safe-regex

What is safe-regex?

The safe-regex package is a utility for checking if a given regular expression is safe and not susceptible to ReDoS (Regular Expression Denial of Service) attacks. It evaluates the complexity of regular expressions and determines if they can potentially cause exponential time complexity issues.

What are safe-regex's main functionalities?

Safety Check

This feature allows developers to check if a regular expression is safe to use, preventing potential ReDoS attacks. The function returns a boolean indicating whether the regex is considered safe.

const safeRegex = require('safe-regex');
const regex = /a+$/;
console.log(safeRegex(regex)); // Outputs: true or false depending on the safety

Other packages similar to safe-regex

vuln-regex-detector

This package is similar to safe-regex as it also checks for potentially vulnerable regular expressions that could lead to ReDoS attacks. It provides a more comprehensive analysis and supports asynchronous API, making it suitable for larger applications compared to safe-regex.

regex-safe

Like safe-regex, regex-safe is designed to ensure that regular expressions are safe from ReDoS attacks. It offers a simple API to validate regex patterns but does not provide the detailed analysis or support for asynchronous operations found in some other packages.

README

safe-regex

Detect potentially catastrophic exponential-time regular expressions by limiting the star height to 1.

WARNING: This module has both false positives and false negatives. Use vuln-regex-detector for improved accuracy.

Example

Suppose you have a script named safe.js:

var safe = require('safe-regex');
var regex = process.argv.slice(2).join(' ');
console.log(safe(regex));

This is its behavior:

$ node safe.js '(x+x+)+y'
false
$ node safe.js '(beep|boop)*'
true
$ node safe.js '(a+){10}'
false
$ node safe.js '\blocation\s*:[^:\n]+\b(Oakland|San Francisco)\b'
true

Methods

const safe = require('safe-regex')

const ok = safe(re, opts={})

Return a boolean ok whether or not the regex re is safe and not possibly catastrophic.

re can be a RegExp object or just a string.

If the re is a string and is an invalid regex, returns false.

• opts.limit - maximum number of allowed repetitions in the entire regex. Default: 25.

Install

With npm do:

npm install safe-regex

Resources

What should I do if my project has a super-linear regex?

1. Confirm that it is reachable by untrusted input.
2. If it is, you can consider whether you can prevent worst-case behavior by trimming the input, revising the regex, or replacing the regex with another algorithm like string functions. For examples, see Table 5 in this article.
3. If none of those solutions looks feasible, you might also consider changing regex engines. The RE2 bindings might work, though test carefully to confirm there are no semantic portability problems.

Further reading

The following documents may be edifying:

• Research brief on the extent of super-linear regexes in practice
• Research brief on the variability of super-linear regex behavior across programming languages
• Comparing regex matching algorithms

Project policies

Versioning

This project follows Semantic Versioning 2.0 (semver).

Here are the project-specific meanings of MAJOR, MINOR, and PATCH updates:

• MAJOR: "Incompatible" API changes were introduced. There are two types in this module:
  • Changes that modify the interface
  • Changes that cause any regexes to be marked as unsafe that were formerly marked as safe
• MINOR: Functionality was added in a backwards-compatible manner. There are two types in this module:
  • Refactoring the analyses but not changing their results
  • Modifying the analyses to reduce false positives, without affecting negatives (false or true)
• PATCH: I don't anticipate using PATCH for this module

License

MIT