experiments

commit 04112f46ff71e5df6aea7a26189757f000d4c70c
parent 1dc59d3ea11042317891142c69303b1fbc340ea4
Author: Vetle Haflan <vetle@haflan.dev>
Date:   Thu, 21 Oct 2021 18:24:43 +0200

Add JWT experiment

Diffstat:
A
go/jwt/main.go
 | 
63
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 63 insertions(+), 0 deletions(-)
diff --git a/go/jwt/main.go b/go/jwt/main.go
@@ -0,0 +1,63 @@
+package main
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"strings"
+
+	//"encoding/json"
+	"fmt"
+	"os"
+)
+
+var secretKey []byte
+var encodedJWTHeader string
+
+func ComputeHmac256(message string) string {
+	h := hmac.New(sha256.New, secretKey)
+	h.Write([]byte(message))
+	return base64.RawURLEncoding.EncodeToString(h.Sum(nil))
+}
+
+func ComputeJWT(payload string) string {
+	data := encodedJWTHeader + "." + base64.RawURLEncoding.EncodeToString([]byte(payload))
+	return fmt.Sprintf("%v.%v", data, ComputeHmac256(data))
+}
+
+func JWTValid(jwt string) bool {
+	parts := strings.Split(jwt, ".")
+	if len(parts) != 3 {
+		return false
+	}
+	return parts[2] == ComputeHmac256(parts[0]+"."+parts[1])
+}
+
+const useMessage = `Commands:
+verify <jwt> : Verify JWT
+gen <payload> : Generate JWP from arbitrary payload
+`
+
+func main() {
+	key := os.Getenv("JWTEX_KEY")
+	if key == "" {
+		fmt.Println("Please define env var JWTEX_KEY")
+		os.Exit(1)
+	}
+	secretKey = []byte(key)
+	encodedJWTHeader = base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"HS256","typ":"JWT"}`))
+
+	if len(os.Args) < 3 {
+		fmt.Println(useMessage)
+		os.Exit(0)
+	}
+	if os.Args[1] == "gen" {
+		fmt.Println(ComputeJWT(os.Args[2]))
+	} else {
+		if JWTValid(os.Args[2]) {
+			fmt.Println("JWT valid")
+		} else {
+			fmt.Println("JWT invalid!")
+		}
+	}
+}