cobalt/src/modules/stream/manage.js

import NodeCache from "node-cache";
import { randomBytes } from "crypto";
import { nanoid } from 'nanoid';

import { decryptStream, encryptStream, generateHmac } from "../sub/crypto.js";
import { streamLifespan } from "../config.js";
import { strict as assert } from "assert";

const streamNoAccess = {
    error: "i couldn't verify if you have access to this stream. go back and try again!",
    status: 401
}
const streamNoExist = {
    error: "this download link has expired or doesn't exist. go back and try again!",
    status: 400
}

const streamCache = new NodeCache({
    stdTTL: streamLifespan/1000,
    checkperiod: 10,
    deleteOnExpire: true
})

streamCache.on("expired", (key) => {
    streamCache.del(key);
})

const internalStreamCache = {};
const hmacSalt = randomBytes(64).toString('hex');

export function createStream(obj) {
    const streamID = nanoid(),
        iv = randomBytes(16).toString('base64url'),
        secret = randomBytes(32).toString('base64url'),
        exp = new Date().getTime() + streamLifespan,
        hmac = generateHmac(`${streamID},${exp},${iv},${secret}`, hmacSalt),
        streamData = {
            exp: exp,
            type: obj.type,
            urls: obj.u,
            service: obj.service,
            filename: obj.filename,
            audioFormat: obj.audioFormat,
            isAudioOnly: !!obj.isAudioOnly,
            copy: !!obj.copy,
            mute: !!obj.mute,
            metadata: obj.fileMetadata || false
        };

    streamCache.set(
        streamID,
        encryptStream(streamData, iv, secret)
    )

    let streamLink = new URL('/api/stream', process.env.API_URL);

    const params = {
        't': streamID,
        'e': exp,
        'h': hmac,
        's': secret,
        'i': iv
    }

    for (const [key, value] of Object.entries(params)) {
        streamLink.searchParams.append(key, value);
    }

    return streamLink.toString();
}

export function getInternalStream(id) {
    return internalStreamCache[id];
}

export function createInternalStream(obj = {}) {
    assert(typeof obj.url === 'string');

    const streamID = nanoid();
    internalStreamCache[streamID] = {
        url: obj.url,
        service: obj.service,
        controller: new AbortController()
    };

    let streamLink = new URL('/api/istream', `http://127.0.0.1:${process.env.API_PORT}`);
    streamLink.searchParams.set('t', streamID);
    return streamLink.toString();
}

export function destroyInternalStream(url) {
    const id = new URL(url).searchParams.get('t');
    assert(id);

    if (internalStreamCache[id]) {
        internalStreamCache[id].controller.abort();
        delete internalStreamCache[id];
    }
}

export function verifyStream(id, hmac, exp, secret, iv) {
    try {
        const ghmac = generateHmac(`${id},${exp},${iv},${secret}`, hmacSalt);
        const cache = streamCache.get(id.toString());

        if (ghmac !== String(hmac)) return streamNoAccess;
        if (!cache) return streamNoExist;

        const streamInfo = JSON.parse(decryptStream(cache, iv, secret));

        if (!streamInfo) return streamNoExist;

        if (Number(exp) <= new Date().getTime())
            return streamNoExist;

        if (!streamInfo.originalUrls) {
            streamInfo.originalUrls = streamInfo.urls;
        }        

        if (typeof streamInfo.originalUrls === 'string') {
            streamInfo.urls = createInternalStream({
                url: streamInfo.originalUrls,
                ...streamInfo
            });
        } else if (Array.isArray(streamInfo.originalUrls)) {
            for (const idx in streamInfo.originalUrls) {
                streamInfo.originalUrls[idx] = createInternalStream({
                    url: streamInfo.originalUrls[idx],
                    ...streamInfo
                });
            }
        } else throw 'invalid urls';

        return streamInfo;
    }
    catch {
        return {
            error: "something went wrong and i couldn't verify this stream. go back and try again!",
            status: 500
        }
    }
}