The existing client side authentication does not handle correctly the partial success flag in SSH_MSG_USERAUTH_FAILURE authentication responses. This commit fixes two problems in ssh library: 1) RetryableAuthMethod() now breaks out from the retry loop and returns when underlying auth method fails with partial success set to true. 2) Book keeping of tried (and failed) auth methods in clientAuthenticate() does not mark an auth method failed if it fails with partial success set to true. Fixes golang/go#23461 Change-Id: Ib2e1a1d54bfe2549496199bb2f66ebbce58d130d Reviewed-on: https://go-review.googlesource.com/88035 Reviewed-by: Han-Wen Nienhuys <hanwen@google.com> Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>