// GoGOST -- Pure Go GOST cryptographic functions library
// Copyright (C) 2015-2024 Sergey Matveev <stargrave@stargrave.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 3 of the License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// DANE's SPKI hash calculator
package main

import (
	"crypto/sha256"
	"crypto/x509"
	"encoding/hex"
	"encoding/pem"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	flag.Parse()
	data, err := io.ReadAll(os.Stdin)
	if err != nil {
		log.Fatal(err)
	}
	b, _ := pem.Decode(data)
	if b == nil || b.Type != "CERTIFICATE" {
		log.Fatal("no CERTIFICATE")
	}
	cer, err := x509.ParseCertificate(b.Bytes)
	if err != nil {
		log.Fatal(err)
	}
	h := sha256.Sum256(cer.RawSubjectPublicKeyInfo)
	fmt.Println(hex.EncodeToString(h[:]))
}