith("/api/v1/identity/internal/");
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
                                    FilterChain filterChain) throws ServletException, IOException {
        String caller = request.getHeader("X-Internal-Service");
        String token = request.getHeader("X-Internal-Token");
        if (caller != null && token != null && properties.allowedCallers().contains(caller)
                && MessageDigest.isEqual(token.getBytes(StandardCharsets.UTF_8),
                properties.token().getBytes(StandardCharsets.UTF_8))) {
            var authentication = UsernamePasswordAuthenticationToken.authenticated(caller, null,
                    List.of(new SimpleGrantedAuthority("ROLE_INTERNAL_SERVICE")));
            SecurityContextHolder.getContext().setAuthentication(authentication);
        }
        filterChain.doFilter(request, response);
    }
}