The verifier can be given default known_hosts files in the constructor, which will be used if the ssh config does not specify a UserKnownHostsFile. If the ssh config does set UserKnownHostsFile, the verifier uses the given files in the order given. Non-existing or unreadable files are ignored.

StrictHostKeyChecking accepts the following values:

ask

Ask the user whether new or changed keys shall be accepted and be added to the known_hosts file.

yes/true

Accept only keys listed in the known_hosts file.

no/false

Silently accept all new or changed keys, add new keys to the known_hosts file.

accept-new

Silently accept keys for new hosts and add them to the known_hosts file.

If StrictHostKeyChecking is not set, or set to any other value, the default value ask is active.

This implementation relies on the ClientSession being a JGitClientSession. By default Apache MINA sshd does not forward the config file host entry to the session, so it would be unknown here which entry it was and what setting of StrictHostKeyChecking should be used. If used with some other session type, the implementation assumes "ask".

Asking the user is done via a CredentialsProvider obtained from the session. If none is set, the implementation falls back to strict host key checking ("yes").

Note that adding a key to the known hosts file may create the file. You can specify in the constructor whether the user shall be asked about that, too. If the user declines updating the file, but the key was otherwise accepted (user confirmed for "ask", or "no" or "accept-new" are active), the key is accepted for this session only.

If several known hosts files are specified, a new key is always added to the first file (even if it doesn't exist yet; see the note about file creation above).