Go and JWT - Simple authentication
I'm currently making an API (with go) and I'm working on the session part. After research about what to use for session, I found JWT really interesting.
However I'm not really sure to understand how to use it after some tutorials. So this is my idea:
func main() {
router := mux.NewRouter().StrictSlash(true)
router.HandleFunc("/login", login)
router.HandleFunc("/logout", logout)
router.HandleFunc("/register", register)
http.ListenAndServe(":8080", router)
}
After those requests handled, I create the differents functions.
func login(w http.ResponseWriter, r *http.Request) {
/*
Here I just have to search in my database (SQL, I know how to do it). If the user is registered, I create a token and give it to him, but how can I do it?
*/
}
func logout(w http.ResponseWriter, r *http.Request) {
/*
I get a token and stop/delete it?
*/
}
func register(w http.ResponseWriter, r *http.Request) {
/*
I search if the user isn't register and then, if it isn't, I create a user in the database (I know how to do it). I connect him but again, how to make a new token?
*/
}
Lot of tutorials on the web seems really hard but I just want something simple. I just want an handle package (code above) which work with a service package to have something like an engine token authentication.
A second point I'm not sure to understand is the saving of the token. If a user connects himself, then what would be best? Each time the user runs their app, the app connects itself and get a new token from saved information (user/password) or the app just save the token forever? And what about the server, is the token managed and saved automatically with JWT or do I have to put it in my sql database?
Thank for your help !
EDIT 1
Thank you ! So after I read your answer, I encapsulated my code (token.go) like it
package services
import (
"fmt"
"github.com/dgrijalva/jwt-go"
"time"
"../models"
)
var tokenEncodeString string = "something"
func createToken(user models.User) (string, error) {
// create the token
token := jwt.New(jwt.SigningMethodHS256)
// set some claims
token.Claims["username"] = user.Username;
token.Claims["password"] = user.Password;
token.Claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
//Sign and get the complete encoded token as string
return (token.SignedString(tokenEncodeString))
}
func parseToken(unparsedToken string) (bool, string) {
token, err := jwt.Parse(unparsedToken, func(token *jwt.Token) (interface{}, error) {
// Don't forget to validate the alg is what you expect:
if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
}
return myLookupKey(token.Header["kid"]), nil
})
if err == nil && token.Valid {
return true, unparsedToken
} else {
return false, ""
}
}
However, I got the following error: "token.go: undefined: myLookupKey" I looked on internet and I found an encapsulated function which have this prototype:
func ExampleParse(myToken string, myLookupKey func(interface{}) (interface{}, error)) {
/* same code in my func parseToken() */
}
So what are the difference between my function and this one? How can I use this one?
Thanks !
Answer
To start, you need to import a JWT library in Golang (go get github.com/dgrijalva/jwt-go). You can find that library documentation in below link.
https://github.com/dgrijalva/jwt-go
Firstly, you need to create a token
// Create the token
token := jwt.New(jwt.SigningMethodHS256)
// Set some claims
token.Claims["foo"] = "bar"
token.Claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
// Sign and get the complete encoded token as a string
tokenString, err := token.SignedString(mySigningKey)
Secondly, parse that token
token, err := jwt.Parse(myToken, func(token *jwt.Token) (interface{}, error) {
// Don't forget to validate the alg is what you expect:
if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
}
return myLookupKey(token.Header["kid"]), nil
})
if err == nil && token.Valid {
deliverGoodness("!")
} else {
deliverUtterRejection(":(")
}
Also, there are some examples for use JWT in GOlang like this https://github.com/slok/go-jwt-example
EDIT-1
package main
import (
"fmt"
"time"
"github.com/dgrijalva/jwt-go"
)
const (
mySigningKey = "WOW,MuchShibe,ToDogge"
)
func main() {
createdToken, err := ExampleNew([]byte(mySigningKey))
if err != nil {
fmt.Println("Creating token failed")
}
ExampleParse(createdToken, mySigningKey)
}
func ExampleNew(mySigningKey []byte) (string, error) {
// Create the token
token := jwt.New(jwt.SigningMethodHS256)
// Set some claims
token.Claims["foo"] = "bar"
token.Claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
// Sign and get the complete encoded token as a string
tokenString, err := token.SignedString(mySigningKey)
return tokenString, err
}
func ExampleParse(myToken string, myKey string) {
token, err := jwt.Parse(myToken, func(token *jwt.Token) (interface{}, error) {
return []byte(myKey), nil
})
if err == nil && token.Valid {
fmt.Println("Your token is valid. I like your style.")
} else {
fmt.Println("This token is terrible! I cannot accept this.")
}
}