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36 lines
1.4 KiB
Markdown
36 lines
1.4 KiB
Markdown
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# Regular Expression
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> Regular Expression Denial of Service (ReDoS) is a type of attack that exploits the fact that certain regular expressions can take an extremely long time to process, causing applications or services to become unresponsive or crash.
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## Denial of Service - ReDoS
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* [tjenkinson/redos-detector](https://github.com/tjenkinson/redos-detector) - A CLI and library which tests with certainty if a regex pattern is safe from ReDoS attacks. Supported in the browser, Node and Deno.
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* [doyensec/regexploit](https://github.com/doyensec/regexploit) - Find regular expressions which are vulnerable to ReDoS (Regular Expression Denial of Service)
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* [devina.io/redos-checker](https://devina.io/redos-checker) - Examine regular expressions for potential Denial of Service vulnerabilities
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### Evil Regex
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Evil Regex contains:
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* Grouping with repetition
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* Inside the repeated group:
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* Repetition
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* Alternation with overlapping
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**Examples**
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* `(a+)+`
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* `([a-zA-Z]+)*`
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* `(a|aa)+`
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* `(a|a?)+`
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* `(.*a){x}` for x \> 10
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These regular expressions can be exploited with `aaaaaaaaaaaaaaaaaaaaaaaa!`
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## References
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* [Regular expression Denial of Service - ReDoS - OWASP - Adar Weidman](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS)
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* [OWASP Validation Regex Repository - OWASP](https://wiki.owasp.org/index.php/OWASP_Validation_Regex_Repository)
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