api/src/core/api.js

import cors from "cors";
import rateLimit from "express-rate-limit";
import { setGlobalDispatcher, ProxyAgent } from "undici";
import { getCommit, getBranch, getRemote, getVersion } from "@imput/version-info";

import jwt from "../security/jwt.js";
import stream from "../stream/stream.js";
import match from "../processing/match.js";

import { env } from "../config.js";
import { extract } from "../processing/url.js";
import { languageCode } from "../misc/utils.js";
import { Bright, Cyan } from "../misc/console-text.js";
import { generateHmac, generateSalt } from "../misc/crypto.js";
import { randomizeCiphers } from "../misc/randomize-ciphers.js";
import { verifyTurnstileToken } from "../security/turnstile.js";
import { friendlyServiceName } from "../processing/service-alias.js";
import { verifyStream, getInternalStream } from "../stream/manage.js";
import { createResponse, normalizeRequest, getIP } from "../processing/request.js";

const git = {
    branch: await getBranch(),
    commit: await getCommit(),
    remote: await getRemote(),
}

const version = await getVersion();

const acceptRegex = /^application\/json(; charset=utf-8)?$/;

const ipSalt = generateSalt();
const corsConfig = env.corsWildcard ? {} : {
    origin: env.corsURL,
    optionsSuccessStatus: 200
}

const fail = (res, code, context) => {
    const { status, body } = createResponse("error", { code, context });
    res.status(status).json(body);
}

export const runAPI = (express, app, __dirname) => {
    const startTime = new Date();
    const startTimestamp = startTime.getTime();

    const serverInfo = JSON.stringify({
        cobalt: {
            version: version,
            url: env.apiURL,
            startTime: `${startTimestamp}`,
            durationLimit: env.durationLimit,
            turnstileSitekey: env.sessionEnabled ? env.turnstileSitekey : undefined,
            services: [...env.enabledServices].map(e => {
                return friendlyServiceName(e);
            }),
        },
        git,
    })

    const apiLimiter = rateLimit({
        windowMs: env.rateLimitWindow * 1000,
        max: env.rateLimitMax,
        standardHeaders: true,
        legacyHeaders: false,
        keyGenerator: req => {
            if (req.authorized) {
                return generateHmac(req.header("Authorization"), ipSalt);
            }
            return generateHmac(getIP(req), ipSalt);
        },
        handler: (req, res) => {
            const { status, body } = createResponse("error", {
                code: "error.api.rate_exceeded",
                context: {
                    limit: env.rateLimitWindow
                }
            });
            return res.status(status).json(body);
        }
    })

    const apiLimiterStream = rateLimit({
        windowMs: env.rateLimitWindow * 1000,
        max: env.rateLimitMax,
        standardHeaders: true,
        legacyHeaders: false,
        keyGenerator: req => generateHmac(getIP(req), ipSalt),
        handler: (req, res) => {
            return res.sendStatus(429)
        }
    })

    app.set('trust proxy', ['loopback', 'uniquelocal']);

    app.use('/', cors({
        methods: ['GET', 'POST'],
        exposedHeaders: [
            'Ratelimit-Limit',
            'Ratelimit-Policy',
            'Ratelimit-Remaining',
            'Ratelimit-Reset'
        ],
        ...corsConfig,
    }));

    app.post('/', apiLimiter);
    app.use('/tunnel', apiLimiterStream);

    app.post('/', (req, res, next) => {
        if (!acceptRegex.test(req.header('Accept'))) {
            return fail(res, "error.api.header.accept");
        }
        if (!acceptRegex.test(req.header('Content-Type'))) {
            return fail(res, "error.api.header.content_type");
        }
        next();
    });

    app.post('/', (req, res, next) => {
        if (!env.sessionEnabled) {
            return next();
        }

        try {
            const authorization = req.header("Authorization");
            if (!authorization) {
                return fail(res, "error.api.auth.jwt.missing");
            }

            if (!authorization.startsWith("Bearer ") || authorization.length > 256) {
                return fail(res, "error.api.auth.jwt.invalid");
            }

            const verifyJwt = jwt.verify(
                authorization.split("Bearer ", 2)[1]
            );

            if (!verifyJwt) {
                return fail(res, "error.api.auth.jwt.invalid");
            }

            req.authorized = true;
        } catch {
            return fail(res, "error.api.generic");
        }
        next();
    });

    app.use('/', express.json({ limit: 1024 }));
    app.use('/', (err, _, res, next) => {
        if (err) {
            const { status, body } = createResponse("error", {
                code: "error.api.invalid_body",
            });
            return res.status(status).json(body);
        }

        next();
    });

    app.post("/session", async (req, res) => {
        if (!env.sessionEnabled) {
            return fail(res, "error.api.auth.not_configured")
        }

        const turnstileResponse = req.header("cf-turnstile-response");

        if (!turnstileResponse) {
            return fail(res, "error.api.auth.turnstile.missing");
        }

        const turnstileResult = await verifyTurnstileToken(
            turnstileResponse,
            req.ip
        );

        if (!turnstileResult) {
            return fail(res, "error.api.auth.turnstile.invalid");
        }

        try {
            res.json(jwt.generate());
        } catch {
            return fail(res, "error.api.generic");
        }
    });

    app.post('/', async (req, res) => {
        const request = req.body;
        const lang = languageCode(req);

        if (!request.url) {
            return fail(res, "error.api.link.missing");
        }

        if (request.youtubeDubBrowserLang) {
            request.youtubeDubLang = lang;
        }

        const { success, data: normalizedRequest } = await normalizeRequest(request);
        if (!success) {
            return fail(res, "error.api.invalid_body");
        }

        const parsed = extract(normalizedRequest.url);

        if (!parsed) {
            return fail(res, "error.api.link.invalid");
        }
        if ("error" in parsed) {
            let context;
            if (parsed?.context) {
                context = parsed.context;
            }
            return fail(res, `error.api.${parsed.error}`, context);
        }

        try {
            const result = await match({
                host: parsed.host,
                patternMatch: parsed.patternMatch,
                params: normalizedRequest,
            });

            res.status(result.status).json(result.body);
        } catch {
            fail(res, "error.api.generic");
        }
    })

    app.get('/tunnel', (req, res) => {
        const id = String(req.query.id);
        const exp = String(req.query.exp);
        const sig = String(req.query.sig);
        const sec = String(req.query.sec);
        const iv = String(req.query.iv);

        const checkQueries = id && exp && sig && sec && iv;
        const checkBaseLength = id.length === 21 && exp.length === 13;
        const checkSafeLength = sig.length === 43 && sec.length === 43 && iv.length === 22;

        if (!checkQueries || !checkBaseLength || !checkSafeLength) {
            return res.status(400).end();
        }

        if (req.query.p) {
            return res.status(200).end();
        }

        const streamInfo = verifyStream(id, sig, exp, sec, iv);
        if (!streamInfo?.service) {
            return res.status(streamInfo.status).end();
        }

        if (streamInfo.type === 'proxy') {
            streamInfo.range = req.headers['range'];
        }

        return stream(res, streamInfo);
    })

    app.get('/itunnel', (req, res) => {
        if (!req.ip.endsWith('127.0.0.1')) {
            return res.sendStatus(403);
        }

        if (String(req.query.id).length !== 21) {
            return res.sendStatus(400);
        }

        const streamInfo = getInternalStream(req.query.id);
        if (!streamInfo) {
            return res.sendStatus(404);
        }

        streamInfo.headers = new Map([
            ...(streamInfo.headers || []),
            ...Object.entries(req.headers)
        ]);

        return stream(res, { type: 'internal', ...streamInfo });
    })

    app.get('/', (_, res) => {
        res.type('json');
        res.status(200).send(serverInfo);
    })

    app.get('/favicon.ico', (req, res) => {
        res.status(404).end();
    })

    app.get('/*', (req, res) => {
        res.redirect('/');
    })

    // handle all express errors
    app.use((_, __, res, ___) => {
        return fail(res, "error.api.generic");
    })

    randomizeCiphers();
    setInterval(randomizeCiphers, 1000 * 60 * 30); // shuffle ciphers every 30 minutes

    if (env.externalProxy) {
        if (env.freebindCIDR) {
            throw new Error('Freebind is not available when external proxy is enabled')
        }

        setGlobalDispatcher(new ProxyAgent(env.externalProxy))
    }

    app.listen(env.apiPort, env.listenAddress, () => {
        console.log(`\n` +
            Bright(Cyan("cobalt ")) + Bright("API ^ω⁠^") + "\n" +

            "~~~~~~\n" +
            Bright("version: ") + version + "\n" +
            Bright("commit: ") + git.commit + "\n" +
            Bright("branch: ") + git.branch + "\n" +
            Bright("remote: ") + git.remote + "\n" +
            Bright("start time: ") + startTime.toUTCString() + "\n" +
            "~~~~~~\n" +

            Bright("url: ") + Bright(Cyan(env.apiURL)) + "\n" +
            Bright("port: ") + env.apiPort + "\n"
        )
    })
}