crypto.go

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
)

func Encrypt(key []byte, plaintext string) (string, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}

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

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

	ciphertext := gcm.Seal(nonce, nonce, []byte(plaintext), nil)
	return base64.StdEncoding.EncodeToString(ciphertext), nil
}

func Decrypt(key []byte, ciphertext string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(ciphertext)
	if err != nil {
		return "", err
	}

	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}

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

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

	nonce, cipherbytes := data[:nonceSize], data[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, cipherbytes, nil)
	if err != nil {
		return "", err
	}

	return string(plaintext), nil
}

func DeriveKey(password string) []byte {
	key := make([]byte, 32)
	for i := 0; i < len(password) && i < 32; i++ {
		key[i] = password[i]
	}
	return key
}

func GetMasterPassword() (string, error) {
	fmt.Print("Enter master password: ")
	var password string
	_, err := fmt.Scanln(&password)
	return password, err
}