encryption.go

package solidgate

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"errors"
	"io"
)

func pkcs7Pad(b []byte, blockSize int) ([]byte, error) {
	if blockSize <= 0 {
		return nil, errors.New("block size less than 0")
	}
	if b == nil {
		return nil, errors.New("empty data to encrypt")
	}
	n := blockSize - (len(b) % blockSize)
	pb := make([]byte, len(b)+n)

	copy(pb, b)
	copy(pb[len(b):], bytes.Repeat([]byte{byte(n)}, n))

	return pb, nil
}

func EncryptCBC(key, data []byte) ([]byte, error) {
	data, err := pkcs7Pad(data, aes.BlockSize)

	if err != nil {
		return nil, err
	}

	block, err := aes.NewCipher(key)

	if err != nil {
		return nil, err
	}

	cipherText := make([]byte, aes.BlockSize+len(data))
	iv := cipherText[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return nil, err
	}

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(cipherText[aes.BlockSize:], data)

	return cipherText, nil
}