[Bug 2073429] [NEW] Jammy clevis forces argon2id for keyslots

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Ghadi Rahme (ghadi-rahme):

Thank you @kylerhornor for the original bug report

[impact]
current version of clevis on jammy uses argon2id instead of pbkdf2 for the encryption algorithm which is not approved by the NIST. An upstream commit (https://github.com/latchset/clevis/commit/71596307516ce2367e6303bd7f7ae7b180b29a35) did make clevis use pbkdf2 instead of argon2id to avoid OOM scenarios on systems with constrained memory. So this fix also resolves this issue on jammy. Noble currently has that fix.
Although argon2id is considered more secure, the maintainer has confirmed that currently the entropy used by clevis is high enough to the point where pbkdf2 is considered secure enough to replace argon2id. Please refer to comment #5 on this links for the maintainers' response:

https://bugzilla.redhat.com/show_bug.cgi?id=1979256

Also the bugzilla thread above is a good read for anyone interested in
knowing more about why this change was made.

[Test Plan]
* Test plan to verify that the new encryption algorithm pbkdf2 is being applied

This test plan was done on a libvirt/kvm virtual machine.

1. setup a jammy VM. Attach to it a tpm2 module (software or pass-
through) and an extra drive.

2. install clevis, clevis-tpm2 and clevis-luks:

$ sudo apt install clevis clevis-tpm2 clevis-luks

3. using lsblk note the name of the extra drive that was attached to the
VM. In this case vdb will be used as an example

4. run the following commands to setup partitions on the drive:

$ sudo parted /dev/vdb -- mklabel gpt
$ sudo parted /dev/vdb -- mkpart primary 0% 100%

5. setup luks and open the drive:

$ sudo cryptsetup luksFormat /dev/vdb1
$ sudo cryptsetup luksOpen /dev/vdb1 <name>

replace <name> with a name of your choosing  also note how vdb1 is used
in this step instead of vdb since we are formatting the partition
created in step 4. Verify these values on your system before running the
commands.

6. finally bind the drive with clevis using tpm2:

$ sudo clevis luks bind -d /dev/vdb1 tpm2
'{"hash":"sha256","key":"rsa","pcr_bank":"sha256","pcr_ids":"6"}'

7. Verify the encryption algorithm being used:
sudo cryptsetup luksDump /dev/vdb1 | grep PBKDF:

Currently this will show as argon2id but after applying the patch I
backported from upstream and repeating step 6 it should show pbkdf2 in
the new keyslot

* Test plan to verify that the new version does no break current disk
encryption that was done with argon2id.

1. On the non patched version of clevis, run all the steps in the first
part of the test plan, and make sure that the output of the final step
shows argon2id.

2. create an ext4 partition on the luks drive:

$ sudo mkfs.ext4 /dev/mapper/<name>
Where <name> is the same value used in step 5 of the first section of the test plan.

3. Mount the drive:
$ sudo mount -t ext4 /dev/mapper/<name> /mount/point/of/your/choice

4. Access the drive via the mount point and write data to it (as an
example create a file and write any data inside it)

5. Unmount and close the luks drive:

$ sudo umount /mount/point/of/your/choice
$ sudo cryptsetup luksClose tpm_Drive

5. Upgrade clevis to the new version that uses pbkdf2.

6. Open the luks drive:

$ sudo cryptsetup luksOpen /dev/vdb1 <name>

7. Mount the drive:

$ sudo mount -t ext4 /dev/mapper/<name> /mount/point/of/your/choice

8. And finally verify that you are able to see and access the data you
had previously written.

[where problems could occur]

* The machine could fail to create the new keyslot
* Although the maintainer says that the entropy is high enough for pbkdf2 to be secure it might not be as secure still as argon2id even tho it is NIST compliant.

[Original Description]
Hello,

clevis released with version 18 on jammy (22.04). For reasons that are a
bit beyond me, the cryptsetup call inside of clevis creates keyslots
using argon2id as the pbkdf. While most folks would say this is
preferable, NIST still has not approved it and it is thus incompatible
with fips 140-3 at this time.

Oddly enough, there was an upstream commit that was implemented to help
with an OOM condition that accidentally forced pbkdf2 rather than
argon2id.

Commit found here:
https://github.com/latchset/clevis/commit/71596307516ce2367e6303bd7f7ae7b180b29a35

Ideally, we need to either just bring that commit back to the jammy
version, or get to the root cause of why cryptsetup in that exact
scenario prefers argon2id.

** Affects: clevis (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: clevis (Ubuntu Jammy)
     Importance: High
     Assignee: Ghadi Rahme (ghadi-rahme)
         Status: In Progress

** Affects: clevis (Ubuntu Noble)
     Importance: Undecided
         Status: Fix Released

** Affects: clevis (Ubuntu Oracular)
     Importance: Undecided
         Status: Fix Released


** Tags: patch
-- 
Jammy clevis forces argon2id for keyslots
https://bugs.launchpad.net/bugs/2073429
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