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https://github.com/0xsobky/regaxor
A regular expression fuzzer.
https://github.com/0xsobky/regaxor
fuzzing regex regexp regular-expression tools
Last synced: 3 months ago
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A regular expression fuzzer.
- Host: GitHub
- URL: https://github.com/0xsobky/regaxor
- Owner: 0xSobky
- License: mpl-2.0
- Created: 2018-03-12T18:53:49.000Z (almost 7 years ago)
- Default Branch: master
- Last Pushed: 2018-03-13T00:02:00.000Z (almost 7 years ago)
- Last Synced: 2024-09-27T01:49:30.024Z (4 months ago)
- Topics: fuzzing, regex, regexp, regular-expression, tools
- Language: JavaScript
- Homepage: https://0xsobky.github.io/Regaxor/
- Size: 1.79 MB
- Stars: 42
- Watchers: 5
- Forks: 5
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
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README
# Regaxor
Regaxor (RegExp Haxxor) is a regular expression fuzzer, written in ECMAScript 6.
## Why do we need it?
Whatever you're coding, regular expressions come in handy in various situations and are often very useful but can also be very tricky to get right. Writing a regex that matches what you expect is easy; writing a regex that ___only___ matches what you expect is virtually impossible (except in trivial cases). That's where this tool comes into play—by fuzzing regular expressions, we can easily detect any issues/gotchas before learning about them the hard way.
### Regex gotchas?!
The following are just some examples of common regex gotchas (NVM the funny titles):
1. In the beginning was the Word
```javascript
let badRegex = /https?:\/\/example\.com\/[\w]*/;
let str = 'Word\nhttps://example.com/';
str.match(badRegex);
// Output: ["https://example.com/", index: 5, input: "Word↵https://example.com/", groups: undefined]
let goodRegex = /^https?:\/\/example\.com\/[\w]*/;
str.match(goodRegex);
// Output: null
'https://example.com/'.match(goodRegex);
// Output: ["https://example.com/", index: 0, input: "https://example.com/", groups: undefined]
```
2. Catch 22
```javascript
let badRegex = /[123]|22/g;
badRegex.exec('22');
// Output: ["2", index: 0, input: "22", groups: undefined]
let goodRegex = /22|[123]/g;
goodRegex.exec('22');
// Output: ["22", index: 0, input: "22", groups: undefined]
```
3. One sneaky dot
```javascript
let str = 'https://exampleXcom';
let badRegex = /^\w+:\/\/example.com$/;
badRegex.exec(str);
// Output: ["https://exampleXcom", index: 0, input: "https://exampleXcom", groups: undefined]
let goodRegex = /^\w+:\/\/example\.com$/;
goodRegex.exec(str);
// Output: null
goodRegex.exec('https://example.com');
// Output: ["https://example.com", index: 0, input: "https://example.com", groups: undefined]
```
4. All or nothing
```javascript
let badRegex = /^\.*|\d+$/g;
'abc'.match(badRegex);
// Output: [""]
let goodRegex = /^[\d.]+$/g;
'abc'.match(goodRegex);
// Output: null
'12.3'.match(goodRegex);
// Output: ["12.3"]
```
5. The word boundary trap
```javascript
let badRegex = /word/;
badRegex.exec('aworda');
// Output: ["word", index: 1, input: "aworda", groups: undefined]
let goodRegex = /\bword\b/;
goodRegex.exec('aworda');
// Output: null
goodRegex.exec('a word');
// Output: ["word", index: 2, input: "a word", groups: undefined]
```
6. Multiline confusion
```javascript
let badRegex = /a.*b/;
badRegex.exec('a\nb');
// Output: null
let alsoBadRegex = /a.*b/m;
alsoBadRegex.exec('a\nb');
// Output: null
let goodRegex = /a[^]*b/;
goodRegex.exec('a\nb');
// Output: ["a↵b", index: 0, input: "a↵b", groups: undefined]
```
7. One escape is not enough
```javascript
let badRegex = 'x\.com';
new RegExp(badRegex).exec('xycom');
// Output: ["xycom", index: 0, input: "xycom", groups: undefined]
let goodRegex = 'x\\.com';
new RegExp(goodRegex).exec('xycom');
// Output: null
new RegExp(goodRegex).exec('x.com');
// Output: ["x.com", index: 0, input: "x.com", groups: undefined]
```
8. Escaping the escaping
```javascript
let str = 'double\\"quotes"';
// Bad.
str.replace(/"/g, '\\"');
// Output: "double\\"quotes\""
// Not bad but not recommended.
str.replace(/(\\|")/g, '\\$1');
// Output: "double\\\"quotes\""
// Better.
str.replace(/\\/g, '\\\\').replace(/"/g, '\\"');
// Output: "double\\\"quotes\""
```
9. Too greedy
```javascript
let badRegex = /<.+><\/.+>/g;
let tags = '';
badRegex.exec(tags);
// Output: ["", index: 0, input: "", groups: undefined]
let notBadRegex = /<.+?><\/.+?>/g;
notBadRegex.exec(tags);
// Output: ["", index: 0, input: "", groups: undefined]
notBadRegex.exec(tags);
// Output: ["", index: 27, input: "", groups: undefined]
```
10. The misplaced hyphen
```javascript
let badRegex = /[\w -$]+/;
'#'.match(badRegex);
// Output: ["#", index: 0, input: "#", groups: undefined]
let goodRegex = /[\w $-]+/;
'#'.match(goodRegex);
// Output: null
'$100 USD'.match(goodRegex);
// Output: ["$100 USD", index: 0, input: "$100 USD", groups: undefined]
```
At times, writing a regex can feel like walking in a minefield. At other times, regular expressions are the wrong answer—or as Jamie Zawinski puts it `Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.`. So, especially in security-sensitive contexts, you're probably better off not using regular expressions unless you really have to....
## Screenshot(s)
[](https://github.com/0xSobky/Regaxor/raw/master/data/images/screenshot.png)
## Credits
* [@0xSobky](https://twitter.com/0xSobky)