ErrDenied was added in [our fork of
x/crypto/ssh](acc6f8fe8d)
to short-circuit auth attempts once one fails.
In the case of our callbacks, this error is returned when SSH policy
check determines that a connection should not be allowed. Both
`NoClientAuthCallback` and `PublicKeyHandler` check the policy and will
fail anyway. The `fakePasswordHandler` returns true only if
`NoClientAuthCallback` succeeds the policy check, so it checks it
indirectly too.
The difference here is that a client might attempt all 2-3 auth methods
instead of just `none` but will fail to authenticate regardless.
Updates #8593
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
Andrew Lytvynov
29e98e18f8