source: phonelux-backend/src/main/java/finki/it/phoneluxbackend/security/CustomAuthorizationFilter.java@ f25d07e

package finki.it.phoneluxbackend.security;

import com.auth0.jwt.JWT;
import com.auth0.jwt.JWTVerifier;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.interfaces.DecodedJWT;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.*;

import static org.springframework.http.HttpHeaders.AUTHORIZATION;
import static org.springframework.http.HttpStatus.FORBIDDEN;
import static org.springframework.http.MediaType.APPLICATION_JSON_VALUE;

public class CustomAuthorizationFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        if(request.getServletPath().equals("/login")){
            filterChain.doFilter(request,response); // not doing anything, just passing the request to the next filter in the filter chain
        }
        else{
            String authorizationHeader = request.getHeader(AUTHORIZATION);
            if(authorizationHeader != null && authorizationHeader.startsWith("Bearer "))
            {
                try {
                    String token = authorizationHeader.substring("Bearer ".length());
                    Algorithm algorithm = Algorithm.HMAC256("secret".getBytes());
                    JWTVerifier verifier = JWT.require(algorithm).build();
                    DecodedJWT decodedJWT = verifier.verify(token);
                    String email = decodedJWT.getSubject();
                    String [] roles = decodedJWT.getClaim("role").asArray(String.class);
                    Collection<SimpleGrantedAuthority> authorities = new ArrayList<>();
                    Arrays.stream(roles).forEach(role -> {
                        authorities.add(new SimpleGrantedAuthority(role));
                    });
                    UsernamePasswordAuthenticationToken authenticationToken =
                            new UsernamePasswordAuthenticationToken(email,null,authorities);

                    SecurityContextHolder.getContext().setAuthentication(authenticationToken);
                    filterChain.doFilter(request,response);

                }catch(Exception exception){
                    response.setHeader("error", exception.getMessage());
                    response.setStatus(FORBIDDEN.value());
                    Map<String,String> error = new HashMap<>();
                    error.put("error_message", exception.getMessage());
                    response.setContentType(APPLICATION_JSON_VALUE);
                    new ObjectMapper().writeValue(response.getOutputStream(),error);
                }
            }
            else{
                filterChain.doFilter(request,response);
            }

        }
    }
}