Date: Tue, 11 Jan 2022 22:52:24 -0600 From: John Helmert III <ajak@...too.org> To: oss-security@...ts.openwall.com Subject: Re: CVE-2021-3979 ceph: Ceph volume does not honour osd_dmcrypt_key_size On Tue, Jan 11, 2022 at 04:10:06PM -0500, Ana McTaggart wrote: > Hi all, > The key length for encrypted devices created using ceph-volume is > incorrect. This is due to a bug in ceph_volume/util/encryption.py, where > upon writing a key using osd_dmcrypt_key_size it does not pass the key size > to the format and open operations following. The default key is then > applied in cryptsetup. All versions since Luminous are assumed affected. At > Red Hat. we have assigned it CVE-2021-3979 and proposed a CVSS score of > 6.5/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N > > See below for the report, credit of Mark Kirkwood. > > We happened to run 'cryptsetup luksDump' on some of our encrypted > devices that were created using ceph-volume and noticed the key length > was wrong: > > e.g: > > markir@...h3:~$ cat /etc/ceph/ceph.conf > ... > [osd] > osd_dmcrypt_type = luks > osd_cryptsetup_parameters = --cipher aes-xts-plain64 > osd_dmcrypt_key_size = 512 > > markir@...h3:~$ sudo cryptsetup luksDump > /dev/mapper/ceph--9e3502c0--a991--44cc--a2a1--0e8e8fb45189-osd--block--aaab9851--5951--429d--8e9d--dbc22ea4c1a1 > > > Version: 1 > Cipher name: aes > Cipher mode: xts-plain64 > Hash spec: sha256 > Payload offset: 4096 > MK bits: 256 <=========== should be 512 > > > This appears to be due to a bug in ceph_volume/util/encryption.py. While > it writes a key using osd_dmcrypt_key_size it does not pass the key size > to the following format and open operations. It looks like that ecause > the key is being passed to cryptsetup on stdin that the length is not > being deduced, and so the default key size is being applied. > > It is fairly simple to patch (see attached - luks operation only, prob > needs plain code path altered similarly). > > In terms of which versions are impacted, we are running Luminous, but > the patch I have attached is against current master, so suspect all > versions since Luminous are in the crosshairs. Was a patch meant to be attached? Is there any report or PR upstream? Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)
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