c - libssh を使用して使用できる認証方法がありません

Question

サーバーで libssh ライブラリを使用してさまざまな方法で認証できますが、認証方法が検出されません。コードのサンプルは次のとおりです。

 #include <libssh/libssh.h>
 #include <stdio.h>

 int main(int,char**)
 {
   ssh_session session = ssh_new();
   unsigned short port = 22;
   int verbosity = SSH_LOG_PROTOCOL;

   ssh_options_set(session, SSH_OPTIONS_HOST, "localhost");
   ssh_options_set(session, SSH_OPTIONS_PORT, &port);
   ssh_options_set(session, SSH_OPTIONS_LOG_VERBOSITY, &verbosity);
   ssh_connect(session);

   int supported_authentication_methods = ssh_userauth_list(session, NULL);

   printf("Supported methods: %d\n", supported_authentication_methods);
   return (0);
 }

そして、これが生成する出力は次のとおりです。

[2015/04/16 19:30:34.367528, 1] ssh_connect:  libssh 0.6.4 (c) 2003-2014 Aris Adamantiadis, Andreas Schneider, and libssh contributors. Distributed under the LGPL, please refer to COPYING file for information about your rights, using threading threads_noop
[2015/04/16 19:30:34.368626, 2] ssh_socket_connect:  Nonblocking connection socket: 5
[2015/04/16 19:30:34.368643, 2] ssh_connect:  Socket connecting, now waiting for the callbacks to work
[2015/04/16 19:30:34.368675, 1] socket_callback_connected:  Socket connection callback: 1 (0)
[2015/04/16 19:30:34.400420, 1] ssh_client_connection_callback:  SSH server banner: SSH-2.0-OpenSSH_6.2
[2015/04/16 19:30:34.400445, 1] ssh_analyze_banner:  Analyzing banner: SSH-2.0-OpenSSH_6.2
[2015/04/16 19:30:34.400456, 1] ssh_analyze_banner:  We are talking to an OpenSSH client version: 6.2 (60200)
[2015/04/16 19:30:34.426885, 2] ssh_packet_dh_reply:  Received SSH_KEXDH_REPLY
[2015/04/16 19:30:34.427292, 2] ssh_client_dh_reply:  SSH_MSG_NEWKEYS sent
[2015/04/16 19:30:34.427311, 2] ssh_packet_newkeys:  Received SSH_MSG_NEWKEYS
[2015/04/16 19:30:34.427908, 2] ssh_packet_newkeys:  Signature verified and valid
Supported methods: 0

出力が示すように、認証方法が検出されません...これは奇妙なことです。なぜなら、パスワードとキーを使用して localhost に確実にログインできるからです...どうしたのですか?