JWT go example signing methods

main.go

import (
        "fmt"
        "io/ioutil"
        "time"

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

func signingWithHMAC() {

        sampleSecret := []byte("your-256-bit-secret")

        newToken := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
                "foo": "bar",
                "nbf": time.Now().Unix(),
        })

        tokenString, err := newToken.SignedString(sampleSecret)
        if err != nil {
                fmt.Errorf("%v", err)
        }

        fmt.Println("HS token:", tokenString)

        token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
                if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
                        return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
                }

                return sampleSecret, nil
        })

        if err != nil {
                fmt.Printf("%v", err)
        }

        claims, ok := token.Claims.(jwt.MapClaims)
        if ok && token.Valid {
                fmt.Println(claims)
        }

}

func signingWithRSA() {
        privateKeyPem, _ := ioutil.ReadFile("sample_key")
        publicKeyPem, _ := ioutil.ReadFile("sample_key.pub")

        privateKey, err := jwt.ParseRSAPrivateKeyFromPEM(privateKeyPem)
        if err != nil {
                fmt.Errorf("%v", err)
        }

        publicKey, err := jwt.ParseRSAPublicKeyFromPEM(publicKeyPem)
        if err != nil {
                fmt.Errorf("%v", err)
        }

        newToken := jwt.NewWithClaims(jwt.SigningMethodRS256, jwt.MapClaims{
                "foo": "bar",
                "nbf": time.Now().Unix(),
        })

        tokenString, err := newToken.SignedString(privateKey)
        if err != nil {
                fmt.Errorf("%v", err)
        }

        fmt.Println("RSA token:", tokenString)

        token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
                if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
                        return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
                }

                return publicKey, nil
        })

        claims, ok := token.Claims.(jwt.MapClaims)
        if ok && token.Valid {
                fmt.Println(claims)
        }
}

func main() {
        signingWithHMAC()
        signingWithRSA()
}