[Bug 2072524] Re: Allow non-owned lockfile writes in /var/lib/libvirt/swtpm/

[Launchpad Bug Tracker]

This bug was fixed in the package swtpm - 0.6.3-0ubuntu3.3

---------------
swtpm (0.6.3-0ubuntu3.3) jammy; urgency=medium

  * d/usr.bin.swtpm:
    - Add sys_admin capability to apparmor profile to allow access to kernel
      modules such as tpm_vtpm_proxy (LP: #2071478)
    - Allow non-owned lockfile write access in /var/lib/libvirt/swtpm/ to fix
      apparmor denials when working with TPM2 locks (LP: #2072524)

 -- Lena Voytek <lena.voytek at canonical.com>  Tue, 30 Jul 2024 15:22:09
-0700

** Changed in: swtpm (Ubuntu Jammy)
       Status: Fix Committed => Fix Released

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Title:
  Allow non-owned lockfile writes in /var/lib/libvirt/swtpm/

Status in swtpm package in Ubuntu:
  Fix Released
Status in swtpm source package in Jammy:
  Fix Released
Status in swtpm source package in Mantic:
  Won't Fix
Status in swtpm source package in Noble:
  Fix Released
Status in swtpm source package in Oracular:
  Fix Released

Bug description:
  [Impact]

  The default apparmor profile for swtpm blocks access to libvirt TPM2
  NVRAM state lockfiles. This causes denials for users who want to view
  TPM states via swtpm's socket API.

  The fix for this should be backported so print-states for libvirt TPM
  works for users by default.

  The issue is fixed by adding non-owner write permissions to the
  /var/lib/libvirt/swtpm/ directory.

  [Test Plan]

  $ sudo apt update && sudo apt dist-upgrade -y
  $ sudo apt install swtpm virt-manager apparmor -y

  # Create a vm with virt-manager that uses a TPM2 device and start it
  # A directory will show up in /var/lib/libvirt/swtpm/ using the vm's ID, such as:
  # /var/lib/libvirt/swtpm/ab930d41-1600-4987-bfb0-34107be38cc5

  # Before fix
  $ sudo swtpm socket --print-states --tpmstate dir=/var/lib/libvirt/swtpm/ab930d41-1600-4987-bfb0-34107be38cc5/tpm2,mode=0600
  swtpm: SWTPM_NVRAM_Lock_Dir: Could not open lockfile: Permission denied

  # After fix
  $ sudo swtpm socket --print-states --tpmstate dir=/var/lib/libvirt/swtpm/ab930d41-1600-4987-bfb0-34107be38cc5/tpm2,mode=0600
  { "type": "swtpm", "states": [] }

  [Where problems could occur]

  This change will provide swtpm greater access to
  /var/lib/libvirt/swtpm/. So if malicious code were to exist within
  swtpm, it would be able to modify and write to files in the directory
  created by other processes.

  Likewise, with a change to the apparmor profile, a conflict will occur
  on update for users that modified their profile directly.

  [Other Info]
   
  The issue was fixed in oracular in 0.7.3-0ubuntu7.

  [Original Description]

  Based on the upstream comment here -
  https://github.com/stefanberger/swtpm/issues/852#issuecomment-2156039973
  - users are having issues with apparmor denials when attempting to use
  TPM2 NVRAM state lockfiles. This is due to the file not being owned by
  the swtpm user. The issue is fixed by allowing write access to non-
  owned lock files in /var/lib/libvirt/swtpm/. This was fixed upstream
  in my pr here - https://github.com/stefanberger/swtpm/pull/868

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