greenlock-express.js/https-middleware.js

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"use strict";
var SanitizeHost = module.exports;
var HttpMiddleware = require("./http-middleware.js");
SanitizeHost.create = function(gl, app) {
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return function(req, res, next) {
function realNext() {
if ("function" === typeof app) {
app(req, res);
} else if ("function" === typeof next) {
next();
} else {
res.statusCode = 500;
res.end("Error: no middleware assigned");
}
}
var hostname = HttpMiddleware.getHostname(req);
// Replace the hostname, and get the safe version
var safehost = HttpMiddleware.sanitizeHostname(req);
// if no hostname, move along
if (!hostname) {
realNext();
return;
}
// if there were unallowed characters, complain
if (safehost.length !== hostname.length) {
res.statusCode = 400;
res.end("Malformed HTTP Header: 'Host: " + hostname + "'");
return;
}
// Note: This sanitize function is also called on plain sockets, which don't need Domain Fronting checks
if (req.socket.encrypted) {
if (req.socket && "string" === typeof req.socket.servername) {
// Workaround for https://github.com/nodejs/node/issues/22389
if (!SanitizeHost._checkServername(safehost, req.socket)) {
res.statusCode = 400;
res.setHeader("Content-Type", "text/html; charset=utf-8");
res.end(
"<h1>Domain Fronting Error</h1>" +
"<p>This connection was secured using TLS/SSL for '" +
(req.socket.servername || "").toLowerCase() +
"'</p>" +
"<p>The HTTP request specified 'Host: " +
safehost +
"', which is (obviously) different.</p>" +
"<p>Because this looks like a domain fronting attack, the connection has been terminated.</p>"
);
return;
}
}
/*
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else if (safehost && !gl._skip_fronting_check) {
// We used to print a log message here, but it turns out that it's
// really common for IoT devices to not use SNI (as well as many bots
// and such).
// It was common for the log message to pop up as the first request
// to the server, and that was confusing. So instead now we do nothing.
//console.warn("no string for req.socket.servername," + " skipping fronting check for '" + safehost + "'");
//gl._skip_fronting_check = true;
}
*/
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}
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// carry on
realNext();
};
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};
var warnDomainFronting = true;
var warnUnexpectedError = true;
SanitizeHost._checkServername = function(safeHost, tlsSocket) {
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var servername = (tlsSocket.servername || "").toLowerCase();
// acceptable: older IoT devices may lack SNI support
if (!servername) {
return true;
}
// acceptable: odd... but acceptable
if (!safeHost) {
return true;
}
if (safeHost === servername) {
return true;
}
if ("function" !== typeof tlsSocket.getCertificate) {
// domain fronting attacks allowed
if (warnDomainFronting) {
// https://github.com/nodejs/node/issues/24095
console.warn(
"Warning: node " +
process.version +
" is vulnerable to domain fronting attacks. Please use node v11.2.0 or greater."
);
warnDomainFronting = false;
}
return true;
}
// connection established with servername and session is re-used for allowed name
// See https://github.com/nodejs/node/issues/24095
var cert = tlsSocket.getCertificate();
try {
// TODO optimize / cache?
// *should* always have a string, right?
// *should* always be lowercase already, right?
//console.log(safeHost, cert.subject.CN, cert.subjectaltname);
var isSubject = (cert.subject.CN || "").toLowerCase() === safeHost;
if (isSubject) {
return true;
}
var dnsnames = (cert.subjectaltname || "").split(/,\s+/);
var inSanList = dnsnames.some(function(name) {
// always prefixed with "DNS:"
return safeHost === name.slice(4).toLowerCase();
});
if (inSanList) {
return true;
}
} catch (e) {
// not sure what else to do in this situation...
if (warnUnexpectedError) {
console.warn("Warning: encoutered error while performing domain fronting check: " + e.message);
warnUnexpectedError = false;
}
return true;
}
return false;
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};