NdoleStudio / httpsms-go

package httpsms

import (

	"crypto/aes"

	"crypto/cipher"

	"crypto/rand"

	"crypto/sha256"

	"encoding/base64"

	"errors"

)

// CipherService is used to encrypt and decrypt SMS messages using the AES-256 algorithm

type CipherService service

// Encrypt the message content using the encryption key

func (service *CipherService) Encrypt(encryptionKey string, content string) (string, error) {

	block, err := aes.NewCipher(service.hash(encryptionKey))

	if err != nil {

		return "", errors.Join(err, errors.New("failed to create new cipher"))

	}

	text := []byte(content)

	iv, err := service.initializationVector()

	if err != nil {

		return "", errors.Join(err, errors.New("failed to create initialization vector"))

	}

	stream := cipher.NewCFBEncrypter(block, iv)

	cipherText := make([]byte, len(text))

	stream.XORKeyStream(cipherText, text)

	return base64.StdEncoding.EncodeToString(append(iv, cipherText...)), nil

}

// Decrypt the message content using the encryption key

func (service *CipherService) Decrypt(encryptionKey string, cipherText string) (string, error) {

	content, err := base64.StdEncoding.DecodeString(cipherText)

	if err != nil {

		return "", errors.Join(err, errors.New("failed to decode cipher in base64"))

	}

	block, err := aes.NewCipher(service.hash(encryptionKey))

	if err != nil {

		return "", errors.Join(err, errors.New("failed to create new cipher"))

	}

	// Decrypt the message

	cipherTextBytes := content[16:]

	stream := cipher.NewCFBDecrypter(block, content[:16])

	stream.XORKeyStream(cipherTextBytes, cipherTextBytes)

	return string(cipherTextBytes), nil

}

// hash a key using the SHA-256 algorithm

func (service *CipherService) hash(key string) []byte {

	sha := sha256.Sum256([]byte(key))

	return sha[:]

}

func (service *CipherService) initializationVector() ([]byte, error) {

	iv := make([]byte, 16)

	_, err := rand.Read(iv)

	return iv, err

}