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From: davidlmontgomery on 20 Dec 2007 17:09
Hi,

My question, in short, is:

Are software firewalls in their default configurations
likely to block a connection from a program *to itself*?

Background:

I am working on a thick-client application that serves
a lot of content as locally generated and modified
web pages.

I've embedded a webserver in that client so that it serves
up pages like http://localhost:<someport>/path/to/content/.
After loading the pages AJAX is used to update the pages.

This approach provides a lot of functionality I want, but I want
to avoid any problems with end-users' firewalls blocking the
localhost connection, or annoying them with warning messages.

I'm sure that these connections *could* be blocked -- my
question is whether such connections are likely to be blocked.
For example, would they be blocked with the default configurations
of popular firewalls. First of all I'm interested in {Windows XP,
Windows Vista} x {Windows Firewall, Norton Firewall, ...}. But
I'm also interested in Mac or Linux data.

Thanks a lot,
David

From: "Mr. Arnold" MR. on 20 Dec 2007 17:53

<davidlmontgomery(a)gmail.com> wrote in message
news:a7c5da14-70ce-4faa-be11-e24e938deb01(a)d4g2000prg.googlegroups.com...
> Hi,
>
> My question, in short, is:
>
> Are software firewalls in their default configurations
> likely to block a connection from a program *to itself*?
>
> Background:
>
> I am working on a thick-client application that serves
> a lot of content as locally generated and modified
> web pages.
>
> I've embedded a webserver in that client so that it serves
> up pages like http://localhost:<someport>/path/to/content/.
> After loading the pages AJAX is used to update the pages.
>
> This approach provides a lot of functionality I want, but I want
> to avoid any problems with end-users' firewalls blocking the
> localhost connection, or annoying them with warning messages.
>
> I'm sure that these connections *could* be blocked -- my
> question is whether such connections are likely to be blocked.
> For example, would they be blocked with the default configurations
> of popular firewalls. First of all I'm interested in {Windows XP,
> Windows Vista} x {Windows Firewall, Norton Firewall, ...}. But
> I'm also interested in Mac or Linux data.
>

The products you're talking about are not FW(s), at best, they are packet
filters. The Loopback IP shouldn't be blocked, and I know XP's and Vista's
FW(s)/packet filters have no rules established to do this. Some of these
other 3rd party solutions shouldn't be blocking on the Loopback IP either,
but I guess you'll have to test your solution against them.

From: Sebastian G. on 20 Dec 2007 18:56
Mr. Arnold wrote:

> Some of these other 3rd party solutions shouldn't be blocking

> on the Loopback IP either, but I guess you'll have to test
> your solution against them.

In my experience, sadly, they do. And because they shouldn't, it's obvious
that they're ridicolously misconfigured by default.
From: Ansgar -59cobalt- Wiechers on 20 Dec 2007 22:59
davidlmontgomery(a)gmail.com <davidlmontgomery(a)gmail.com> wrote:
> My question, in short, is:
>
> Are software firewalls in their default configurations likely to block
> a connection from a program *to itself*?

Not sure about how likely that is, but some Personal Firewalls do that,
yes. However, the packet filters that come with the operating systems
(Windows Firewall, ipfw, netfilter, ...) don't.

cu
59cobalt
--
"If a software developer ever believes a rootkit is a necessary part of
their architecture they should go back and re-architect their solution."
--Mark Russinovich
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