[Bug 1882098] Re: Packagekit lets user install untrusted local packages in Bionic and Focal

[Esko Järnfors]

Thanks for triaging and investigating this, Julian!

A fix for at least the aptcc backend would be highly appreciated -- I'd
hope the other backends will fix this on their own if they care about
it.

The point of packagekit+policykit is to enable people to do (at least
somewhat limited) stuff without explicit root access -- otherwise you'd
just give them sudo rights and be done with it. In the current
situation, granting a user the right to install ("trusted") packages
actually grants them rights to place arbitrary files in the filesystem
and execute arbitrary code (package scripts) as root, which is at the
very very least highly misleading.

I took a cursory look at the earlier apt backend written in python
(which is now deleted from the packagekit tree) and it at least looked
like it had some logic to decide whether a package can be trusted or not
so it didn't seem like checking where the package is coming from would
be unprecedented.

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https://bugs.launchpad.net/bugs/1882098

Title:
  Packagekit lets user install untrusted local packages in Bionic and
  Focal

Status in packagekit package in Ubuntu:
  Triaged

Bug description:
  We have packagekit configured to allow users to install trusted
  packages from preconfigured repositories, but disallowed them to
  install any untrusted packages.

  The policykit configuration we use is following:

  [tld.univ.packagekit]
  Identity=unix-group:adm;
  Action=org.freedesktop.packagekit.package-install;org.freedesktop.packagekit.package-reinstall;org.freedesktop.packagekit.package-remove;org.freedesktop.packagekit.system-sources-refresh;org.freedesktop.packagekit.system-update;org.freedesktop.packagekit.repair-system;
  ResultAny=auth_self
  ResultActive=auth_self
  ResultInactive=auth_self

  [tld.univ.packagekit-deny]
  Identity=unix-user:*;
  Action=org.freedesktop.packagekit.package-install-untrusted;
  ResultAny=no

  We would expect this to prevent users from installing local packages
  downloaded from random repositories, however this does not seem to be
  the case.

  pkcon install-local random_package.deb will happily prompt for the
  user to authenticate and will install the package, while pkcon
  --allow-untrusted install-local random_package.deb will prompt for
  root password, which the user does not have.

  Our initial toughts was that the issue would be in packagekitd, but
  after further investigations it looks like the issue could be in aptcc
  backend.

  We are more than happy to provide you with further details, but the
  above should be enough to reproduce the issue.

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