在golang中对AES解密的紧急返回

Question

I have implemented AES encryption on an angular app which sends encrypted string to a REST api written in golang which then decrypts it to verify if its a valid key or not.

Encryption and decryption is working on angular app and golang separately but rest API returns Panic when we decrypt string sent from angular app

Following is my code on app to encrypt in component file

import * as CryptoJS from 'crypto-js';

var key = "NPZ8fvABP5pKwU3"; // passphrase used to encrypt 
let encrypted_text = CryptoJS.AES.encrypt('Hello World', 'NPZ8fvABP5pKwU3');

When I decrypt it with following code it returns "Hello World" on angular app

var bytes  = CryptoJS.AES.decrypt(encrypted_text.toString(), 'NPZ8fvABP5pKwU3');
var plaintext = bytes.toString(CryptoJS.enc.Utf8);
console.log(plaintext);

It fails to return same text in rest api with following code in main.go file

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/md5"
    "crypto/rand"
    "encoding/hex"
    "fmt"
    "io"
)

func decrypt(data []byte, passphrase string) []byte {
    key := []byte(createHash(passphrase))
    block, err := aes.NewCipher(key)
    if err != nil {
        panic(err.Error())
    }
    gcm, err := cipher.NewGCM(block)
    if err != nil {
        panic(err.Error())
    }
    nonceSize := gcm.NonceSize()
    nonce, ciphertext := data[:nonceSize], data[nonceSize:]
    plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
    if err != nil {
        panic(err.Error())
    }
    return plaintext
}

func main() {
    key2 := "NPZ8fvABP5pKwU3"
    key3 := []byte("encrypted string from angular app")

    plaintext := decrypt(key3, key2)
    fmt.Printf(string(plaintext))
}

func createHash(key string) string {
 hasher := md5.New()
 hasher.Write([]byte(key))
 return hex.EncodeToString(hasher.Sum(nil))
}

https://play.golang.org/p/iGYyg0RB-Zi

returned error

panic: cipher: message authentication failed

Answer 1

You don't need to use createHash function, just use the key. The problem is that your key is 15 bytes long while aes.NewCipher expects either 16, 24 or 32 bytes. Just change you key and use this code:

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/md5"

    "encoding/hex"
    "fmt"
)

func decrypt(data []byte, passphrase string) []byte {
    key := []byte(passphrase)
    block, err := aes.NewCipher(key)
    if err != nil {
        panic(err.Error())
    }
    gcm, err := cipher.NewGCM(block)
    if err != nil {
        panic(err.Error())
    }
    nonceSize := gcm.NonceSize()
    nonce, ciphertext := data[:nonceSize], data[nonceSize:]
    plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
    if err != nil {
        panic(err.Error())
    }
    return plaintext
}

func main() {
    key2 := "NPZ8fvABP5pKwU3"
    key3 := []byte("encrypted string from angular app")

    plaintext := decrypt(key3, key2)
    fmt.Printf(string(plaintext))
}