cloudflare-worker-for-proxy.js

'use strict'

/**
 * static files (404.html, sw.js, conf.js)
 */
const ASSET_URL = 'https://etherdream.github.io/jsproxy'

const JS_VER = 10
const MAX_RETRY = 1

/** @type {RequestInit} */
const PREFLIGHT_INIT = {
    status: 204,
    headers: new Headers({
        'access-control-allow-origin': '*',
        'access-control-allow-methods': 'GET,POST,PUT,PATCH,TRACE,DELETE,HEAD,OPTIONS',
        'access-control-max-age': '1728000',
    }),
}

/**
 * @param {any} body
 * @param {number} status
 * @param {Object<string, string>} headers
 */
function makeRes(body, status = 200, headers = {}) {
    headers['--ver'] = JS_VER
    headers['access-control-allow-origin'] = '*'
    return new Response(body, {
        status,
        headers
    })
}

/**
 * @param {string} urlStr
 */
function newUrl(urlStr) {
    try {
        return new URL(urlStr)
    } catch (err) {
        return null
    }
}

addEventListener('fetch', e => {
    const ret = fetchHandler(e)
        .catch(err => makeRes('cfworker error:\n' + err.stack, 502))
    e.respondWith(ret)
})

/**
 * @param {FetchEvent} e
 */
async function fetchHandler(e) {
    const req = e.request
    const urlStr = req.url
    const urlObj = new URL(urlStr)
    const path = urlObj.href.substr(urlObj.origin.length)

    if (urlObj.protocol === 'http:') {
        urlObj.protocol = 'https:'
        return makeRes('', 301, {
            'strict-transport-security': 'max-age=99999999; includeSubDomains; preload',
            'location': urlObj.href,
        })
    }

    if (path.startsWith('/http/')) {
        return httpHandler(req, path.substr(6))
    }

    switch (path) {
        case '/http':
            return makeRes('请更新 cfworker 到最新版本!')
        case '/ws':
            return makeRes('not support', 400)
        case '/works':
            return makeRes('it works')
        default:
            // static files
            return fetch(ASSET_URL + path)
    }
}

/**
 * @param {Request} req
 * @param {string} pathname
 */
function httpHandler(req, pathname) {
    const reqHdrRaw = req.headers
    if (reqHdrRaw.has('x-jsproxy')) {
        return Response.error()
    }

    // preflight
    if (req.method === 'OPTIONS' &&
        reqHdrRaw.has('access-control-request-headers')
    ) {
        return new Response(null, PREFLIGHT_INIT)
    }

    let acehOld = false
    let rawSvr = ''
    let rawLen = ''
    let rawEtag = ''

    const reqHdrNew = new Headers(reqHdrRaw)
    reqHdrNew.set('x-jsproxy', '1')

    // 此处逻辑和 http-dec-req-hdr.lua 大致相同
    // https://github.com/EtherDream/jsproxy/blob/master/lua/http-dec-req-hdr.lua
    const refer = reqHdrNew.get('referer')
    const query = refer.substr(refer.indexOf('?') + 1)
    if (!query) {
        return makeRes('missing params', 403)
    }
    const param = new URLSearchParams(query)

    for (const [k, v] of Object.entries(param)) {
        if (k.substr(0, 2) === '--') {
            // 系统信息
            switch (k.substr(2)) {
                case 'aceh':
                    acehOld = true
                    break
                case 'raw-info':
                    [rawSvr, rawLen, rawEtag] = v.split('|')
                    break
            }
        } else {
            // 还原 HTTP 请求头
            if (v) {
                reqHdrNew.set(k, v)
            } else {
                reqHdrNew.delete(k)
            }
        }
    }
    if (!param.has('referer')) {
        reqHdrNew.delete('referer')
    }

    // cfworker 会把路径中的 `//` 合并成 `/`
    const urlStr = pathname.replace(/^(https?):\/+/, '$1://')
    const urlObj = newUrl(urlStr)
    if (!urlObj) {
        return makeRes('invalid proxy url: ' + urlStr, 403)
    }

    /** @type {RequestInit} */
    const reqInit = {
        method: req.method,
        headers: reqHdrNew,
        redirect: 'manual',
    }
    if (req.method === 'POST') {
        reqInit.body = req.body
    }
    return proxy(urlObj, reqInit, acehOld, rawLen, 0)
}

/**
 *
 * @param {URL} urlObj
 * @param {RequestInit} reqInit
 * @param {number} retryTimes
 */
async function proxy(urlObj, reqInit, acehOld, rawLen, retryTimes) {
    const res = await fetch(urlObj.href, reqInit)
    const resHdrOld = res.headers
    const resHdrNew = new Headers(resHdrOld)

    let expose = '*'

    for (const [k, v] of resHdrOld.entries()) {
        if (k === 'access-control-allow-origin' ||
            k === 'access-control-expose-headers' ||
            k === 'location' ||
            k === 'set-cookie'
        ) {
            const x = '--' + k
            resHdrNew.set(x, v)
            if (acehOld) {
                expose = expose + ',' + x
            }
            resHdrNew.delete(k)
        } else if (acehOld &&
            k !== 'cache-control' &&
            k !== 'content-language' &&
            k !== 'content-type' &&
            k !== 'expires' &&
            k !== 'last-modified' &&
            k !== 'pragma'
        ) {
            expose = expose + ',' + k
        }
    }

    if (acehOld) {
        expose = expose + ',--s'
        resHdrNew.set('--t', '1')
    }

    // verify
    if (rawLen) {
        const newLen = resHdrOld.get('content-length') || ''
        const badLen = (rawLen !== newLen)

        if (badLen) {
            if (retryTimes < MAX_RETRY) {
                urlObj = await parseYtVideoRedir(urlObj, newLen, res)
                if (urlObj) {
                    return proxy(urlObj, reqInit, acehOld, rawLen, retryTimes + 1)
                }
            }
            return makeRes(res.body, 400, {
                '--error': `bad len: ${newLen}, except: ${rawLen}`,
                'access-control-expose-headers': '--error',
            })
        }

        if (retryTimes > 1) {
            resHdrNew.set('--retry', retryTimes)
        }
    }

    let status = res.status

    resHdrNew.set('access-control-expose-headers', expose)
    resHdrNew.set('access-control-allow-origin', '*')
    resHdrNew.set('--s', status)
    resHdrNew.set('--ver', JS_VER)

    resHdrNew.delete('content-security-policy')
    resHdrNew.delete('content-security-policy-report-only')
    resHdrNew.delete('clear-site-data')

    if (status === 301 ||
        status === 302 ||
        status === 303 ||
        status === 307 ||
        status === 308
    ) {
        status = status + 10
    }

    return new Response(res.body, {
        status,
        headers: resHdrNew,
    })
}

/**
 * @param {URL} urlObj
 */
function isYtUrl(urlObj) {
    return (
        urlObj.host.endsWith('.googlevideo.com') &&
        urlObj.pathname.startsWith('/videoplayback')
    )
}

/**
 * @param {URL} urlObj
 * @param {number} newLen
 * @param {Response} res
 */
async function parseYtVideoRedir(urlObj, newLen, res) {
    if (newLen > 2000) {
        return null
    }
    if (!isYtUrl(urlObj)) {
        return null
    }
    try {
        const data = await res.text()
        urlObj = new URL(data)
    } catch (err) {
        return null
    }
    if (!isYtUrl(urlObj)) {
        return null
    }
    return urlObj
}