PEM encoded private RSA key in Go

pem.go

package main

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
)

func decodePrivateKey(r io.Reader) (*rsa.PrivateKey, error) {

	keydata, err := ioutil.ReadAll(r)
	if err != nil {
		return nil, err
	}

	var keybytes []byte

	for {
		block, rest := pem.Decode(keydata)

		if block == nil {
			return nil, errors.New("pem decode of private key failed")
		}

		if block.Type != "RSA PRIVATE KEY" {
			keydata = rest
			continue
		}

		keybytes = block.Bytes

		break
	}

	return x509.ParsePKCS1PrivateKey(keybytes)

}

func main() {

	f, err := os.Open("test.pem")
	if err != nil {
		log.Fatal(err)
	}

	defer f.Close()

	private, err := decodePrivateKey(f)
	if err != nil {
		log.Fatal(err)
	}

	public := private.PublicKey

	secretMessage := []byte("send reinforcements, we're going to advance")
	label := []byte("orders")

	rng := rand.Reader

	ciphertext, err := rsa.EncryptOAEP(sha256.New(), rng, &public, secretMessage, label)
	if err != nil {
		log.Fatal(err)
		return
	}

	fmt.Printf("%x\n", ciphertext)
}