无法解密Xor-Base64文本

Question

I am using the below code to encrypt and decrypt the data. Now I want to encrypt the data from Node JS and want to decrypt the data from Go lang. But I am not able to achieve it using GO lang.

var B64XorCipher = {
  encode: function(key, data) {
    return new Buffer(xorStrings(key, data),'utf8').toString('base64');
  },
  decode: function(key, data) {
    data = new Buffer(data,'base64').toString('utf8');
    return xorStrings(key, data);
  }
};

function xorStrings(key,input){
  var output='';
  for(var i=0;i<input.length;i++){
    var c = input.charCodeAt(i);
    var k = key.charCodeAt(i%key.length);
    output += String.fromCharCode(c ^ k);
  }
  return output;
}

From go I am trying to decode like below I am not able to achieve it.

bytes, err := base64.StdEncoding.DecodeString(actualInput)
encryptedText := string(bytes)
fmt.Println(EncryptDecrypt(encryptedText, "XXXXXX"))

func EncryptDecrypt(input, key string) (output string) {
    for i := range input {
        output += string(input[i] ^ key[i%len(key)])
    }

    return output
}

Can someone help me to resolve it.

Answer 1

You should use DecodeRuneInString instead of just slice string to byte.

Solution in playground: https://play.golang.org/p/qi_6S1J_dZU

package main

import (
    "fmt"
    "unicode/utf8"
)

func main() {
    fmt.Println("Hello, playground")
    k:="1234fd23434"
    input:="The 我characterode我 113 is equal to q"
    fmt.Println(EncryptDecrypt(input,k))

    // expect: "eZV扷ZRFRWEWA[戣[@GRX@^B"

}

func EncryptDecrypt(input, key string) (output string) {
    keylen := len(key)
    count := len(input)
    i := 0
    j := 0
    for i < count {
        c, n := utf8.DecodeRuneInString(input[i:])
        i += n
        k, m := utf8.DecodeRuneInString(key[j:])
        j += m
        if j >= keylen {
            j = 0
        }

        output += string(c ^ k)
    }

    return output
}

compared to your js result

function xorStrings(key,input){
  var output='';
  for(var i=0;i<input.length;i++){
    var c = input.charCodeAt(i);
    var k = key.charCodeAt(i%key.length);
    output += String.fromCharCode(c ^ k);
  }
  return output;
}

console.log(xorStrings('1234fd23434',"The 我characterode我 113 is equal to q"))
// expect: "eZV扷ZRFRWEWA[戣[@GRX@^B"

The test result is the same.

Here is why.

In go, when you range a string, you iterate bytes, but javascript charCodeAt is for character,not byte. In utf-8, the character is maybe 2 or 3 bytes long. So that is why you got different output.

Test in playground https://play.golang.org/p/XawI9aR_HDh

package main

import (
    "fmt"
    "unicode/utf8"
)

var sentence = "The 我quick brown fox jumps over the lazy dog."

var index = 4

func main() {
    fmt.Println("slice of string...")
    fmt.Printf("The byte at %d is |%s|, |%s| is 3 bytes long.
",index,sentence[index:index+1],sentence[index:index+3])

    fmt.Println("runes of string...")
    ru, _ := utf8.DecodeRuneInString(sentence[index:])
    i := int(ru)
    fmt.Printf("The character code at %d is|%s|%d|    
",index, string(ru), i)
}

The output is

slice of string...
The byte at 4 is |�|, |我| is 3 bytes long.
runes of string...
The character code at 4 is|我|25105|