pastepass/db/crypto.go

package db

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"errors"
	"fmt"
	"io"
	random "math/rand"
)

func encrypt(text string, key string) ([]byte, error) {
	c, err := aes.NewCipher([]byte(key))
	if err != nil {
		return nil, err
	}

	gcm, err := cipher.NewGCM(c)
	if err != nil {
		return nil, err
	}

	nonce := make([]byte, gcm.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}

	return gcm.Seal(nonce, nonce, []byte(text), nil), nil
}

func decrypt(ciphertext []byte, key string) (string, error) {
	c, err := aes.NewCipher([]byte(key))
	if err != nil {
		return "", fmt.Errorf("failed to create cipher: %w", err)
	}

	gcm, err := cipher.NewGCM(c)
	if err != nil {
		return "", fmt.Errorf("failed to create GCM: %w", err)
	}

	nonceSize := gcm.NonceSize()
	if len(ciphertext) < nonceSize {
		return "", errors.New("ciphertext too short")
	}

	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return "", fmt.Errorf("failed to decrypt: %w", err)
	}

	return string(plaintext), nil
}

var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

const keyLength = 32

func randomKey() string {
	b := make([]rune, keyLength)
	for i := range b {
		b[i] = letterRunes[random.Intn(len(letterRunes))]
	}
	return string(b)
}