On Tue, Feb 7, 2023 at 3:59 AM Vieri <[email protected]> wrote:
>
> OK, I just got bitten by my own system.
>
> Guacamole is behind a reverse-proxy with ModSecurity.
> Sending variables as ${} is considered a potential attack, so I get this in 
> the WAF:
>
> [id "932130"] [msg "Remote Command Execution: Unix Shell Expression Found"] 
> [data "Matched Data: ${guac_username}_${guac_date}_${guac_time} found within 
> ARGS:parameters.recording-name: 
> test_rdp_${guac_username}_${guac_date}_${guac_time}"]
>
> Sorry for the misleading messages in this ML!
>
> I guess I can deactivate this Rule by ID for my Guacamole virtual domain.
> However, would it be possible for the Guacamole Client to somehow encrypt or 
> base64-encode the HTTP requests so it doesn't trigger this ModSecurity rule?
>

Yes, it would be possible to do such a thing, but it seems like a
fairly extreme way to resolve the issue. I would imagine that the WAF
has ways to create exceptions for the rules, rather than de-activating
them entirely, and that seems a more reasonable approach than either
de-activating the rule entirely or modifying the source code.

-Nick

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