Understanding the Handshake

The Ulterius server has multiple websocket endpoints to ensure data does not become congested.

• api
• screenshare
• webcam
• terminal

Excluding terminal which has its own unique handshake process, the api, screeshare and webcam endpoint share an authentication state. Once you authenticate one you'll be able to send messages to the others without needing to rehandshake.

When you initially connect to the server, you should target the api endpoint which is located here by default

ws://127.0.0.1:22007/api

Upon connection a unique RSA key pair is generated for you and the public key is sent over as the following json

{"endpoint":"connectedToUlterius","results":{"message":"Ulterius server online!","publicKey":"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"}}

You'll be using this public key to encrypt the AES credentials the server will use to encrypt your connections traffic.

You'll need to generate an AES key and iv, an example of which can be seen here

function generateHexString(length: number) {
    let ret = ""
    while (ret.length < length) {
        ret += Math.random().toString(16).substring(2)
    }
    return ret.substring(0, length)
}
 let key = generateHexString(16)
 let iv = generateHexString(16)

Once generated, encrypt the keys using the public key that was sent to you, then send a message body to the server with the results. Here is an example.

{"endpoint":"aeshandshake","synckey":"normal1","args":["AmDk/RxzIq6NR8W5x5+Dn3kdSveb6+Ec39Aq0QK4Tg67ZDIO4r4gOZCmQ5++2+O74GT714cJvn2MTzjvYxj+NauW8KUQL8TcHuBB9bjqVFpBuGHnIofQsJK5uplVyFgiPyiT5c6e2/W89PmLwYHupUcsUXbuTN5jCtqFQECeeOe4uIBckFAPE/5YV729s1AvEHBg/ihmQQsAQ1pPAjEuc930e+yQmAJuOsRRfTW2BN47IGj34mO0MHjbIf4QJasMm/3bFNQj1uDqI81x7OtTtyVDTkZp4udOVc+sLLAFolRZhquCSJMsZfb40Et5spOc233tEXyo11OS6FsXJnISrw==","bev4Xv1bo7jyGg6S0WiVRj31VUzfjgV3Q31mk+2FQywjomYdoijP9RftRJrFgsFClmazp4vXf89RGV/PVSaO3sjalucQQRVt8iCKMPUL6xbHglcFuyi2IK9jb4lfn6Zepw2/z29Y6YXmQ91u9uludSM/1+Ps0kbkXz8LHG7M9Ig/LB/FoFZiYyiexu3gsOiqAdEGR09QvgtoUAB8JMhjZo4m/5Fh88Zh0psBHv3viN8zndKYoSf4pGog8abk37nwV0tGLJYzbzNIdYogtqAeJT0Ew0/IfldG81q+IG1yYR9B4iHIvvZ5lo8K5IT0kW/v+oIabS+ZLU2z8JeyvPkc5Q=="]}

You should start getting use to this json structure for messages so lets cover a few entries.

• The "endpoint" field is the name of the endpoint you wish to target, in this case "aeshandshake", you can see a full list of endpoints here
• The "synckey" field is optional and allows you to pair request and responses. The response from the server will contain the sync key set during the request.
• The "args" field allows you to put arguments for individual endpoints, arguments should be placed in the correct order when being sent to the server. In this case, the first argument is the encrypted KEY while the second is the encrypted IV.

If your AES handshake is accepted, you'll receive an encrypted reply which should be decrypted using the AES credentials you generated. Otherwise it will be a plain text json body stating there was an error.

See Understanding the Packet Body for handling replies