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Date: Mon, 22 Apr 2024 18:10:27 -0400
From: Demi Marie Obenour <>
Subject: Re: Linux: Disabling network namespaces

On Mon, Apr 22, 2024 at 02:33:56PM +0000, Jordan Glover wrote:
> On Sunday, April 21st, 2024 at 10:06 PM, Solar Designer <> wrote:
> > In what exact way would nested namespaces bypass the security design of
> > Flatpak? Is this about the kernel's attack surface exposed by
> > capabilities in a namespace or something else? I guess capabilities are
> > also dropped in the nested namespace?
> In flatpak, apps in container communicate with host through portals[1] using dbus.
> Portals identify particular app through unique appid (i.e. "org.mozilla.firefox"
> for firefox) and grant some permissions according to that. appid is read from
> /.flatpak-info that exist inside container and is immutable there. If namespaces
> were available inside sandbox then malicious app could leverage mount namespace
> to mount crafted /.flatpak-info containing arbitrary data and lie to the portal
> about appid - it could tell portal that it's org.mozilla.firefox when it isn't.
> [1]
> Jordan

Why is the appid read from /.flatpak-info, instead of having the flatpak
process that spawned the container pass the info to the dbus proxy along
with the FD used to communicate with the container?
Demi Marie Obenour (she/her/hers)
Invisible Things Lab

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