/*
tofuproxy -- flexible HTTP/HTTPS proxy, TLS terminator, X.509 TOFU
             manager, WARC/geminispace browser
Copyright (C) 2021-2023 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/>.
*/

package tofuproxy

import (
	"crypto"
	"crypto/ed25519"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"log"
	"math/big"
	"sync"
	"time"
)

type Keypair struct {
	cert *x509.Certificate
	prv  crypto.PrivateKey
}

var (
	hostCerts  = make(map[string]*Keypair)
	hostCertsM sync.Mutex
	Serial     *big.Int
)

func init() {
	max := big.NewInt(0)
	max = max.SetBit(max, 128, 1)
	var err error
	Serial, err = rand.Int(rand.Reader, max)
	if err != nil {
		panic(err)
	}
}

func newKeypair(
	host string,
	caCert *x509.Certificate,
	caPrv crypto.PrivateKey,
) *Keypair {
	pub, prv, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		log.Fatalln(err)
	}
	notBefore := time.Now()
	notAfter := notBefore.Add(24 * time.Hour)
	Serial = Serial.Add(Serial, big.NewInt(1))
	template := x509.Certificate{
		SerialNumber: Serial,
		Subject:      pkix.Name{CommonName: host},
		DNSNames:     []string{host},
		NotBefore:    notBefore,
		NotAfter:     notAfter,
	}
	certRaw, err := x509.CreateCertificate(
		rand.Reader, &template, caCert, pub, caPrv,
	)
	if err != nil {
		log.Fatalln(err)
	}
	cert, err := x509.ParseCertificate(certRaw)
	if err != nil {
		log.Fatalln(err)
	}
	return &Keypair{cert, prv}
}