Auto forwarding ports, but only to localhost

Auto forwarding ports, but only to localhost

[Jan Wrobel]

Hi,

For pasta, would you consider an option to enable automatic forwarding
of ports bound in a namespace, but make the forwarded ports available
only via localhost, not all addresses?

I'm working on a sandboxing program which uses pasta. The option -t
"auto" is super convenient, but requires extra care, without proper
firewall setup bound ports become automatically available to outside
world. For a sandboxing program like mine, it is not a safe default to
run with, because the program shouldn't assume the user will have a
firewall configured.

If something like "localhost/auto" was supported, it would match the
convenience of "auto", no manual port mapping config would be needed,
but would be safer for uses cases where exposing ports to outside
world is problematic.

Cheers,
Jan

Re: Auto forwarding ports, but only to localhost

[David Gibson]

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On Thu, Nov 27, 2025 at 01:48:54PM +0100, Jan Wrobel wrote:
> Hi,
> 
> For pasta, would you consider an option to enable automatic forwarding
> of ports bound in a namespace, but make the forwarded ports available
> only via localhost, not all addresses?
> 
> I'm working on a sandboxing program which uses pasta. The option -t
> "auto" is super convenient, but requires extra care, without proper
> firewall setup bound ports become automatically available to outside
> world. For a sandboxing program like mine, it is not a safe default to
> run with, because the program shouldn't assume the user will have a
> firewall configured.
> 
> If something like "localhost/auto" was supported, it would match the
> convenience of "auto", no manual port mapping config would be needed,
> but would be safer for uses cases where exposing ports to outside
> world is problematic.

Short answer: yes, but it might be a while.

Long answer:

We want to make our forwarding / NAT configuration more flexible in
ways that would allow a bunch of things, including this.  There are a
lot of different features people have requested, each individually
simple, but together adding up to quite a lot of work.  I'm actively
working on making our internal data structures more flexible to allow
more general configuration.  However, it's fairly slow going, between
other firefighting and unravelling some technical debt.

If you want to make sure your specific use case isn't forgotten, the
best way would be to file a ticket for it on passt.top - it will
probably be blocked on https://bugs.passt.top/show_bug.cgi?id=140 but
that will keep a record to look back at later.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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Re: Auto forwarding ports, but only to localhost

[Jan Wrobel]

On Fri, Nov 28, 2025 at 2:10 AM David Gibson
<david@gibson.dropbear.id.au> wrote:
>
> On Thu, Nov 27, 2025 at 01:48:54PM +0100, Jan Wrobel wrote:
> > Hi,
> >
> > For pasta, would you consider an option to enable automatic forwarding
> > of ports bound in a namespace, but make the forwarded ports available
> > only via localhost, not all addresses?
> >
> > I'm working on a sandboxing program which uses pasta. The option -t
> > "auto" is super convenient, but requires extra care, without proper
> > firewall setup bound ports become automatically available to outside
> > world. For a sandboxing program like mine, it is not a safe default to
> > run with, because the program shouldn't assume the user will have a
> > firewall configured.
> >
> > If something like "localhost/auto" was supported, it would match the
> > convenience of "auto", no manual port mapping config would be needed,
> > but would be safer for uses cases where exposing ports to outside
> > world is problematic.
>
> Short answer: yes, but it might be a while.
>
> Long answer:
>
> We want to make our forwarding / NAT configuration more flexible in
> ways that would allow a bunch of things, including this.  There are a
> lot of different features people have requested, each individually
> simple, but together adding up to quite a lot of work.  I'm actively
> working on making our internal data structures more flexible to allow
> more general configuration.  However, it's fairly slow going, between
> other firefighting and unravelling some technical debt.
>
> If you want to make sure your specific use case isn't forgotten, the
> best way would be to file a ticket for it on passt.top - it will
> probably be blocked on https://bugs.passt.top/show_bug.cgi?id=140 but
> that will keep a record to look back at later.

Thanks, for considering adding this feature!

I'll add the ticket, but currently there is some problem with the
passt ticket system. I've seen it working at some point but today and
yesterday https://passt.top/passt/bugs is just an empty page, and
https://bugs.passt.top/index.cgi gives 403 error

Cheers,
Jan

Re: Auto forwarding ports, but only to localhost

[David Gibson]

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On Fri, Nov 28, 2025 at 12:03:06PM +0100, Jan Wrobel wrote:
> On Fri, Nov 28, 2025 at 2:10 AM David Gibson
> <david@gibson.dropbear.id.au> wrote:
> >
> > On Thu, Nov 27, 2025 at 01:48:54PM +0100, Jan Wrobel wrote:
> > > Hi,
> > >
> > > For pasta, would you consider an option to enable automatic forwarding
> > > of ports bound in a namespace, but make the forwarded ports available
> > > only via localhost, not all addresses?
> > >
> > > I'm working on a sandboxing program which uses pasta. The option -t
> > > "auto" is super convenient, but requires extra care, without proper
> > > firewall setup bound ports become automatically available to outside
> > > world. For a sandboxing program like mine, it is not a safe default to
> > > run with, because the program shouldn't assume the user will have a
> > > firewall configured.
> > >
> > > If something like "localhost/auto" was supported, it would match the
> > > convenience of "auto", no manual port mapping config would be needed,
> > > but would be safer for uses cases where exposing ports to outside
> > > world is problematic.
> >
> > Short answer: yes, but it might be a while.
> >
> > Long answer:
> >
> > We want to make our forwarding / NAT configuration more flexible in
> > ways that would allow a bunch of things, including this.  There are a
> > lot of different features people have requested, each individually
> > simple, but together adding up to quite a lot of work.  I'm actively
> > working on making our internal data structures more flexible to allow
> > more general configuration.  However, it's fairly slow going, between
> > other firefighting and unravelling some technical debt.
> >
> > If you want to make sure your specific use case isn't forgotten, the
> > best way would be to file a ticket for it on passt.top - it will
> > probably be blocked on https://bugs.passt.top/show_bug.cgi?id=140 but
> > that will keep a record to look back at later.
> 
> Thanks, for considering adding this feature!
> 
> I'll add the ticket, but currently there is some problem with the
> passt ticket system. I've seen it working at some point but today and
> yesterday https://passt.top/passt/bugs is just an empty page, and
> https://bugs.passt.top/index.cgi gives 403 error

Oh, weird.  https://bugs.passt.top is the address to use, but I
haven't noticed it being down in the last couple of days.  It seems to
me working for me right now.

Note that signing up for an account is likely to be somewhat slow -
Stefano has to manually intervene for each sign up, to avoid
inundation by bots.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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Re: Auto forwarding ports, but only to localhost

[Stefano Brivio]

On Fri, 28 Nov 2025 12:03:06 +0100
Jan Wrobel <jan@mixedbit.org> wrote:

> On Fri, Nov 28, 2025 at 2:10 AM David Gibson
> <david@gibson.dropbear.id.au> wrote:
> >
> > On Thu, Nov 27, 2025 at 01:48:54PM +0100, Jan Wrobel wrote:  
> > > Hi,
> > >
> > > For pasta, would you consider an option to enable automatic forwarding
> > > of ports bound in a namespace, but make the forwarded ports available
> > > only via localhost, not all addresses?
> > >
> > > I'm working on a sandboxing program which uses pasta. The option -t
> > > "auto" is super convenient, but requires extra care, without proper
> > > firewall setup bound ports become automatically available to outside
> > > world. For a sandboxing program like mine, it is not a safe default to
> > > run with, because the program shouldn't assume the user will have a
> > > firewall configured.
> > >
> > > If something like "localhost/auto" was supported, it would match the
> > > convenience of "auto", no manual port mapping config would be needed,
> > > but would be safer for uses cases where exposing ports to outside
> > > world is problematic.  
> >
> > Short answer: yes, but it might be a while.
> >
> > Long answer:
> >
> > We want to make our forwarding / NAT configuration more flexible in
> > ways that would allow a bunch of things, including this.  There are a
> > lot of different features people have requested, each individually
> > simple, but together adding up to quite a lot of work.  I'm actively
> > working on making our internal data structures more flexible to allow
> > more general configuration.  However, it's fairly slow going, between
> > other firefighting and unravelling some technical debt.
> >
> > If you want to make sure your specific use case isn't forgotten, the
> > best way would be to file a ticket for it on passt.top - it will
> > probably be blocked on https://bugs.passt.top/show_bug.cgi?id=140 but
> > that will keep a record to look back at later.  
> 
> Thanks, for considering adding this feature!
> 
> I'll add the ticket, but currently there is some problem with the
> passt ticket system. I've seen it working at some point but today and
> yesterday https://passt.top/passt/bugs is just an empty page, and
> https://bugs.passt.top/index.cgi gives 403 error

Weird, sorry for the inconvenience, both work for me. I did some
maintenance last week but I didn't expect any downtime as a result.

Can you try again and, if things fail, give me an exact timestamp of
when you tried, so that I can try to find out something from logs?

-- 
Stefano

Re: Auto forwarding ports, but only to localhost

[Stefano Brivio]

On Mon, 1 Dec 2025 11:12:20 +0100
Jan Wrobel <jan@mixedbit.org> wrote:

> This still doesn't work for me with the same 403 error. Perhaps it works
> for you because you already have an account and are logged-in to the ticket
> system? Try accessing https://bugs.passt.top/index.cgi from a private
> browser window, maybe then you will also trigger the error?
> 
> Today the failure happened for example at Mon, 01 Dec 2025 10:02:47 GMT

Oops, my bad! The whole registered subnet was denied access,
specifically for Bugzilla, because of some recent "AI" bot scraping
from there.

I'll need to come up with a better approach. I don't want to make it
slower for everybody with Anubis (https://anubis.techaro.lol/) but the
risk of banning people like it happened to you is also pretty bad. :(

Maybe it would make sense to use Anubis just for Bugzilla. The rest
seems to be fast/robust enough for the moment.

It should work now. Sorry for that.

-- 
Stefano

Re: Auto forwarding ports, but only to localhost

[Jan Wrobel]

On Mon, Dec 1, 2025 at 11:32 AM Stefano Brivio <sbrivio@redhat.com> wrote:
>
> On Mon, 1 Dec 2025 11:12:20 +0100
> Jan Wrobel <jan@mixedbit.org> wrote:
>
> > This still doesn't work for me with the same 403 error. Perhaps it works
> > for you because you already have an account and are logged-in to the ticket
> > system? Try accessing https://bugs.passt.top/index.cgi from a private
> > browser window, maybe then you will also trigger the error?
> >
> > Today the failure happened for example at Mon, 01 Dec 2025 10:02:47 GMT
>
> Oops, my bad! The whole registered subnet was denied access,
> specifically for Bugzilla, because of some recent "AI" bot scraping
> from there.
>
> I'll need to come up with a better approach. I don't want to make it
> slower for everybody with Anubis (https://anubis.techaro.lol/) but the
> risk of banning people like it happened to you is also pretty bad. :(
>
> Maybe it would make sense to use Anubis just for Bugzilla. The rest
> seems to be fast/robust enough for the moment.
>
> It should work now. Sorry for that.

Thanks, it works well now. I've added a ticket.

Cheers,
Jan