hmac_example_test.go

package jwt_test

import (
	"fmt"
	"os"
	"time"

	"github.com/golang-jwt/jwt/v4"
)

// For HMAC signing method, the key can be any []byte. It is recommended to generate
// a key using crypto/rand or something equivalent. You need the same key for signing
// and validating.
var hmacSampleSecret []byte

func init() {
	// Load sample key data
	if keyData, e := os.ReadFile("test/hmacTestKey"); e == nil {
		hmacSampleSecret = keyData
	} else {
		panic(e)
	}
}

// Example creating, signing, and encoding a JWT token using the HMAC signing method
func ExampleNew_hmac() {
	// Create a new token object, specifying signing method and the claims
	// you would like it to contain.
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
		"foo": "bar",
		"nbf": time.Date(2015, 10, 10, 12, 0, 0, 0, time.UTC).Unix(),
	})

	// Sign and get the complete encoded token as a string using the secret
	tokenString, err := token.SignedString(hmacSampleSecret)

	fmt.Println(tokenString, err)
	// Output: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJuYmYiOjE0NDQ0Nzg0MDB9.u1riaD1rW97opCoAuRCTy4w58Br-Zk-bh7vLiRIsrpU <nil>
}

// Example parsing and validating a token using the HMAC signing method
func ExampleParse_hmac() {
	// sample token string taken from the New example
	tokenString := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJuYmYiOjE0NDQ0Nzg0MDB9.u1riaD1rW97opCoAuRCTy4w58Br-Zk-bh7vLiRIsrpU"

	// Parse takes the token string and a function for looking up the key. The latter is especially
	// useful if you use multiple keys for your application.  The standard is to use 'kid' in the
	// head of the token to identify which key to use, but the parsed token (head and claims) is provided
	// to the callback, providing flexibility.
	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		// Don't forget to validate the alg is what you expect:
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
		}

		// hmacSampleSecret is a []byte containing your secret, e.g. []byte("my_secret_key")
		return hmacSampleSecret, nil
	})

	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
		fmt.Println(claims["foo"], claims["nbf"])
	} else {
		fmt.Println(err)
	}

	// Output: bar 1.4444784e+09
}