在GOLang上用PHP解密的AES-CBC-256 Mcrypt_RIJNDAEL解密

Question

I try to rewrite some old code made in php5.6 (CodeIgniter) in go, but I'm banging my head with decryption on go. I managed to decode MCRYPT_RIJNDAEL_128 from php to go, where the iv size is 16 characters, but I can't do it on 256 - iv is 32. I don't want to use go_mcrypt because that's strict on libcrypt headers, so I tried using go classic encrypt libs AES cipher with CBC mode, but on 256 it complains about IV length... The php IV has 32 characters not 16 as expected..

The php part works well...

private $CIPHER_KEY = "12345678901234567890123456789012";

    private function Encrypt($toEncrypt=null){
        $iv_size = $this->ivSize = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
        $iv = $this->ivKey = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $this->B64IV = base64_encode($iv);
        return base64_encode($iv . mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $this->CIPHER_KEY, $toEncrypt, MCRYPT_MODE_CBC, $iv));
    }

this is the PHP result:

KEY: 12345678901234567890123456789012
IV: Egu4tSySXluBLi5dcMzHbZHVSOS7jdNwUKUFlZ8dL1w=
ENC: Egu4tSySXluBLi5dcMzHbZHVSOS7jdNwUKUFlZ8dL1yATFjg26/Nav7cWtlJJL3djhUCND6KV8r/JL7owboKFA==
IV Size: 32

IV is included in the encrypted text... (and has 32 chars)

mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC); return 32

func main(){
   key := []byte("12345678901234567890123456789012")

   iv,_ := base64.StdEncoding.DecodeString("Egu4tSySXluBLi5dcMzHbZHVSOS7jdNwUKUFlZ8dL1w=")
   encText,_  := base64.StdEncoding.DecodeString("Egu4tSySXluBLi5dcMzHbZHVSOS7jdNwUKUFlZ8dL1yATFjg26/Nav7cWtlJJL3djhUCND6KV8r/JL7owboKFA==")
//   iv := encText[:32] // also tried to get the iv from encoded string


   fmt.Printf("Key Len: %d
IV  Len: %d
ENC Len: %d
",len(key),len(iv),len(encText))

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

    if len(encText) < aes.BlockSize {
        panic("cipherText too short")
    }

    cipherText := encText[32:]
    if len(cipherText)%aes.BlockSize != 0 {
        panic("cipherText is not a multiple of the block size")
    }

    mode := cipher.NewCBCDecrypter(block, iv)
    mode.CryptBlocks(cipherText, cipherText)

    cipherText, _ = pkcs7.Unpad(cipherText, aes.BlockSize)

   fmt.Printf("Dec: %s
",cipherText)

}

Key Len: 32 IV Len: 32 ENC Len: 64 panic: cipher.NewCBCDecrypter: IV length must equal block size

goroutine 1 [running]: crypto/cipher.NewCBCDecrypter(0x10e7c20, 0xc00009a030, 0xc00008a000, 0x20, 0x42, 0x0, 0x0)

IV size is 32 but the block size is 16.

Answer 1

This works in Linux - for anyone courious how to decode with IV 32 characters

apt install libmcrypt-dev

go get "github.com/tblyler/go-mcrypt"

import (
  "fmt"
  "github.com/tblyler/go-mcrypt"
  "encoding/base64"
)

const (
   KEY = "12345678901234567890123456789012"
   ENC = "Egu4tSySXluBLi5dcMzHbZHVSOS7jdNwUKUFlZ8dL1yATFjg26/Nav7cWtlJJL3djhUCND6KV8r/JL7owboKFA=="
)

func main(){
    encText, _ := base64.StdEncoding.DecodeString(ENC)

    iv := encText[:32]
    toDecrypt := encText[32:]

    fmt.Printf("Key Len: %d
",len(KEY))
    fmt.Printf("IV  Len: %d
",len(iv))

    decText, err := mcrypt.Decrypt([]byte(KEY),iv,[]byte(toDecrypt))
    if err != nil { panic(err) }

    fmt.Printf("%s
",decText)
}