experiments

All kinds of coding experiments
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main.go (1283B)

      1 package main
      2 
      3 import (
      4 	"crypto/hmac"
      5 	"crypto/sha256"
      6 	"encoding/base64"
      7 	"strings"
      8 
      9 	//"encoding/json"
     10 	"fmt"
     11 	"os"
     12 )
     13 
     14 var secretKey []byte
     15 var encodedJWTHeader string = base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"HS256","typ":"JWT"}`))
     16 
     17 func ComputeHmac256(message string) string {
     18 	h := hmac.New(sha256.New, secretKey)
     19 	h.Write([]byte(message))
     20 	return base64.RawURLEncoding.EncodeToString(h.Sum(nil))
     21 }
     22 
     23 func ComputeJWT(payload string) string {
     24 	data := encodedJWTHeader + "." + base64.RawURLEncoding.EncodeToString([]byte(payload))
     25 	return fmt.Sprintf("%v.%v", data, ComputeHmac256(data))
     26 }
     27 
     28 func JWTValid(jwt string) bool {
     29 	parts := strings.Split(jwt, ".")
     30 	if len(parts) != 3 {
     31 		return false
     32 	}
     33 	return parts[2] == ComputeHmac256(parts[0]+"."+parts[1])
     34 }
     35 
     36 const useMessage = `Commands:
     37 verify <jwt> : Verify JWT
     38 gen <payload> : Generate JWP from arbitrary payload
     39 `
     40 
     41 func main() {
     42 	key := os.Getenv("JWTEX_KEY")
     43 	if key == "" {
     44 		fmt.Println("Please define env var JWTEX_KEY")
     45 		os.Exit(1)
     46 	}
     47 	secretKey = []byte(key)
     48 	if len(os.Args) < 3 {
     49 		fmt.Println(useMessage)
     50 		os.Exit(0)
     51 	}
     52 	if os.Args[1] == "gen" {
     53 		fmt.Println(ComputeJWT(os.Args[2]))
     54 	} else {
     55 		if JWTValid(os.Args[2]) {
     56 			fmt.Println("JWT valid")
     57 		} else {
     58 			fmt.Println("JWT invalid!")
     59 		}
     60 	}
     61 }