Re: [Mod-security-developers] Macro expansion in operators

[Marc S. <mar...@ap...>]

The main goal is to be able to extend a pattern incrementally. This is especially useful in shared environments, but not limited to this case.

Example: you define you general policy to accept only certain characters
   SecRule ARGS "@validateByteRange 32-90"

In a location, you want an exception to accept some additional characters (CR/LF):
   <Location /...>
    SecRule ARGS "@validateByteRange 10,13,32-90"
   </Location>

In case you extend your global policy (let's say 32-95), your exception doesn't follow it. You are obliged to keep them aligned (you'll forget to do this if they are disseminated in several files).

The solution could be:
   SecAction "phase:1,setvar:tx.allowedRange=32-90"

   <Location /...>
    SecAction "phase:2,setvar:tx.allowedRange=%{tx.allowedRange},10,13"
   </Location>

   SecRule ARGS "@validateByteRange %{tx.allowedRange}" "phase:2,..."

Same for ipMatch

Marc

On 05-02-19 17:54, Felipe Costa wrote:

Hi Marc,


There is no specific reason. As there is a computational cost for macro expansion, we may have it only where/when it is extremely necessary. Do you have a specific use case?


Br.,

Felipe "Zimmerle" Costa

Security Researcher, Lead Developer ModSecurity


________________________________
From: Marc Stern <mar...@ap...><mailto:mar...@ap...>
Sent: Friday, February 1, 2019 12:16:20 PM
To: mod...@li...<mailto:mod...@li...>
Subject: [Mod-security-developers] Macro expansion in operators

Can somebody explain me why the operators below don't perform macro
expansion; they're using plain strings, not pre-calculated patterns:
  - ipMatch
  - validateByteRange

Would a pull request implementing this be accepted?

Marc Stern

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