jwt_maker.go

package token

import (
	"errors"
	"fmt"
	"time"

	"github.com/golang-jwt/jwt"
)

const minSecretKeySize = 32

//implements Maker interface
type JWTMaker struct {
	secretKey string
}

func NewJWTMaker(secretKey string) (Maker, error) {
	if len(secretKey) < minSecretKeySize {
		return nil, fmt.Errorf("invalid key size: must be at least %d characters", minSecretKeySize)
	}
	return &JWTMaker{secretKey}, nil
}

func (maker *JWTMaker) CreateToken(username string, duration time.Duration) (string, error) {
	payload, err := NewPayload(username, duration)
	if err != nil {
		return "", err
	}
	jwtToken := jwt.NewWithClaims(jwt.SigningMethodHS256, payload)
	return jwtToken.SignedString([]byte(maker.secretKey))
}

func (maker *JWTMaker) VerifyToken(token string) (*Payload, error) {
	keyFunc := func(token *jwt.Token) (interface{}, error) {
		// convert token.Method since we here uses SigningMethodHS256
		_, ok := token.Method.(*jwt.SigningMethodHMAC)
		if !ok {
			// algorithm of token does not match our signing algorithm
			return nil, ErrInvalidToken
		}
		return []byte(maker.secretKey), nil
	}
	jwtToken, err := jwt.ParseWithClaims(token, &Payload{}, keyFunc)
	if err != nil {
		verr, ok := err.(*jwt.ValidationError)
		if ok && errors.Is(verr.Inner, ErrExpireToken) {
			return nil, ErrExpireToken
		}
		return nil, ErrInvalidToken
	}

	payload, ok := jwtToken.Claims.(*Payload)
	if !ok {
		return nil, ErrInvalidToken
	}
	return payload, nil
}