[Bug 1843708] Re: [SRU] Key-pair is not updated during the rebuild

[Hua Zhang]

Hi Łukasz, after rebuilding a VM with different keypairs on bionic, we
can use the old keypair for ssh login, but we cannot use the new
keypair. This is not 'expected behaviour' for nova rebuild. bionic uses
17.0.13, which has this issue.

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Title:
  [SRU] Key-pair is not updated during the rebuild

Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive rocky series:
  Won't Fix
Status in Ubuntu Cloud Archive stein series:
  Fix Released
Status in Ubuntu Cloud Archive train series:
  Fix Released
Status in Ubuntu Cloud Archive ussuri series:
  Fix Released
Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) queens series:
  Fix Released
Status in OpenStack Compute (nova) rocky series:
  Fix Released
Status in OpenStack Compute (nova) stein series:
  Fix Released
Status in OpenStack Compute (nova) train series:
  Fix Released
Status in OpenStack Compute (nova) ussuri series:
  Fix Released
Status in nova package in Ubuntu:
  Invalid
Status in nova source package in Bionic:
  New
Status in nova source package in Focal:
  Fix Released

Bug description:
  [Impact]

  During rebuilds, the customer was unable to update the instance's
  keypair.

  [Test Case]

  - create a bionic openstack test env

  - choose the key 'testkey' to create an instance

  openstack keypair create mykey --public-key ~/.ssh/id_rsa.pub 
  openstack keypair create testkey --public-key /home/ubuntu/testkey.pub
  openstack server create --flavor m1.small --image jammy --key-name testkey --network=$(openstack network show private -f value -c id)  i1

  - create a new instance from the snapshot and choose a different
  keypair 'mykey' at rebuild time

  openstack --os-compute-api-version 2.54 server rebuild --image jammy --key-name mykey --name i1 i1
  sudo ip netns exec qrouter-xxx ssh ubuntu at 192.168.21.4 -i ~/testkey.priv -v
  sudo ip netns exec qrouter-xxx ssh ubuntu at 192.168.21.4 -i ~/id_rsa -v

  the new instance should accept the new key and reject the old key, but
  the result is the new instance rejects the new key but old key still
  works.

  [Regression Potential]

  This fix 6a7a78a44 is already in stable/queens and all versions since
  queens, bionic uses 17.0.13 rather than stable/queens, we just SRU
  this fix to 17.0.13 so there can't be any regression theoretically. On
  the other hand, code change is limited to _save_keypairs according to
  https://review.opendev.org/c/openstack/nova/+/683043/19/nova/objects/instance.py
  so the regressions is also limited in _save_keypairs . The test will
  also ensure that other logic beyond _save_keypairs. I have tested this
  fix, it works. so I think it's safe.

  [Others]

  Original Bug Description Below
  ===========

  When we want to rebuild an instance and change the keypair we can specified it with :
  openstack --os-compute-api-version 2.54 server rebuild --image "Debian 10" --key-name key1 instance1

  This comes from this implementation :
  https://review.opendev.org/#/c/379128/
  https://specs.openstack.org/openstack/nova-specs/specs/queens/implemented/rebuild-keypair-reset.html

  But when rebuilding the instance, Cloud-Init will set the key in authorized_keys from
  http://169.254.169.254/openstack/latest/meta_data.json

  And this meta_data.json uses the keys from instance_extra tables
  But the keypair will be updated in the 'instances' table but not in the 'instance_extra' table.

  So the keypair is not updated inside the VM

  May be this is the function for saving the keypair, but the save() do nothing :
  https://opendev.org/openstack/nova/src/branch/master/nova/objects/instance.py#L714

  Steps to reproduce
  ==================

  - Deploy a DevStack
  - Boot an instance with keypair key1
  - Rebuild it with key2
  - A nova show will show the key_name key2, keypairs object in table instance_extra is not updated and you cannot connect with key2 to the instance

  Expected result
  ===============
  Connecte to the Vm with the new keypair added during the rebuild call

  Actual result
  =============
  The keypair added during the rebuild call is not set in the VM

  Environment
  ===========
  I tested it on a Devstack from master and we have the behaviour.
  NOVA : commit 5fa49cd0b8b6015aa61b4312b2ce1ae780c42c64

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