102 lines
2.2 KiB
Go
102 lines
2.2 KiB
Go
// Copyright 2024 Patial Tech (Ankit Patial).
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//
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// This file is part of code.patial.tech/go/appcore, which is MIT licensed.
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// See http://opensource.org/licenses/MIT
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package crypto
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"encoding/hex"
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"fmt"
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"io"
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)
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// NewEncryptionKey will generate new key as base64 encoded string
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//
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// should be of 16, 24 or 32 bytes in length
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func NewEncryptionKey(size uint8) (string, error) {
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b, err := RandomBytes(size)
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if err != nil {
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return "", err
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}
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return base64.StdEncoding.EncodeToString(b), nil
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}
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func decodeEncryptionKey(str string) ([]byte, error) {
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return base64.StdEncoding.DecodeString(str)
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}
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// Encrypt text using the encyption key
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func Encrypt(key, text string) (string, error) {
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b, err := decodeEncryptionKey(key)
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if err != nil {
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return "", fmt.Errorf("decrypted base64 string: %w", err)
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}
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gcm, err := getGCM(b)
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if err != nil {
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return "", err
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}
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// create a nonce. Nonce should be from GCM
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nonce := make([]byte, gcm.NonceSize())
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if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
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return "", err
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}
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// encrypt the data using gcm.Seal
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ciphertext := gcm.Seal(nonce, nonce, []byte(text), nil) // prefix nonce to the ciphertext
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return fmt.Sprintf("%x", ciphertext), nil
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}
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// Decrypt text using the encryption key
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func Decrypt(key, text string) (string, error) {
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b, err := decodeEncryptionKey(key)
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if err != nil {
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return "", fmt.Errorf("decrypted base64 string: %w", err)
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}
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// create a new Cipher Block from the key
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gcm, err := getGCM(b)
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if err != nil {
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return "", err
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}
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nonceSize := gcm.NonceSize()
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enc, err := hex.DecodeString(text)
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if err != nil {
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return "", err
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}
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nonce, ciphertext := enc[:nonceSize], enc[nonceSize:]
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// decrypt
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plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return "", err
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}
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return string(plaintext), nil
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}
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func getGCM(key []byte) (gcm cipher.AEAD, err error) {
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// cipher block from the key
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b, err := aes.NewCipher(key)
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if err != nil {
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return gcm, err
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}
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// GCM - https://en.wikipedia.org/wiki/Galois/Counter_Mode
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// https://golang.org/pkg/crypto/cipher/#NewGCM
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gcm, err = cipher.NewGCM(b)
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if err != nil {
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return gcm, err
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}
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return gcm, nil
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}
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