Host key check fails in ssh migration when hostnames are upper case

[Brett Milford]

Whilst hostnames are case independent, the hash produced for known_hosts is case sensitive.
When hostnames are uppercase nova-cc stores the host keys for this hostname but not it's lowercase variant. When this hostname is used in ssh migration, the host key check fails it is checking for the hash of the lowercase variant.

[Alex Kavanagh (ajkavanagh)]

Please could you add the versions of the charm and openstack that this is occurring on, and what is failing (with a stack trace if possible).

[Brett Milford (brettmilford)]

The issue was originally found with cs:nova-compute-296, cs:nova-cloud-controller-324 deployed on bionic. However I've been unable to reproduce the bug in a clean environment.

Notably openssh-client 7.6p1 appears to unconditionally lowercase hosts https://github.com/openssh/openssh-portable/blob/V_7_6_P1/ssh.c#L1030

Whilst in latter versions, such as that in focal, calls lowercase hosts if they aren't an address.
https://github.com/openssh/openssh-portable/blob/V_8_2_P1/ssh.c#L1142-L1143

[Launchpad Janitor (janitor)]

[Expired for OpenStack nova-cloud-controller charm because there has been no activity for 60 days.]