CipherLink

Optional encryption and signing of the whole Connect answer.

Optional. Enable in Connect Settings > Response > Encryption. The entire JSON response is encrypted, for both success and error responses.

Keep in mind

Payload: AES-256-CBC with PKCS#7 padding, then Base64.
Signature: RSA-SHA256 over the Base64 payload string, then Base64.
Marked answers: Encrypted answers carry the X-CipherLink header.
Random field: The decrypted JSON holds an extra random field at the root. Ignore it.

Envelope

Encrypted answer

{
    "sig": "<BASE64_RSA_SIGNATURE>",
    "payload": "<BASE64_AES_CIPHERTEXT>"
}

Decoding

Decode sig from Base64.
Verify RSA-SHA256 over the payload string.
Decode payload from Base64.
Decrypt AES-256-CBC.
Parse the JSON and ignore the unknown random field at the root.

$envelope = json_decode($body, true);
$signature = base64_decode($envelope['sig']);

if (openssl_verify($envelope['payload'], $signature, RSA_PUBLIC_KEY, OPENSSL_ALGO_SHA256) !== 1) {
    throw new RuntimeException('Bad signature');
}

$json = openssl_decrypt($envelope['payload'], 'aes-256-cbc', AES_KEY, 0, AES_IV);
$answer = json_decode($json, true);

import base64, json
from cryptography.hazmat.primitives import hashes, padding, serialization
from cryptography.hazmat.primitives.asymmetric import padding as rsa
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes

envelope = json.loads(body)
public_key = serialization.load_pem_public_key(RSA_PUBLIC_KEY)
public_key.verify(base64.b64decode(envelope["sig"]), envelope["payload"].encode(), rsa.PKCS1v15(), hashes.SHA256())

decryptor = Cipher(algorithms.AES(AES_KEY), modes.CBC(AES_IV)).decryptor()
padded = decryptor.update(base64.b64decode(envelope["payload"])) + decryptor.finalize()
unpadder = padding.PKCS7(128).unpadder()
answer = json.loads(unpadder.update(padded) + unpadder.finalize())

Client config

Copy these from Connect Settings into the mod. The values below are placeholders.

Name	Value	Size
`aes_key`	`<AES_KEY_FROM_CONNECT_SETTINGS>`	32 bytes
`aes_iv`	`<AES_IV_FROM_CONNECT_SETTINGS>`	16 bytes
`rsa_public_key`	`<RSA_PUBLIC_KEY_FROM_CONNECT_SETTINGS>`	—
`tls_public_key_pin`	`<TLS_PIN_IF_CONFIGURED>`	—

TLS pin

If your settings show a TLS public key pin, check it on every connection before sending the key.

#Keep in mind

#Envelope

#Decoding

#Client config

Keep in mind

Envelope

Decoding

Client config