Golang使用AES加密数据

Question

I'm not sure if this is the right place to ask this. But I have no experience with C# and have been tasked to convert a security piece of code to Golang

I was wondering if i'm missing out on something here.

The C# code uses a Rijndael class to encrypt a bit of data. The key value and iv value is written out in the byte code like this

   public static byte[] Key = new byte[]{0xx, 0xx, 0xx, 0xx, 0xx,
                    0xx4, 0xxx, 0xxx, 0xxx, 0xxx, xxx, 0xxx,
                    0xxx, 0xxx, 0xxx, 0xxx};

public static byte[] IV = new byte[] // save structure as above with 16 in length

then theres a bit of code which does this

Rijndael alg = Rijndael.Create();
                alg.Key = Key;
                alg.IV = IV;
                CryptoStream cs = new CryptoStream(ms,
                alg.CreateEncryptor(), CryptoStreamMode.Write);
                cs.Write(dataWithoutHeader, 0, dataWithoutHeader.Length);
                cs.Close();

the function sends out byte[] data as output

I'm trying to mimic this is golang like this

func StartEncryption(message []byte) []byte {
    var key = []byte {// same as C# } 

    var iv = []byte{ // same as C# }

    var err error
    fmt.Printf("\n length of key %+v \n, \n length of iv \n %+v \n", len(key), len(iv))
    // Encrypt
    encrypted := make([]byte, len(message))
    err = EncryptAESCFB(encrypted, []byte(message), key, iv)
    if err != nil {
        panic(err)
    }
    return encrypted
}

The Encryption function

func EncryptAESCFB(dst, src, key, iv []byte) error {
    aesBlockEncrypter, err := aes.NewCipher([]byte(key))
    if err != nil {
        return err
    }
    aesEncrypter := cipher.NewCFBEncrypter(aesBlockEncrypter, iv)
    aesEncrypter.XORKeyStream(dst, src)
    return nil
}

The output of this is sent over an API whose output needs to be decrypted. I'm using this below

func decryptMessage(message []byte)error{
    var key = []byte{ // same as C# }

    var iv = []byte{ // same as C#  }

    // Remove the head part of the response (45 bytes)
    responseBody := message[45:]

    decrypted := make([]byte, len(responseBody))

    err := DecryptAESCFB(decrypted, responseBody, key, iv)

    if err != nil {
        fmt.Printf("\n error : \n %+v \n", err)
    }
    return nil
}

func DecryptAESCFB(dst, src, key, iv []byte) error {
    aesBlockDecrypter, err := aes.NewCipher([]byte(key))
    if err != nil {
        return nil
    }
    aesDecrypter := cipher.NewCFBDecrypter(aesBlockDecrypter, iv)
    aesDecrypter.XORKeyStream(dst, src)
    return nil
}

The decryptor gives me gibberish - Am i going wrong somewhere?

My question boils down to 2 questions

1. Would the C# function using the rijndael class and the golang functiony yield the same output or should i be doing something more/less

2. Is the byte array the right data to store the key, IV in - ie its not the same used in C# when copied to GO

Answer 1

There's a few problems with the code you posted.

1. Don't store the key in a byte array, because that means that you are hard-coding it. Instead generate a random 256-bit key, encode it to a hex string, then store that outside of your program and read it in using a config library like viper .
2. Don't hard-code the IV. You should be generating a new IV for every single message. Reusing the same IV weakens your encryption significantly. For every message that you encrypt, generate a random IV and prepend it to the message. When you attempt to decrypt it, read the IV off of the first n bytes and then decrypt.
3. You should use authenticated encryption as a measure of protection against chosen ciphertext attacks. GCM mode provides authentication for you.

Here is an example. Playground Link

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/rand"
    "encoding/hex"
    "fmt"
    "os"
)

var (
    key       = randBytes(256 / 8)
    gcm       cipher.AEAD
    nonceSize int
)

// Initilze GCM for both encrypting and decrypting on program start.
func init() {
    block, err := aes.NewCipher(key)
    if err != nil {
        fmt.Printf("Error reading key: %s\n", err.Error())
        os.Exit(1)
    }

    fmt.Printf("Key: %s\n", hex.EncodeToString(key))

    gcm, err = cipher.NewGCM(block)
    if err != nil {
        fmt.Printf("Error initializing AEAD: %s\n", err.Error())
        os.Exit(1)
    }

    nonceSize = gcm.NonceSize()
}

func randBytes(length int) []byte {
    b := make([]byte, length)
    rand.Read(b)
    return b
}

func encrypt(plaintext []byte) (ciphertext []byte) {
    nonce := randBytes(nonceSize)
    c := gcm.Seal(nil, nonce, plaintext, nil)
    return append(nonce, c...)
}

func decrypt(ciphertext []byte) (plaintext []byte, err error) {
    if len(ciphertext) < nonceSize {
        return nil, fmt.Errorf("Ciphertext too short.")
    }
    nonce := ciphertext[0:nonceSize]
    msg := ciphertext[nonceSize:]
    return gcm.Open(nil, nonce, msg, nil)
}

func main() {
    fmt.Println("Encrypting...")
    msg := []byte("The quick brown fox jumped over the lazy dog.")
    ciphertext := encrypt(msg)
    fmt.Printf("Encrypted message: %v\n", ciphertext)

    fmt.Println("Decrypting...")
    plaintext, err := decrypt(ciphertext)
    if err != nil {
        // Don't display this message to the end-user, as it could potentially
        // give an attacker useful information. Just tell them something like "Failed to decrypt."
        fmt.Printf("Error decryping message: %s\n", err.Error())
        os.Exit(1)
    }
    fmt.Printf("Decrypted message: %s\n", string(plaintext))
}