ssh: T7839: fix warning on deprecated algorithms during commit

The list calculation of in-use but deprecated SSH hostkey algorithms was wrong.
This was implemented in commit 6deda171e ("ssh: T7839: add deprecation warning
for DSA hostkey-algorithm usage"). It always returned the content of the list
of deprecated algorithms, but not the list of deprecated algorithms actually -
in use - by the configuration. This has been corrected.

Before:
  DEPRECATION WARNING: Support for SSH-DSA keys is deprecated and will
  be removed in VyOS 1.6. Please update affected keys to a supported
  algorithm (e.g., RSA, ECDSA or ED25519) to avoid authentication
  failures after the upgrade. The following hostkey-algorithms are in
  use: ssh-dss, ssh-dss-cert-v01@openssh.com

After:
  DEPRECATION WARNING: Support for SSH-DSA keys is deprecated and will
  be removed in VyOS 1.6. Please update affected keys to a supported
  algorithm (e.g., RSA, ECDSA or ED25519) to avoid authentication
  failures after the upgrade. The following hostkey-algorithms are in
  use: ssh-dss

The generation of the MOTD was not affected!

1 files changed, 2 insertions, 4 deletions

diff --git a/src/conf_mode/service_ssh.py b/src/conf_mode/service_ssh.py
index ca0e66207..dca021d02 100755
--- a/src/conf_mode/service_ssh.py
+++ b/src/conf_mode/service_ssh.py
@@ -111,10 +111,8 @@ def verify(ssh):
         verify_pki_openssh_key(ssh, ssh['trusted_user_ca'])
 
     if 'hostkey_algorithm' in ssh:
-        tmp = any(item in deprecated_algos for item in ssh['hostkey_algorithm'])
-        if deprecated_algos:
-            tmp = ', '.join(deprecated_algos)
-            DeprecationWarning(f'{SSH_DSA_DEPRECATION_WARNING} {tmp}')
+        tmp = [algo for algo in ssh['hostkey_algorithm'] if algo in deprecated_algos]
+        if tmp: DeprecationWarning(f'{SSH_DSA_DEPRECATION_WARNING} {", ".join(tmp)}')
 
     verify_vrf(ssh)
     return None