porter/internal/encryption/encrypt.go

package encryption

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

// This file is copied from: https://github.com/gtank/cryptopasta

// NewEncryptionKey generates a random 256-bit key for Encrypt() and
// Decrypt(). It panics if the source of randomness fails.
func NewEncryptionKey() *[32]byte {
	key := [32]byte{}
	_, err := io.ReadFull(rand.Reader, key[:])
	if err != nil {
		panic(err)
	}
	return &key
}

// NewRandomString generates a random string.
// It panics if the source of randomness fails.
func GenerateRandomBytes(n int) (string, error) {
	b := make([]byte, n)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}

	return hex.EncodeToString(b), nil
}

// Encrypt encrypts data using 256-bit AES-GCM.  This both hides the content of
// the data and provides a check that it hasn't been altered. Output takes the
// form nonce|ciphertext|tag where '|' indicates concatenation.
func Encrypt(plaintext []byte, key *[32]byte) (ciphertext []byte, err error) {
	block, err := aes.NewCipher(key[:])
	if err != nil {
		return nil, err
	}

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

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

	return gcm.Seal(nonce, nonce, plaintext, nil), nil
}

// Decrypt decrypts data using 256-bit AES-GCM.  This both hides the content of
// the data and provides a check that it hasn't been altered. Expects input
// form nonce|ciphertext|tag where '|' indicates concatenation.
func Decrypt(ciphertext []byte, key *[32]byte) (plaintext []byte, err error) {
	block, err := aes.NewCipher(key[:])
	if err != nil {
		return nil, err
	}

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

	if len(ciphertext) < gcm.NonceSize() {
		return nil, errors.New("malformed ciphertext")
	}

	return gcm.Open(nil,
		ciphertext[:gcm.NonceSize()],
		ciphertext[gcm.NonceSize():],
		nil,
	)
}