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Re: Limit what packages my be installed



Hi,

On Thu, Jan 09, 2020 at 11:03:35AM +0100, Mikael Pahmp wrote:
> product (based on Yocto) using apt. The customer should only be allowed to
> install/alter software by installing packages signed by us. My idea is that

As that is pointing in the direction of "Tivoization" you will encounter
at least some opposition. It also feels like the first thing many
customers do in such a situation is look for a jailbreak as they
consider it an anti-feature (if not a reason to not buy). If it would be
me, I would invest more in the creation of features (hopefully) future
customers can actually make use of rather than implementing reasons to not
be customers, but that might be just my opinion.


> the user will not have root access but will be allowed to execute apt-get
> specifically using sudo from an "admin" user account (configured in
> /etc/sudoers). We will deliver the product with a pre-installed pgp key
> with which packages should be approved.

You don't want to expose apt (and many other) tools directly in that
case. You will need a wrapper. Debian Developers have access to
porterboxes and are allowed to run certain apt commands there (chrooted
though, but chroots can be escaped, so that is why) via the wrapper:
dd-schroot-cmd
https://salsa.debian.org/dsa-team/mirror/dsa-puppet/blob/master/modules/porterbox/files/dd-schroot-cmd

Of course, that is only slightly related to your usecase and DDs are (to
a certain degree) well-behaving.


> Do you think it is possible at all to get the "security" we want this way?

It certainly is possible, but apt is not designed in a way that would
make that particular easy. There are countless ways of allowing a user
who can run apt to gain root simply as apt assumes that a user who can
run it is root already. Stuff like hooks, APT_CONFIG and direct
.deb-file installation can't be features if you don't trust your users.


Best regards

David Kalnischkies

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