F21 System Wide Change: Workstation: Disable firewall

Miloslav Trmač mitr at volny.cz
Thu Apr 17 21:14:53 UTC 2014

Just some clarifications so that we are all on the same page; those don't
significantly affect the larger discussion though...

2014-04-15 17:40 GMT+02:00 Andrew Lutomirski <luto at mit.edu>:

> Can someone explain what threat is effectively mitigated by a firewall
> on a workstation machine?  Here are some bad answers:

>   - WebRTC, VOIP, etc. issues?  These use NAT traversal techniques that
> are specifically designed to prevent your firewall from operating as
> intended.

That's imprecise; NAT traversal techniques are designed to allow a
*specific* counterparty through the firewall, not everyone on the Internet
like disabling the firewall would do.

  - DLNA / Chromecast / whatever: wouldn't it be a lot more sensible
> for these things to be off until specifically requested?

That would be about equivalent to controlling them only via a firewall.

>  Who actually
> uses a so-called "zone" UI correctly to configure them?

"Who actually uses any other UI correctly to configure sharing
zones?"—nobody because there apparently isn't any.  Firewalld has a zone
implementation that can be improved upon.

>  How about
> having an API where things like DLNA can simply not run until you're
> connected to your home network?

Firewalld has a zone implementation that can be improved upon.

Also, having a firewall on exposes you to a huge attack surface in
> iptables, and it doesn't protect against attacks targeting the
> kernel's IP stack.

*Nothing* will ever protect you against attacks targetting the kernel's IP
sack, that's a strawman.  And the entire premise of a firewall is that the
attack surface of the firewall (iptables in this case) is smaller than the
attack premise of applications behind; intuitively it's very likely to be
true, and AFAICT it's also been true historically.
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