Date: Tue, 11 Jan 2022 16:10:06 -0500 From: Ana McTaggart <amctagga@...hat.com> To: oss-security@...ts.openwall.com Cc: Mark Kirkwood <markkirkwood@...alystcloud.nz> Subject: CVE-2021-3979 ceph: Ceph volume does not honour osd_dmcrypt_key_size 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. Ana McTaggart Red Hat Product Security Red Hat Remote <https://www.redhat.com> secalert@...hat.com for urgent response amct@...hat.com Pronouns:They/Them/Theirs
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