ink-identity-keys-example.go

package main

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"

	"github.com/docker/libtrust"
)

// Create a thumbprint accoring to draft 31 of JWK Thumbprint
// https://datatracker.ietf.org/doc/draft-jones-jose-jwk-thumbprint/
func makeThumbprint(rsaKey libtrust.PrivateKey) string {
	// TODO This is a very ungly hack.
	// libtrust.PrivateKey.toMap() is not public
	// libtrust.util.joseBase64UrlEncode() etc are not public.
	// So didn't really find a way to get them out of the object! :/

	// Convert the rsaKey to JSON
	privateJWKJSON, _ := json.MarshalIndent(rsaKey, "", "")
	// And then back to a map
	var data interface{}
	json.Unmarshal(privateJWKJSON, &data)
	privateJWKMap := data.(map[string]interface{})
	// Now we just create a new map and push only what we need.
	jwkSimple := make(map[string]interface{})
	jwkSimple["e"] = privateJWKMap["e"]
	jwkSimple["kty"] = privateJWKMap["kty"]
	jwkSimple["n"] = privateJWKMap["n"]
	// Marshal it into a json as required by JKT
	jwkJsonString, _ := json.Marshal(jwkSimple)
	// Finally SHA256 it, encode in HEX and return it
	hash := sha256.New()
	hash.Write(jwkJsonString)
	thumbprint := hash.Sum(nil)
	jwtHex := hex.EncodeToString(thumbprint)

	return jwtHex
}

func main() {
	// Generate RSA 2048 Key
	fmt.Printf("Generating RSA 2048-bit Key")
	rsaKey, _ := libtrust.GenerateRSA2048PrivateKey()

	// Create JWK for Private Key
	privateJWKJSON, _ := json.MarshalIndent(rsaKey, "", "    ")
	fmt.Printf("JWK Private Key (identity._jwk): \n%s\n\n", string(privateJWKJSON))

	// Create JWK for Public Key
	publicJWKJSON, _ := json.MarshalIndent(rsaKey.PublicKey(), "", "    ")
	fmt.Printf("JWK Public Key (identity.jwk): \n%s\n\n", string(publicJWKJSON))

	// Create Thumbprint for Private Key
	thumbprint := makeThumbprint(rsaKey)
	fmt.Printf("Identity Thumbprint Hex String (identity.id): \n%s", thumbprint)
}