I lived with knowledge that one needs to provide his login password to unlock the login keychain. This does not seem to be entirely true after upgrading Tahoe to 26.4.
For example, on 26.3:
- Go to ~/Library/Keychains
- Copy login.keychain-db to different name, say test.keychain-db.
- Double-click on test.keychain-db -> this should open Keychain Access with test in Custom keychains section, it will appear locked.
- Select test keychain and press Cmd+L to unlock it.
- When prompted, provide your login password.
- Result: the keychain is unlocked.
When I preform above sequence of steps on 26.4 I am not able to unlock the copied keychain (the original login keychain appears implicitly unlocked).