annonet/proxyPolicyPatch.js

const fs = require("fs");

const target = process.argv[2];
if (!target) {
  throw new Error("server.js path is required");
}

let source = fs.readFileSync(target, "utf8");

const replaceOnce = (label, before, after) => {
  const first = source.indexOf(before);
  if (first === -1) {
    throw new Error(`proxy patch failed: ${label} pattern not found`);
  }
  if (source.indexOf(before, first + before.length) !== -1) {
    throw new Error(`proxy patch failed: ${label} pattern matched more than once`);
  }
  source = source.slice(0, first) + after + source.slice(first + before.length);
};

const replaceAllCount = (label, before, after, expectedCount) => {
  const parts = source.split(before);
  const count = parts.length - 1;
  if (count !== expectedCount) {
    throw new Error(`proxy patch failed: ${label} expected ${expectedCount} matches, found ${count}`);
  }
  source = parts.join(after);
};

replaceOnce(
  "referer target guard",
  [
    "    if (!PRIVATE_IP.test(parsedUpstream.hostname)) {",
    "      return null;",
    "    }"
  ].join("\n"),
  [
    "    if (!isProxyTargetAllowed(parsedUpstream)) {",
    "      return null;",
    "    }"
  ].join("\n")
);

replaceOnce(
  "cookie target guard",
  [
    "    if (!PRIVATE_IP.test(parsed.hostname)) {",
    "      return null;",
    "    }"
  ].join("\n"),
  [
    "    if (!isProxyTargetAllowed(parsed)) {",
    "      return null;",
    "    }"
  ].join("\n")
);

replaceOnce(
  "resource rewrite hook",
  [
    "  cleaned = rewriteUpstreamAbsoluteAssetUrls(cleaned, annotationSite);",
    "",
    "  if (cleaned.includes(\"</head>\")) {"
  ].join("\n"),
  [
    "  cleaned = rewriteUpstreamAbsoluteAssetUrls(cleaned, annotationSite);",
    "  cleaned = rewriteProxyResourceUrls(cleaned, annotationUrl || annotationSite, apiBase);",
    "",
    "  if (cleaned.includes(\"</head>\")) {"
  ].join("\n")
);

replaceOnce(
  "dev asset target guard",
  [
    "    if (!PRIVATE_IP.test(upstreamAssetUrl.hostname)) {",
    "      return res.status(403).json({ error: \"only private/LAN addresses allowed\" });",
    "    }"
  ].join("\n"),
  [
    "    if (!isProxyTargetAllowed(upstreamAssetUrl)) {",
    "      return res.status(403).json({ error: \"target host is not allowed by proxy policy\" });",
    "    }"
  ].join("\n")
);

replaceOnce(
  "proxy policy block",
  [
    "// Server-side proxy — fetches target page and injects the annotation overlay.",
    "// Restricted to private/LAN IP ranges only to prevent SSRF abuse.",
    "const PRIVATE_IP = /^(localhost|127\\.\\d+\\.\\d+\\.\\d+|10\\.\\d+\\.\\d+\\.\\d+|172\\.(1[6-9]|2\\d|3[01])\\.\\d+\\.\\d+|192\\.168\\.\\d+\\.\\d+)/i;"
  ].join("\n"),
  [
    "// Server-side proxy target policy. Public production targets must be explicitly",
    "// allowlisted. Private/LAN targets are disabled by default and can be enabled",
    "// only for trusted local-development deployments.",
    "const PRIVATE_IP = /^(localhost|127\\.\\d+\\.\\d+\\.\\d+|10\\.\\d+\\.\\d+\\.\\d+|172\\.(1[6-9]|2\\d|3[01])\\.\\d+\\.\\d+|192\\.168\\.\\d+\\.\\d+|169\\.254\\.\\d+\\.\\d+|::1|\\[::1\\])$/i;",
    "const PROXY_ALLOW_PRIVATE = [\"1\", \"true\", \"yes\"].includes(",
    "  String(process.env.ANNONET_PROXY_ALLOW_PRIVATE || \"\").trim().toLowerCase()",
    ");",
    "const PROXY_ALLOWED_HOSTS = String(process.env.ANNONET_PROXY_ALLOWED_HOSTS || \"\")",
    "  .split(\",\")",
    "  .map((value) => value.trim().toLowerCase())",
    "  .filter(Boolean);",
    "",
    "const proxyHostMatches = (hostname, pattern) => {",
    "  if (pattern === hostname) return true;",
    "  if (pattern.startsWith(\"*.\")) {",
    "    const suffix = pattern.slice(1);",
    "    return hostname.endsWith(suffix) && hostname.length > suffix.length;",
    "  }",
    "  return false;",
    "};",
    "",
    "const isProxyTargetAllowed = (parsed) => {",
    "  if (!parsed || ![\"http:\", \"https:\"].includes(parsed.protocol)) return false;",
    "  if (parsed.username || parsed.password) return false;",
    "",
    "  const hostname = String(parsed.hostname || \"\").trim().toLowerCase();",
    "  if (!hostname) return false;",
    "  if (PRIVATE_IP.test(hostname)) return PROXY_ALLOW_PRIVATE;",
    "",
    "  return PROXY_ALLOWED_HOSTS.some((pattern) => proxyHostMatches(hostname, pattern));",
    "};",
    "",
    "const toProxyResourceUrl = (rawValue, pageUrl, apiBase) => {",
    "  const raw = String(rawValue || \"\").trim();",
    "  if (!raw || raw.startsWith(\"#\") || /^(?:data:|blob:|javascript:|mailto:|tel:)/i.test(raw)) return rawValue;",
    "",
    "  try {",
    "    const base = new URL(pageUrl);",
    "    const resolved = new URL(raw, base);",
    "    if (resolved.origin !== base.origin) return rawValue;",
    "    return apiBase + \"/api/proxy?url=\" + encodeURIComponent(resolved.toString());",
    "  } catch (_error) {",
    "    return rawValue;",
    "  }",
    "};",
    "",
    "const rewriteProxyResourceUrls = (html, pageUrl, apiBase) => {",
    "  return String(html || \"\").replace(",
    "    /(<(?:script|link|img|source|video|audio|iframe)\\b[^>]*?\\s(?:src|href|poster)=[\"'])([^\"']+)([\"'])/gi,",
    "    (_match, prefix, value, suffix) => prefix + toProxyResourceUrl(value, pageUrl, apiBase) + suffix",
    "  );",
    "};",
    "",
    "const rewriteProxyCssUrls = (css, pageUrl, apiBase) => {",
    "  return String(css || \"\").replace(",
    "    /url\\(\\s*([\"']?)([^)\"']+)\\1\\s*\\)/gi,",
    "    (_match, quote, value) => {",
    "      const rewritten = toProxyResourceUrl(value, pageUrl, apiBase);",
    "      return \"url(\" + quote + rewritten + quote + \")\";",
    "    }",
    "  );",
    "};"
  ].join("\n")
);

replaceOnce(
  "redirect target guard",
  [
    "      if (!PRIVATE_IP.test(next.hostname)) {",
    "        // Redirect leaves private network — stop following, return current response.",
    "        return { response, allSetCookies, finalUrl: url };",
    "      }"
  ].join("\n"),
  [
    "      if (!isProxyTargetAllowed(next)) {",
    "        const error = new Error(\"redirect target host is not allowed by proxy policy\");",
    "        error.status = 403;",
    "        throw error;",
    "      }"
  ].join("\n")
);

replaceAllCount(
  "main proxy target guards",
  [
    "    if (!PRIVATE_IP.test(parsed.hostname)) {",
    "      return res.status(403).json({ error: \"only private/LAN addresses allowed\" });",
    "    }"
  ].join("\n"),
  [
    "    if (!isProxyTargetAllowed(parsed)) {",
    "      return res.status(403).json({ error: \"target host is not allowed by proxy policy\" });",
    "    }"
  ].join("\n"),
  2
);

replaceOnce(
  "proxied CSS rewrite",
  [
    "    if (!contentType.includes(\"text/html\")) {",
    "      const body = await upstream.arrayBuffer();",
    "      res.set(\"Content-Type\", contentType);",
    "      return res.send(Buffer.from(body));",
    "    }"
  ].join("\n"),
  [
    "    if (!contentType.includes(\"text/html\")) {",
    "      res.set(\"Content-Type\", contentType);",
    "      if (contentType.includes(\"text/css\")) {",
    "        const css = await upstream.text();",
    "        return res.send(rewriteProxyCssUrls(css, finalUrl, apiBase));",
    "      }",
    "      const body = await upstream.arrayBuffer();",
    "      return res.send(Buffer.from(body));",
    "    }"
  ].join("\n")
);

if (source.includes("only private/LAN addresses allowed")) {
  throw new Error("proxy patch failed: stale LAN-only error remains");
}

fs.writeFileSync(target, source);
console.log("Applied annoNet public proxy allowlist patch");