我在尝试连接到需要公钥的 SFTP 服务器时遇到问题和密码验证。
源服务器是完全最新的 CentOS 7 服务器（SFTP 调试显示OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017）。目的是使用一个简单的 bash 脚本来抓取大量文件。
当连接时没有指定首选的身份验证顺序（即使用默认顺序publickey,password），它会陷入提供密钥而从不请求密码的循环：
sftp -v -i uat.key -oBatchMode=no <username>@<host>
...
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: password,publickey
debug1: Next authentication method: publickey
debug1: Trying private key: uat.key
Authenticated with partial success.
debug1: Authentications that can continue: password,publickey
debug1: Trying private key: uat.key
Authenticated with partial success.
debug1: Authentications that can continue: password,publickey
debug1: Trying private key: uat.key
Authenticated with partial success.
...loops forever
当逆转身份验证方法时，它会在继续之前请求密码3次（成功！），这显然会导致自动化问题：
sftp -v -i uat.key -oPreferredAuthentications=password,publickey -oBatchMode=no <username>@<host>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: password,publickey
debug1: Next authentication method: password
<username>@<host>'s password:
Authenticated with partial success.
debug1: Authentications that can continue: password,publickey
Permission denied, please try again.
<username>@<host>'s password:
Authenticated with partial success.
debug1: Authentications that can continue: password,publickey
Permission denied, please try again.
<username>@<host>'s password:
Authenticated with partial success.
debug1: Authentications that can continue: password,publickey
debug1: Next authentication method: publickey
debug1: Trying private key: uat.key
debug1: Authentication succeeded (publickey).
Authenticated to <username>@<host> ([<ip>]:22).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: pledge: network
debug1: Sending environment.
debug1: Sending env LANG = en_GB.UTF-8
debug1: Sending subsystem: sftp
Connected to <username>@<host>.
sftp> exit
我的挖掘让我发现了这一点IBM 文章从 2012 年开始涵盖第二个问题，但是我无法找到第一个命令中部分身份验证循环的解决方法。
有谁更了解 OpenSSH 吗？可以解释一下这个问题吗？