Porting AES encryption functionality to node.js

Question content

I am trying to port a go program (https://github.com/mckael/samtv) to node.js, which can be passed "smartview" api controls Samsung TV

There is an "aes encryption" feature in the program that I'm having trouble porting to node.

func (s *smartviewsession) aesencrypt(plaindata []byte) ([]byte, error) {
    //logrus.debugf("aesencrypt(%#v) : '%s'", plaindata, string(plaindata))
    //logrus.debugf("session id:  %d", s.sessionid)
    //logrus.debugf("session key: '%x'\n  %v", string(s.sessionkey), s.sessionkey)

    // create cipher block
    block, err := aes.newcipher(s.sessionkey)
    if err != nil {
        return nil, err
    }

    bs := block.blocksize()
    //logrus.debugf("block size: %d", bs)

    // add padding
    padding := bs - len(plaindata)%bs
    padtext := bytes.repeat([]byte{byte(padding)}, padding)
    //logrus.debugf("padding: %d byte(s)", padding)
    plaindata = append(plaindata, padtext...)

    // encrypt
    ciphertext := make([]byte, len(plaindata))
    for cipherrange := ciphertext; len(plaindata) > 0; {
        block.encrypt(cipherrange, plaindata[:bs])
        plaindata = plaindata[bs:]
        cipherrange = cipherrange[bs:]
    }

    //logrus.debugf("ciphertext: %#v", ciphertext)
    return ciphertext, nil
}

The problem I'm facing now is that I don't know what algorithmthim to use, or where I need to specify in my node.js function the "initial vector" comes from:

const SESSION_KEY = "59e8ca4b09f2a19ab5421cf55d604c7c";

var aesEncrypt = ((val, algo = "aes-256-cbc") => {
    let cipher = crypto.createCipheriv(algo, SESSION_KEY, IV);
    let encrypted = cipher.update(val, 'utf8', 'base64');
    encrypted += cipher.final('base64');
    return encrypted;
});

Can I use crypto.createcipher(...) instead? But it's been deprecated, and it feels like the padding stuff is important.

I know nothing about encryption. Any tips are welcome.

Note: In the go function, s.sessionkey has the same value as session_key = "59e8ca4b09f2a19ab5421cf55d604c7c" in node.js

Solution

go code applies aes in ecb mode and uses pkcs#7 padding. aes variants Implicit Derived from the key size, e.g. aes-128 for 16 byte keys. The ciphertext is returned as []byte.

In the nodejs code, the aes variant and mode are explicitly specified, such as aes-128-ecb. ecb mode does not apply IVs, so must be specified as null in createcipheriv(). Use padding pkcs#7 (default). The ciphertext can be returned as buffer, which is closest to []byte.

The published key 59e8ca4b09f2a19ab5421cf55d604c7c looks like a hex-encoded key, it is hex-decoded 16 bytes large and therefore corresponds to aes-128. Hexadecimal decoding can be implemented in go using the encoding/hex package, for example with hex.decodestring("59e8ca4b09f2a19ab5421cf55d604c7c").

Nodejs code example using aes-128 (16 byte key) and pkcs#7 padding in ecb mode:

var crypto = require('crypto');

const SESSION_KEY = Buffer.from("59e8ca4b09f2a19ab5421cf55d604c7c", "hex");

var aesEncrypt = ((val, algo = "aes-128-ecb") => {
    let cipher = crypto.createCipheriv(algo, SESSION_KEY, null);
    return Buffer.concat([cipher.update(val, 'utf8'), cipher.final()]);
});

var ciphertext = aesEncrypt("The quick brown fox jumps over the lazy dog");
console.log(ciphertext.toString('base64')); // T/uQforseVFkY93mqwpwCGVVnEFDTT5Gle8a8XUxCfOXCfYUo3uCJ/nwzCIJ9xqf

The go code gives the same results using the same key (hex decoding) and base64 encoding of plaintext and ciphertext.

For completeness: the key can also be encoded in utf-8 and then generate a 32-byte key, such as key := []byte("59e8ca4b09f2a19ab5421cf55d604c7c") and ## in the go code #const session_key = buffer.from("59e8ca4b09f2a19ab5421cf55d604c7c", "utf-8") nodejs code. In nodejs code, aes-256-ecb must also be applied. Ultimately, the key specification must provide information on which encoding to use.

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