Initial commit of utilities

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

cmd/ircmirror/keycache.go

@@ -0,0 +1,61 @@
+/* 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
+}