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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2021 Jason A. Donenfeld. All Rights Reserved.
*/
package main
import (
"crypto/rand"
"encoding/base64"
"errors"
"log"
"os"
"strings"
)
const privateKeyCacheFile = "./private-key.cache"
func loadCachedPrivateKey() ([]byte, error) {
bytes, err := os.ReadFile(privateKeyCacheFile)
if err != nil {
return nil, err
}
log.Println("Loading cached private key from file")
privateKeyB64 := strings.TrimSpace(string(bytes))
privateKey, err := base64.StdEncoding.DecodeString(privateKeyB64)
if err != nil {
return nil, err
}
if len(privateKey) != 32 {
return nil, errors.New("invalid private key")
}
return privateKey, nil
}
func saveCachedPrivateKey(privateKey []byte) error {
if len(privateKey) != 32 {
return errors.New("invalid private key")
}
return os.WriteFile(privateKeyCacheFile, []byte(base64.StdEncoding.EncodeToString(privateKey)+"\n"), 0600)
}
func loadOrGeneratePrivateKey() ([]byte, error) {
privateKey, err := loadCachedPrivateKey()
if err == nil {
return privateKey, nil
}
log.Println("Generating new private key")
var k [32]byte
_, err = rand.Read(k[:])
if err != nil {
return nil, err
}
k[0] &= 248
k[31] = (k[31] & 127) | 64
err = saveCachedPrivateKey(k[:])
if err != nil {
return nil, err
}
return k[:], nil
}
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