auth_header_jwt.go

package rest

import (
	"fmt"
	"github.com/golang-jwt/jwt"
	"net/http"
)

func AuthenticationJwt(headerName, secret string, userCondition func(claims map[string]interface{}) error) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		fn := func(w http.ResponseWriter, r *http.Request) {
			if r.Header[headerName] == nil {
				http.Error(w, "Can not find token in header", http.StatusForbidden)
				return
			}

			token, _ := jwt.Parse(r.Header[headerName][0], func(token *jwt.Token) (interface{}, error) {
				if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
					return nil, fmt.Errorf("[ERROR] There was an error in parsing")
				}

				return []byte(secret), nil
			})

			if token == nil {
				http.Error(w, "Invalid token", http.StatusUnauthorized)
				return
			}

			if !token.Valid {
				http.Error(w, "Forbidden", http.StatusForbidden)
				return
			}

			claims, ok := token.Claims.(jwt.MapClaims)

			if !ok {
				w.Write([]byte("couldn't parse claims"))
				w.WriteHeader(http.StatusUnauthorized)
				return
			}

			if err := userCondition(claims); err != nil {
				http.Error(w, err.Error(), http.StatusUnauthorized)
				return
			}

			next.ServeHTTP(w, r)
		}
		return http.HandlerFunc(fn)
	}
}