jwt_maker.go

package token

import (
	"fmt"
	"time"

	"github.com/dgrijalva/jwt-go"
)

const minSecretKeySize = 32

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) {
	jwtToken, err := jwt.ParseWithClaims(token, &Payload{}, func(token *jwt.Token) (interface{}, error) {
		// Verify the signing algorithm
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, ErrInvalidToken
		}

		// Return the secret key
		return []byte(maker.secretKey), nil
	})
	if err != nil {
		return nil, err
	}

	// Verify the token is valid
	payload, ok := jwtToken.Claims.(*Payload)
	if !ok {
		return nil, ErrInvalidToken
	}

	return payload, nil
}