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favicon-request.js
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favicon-request.js
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/* eslint-disable no-console */
const path = require('path');
const fs = require('fs');
const http = require('http');
const https = require('https');
const { URL } = require('url');
const MAX_REDIRECTS = 3;
const MAX_RESPONSE_CHUNKS = 1000;
const KNOWN_ICONS = {
'gmail.com': 'https://ssl.gstatic.com/ui/v1/icons/mail/rfr/gmail.ico'
};
const DEBUG = process.env.DEBUG_FAVICON;
const IP_THROTTLING_MS = +(process.env.IP_THROTTLING_MS || 1000);
const IP_THROTTLING_AGGRESSIVE_LOCKDOWN_DETECTION_THRESHOLD = +(
process.env.IP_THROTTLING_AGGRESSIVE_LOCKDOWN_DETECTION_THRESHOLD || 100
);
const IP_THROTTLING_AGGRESSIVE_LOCKDOWN_TIME_MS = +(
process.env.IP_THROTTLING_AGGRESSIVE_LOCKDOWN_TIME_MS || 60 * 60 * 1000
);
const lastRequestDatePerIp = new Map();
const bannedReferrers = {};
fs.readFileSync(path.resolve(__dirname, 'conf/banned-referrers.txt'), 'utf8')
.split('\n')
.map((line) => line.trim())
.filter((line) => line && !line.startsWith('#'))
.forEach((line) => {
bannedReferrers[line] = true;
});
function faviconApp(req, res) {
if (req.url === '/favicon.ico') {
res.writeHead(204);
res.end();
return;
}
if (req.url === '/') {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.end(
'This is a service for loading website favicons with CORS\n\n' +
'Usage: GET /domain.com\n' +
'Questions, source code: https://github.com/keeweb/favicon-proxy'
);
return;
}
let blockStatusCode = 0;
let blockReason = '';
if (req.headers.referer) {
let refererDomain = req.headers.referer.match(/^\w+:\/\/([^/?]+)/);
if (refererDomain) {
refererDomain = refererDomain[1].toLowerCase();
}
if (bannedReferrers[refererDomain]) {
blockReason = 'Forbidden';
blockStatusCode = 403;
}
}
const clientIp = req.headers['cf-connecting-ip'] || req.connection.remoteAddress;
const now = new Date();
if (needThrottle(clientIp, now)) {
blockReason = 'Too many requests';
blockStatusCode = 429;
}
console.log(
now.toISOString(),
'GET',
req.url,
req.headers.origin || '-',
req.headers.referer || '-',
req.headers['user-agent'] || '-',
clientIp,
req.headers['cf-ipcountry'] || '-',
blockReason || '-'
);
if (blockReason) {
return returnError(blockStatusCode || 403, res, blockReason);
}
const domain = req.url.substr(1).toLowerCase();
if (domain.indexOf('.') < 0 || domain.match(/[\/:?]|(\.\.)/)) {
return returnError(404, res, 'Usage: GET /domain.com');
}
if (domain.indexOf('keeweb.info') >= 0) {
return returnError(403, res, 'No, I cannot get my own favicon');
}
const faviconUrl = KNOWN_ICONS[domain] || 'http://' + domain + '/favicon.ico';
loadResource(faviconUrl)
.then((srvRes) => {
const contentType = srvRes.headers['content-type'];
if (contentType.startsWith('image/') || contentType === 'application/octet-stream') {
return pipeResponse(res, srvRes);
} else {
throw 'Bad content-type';
}
})
.catch((e) => {
if (e === 'Status 404' || e === 'Bad content-type') {
loadResource('http://' + domain)
.then((srvRes) => {
readHtml(srvRes)
.then((html) => {
const iconUrl = getIconUrl(html, domain);
if (iconUrl) {
loadResource(iconUrl)
.then((srvRes) => {
pipeResponse(res, srvRes);
})
.catch((e) => returnError(500, res, e));
} else {
returnError(404, res, 'No favicon');
}
})
.catch((e) => returnError(500, res, e));
})
.catch((e) => returnError(500, res, e));
} else {
returnError(500, res, e);
}
});
}
function loadResource(url, redirectNum) {
DEBUG && console.log('GET', url);
return new Promise((resolve, reject) => {
const proto = url.startsWith('https://')
? https
: url.startsWith('http://')
? http
: undefined;
if (!proto) {
return reject('Invalid protocol');
}
if (/:\/\/(127\.|192\.|0\.0\.|localhost|(\w+\.)?keeweb\.info)/i.test(url)) {
return reject('Bad redirect: ' + url);
}
const serverReq = proto.get(url, (srvRes) => {
DEBUG && console.log(srvRes.statusCode);
if (srvRes.statusCode > 300 && srvRes.statusCode < 400 && srvRes.headers.location) {
const redirectLocation = srvRes.headers.location;
try {
new URL(redirectLocation);
} catch {
DEBUG && console.log(`Bad redirect: ${redirectLocation}`);
return reject('Bad redirect');
}
if (redirectNum > MAX_REDIRECTS) {
reject('Too many redirects');
} else {
resolve(loadResource(redirectLocation, (redirectNum || 0) + 1));
}
} else if (srvRes.statusCode === 200) {
resolve(srvRes);
} else {
reject('Status ' + srvRes.statusCode);
}
});
serverReq.on('error', (e) => {
reject(e.message);
});
serverReq.end();
});
}
function readHtml(stream) {
return new Promise((resolve, reject) => {
const chunks = [];
stream.on('data', (chunk) => {
if (chunks.length > MAX_RESPONSE_CHUNKS) {
return reject('Response too large');
} else {
chunks.push(chunk);
}
});
stream.on('error', () => {
reject('HTML read error');
});
stream.on('end', () => {
resolve(Buffer.concat(chunks).toString('utf8'));
});
});
}
function getIconUrl(html, domain) {
const MAX_SIZE = 96;
let match;
const re = /<link\s+[^>]*rel=["']?(?:shortcut )?icon["']?[^>]*>/g;
let iconHref,
iconSize = 0;
do {
match = re.exec(html);
if (match) {
let href = /href=(["'])([^'"]+)"*\1/.exec(match[0]);
if (href) {
href = href[2];
}
const sizes = /sizes=["']?(\d+)/.exec(match[0]);
if (sizes) {
const size = +sizes[1];
if (size && size > iconSize && size <= MAX_SIZE) {
iconHref = href;
iconSize = size;
}
} else if (!iconHref) {
iconHref = href;
}
}
} while (match);
if (/\.(png|jpg|svg|gif|ico)/.test(iconHref)) {
if (iconHref.indexOf('://') > 0) {
return iconHref;
} else {
if (!iconHref.startsWith('/')) {
iconHref = '/' + iconHref;
}
if (iconHref.startsWith('//')) {
return 'http:' + iconHref;
}
return 'http://' + domain + iconHref;
}
}
}
function pipeResponse(res, srvRes) {
res.writeHead(200, {
'Content-Type': 'image/x-icon',
'Access-Control-Allow-Origin': '*'
});
srvRes.pipe(res, { end: true });
}
function needThrottle(clientIp, now) {
if (!IP_THROTTLING_MS) {
return false;
}
let lastRequestDate = lastRequestDatePerIp.get(clientIp);
let throttled = false;
let newLastRequestDate = now.getTime();
if (lastRequestDate) {
const dateDiff = now - lastRequestDate;
if (dateDiff < IP_THROTTLING_MS) {
if (
IP_THROTTLING_AGGRESSIVE_LOCKDOWN_DETECTION_THRESHOLD &&
IP_THROTTLING_AGGRESSIVE_LOCKDOWN_TIME_MS &&
dateDiff < IP_THROTTLING_AGGRESSIVE_LOCKDOWN_DETECTION_THRESHOLD
) {
newLastRequestDate += IP_THROTTLING_AGGRESSIVE_LOCKDOWN_TIME_MS;
}
throttled = true;
}
}
lastRequestDatePerIp.set(clientIp, newLastRequestDate);
if (lastRequestDatePerIp.size > 50) {
for (const [ip, dt] of lastRequestDatePerIp.entries()) {
if (now - dt > IP_THROTTLING_MS) {
lastRequestDatePerIp.delete(ip);
}
}
}
return throttled;
}
function returnError(code, res, err) {
res.writeHead(code, { 'Content-Type': 'text/plain' });
return res.end(String(err));
}
module.exports = faviconApp;