Golang: aes-256-cbc ecrypt/decrypt examples (with iv, blockSize)

main.go

package main


// Working example: https://goplay.space/#Sa7qCLm6w65
import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"encoding/hex"
	"fmt"
)

func main() {
	key := "12345678901234567890123456789012"
	iv := "1234567890123456"
	plaintext := "abcdefghijklmnopqrstuvwxyzABCDEF"
	fmt.Println("Data to encode: ", plaintext)

	cipherText := fmt.Sprintf("%v", Ase256Encode(plaintext, key, iv, aes.BlockSize))
	fmt.Println("Encode Result:\t", cipherText)
	fmt.Println("Decode Result:\t", Ase256Decode(cipherText, key, iv))

}

func Ase256Encode(plaintext string, key string, iv string, blockSize int) string {
	bKey := []byte(key)
	bIV := []byte(iv)
	bPlaintext := PKCS5Padding([]byte(plaintext), blockSize, len(plaintext))
	block, err := aes.NewCipher(bKey)
	if err != nil {
		panic(err)
	}
	ciphertext := make([]byte, len(bPlaintext))
	mode := cipher.NewCBCEncrypter(block, bIV)
	mode.CryptBlocks(ciphertext, bPlaintext)
	return hex.EncodeToString(ciphertext)
}

func Ase256Decode(cipherText string, encKey string, iv string) (decryptedString string) {
	bKey := []byte(encKey)
	bIV := []byte(iv)
	cipherTextDecoded, err := hex.DecodeString(cipherText)
	if err != nil {
		panic(err)
	}

	block, err := aes.NewCipher(bKey)
	if err != nil {
		panic(err)
	}

	mode := cipher.NewCBCDecrypter(block, bIV)
	mode.CryptBlocks([]byte(cipherTextDecoded), []byte(cipherTextDecoded))
	return string(cipherTextDecoded)
}

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

hey, i want to tell u somethin, i tested and messed around, encrypting a text will give u the result with a trailing spaces, so you should use strings.TrimSpace func,

you can see the result here, i've modified and adjusted some func for my project.
https://goplay.space/#lBRpljKVjiY

or maybe you can use this func, it will automatically remove trailing white spaces
https://goplay.space/#ExdbpOHVp-0

maybe even better: https://goplay.space/#F_vCnIbq8wY

Hey, I'm kinda new to golang and I also had some trouble with those trailing spaces.... I came with this function thats also a good implementation:

func PKCS5UnPadding(src []byte) []byte {
	length := len(src)
	unpadding := int(src[length-1])
	return src[:(length - unpadding)]
}

Just pass cipherTextDecoded to PKCS5UnPadding

Thanks a lot @bojcheski and @NotYusta for highlighting this.

@NotYusta This https://goplay.space/#F_vCnIbq8wY works as expected.

Use this function if you gonna encrypt plaintext without padding. It will resolve issue trailing spaces.

func AES256Encode(plaintext string, key string, iv string) string {
	bKey := []byte(key)
	bIV := []byte(iv)
	block, err := aes.NewCipher(bKey)
	if err != nil {
		panic(err)
	}
	ciphertext := make([]byte, len(plaintext))
	mode := cipher.NewCBCEncrypter(block, bIV)
	mode.CryptBlocks(ciphertext, []byte(plaintext))
	return hex.EncodeToString(ciphertext)
}

Do not forget to use PKCS5UnPadding() while decoding the string !!!!!!!!!!!!!!!!

func Ase256(plaintext string, key string, iv string, blockSize int) (string, error) {
    bKey := []byte(key)
    bIV := []byte(iv)
    bPlaintext := PKCS5Padding([]byte(plaintext), blockSize, len(plaintext))
    block, err := aes.NewCipher(bKey)
    if err != nil {
        return "", err
    }
    ciphertext := make([]byte, len(bPlaintext))
    mode := cipher.NewCBCEncrypter(block, bIV)
    mode.CryptBlocks(ciphertext, bPlaintext)
    return hex.EncodeToString(ciphertext), nil
}
func PKCS5UnPadding(src []byte) []byte {
    length := len(src)
    unpadding := int(src[length-1])
    return src[:(length - unpadding)]
}
func PKCS5Padding(ciphertext []byte, blockSize int, after int) []byte {
    padding := (blockSize - len(ciphertext)%blockSize)
    padtext := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(ciphertext, padtext...)
}
func Ase256Decode(cipherText string, encKey string, iv string) (decryptedString string) {
    bKey := []byte(encKey)
    bIV := []byte(iv)
    cipherTextDecoded, err := hex.DecodeString(cipherText)
    if err != nil {
        panic(err)
    }
    block, err := aes.NewCipher(bKey)
    if err != nil {
        panic(err)
    }
    mode := cipher.NewCBCDecrypter(block, bIV)
    mode.CryptBlocks([]byte(cipherTextDecoded), []byte(cipherTextDecoded))
    return string(PKCS5UnPadding(cipherTextDecoded))
}

Hi all
I wanted to encrypt and decrypt using a key of length 43 which I am getting from hashicorp vault

https://goplay.space/#C3TFPoaDmeb

how can I make this work? can you pls suggest