Trying to sign with an expired signing subkey shouldn't be possible because it anyway fails with "Unusable secret key".
This is similar to T6742 except that it's about a single certificate and about signing.
Reproduce:
- You need a valid certificate with certify-only primary (sub)key and expired signing subkey. (Hint: Use gpg --edit-key to add the signing subkey and specify seconds=5 as expiration to add an expired signing subkey.)
- Set the fingerprint of this certificate as [SignEncryptKeys] SigningKey in kleopatrarc.
- Start Kleopatra, open the notepad, and select the Recipients tab.
- Uncheck "Encrypt for me". (This isn't really necessary but it avoids unrelated complications.)
Expected:
- The signing certificate is marked with the error icon (red icon with X).
- The Sign Notepad button is disabled.
Actual:
- The signing certificate is marked with the green "all good" icon. -> Not OK
- A message below the signing certificate reads "This certificate is expired." -> OK
- The Sign Notepad button is enabled. -> Not OK
- Trying to sign fails with Unusable secret key -> OK (but the user should be spared this error)