feat: supporting PCRE patterns for CommonWebAttack & BadCrawler threats

[dwisiswant0]

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Summary

Previously, there were some CommonWebAttack and BadCrawler threat patterns that could not compile with the built-in regexp because they had negative lookahead (PCRE) properties.

As a workaround, use go-pcre as an alternative way if the built-in regexp doesn't compile the pattern.

Proposed of changes

This PR fixes/implements the following bugs/features:

• Bug [known-issue] unable to compile some CommonWebAttack & BadCrawler patterns #4

How has this been tested?

Proof:

Run simple server:

$ go run examples/simple/main.go

Test for

• CommonWebAttack threat:

$ curl localhost:3000 -so /dev/null -w "%{http_code}\n" -A X -d "body=%22autofocus%20%27%20onfocus%3D%27alert%28document.domain%29%27%22%22"
403

Payload by Aidil Arief (https://hackerone.com/aidilarf_2000).

• BadCrawler threat:

$ curl localhost:3000 -so /dev/null -w "%{http_code}\n" -A "Yandex"
403
$ curl localhost:3000 -so /dev/null -w "%{http_code}\n" -A "YandexSearch"
200

Closing issues

Fixes #4

Checklist:

• My code follows the code style of this project.
• My changes successfully ran and pass linters locally (run make lint).
• I have written new tests for my changes.
  • My changes successfully ran and pass tests locally.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.