Bug 1716674

Summary: Anaconda kickstart LUKS no option to set key size / incorrect documentation
Product: Red Hat Enterprise Linux 7 Reporter: jan
Component: python-blivetAssignee: Vojtech Trefny <vtrefny>
Status: CLOSED ERRATA QA Contact: Release Test Team <release-test-team-automation>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.6CC: jan, jkonecny, jstodola, rhandlin, zveleba
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: python-blivet-0.61.15.75-1 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1740210 (view as bug list) Environment:
Last Closed: 2020-03-31 19:45:49 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description jan 2019-06-03 21:28:56 UTC 
Description of problem:
There is no option with kickstart to set the key size for a LUKS volume. Only when no "--cipher" option is set the key size defaults to 512 bits, otherwise the default LUKS option is used. Making it impossible to use 512 bits with any cipher other than aes-xts-plain64.

Furthermore the documentation about this is incomplete/incorrect.
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/security_guide/sec-encryption#sec-Using_LUKS_Disk_Encryption
Says: "The default key size for LUKS is 256 bits. The default key size for LUKS with Anaconda (XTS mode) is 512 bits."
However, when the "--cipher" option is set the key size fals back to the LUKS default. So for example when using serpent (XTS mode) the key size is 256 bits.

How reproducible:
Use a kickstart file to install RHEL and check the partition afterwards with cryptsetup luksDump

Steps to Reproduce:
part ... --encrypted --passphrase=temppass
part ... --encrypted --passphrase=temppass --cipher=aes-xts-plain64
part ... --encrypted --passphrase=temppass --cipher=serpent-xts-plain64
part ... --encrypted --passphrase=temppass --key-size=512
part ... --encrypted --passphrase=temppass --key-size=512 --cipher=serpent-xts-plain64

Expected results:
master key size: 512
master key size: 512
master key size: 512
master key size: 512
master key size: 512

Actual results:
master key size: 512
master key size: 256
master key size: 256
master key size: N/A
master key size: N/A

Additional info:
To make the documentation sound:
https://github.com/storaged-project/blivet/blob/rhel7-branch/blivet/formats/luks.py
This:
        if not self.exists and not self.cipher:
            self.cipher = "aes-xts-plain64"
            if not self.key_size:
                # default to the max (512 bits) for aes-xts
                self.key_size = 512
Should be changed to something like this:
        if not self.exists
            if not self.cipher:
                self.cipher = "aes-xts-plain64"
            if not self.key_size and "xts" in self.cipher:
                # default to the max (512 bits) fot xts
                self.key_size = 512
Comment 2 Jiri Konecny 2019-06-05 09:01:25 UTC 
The code you are talking about is in our storage library. Switching components.
Comment 3 jan 2019-06-05 14:53:51 UTC 
Well the code is the only code I found that touches the key-size during installation (apart from the LUKS defaults). However this is only part of the problem. To support setting the key-size in anaconda/kickstart configurations code needs to be added to anaconda/pykickstart. Furthermore the docs needs to be corrected.
Comment 5 Zdenek Veleba 2020-01-31 11:06:14 UTC 
Verified, the default key size is now 512.
Comment 7 errata-xmlrpc 2020-03-31 19:45:49 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:1060