JAVA AES ECB加密到Golang迁移

Question

I try to port a Java implementation of AES decryption to Golang. I need to decrypt data that is previously encrypted by the JAVA code using Golang. But so far I have no luck decrypting it.

The Java code is:

private static byte[] pad(final String password) {
    String key;
    for (key = password; key.length() < 16; key = String.valueOf(key) + key) {}
    return key.substring(0, 16).getBytes();
}

public static String encrypt(String password, String message) throws Exception
{    
  SecretKeySpec skeySpec = new SecretKeySpec(pad(password), "AES");
  Cipher cipher = Cipher.getInstance("AES");
  cipher.init(1, skeySpec);

  byte[] encrypted = cipher.doFinal(message.getBytes());
  return Hex.encodeHexString(encrypted);
}

public static String decrypt(String password, String message)
throws Exception {

  SecretKeySpec skeySpec = new SecretKeySpec(pad(password), "AES");

  Cipher cipher = Cipher.getInstance("AES");
  cipher.init(1, skeySpec);

  cipher.init(2, skeySpec);
  byte[] original = cipher.doFinal(Hex.decodeHex(message.toCharArray()));
  return new String(original);
}

I tried implementations like Cryptography GIST or

func decrypt(passphrase, data []byte) []byte {
  cipher, err := aes.NewCipher([]byte(passphrase))
  if err != nil {
    panic(err)
  }
  decrypted := make([]byte, len(data))
  size := 16

  for bs, be := 0, size; bs < len(data); bs, be = bs+size, be+size {
    cipher.Decrypt(decrypted[bs:be], data[bs:be])
  }

  return decrypted
}
hx, _ := hex.DecodeString(hexString)
res := decrypt([]byte(password), hx)

No error is thrown, and a string is returned. But this string is not anywhere close to the encrypted data. Any help is very much appreciated! Thanks!

Answer 1

Java adds a padding by default with the PKCS5 algorithm. In your Go code, you have to remove that padding with something like this (before returning the decrypted value):

func pkcs5UnPadding(src []byte) []byte {
    length := len(src)
    if length%64 == 0 {
        return src
    }
    unpadding := int(src[length-1])
    return src[:(length - unpadding)]
}