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

[Lena Voytek]

[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

[Launchpad Janitor (janitor)]

This bug was fixed in the package swtpm - 0.7.3-0ubuntu7

---------------
swtpm (0.7.3-0ubuntu7) oracular; 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 <email address hidden> Tue, 09 Jul 2024 06:06:00 -0700

[Lena Voytek (lvoytek)]

Removing mantic - eol

[Timo Aaltonen (tjaalton)]

Hello Lena, or anyone else affected,

Accepted swtpm into jammy-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/swtpm/0.6.3-0ubuntu3.3 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-jammy to verification-done-jammy. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-jammy. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Timo Aaltonen (tjaalton)]

Hello Lena, or anyone else affected,

Accepted swtpm into noble-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/swtpm/0.7.3-0ubuntu5.24.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-noble to verification-done-noble. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-noble. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Ubuntu SRU Bot (ubuntu-sru-bot)]

All autopkgtests for the newly accepted swtpm (0.6.3-0ubuntu3.3) for jammy have finished running.
The following regressions have been reported in tests triggered by the package:

swtpm/0.6.3-0ubuntu3.3 (armhf)
swtpm/unknown (s390x)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/jammy/update_excuses.html#swtpm

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

[Lena Voytek (lvoytek)]

Verified for noble and jammy:

Enabled proposed then created a windows 11 vm with virt-manager using the TPM v2.0 addition.
Started the vm, then ran:

$ sudo swtpm socket --print-states --tpmstate dir=/var/lib/libvirt/swtpm/aa5b37e8-6edf-4f2e-8550-7316cab991c6/tpm2,mode=0600
{ "type": "swtpm", "states": [] }

[Ubuntu SRU Bot (ubuntu-sru-bot)]

All autopkgtests for the newly accepted swtpm (0.7.3-0ubuntu5.24.04.1) for noble have finished running.
The following regressions have been reported in tests triggered by the package:

swtpm/unknown (s390x)
tpm2-pytss/unknown (armhf)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/noble/update_excuses.html#swtpm

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!