John Davidson

Message:

I am trying to achieve AES-256-CBC encryption in golang. I have a working PHP code that has been used for years. I am getting encrypted values in Golang, but the values don't match the output from PHP one, for the same payload/key/iv combination.

For simplification I am hardcoding the payload/key/iv in below codes. I have also removed verbose error messaging from my go code.

This is my GO code

func encryption() {

    plaintext := []byte("12345678912345678912345678900000")

    key, _ := base64.StdEncoding.DecodeString("cidRgzwfcgztwae/mccalIeedOAmA/CbU3HEqWz1Ejk=")

    iv, _ := hex.DecodeString("162578ddce177a4a7cb2f7c738fa052d")



    /*php seem to use PKCS7 padding to make the source string match the blocksize 

     requirement for AES-256-CBC.

     From what I understand, I need to do padding manually in Golang. 

     Correct me if wrong */

    plaintext, _ = Pkcs7Pad(plaintext, aes.BlockSize)



    block, _ := aes.NewCipher(key)



    ciphertext := make([]byte, aes.BlockSize+len(plaintext))



    mode := cipher.NewCBCEncrypter(block, iv)



    mode.CryptBlocks(ciphertext[aes.BlockSize:], plaintext)



    fmt.Printf("EncryptedText %v\n", string(ciphertext))

    fmt.Printf("EncryptedText as hex %v\n", hex.EncodeToString(ciphertext))

}



func Pkcs7Pad(b []byte, blocksize int) ([]byte, error) {

    if blocksize <= 0 {

        return nil, errors.New("Invalid block size")

    }

    if b == nil || len(b) == 0 {

        return nil, errors.New("Invalid block size")

    }

    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

}

And my Go output is

EncryptedText |8??X?z??F ?0ĺe?,??G?V?

Gce??dM????z?,*ȁҼ

EncryptedText as hex 7c38bad658907a81d14620c930c4ba658c1f022cdb1392479856cc0a471d6365dfc5644db6b28cef7ac02c2ac881d2bc

I have a PHP code to do the same task, which gives me a different output.

function encryption() {

    $plaintext = "12345678912345678912345678900000";

    $key = base64_decode("cidRgzwfcgztwae/mccalIeedOAmA/CbU3HEqWz1Ejk=");

    $iv = hex2bin("162578ddce177a4a7cb2f7c738fa052d");



    //php openssl_encrypt function seem to use pkcs7pad to make the source string match the blocksize requirement for AES-256-CBC



    $ciphertext = openssl_encrypt($plaintext, 'AES-256-CBC', $key, 0, $iv );

    print $ciphertext;

}

and the PHP output is

fDi61liQeoHRRiDJMMS6ZYwfAizbE5JHmFbMCkcdY2XfxWRNtrKM73rALCrIgdK8

Obviously, I would like to get my Golang implementation to get the same output as PHP. As I require communication with my Golang code and existing PHP code, I would like to get encryption and decryption work same in both PHP and Golang.

Any ideas?

---

My Answer:
secret message to encrypt") key := []byte("0123456789abcdef0123456789abcdef") iv := []byte("0123456789abcdef") block, _ := aes.NewCipher(key) ciphertext := make([]byte, len(plaintext)) mode := cipher.NewCBCEncrypter(block, iv) mode.CryptBlocks(ciphertext, plaintext) fmt.Printf("%x\n", ciphertext)}_This is my PHP code_php_The output from the GO code is not matching the output from the PHP code. What am I doing wrong?_