Cloudflare Worker 反向代理尝试

前言

由于友链页面有使用图片的要求，同时为其他人的站点提供相关的图片资源（虽然使用现成的 GitHub Page 就可以基本实现，但是 Page 所在的仓库是公开的），尝试通过 GitHub 作为图床解决这个问题。然而，访问速度和稳定性都无法得到保证，为此通过网上搜索学习了一下反向代理 (Reverse Proxy) 的相关知识。

什么事反向代理

在这之前，先来看看什么是正向代理 ¹ (Forward Proxy)：

客户端通过代理服务器去请求服务器的资源。

Two computers connected via a proxy server. The first computer says to the proxy server: "ask the second computer what the time is".

使用正向代理需要客户端进行一些设置，即配置代理服务器。

而反向代理 ² 是指代理服务器向服务器转交请求，并返回内容给客户端，客户端将其认为是原始服务器。

A proxy server connecting the Internet to an internal network.

搭建反向代理服务

创建图床仓库

在 GitHub 中创建一个仓库，可以选择是否是私密的。

在 Personal Access Tokens (Classic) 处创建一个新的 token，勾选 repo 下所有权限。

过期时间我偷懒选了永不过期，不过这样肯定会导致安全性降低的。生成 token 后放在安全的地方，刷新后就看不见了。

配置 Worker

Cloudflare Workers 提供了这样的服务，但是免费使用具有一定的请求限制。在仪表板中添加一个 Worker，这里命名为 assets。使用的代码如下：

const upstream = "raw.githubusercontent.com";

// Custom pathname for the upstream website.
// (1) 填写代理的路径，格式为 /<用户>/<仓库名>/<分支>
const upstream_path = "/avasummer/assets/main";

// github personal access token.
// (2) 填写github令牌
const github_token = "your_tokenhere";

// Website you intended to retrieve for users using mobile devices.
const upstream_mobile = upstream;

// Countries and regions where you wish to suspend your service.
const blocked_region = [];

// IP addresses which you wish to block from using your service.
const blocked_ip_address = ["0.0.0.0", "127.0.0.1"];

// Whether to use HTTPS protocol for upstream address.
const https = true;

// Whether to disable cache.
const disable_cache = false;

// Replace texts.
const replace_dict = {
  $upstream: "$custom_domain",
};

addEventListener("fetch", (event) => {
  event.respondWith(fetchAndApply(event.request));
});

async function fetchAndApply(request) {
  const region = request.headers.get("cf-ipcountry")?.toUpperCase();
  const ip_address = request.headers.get("cf-connecting-ip");
  const user_agent = request.headers.get("user-agent");

  let response = null;
  let url = new URL(request.url);
  let url_hostname = url.hostname;

  if (https == true) {
    url.protocol = "https:";
  } else {
    url.protocol = "http:";
  }

  if (await device_status(user_agent)) {
    var upstream_domain = upstream;
  } else {
    var upstream_domain = upstream_mobile;
  }

  url.host = upstream_domain;
  if (url.pathname == "/") {
    url.pathname = upstream_path;
  } else {
    url.pathname = upstream_path + url.pathname;
  }

  if (blocked_region.includes(region)) {
    response = new Response(
      "Access denied: WorkersProxy is not available in your region yet.",
      {
        status: 403,
      }
    );
  } else if (blocked_ip_address.includes(ip_address)) {
    response = new Response(
      "Access denied: Your IP address is blocked by WorkersProxy.",
      {
        status: 403,
      }
    );
  } else {
    let method = request.method;
    let request_headers = request.headers;
    let new_request_headers = new Headers(request_headers);

    new_request_headers.set("Host", upstream_domain);
    new_request_headers.set("Referer", url.protocol + "//" + url_hostname);
    new_request_headers.set("Authorization", "token " + github_token);

    let original_response = await fetch(url.href, {
      method: method,
      headers: new_request_headers,
      body: request.body,
    });

    connection_upgrade = new_request_headers.get("Upgrade");
    if (connection_upgrade && connection_upgrade.toLowerCase() == "websocket") {
      return original_response;
    }

    let original_response_clone = original_response.clone();
    let original_text = null;
    let response_headers = original_response.headers;
    let new_response_headers = new Headers(response_headers);
    let status = original_response.status;

    if (disable_cache) {
      new_response_headers.set("Cache-Control", "no-store");
    } else {
      new_response_headers.set("Cache-Control", "max-age=43200000");
    }

    new_response_headers.set("access-control-allow-origin", "*");
    new_response_headers.set("access-control-allow-credentials", true);
    new_response_headers.delete("content-security-policy");
    new_response_headers.delete("content-security-policy-report-only");
    new_response_headers.delete("clear-site-data");

    if (new_response_headers.get("x-pjax-url")) {
      new_response_headers.set(
        "x-pjax-url",
        response_headers
          .get("x-pjax-url")
          .replace("//" + upstream_domain, "//" + url_hostname)
      );
    }

    const content_type = new_response_headers.get("content-type");
    if (
      content_type != null &&
      content_type.includes("text/html") &&
      content_type.includes("UTF-8")
    ) {
      original_text = await replace_response_text(
        original_response_clone,
        upstream_domain,
        url_hostname
      );
    } else {
      original_text = original_response_clone.body;
    }

    response = new Response(original_text, {
      status,
      headers: new_response_headers,
    });
  }
  return response;
}

async function replace_response_text(response, upstream_domain, host_name) {
  let text = await response.text();

  var i, j;
  for (i in replace_dict) {
    j = replace_dict[i];
    if (i == "$upstream") {
      i = upstream_domain;
    } else if (i == "$custom_domain") {
      i = host_name;
    }

    if (j == "$upstream") {
      j = upstream_domain;
    } else if (j == "$custom_domain") {
      j = host_name;
    }

    let re = new RegExp(i, "g");
    text = text.replace(re, j);
  }
  return text;
}

async function device_status(user_agent_info) {
  var agents = [
    "Android",
    "iPhone",
    "SymbianOS",
    "Windows Phone",
    "iPad",
    "iPod",
  ];
  var flag = true;
  for (var v = 0; v < agents.length; v++) {
    if (user_agent_info.indexOf(agents[v]) > 0) {
      flag = false;
      break;
    }
  }
  return flag;
}

部署 Worker，然后在设置 - 域和路由中添加自定义域：

现在您的图床应该可以正常访问了。

helloworld.jpg (300×384): https://assets.summ2.link/helloworld.jpg

小彩蛋

众所周知，似乎在 2020 年前后，Pixiv 就无法被直接访问了。下面借此机会，尝试搭建一个 Pixiv 图床的反向代理服务。由于 i.pximg.net 的盗链保护，得把之前的代码做一些修改。

// Website you intended to retrieve for users.
const upstream = "i.pximg.net";

// Website you intended to retrieve for users using mobile devices.
const upstream_mobile = upstream;

// Countries and regions where you wish to suspend your service.
const blocked_region = [];

// IP addresses which you wish to block from using your service.
const blocked_ip_address = ["0.0.0.0", "127.0.0.1"];

// Whether to use HTTPS protocol for upstream address.
const https = true;

// Whether to disable cache.
const disable_cache = false;

// Replace texts.
const replace_dict = {
  $upstream: "$custom_domain",
};

addEventListener("fetch", (event) => {
  event.respondWith(fetchAndApply(event.request));
});

async function fetchAndApply(request) {
  const region = request.headers.get("cf-ipcountry")?.toUpperCase();
  const ip_address = request.headers.get("cf-connecting-ip");
  const user_agent = request.headers.get("user-agent");

  let response = null;
  let url = new URL(request.url);
  let url_hostname = url.hostname;

  if (https == true) {
    url.protocol = "https:";
  } else {
    url.protocol = "http:";
  }

  if (await device_status(user_agent)) {
    var upstream_domain = upstream;
  } else {
    var upstream_domain = upstream_mobile;
  }

  url.host = upstream_domain;
/*  if (url.pathname == "/") {
    url.pathname = upstream_path;
  } else {
    url.pathname = upstream_path + url.pathname;
  }*/

  if (blocked_region.includes(region)) {
    response = new Response(
      "Access denied: WorkersProxy is not available in your region yet.",
      {
        status: 403,
      }
    );
  } else if (blocked_ip_address.includes(ip_address)) {
    response = new Response(
      "Access denied: Your IP address is blocked by WorkersProxy.",
      {
        status: 403,
      }
    );
  } else {
    let method = request.method;
    let request_headers = request.headers;
    let new_request_headers = new Headers(request_headers);

    new_request_headers.set('Referer', 'https://www.pixiv.net/');

    let original_response = await fetch(url.href, {
      method: method,
      headers: new_request_headers,
      body: request.body,
    });

    connection_upgrade = new_request_headers.get("Upgrade");
    if (connection_upgrade && connection_upgrade.toLowerCase() == "websocket") {
      return original_response;
    }

    let original_response_clone = original_response.clone();
    let original_text = null;
    let response_headers = original_response.headers;
    let new_response_headers = new Headers(response_headers);
    let status = original_response.status;

    if (disable_cache) {
      new_response_headers.set("Cache-Control", "no-store");
    } else {
      new_response_headers.set("Cache-Control", "max-age=43200000");
    }

    new_response_headers.set("access-control-allow-origin", "*");
    new_response_headers.set("access-control-allow-credentials", true);
    new_response_headers.delete("content-security-policy");
    new_response_headers.delete("content-security-policy-report-only");
    new_response_headers.delete("clear-site-data");

    if (new_response_headers.get("x-pjax-url")) {
      new_response_headers.set(
        "x-pjax-url",
        response_headers
          .get("x-pjax-url")
          .replace("//" + upstream_domain, "//" + url_hostname)
      );
    }

    const content_type = new_response_headers.get("content-type");
    if (
      content_type != null &&
      content_type.includes("text/html") &&
      content_type.includes("UTF-8")
    ) {
      original_text = await replace_response_text(
        original_response_clone,
        upstream_domain,
        url_hostname
      );
    } else {
      original_text = original_response_clone.body;
    }

    response = new Response(original_text, {
      status,
      headers: new_response_headers,
    });
  }
  return response;
}

async function replace_response_text(response, upstream_domain, host_name) {
  let text = await response.text();

  var i, j;
  for (i in replace_dict) {
    j = replace_dict[i];
    if (i == "$upstream") {
      i = upstream_domain;
    } else if (i == "$custom_domain") {
      i = host_name;
    }

    if (j == "$upstream") {
      j = upstream_domain;
    } else if (j == "$custom_domain") {
      j = host_name;
    }

    let re = new RegExp(i, "g");
    text = text.replace(re, j);
  }
  return text;
}

async function device_status(user_agent_info) {
  var agents = [
    "Android",
    "iPhone",
    "SymbianOS",
    "Windows Phone",
    "iPad",
    "iPod",
  ];
  var flag = true;
  for (var v = 0; v < agents.length; v++) {
    if (user_agent_info.indexOf(agents[v]) > 0) {
      flag = false;
      break;
    }
  }
  return flag;
}

事实上实现基本的反代功能，只需要如下代码：

export default {
  async fetch(request) {
    const url = new URL(request.url);
    url.hostname = 'i.pximg.net';

    const proxyRequest = new Request(url, request);
    proxyRequest.headers.set('Referer', 'https://www.pixiv.net/');

    return fetch(proxyRequest);
  },
};

部署在 pixiv.summ2.link 上，它可以成功配置在 PixEz（一个 Pixiv 第三方客户端）中。

Example:

https://pixiv.summ2.link/img-original/img/2023/11/20/18/53/42/113565191_p0.jpg

参考

---

1. https://en.wikipedia.org/wiki/Proxy_server↩︎

2. https://en.wikipedia.org/wiki/Reverse_proxy↩︎