AES/CBC/PKCS5Padding implementation by Golang

AES.go

package main

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"fmt"
)

func main() {
	src := "NIJOAHS000000000"
	key := []byte("1234567890123456")

	fmt.Println("SOURCE!:", []byte(src))

	encrypted := AESEncrypt(src, key)
	fmt.Println("ENCRYPT:", encrypted)

	decrypted := AESDecrypt(encrypted, key)
	fmt.Println("DECRYPT:", decrypted)
}

func AESEncrypt(src string, key []byte) []byte {
	block, err := aes.NewCipher(key)
	if err != nil {
		fmt.Println("key error1", err)
	}
	if src == "" {
		fmt.Println("plain content empty")
	}
	ecb := cipher.NewCBCEncrypter(block, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
	content := []byte(src)
	content = PKCS5Padding(content, block.BlockSize())
	crypted := make([]byte, len(content))
	ecb.CryptBlocks(crypted, content)

	return crypted
}

func AESDecrypt(crypt []byte, key []byte) []byte {
	block, err := aes.NewCipher(key)
	if err != nil {
		fmt.Println("key error1", err)
	}
	if len(crypt) == 0 {
		fmt.Println("plain content empty")
	}
	ecb := cipher.NewCBCDecrypter(block, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
	decrypted := make([]byte, len(crypt))
	ecb.CryptBlocks(decrypted, crypt)

	return PKCS5Trimming(decrypted)
}

func PKCS5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}

func PKCS5Trimming(encrypt []byte) []byte {
	padding := encrypt[len(encrypt)-1]
	return encrypt[:len(encrypt)-int(padding)]
}

PKCS5Trimming has an error ; if the params did not padding will suffer an error;eg: 1111222233334444

Strictly speking PCKS5 always uses a blocksize of 8. What you have implemented is an attempt at PKCS7 wich takes in blocksize as parameter.

From Wikipedia about PKCS7 Padding:

f the length of the original data is an integer multiple of the block size B, then an extra block of bytes with value B is added. This is necessary so the deciphering algorithm can determine with certainty whether the last byte of the last block is a pad byte indicating the number of padding bytes added or part of the plaintext message.

if padding == 0 { padding = blockSize }