tslint-config-security

TSLint security rules

Inspired by eslint-plugin-security

How to use

• Install package:

npm i tslint-config-security --save-dev  --production

• Update your tslint.json:

{
  "extends": ["tslint-config-security"]
}

By default tslint-config-security enables all rules, but you may disable any of them (not recommended):

{
  "extends": ["tslint-config-security"],
  "rules": {
    "tsr-detect-html-injection": false,
    "tsr-detect-unsafe-regexp": false
  }
}

Rules

All rules start from the prefix tsr- (TSLint Security Rule) to prevent name collisions.

tsr-detect-unsafe-regexp

Locates potentially unsafe regular expressions, which may take a very long time to run, blocking the event loop.

Examples: test/rules/tsr-detect-unsafe-regexp/default/test.ts.lint

More information:

• https://web.archive.org/web/20170131192028/https://blog.liftsecurity.io/2014/11/03/regular-expression-dos-and-node.js#regular-expression-dos-and-nodejs
• https://snyk.io/blog/redos-and-catastrophic-backtracking

tsr-detect-non-literal-buffer

Detects variable in new Buffer argument

Examples: test/rules/tsr-detect-non-literal-buffer/default/test.ts.lint

tsr-detect-buffer-noassert

Detects calls to Buffer with noAssert flag set

From the Node.js API docs: "Setting noAssert to true skips validation of the offset. This allows the offset to be beyond the end of the Buffer."

Examples: test/rules/tsr-detect-buffer-noassert/default/test.ts.lint

tsr-detect-child-process

Detects instances of child_process & non-literal exec()

More information: https://web.archive.org/web/20170129010544/https://blog.liftsecurity.io/2014/08/19/Avoid-Command-Injection-Node.js#avoiding-command-injection-in-nodejs

Examples: test/rules/tsr-detect-child-process/default/test.ts.lint

tsr-disable-mustache-escape

Detects object.escapeMarkup = false, which can be used with some template engines to disable escaping of HTML entities. This can lead to Cross-Site Scripting (XSS) vulnerabilities.

More information: https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)

Examples: test/rules/tsr-disable-mustache-escape/default/test.ts.lint

tsr-detect-eval-with-expression

Detects eval(variable) which can allow an attacker to run arbitrary code inside your process.

More information: http://security.stackexchange.com/questions/94017/what-are-the-security-issues-with-eval-in-javascript

Examples: test/rules/tsr-detect-eval-with-expression/default/test.ts.lint

tsr-detect-no-csrf-before-method-override

Detects Express csrf middleware setup before method-override middleware. This can allow GET requests (which are not checked by csrf) to turn into POST requests later.

More information: http://blog.nibblesec.org/2014/05/nodejs-connect-csrf-bypass-abusing.html

Examples: test/rules/tsr-detect-no-csrf-before-method-override/default/test.ts.lint

tsr-detect-non-literal-fs-filename

Detects variable in filename argument of fs calls, which might allow an attacker to access anything on your system.

More information: https://www.owasp.org/index.php/Path_Traversal

Known limitations

Due to the known issues in the typed TSLint rules:

• https://github.com/Microsoft/vscode-tslint/issues/70
• https://github.com/Microsoft/vscode-tslint/blob/master/tslint/README.md#how-can-i-use-tslint-rules-that-require-type-information
• https://github.com/Microsoft/vscode-tslint/issues/70

tslint-config-security module will analyze methods only on fs variable or on 'fs' module. E.g.:

const fs = require('fs');
 
fs.open(somePath); // triggers the error
require('fs').symlink(path1, path2); // triggers the error
require("fs").symlink(path1, path2); // triggers the error
 
const myFs = require('fs');
 
myFs.open(somePath); // no error

More examples: test/rules/tsr-detect-non-literal-fs-filename/default/test.ts.lint

tsr-detect-non-literal-regexp

Detects RegExp(variable), which might allow an attacker to DOS your server with a long-running regular expression.

More information:

• https://web.archive.org/web/20170131192028/https://blog.liftsecurity.io/2014/11/03/regular-expression-dos-and-node.js#regular-expression-dos-and-nodejs

Examples: test/rules/tsr-detect-non-literal-regexp/default/test.ts.lint

tsr-detect-non-literal-require

Detects require(variable), which might allow an attacker to load and run arbitrary code, or access arbitrary files on disk.

More information:

• http://www.bennadel.com/blog/2169-where-does-node-js-and-require-look-for-modules.htm
• https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-dynamic-require.md

Examples: test/rules/tsr-detect-non-literal-require/default/test.ts.lint

tsr-detect-possible-timing-attacks

Detects insecure comparisons (==, !=, !== and ===), which check input sequentially.

More information: https://snyk.io/blog/node-js-timing-attack-ccc-ctf/

Examples: test/rules/tsr-detect-possible-timing-attacks/default/test.ts.lint

tsr-detect-pseudo-random-bytes

Detects if pseudoRandomBytes() is in use, which might not give you the randomness you need and expect.

More information: http://stackoverflow.com/questions/18130254/randombytes-vs-pseudorandombytes

Examples: test/rules/tsr-detect-pseudo-random-bytes/default/test.ts.lint

tsr-detect-html-injection

Detects HTML injections:

• document.write(variable)
• document.writeln(variable)
• Element.innerHTML = variable;
• Element.outerHTML = variable;
• el.insertAdjacentHTML(variable);

More examples: test/rules/tsr-detect-html-injection/default/test.ts.lint

tsr-detect-sql-literal-injection

Detects possible SQL injections in string literals:

// invalid
const userId = 1;
const query1 = `SELECT * FROM users WHERE id = ${userId}`;
const query2 = `SELECT * FROM users WHERE id = ` + userId;
const query3 = 'SELECT * FROM users WHERE id =' + userId;
 
const columns = 'id, name';
Users.query(`SELECT ${columns} FROM users`);
 
// valid
const userId = 1;
const query = sql`SELECT * FROM users WHERE id = ${userId}`;
db.query(query);
 
// See https://github.com/mysqljs/mysql
db.query('SELECT * FROM `books` WHERE `author` = ?', ['David'], function (error, results, fields) {
  //...
});

More examples: test/rules/tsr-detect-sql-literal-injection/default/test.ts.lint

tsr-detect-unsafe-cross-origin-communication

Detects when all windows & frames on your page (including ones that were injected by 3rd-party scripts) may receive your data.

Always provide a specific targetOrigin, not *, if you know where the other window's document should be located. Failing to provide a specific target discloses the data you send to any interested malicious site. https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage

const myWindow = document.getElementById('myIFrame').contentWindow;
 
myWindow.postMessage(message, "*"); // Noncompliant

tsr-detect-unsafe-properties-access

Detects a potential unsafe access to the object properties

/* 
 
It equals to `new Function(prop3)`
 
const a = {};
 
a["constructor"]["constructor"]("alert(1)")()
 */
 
// unsafe
obj[prop1][prop2](prop3)
 
// unsafe
obj[prop1][prop2](prop3)()  
 

More information:

• Web Puzzlers - Securing Dynamic Systems
• Defensive JavaScript

Solutions:

• use Map
• use .hasOwnProperty check
• use Content-Security-Policy on your page