jwt validation with cgo and openssl

main.go

package main

// https://github.com/nodejs/node/blob/master/src/node_crypto.cc#L4374

import (
	"log"
	"strings"

	"github.com/spacemonkeygo/openssl"
)

/*
CGO_CFLAGS="-I /usr/local/opt/openssl/include/" CGO_LDFLAGS="-L/usr/local/opt/openssl@1.0/lib" go run --ldflags '-extldflags "-static"' main_openssl.go
*/

func main() {
	const token = "eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiQmVuamFtaW4gQm91ZHJlYXUiLCJ1c2VyX3JvbGVzIjoiQWRtaW4iLCJzdWIiOiJzZXJpb3VzYmVuIiwiaWF0IjoxNDk3MzY2MDUxfQ.SJrhbZDfb2dPzJuZml4BCWNS5IWSo9_dMOJfZW3YHx_5-qneJE-mUi4tDEUQedjmu2hb5O9pP5mUY_r6cnSBs"
	const pubPEM = `-----BEGIN PUBLIC KEY-----
MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEHmtsC5qTi1O17410zIACT0f1iB8iAmIY
hJ3Qq2bFGiBBBvNn4JwO4LO84hhj0mhDTgW7CHyGgOn6Nq2bHcF//g==
-----END PUBLIC KEY-----`
	parts := strings.Split(token, ".")
	data := strings.Join(parts[0:2], ".")

	pub, err := openssl.LoadECPublicKeyFromPEM([]byte(pubPEM))
	if err != nil {
		log.Fatalln("EC PK from PEM", err)
	}

	log.Println("data", data)
	log.Println("signature", parts[2])

	err = pub.VerifyPKCS1v15(openssl.SHA256_Method, []byte(data), []byte(parts[2]))
	if err != nil {
		log.Fatalln("Not valid", err)
	}
	log.Println("Valid")
}

patches.go

func ValidateJWT(data, sig []byte) error {
	ctx := C.X_EVP_MD_CTX_new()
	defer C.X_EVP_MD_CTX_free(ctx)
	C.ERR_load_crypto_strings()

	if 1 != C.X_EVP_VerifyInit(ctx, method) {
		return errors.New("verifypkcs1v15: failed to init verify")
	}
	if len(data) > 0 {
		if 1 != C.X_EVP_VerifyUpdate(
			ctx, unsafe.Pointer(&data[0]), C.uint(len(data))) {
			return errors.New("verifypkcs1v15: failed to update verify")
		}
	}
	if 1 != C.X_EVP_VerifyFinal(ctx, ((*C.uchar)(unsafe.Pointer(&sig[0]))), C.uint(len(sig)), key.key) {
		msg := C.ERR_error_string(500, nil)
		return errors.New("verifypkcs1v15: failed to finalize verify " + C.GoString(msg))
	}
	return nil
}