AES encryption + AAD

aesutil.go

package aesutil

import (
	"crypto/aes"
	"crypto/cipher"
	crypto_rand "crypto/rand"
	"errors"
)

const (
	KeySize = 32
	IVSize  = 12
)

func Encrypt(key, plaintext, additionalData []byte) ([]byte, error) {
	if len(key) != KeySize {
		return nil, errors.New("invalid key length")
	}
	iv := make([]byte, IVSize)
	_, err := crypto_rand.Read(iv)
	if err != nil {
		return nil, err
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	ciphertextCombo := aesgcm.Seal(iv, iv, plaintext, additionalData)

	return ciphertextCombo, nil
}

func Decrypt(key, ciphertextCombo, additionalData []byte) ([]byte, error) {
	if len(key) != KeySize {
		return nil, errors.New("invalid key length")
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	ivSize := aesgcm.NonceSize()
	iv, ciphertext := ciphertextCombo[:ivSize], ciphertextCombo[ivSize:]
	plaintext, err := aesgcm.Open(nil, iv, ciphertext, additionalData)
	if err != nil {
		return nil, err
	}

	return plaintext, nil
}