我的问题是，我无法通过 ssh 端口 22 使用公钥成功登录服务器（它提示我输入密码）。但棘手的是，我可以在连接到除 22 之外的任何其他端口时使用公钥授权自己访问服务器。
我的服务器运行的是 Ubuntu 16.04.7 LTS，客户端运行的是 Mint 19.1。以下是sshd_config服务器端的内容：
Port 22
Protocol 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
UsePrivilegeSeparation yes
KeyRegenerationInterval 3600
ServerKeyBits 1024
SyslogFacility AUTH
LogLevel DEBUG3
LoginGraceTime 120
PermitRootLogin yes
StrictModes yes
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile %h/.ssh/authorized_keys
IgnoreRhosts yes
RhostsRSAAuthentication no
HostbasedAuthentication no
PermitEmptyPasswords no
ChallengeResponseAuthentication no
X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
AcceptEnv LANG LC_*
Subsystem sftp /usr/lib/openssh/sftp-server
UsePAM yes
.ssh和 的权限authorized_keys：
drwx------ 2 root root 4096 Jan 23 22:22 .ssh
-rw------- 1 root root 274 Jan 23 22:21 authorized_keys
客户端输出：
:~$ ssh -v -o PreferredAuthentications=publickey [email protected]
OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n 7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 192.168.99.1 [192.168.99.1] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_dsa-cert type -1
debug1: identity file /home/bogdan/.ssh/id_ecdsa type 2
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/bogdan/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.10
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.10 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.99.1:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:m4b0N5FhxN6qz1KyUIkKWKjVWwV5eGorJ1xq0rLNCGw
debug1: Host '192.168.99.1' is known and matches the ECDSA host key.
debug1: Found key in /home/bogdan/.ssh/known_hosts:198
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: password
debug1: No more authentication methods to try.
[email protected]: Permission denied (password).
服务器输出：
root@eve-ng:~/.ssh# /usr/sbin/sshd -d
debug1: sshd version OpenSSH_7.2, OpenSSL 1.0.2g 1 Mar 2016
...
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
debug1: Set /proc/self/oom_score_adj from 0 to -1000
debug1: Bind to port 22 on 0.0.0.0.
Server listening on 0.0.0.0 port 22.
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
Connection from 192.168.50.11 port 60398 on 192.168.99.1 port 22
debug1: Client protocol version 2.0; client software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 pat OpenSSH* compat 0x04000000
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.10
debug1: permanently_set_uid: 107/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: algorithm: [email protected] [preauth]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth]
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user root service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: PAM: initializing for "root"
debug1: PAM: setting PAM_RHOST to "192.168.50.11"
debug1: PAM: setting PAM_TTY to "ssh"
Connection closed by 192.168.50.11 port 60398 [preauth]
debug1: do_cleanup [preauth]
debug1: monitor_read_log: child log fd closed
debug1: do_cleanup
debug1: PAM: cleanup
debug1: Killing privsep child 20063
debug1: audit_event: unhandled event 12
连接到另一个端口时服务器的输出：
root@eve-ng:~/.ssh# /usr/sbin/sshd -d -p 2222
debug1: sshd version OpenSSH_7.2, OpenSSL 1.0.2g 1 Mar 2016
...
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
debug1: rexec_argv[2]='-p'
debug1: rexec_argv[3]='2222'
debug1: Set /proc/self/oom_score_adj from 0 to -1000
debug1: Bind to port 2222 on 0.0.0.0.
Server listening on 0.0.0.0 port 2222.
debug1: Bind to port 2222 on ::.
Server listening on :: port 2222.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
Connection from 192.168.50.11 port 45264 on 192.168.99.1 port 2222
debug1: Client protocol version 2.0; client software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 pat OpenSSH* compat 0x04000000
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.10
debug1: permanently_set_uid: 107/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: algorithm: [email protected] [preauth]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth]
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user root service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: PAM: initializing for "root"
debug1: PAM: setting PAM_RHOST to "192.168.50.11"
debug1: PAM: setting PAM_TTY to "ssh"
debug1: userauth-request for user root service ssh-connection method publickey [preauth]
debug1: attempt 1 failures 0 [preauth]
debug1: userauth_pubkey: test whether pkalg/pkblob are acceptable for ECDSA SHA256:V5LuRENcNKem8Z4vFJvUkaChlHbuAbMH1e8tSxhRDEE [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: trying public key file /root/.ssh/authorized_keys
debug1: fd 4 clearing O_NONBLOCK
debug1: matching key found: file /root/.ssh/authorized_keys, line 1 ECDSA SHA256:V5LuRENcNKem8Z4vFJvUkaChlHbuAbMH1e8tSxhRDEE
debug1: restore_uid: 0/0
Postponed publickey for root from 192.168.50.11 port 45264 ssh2 [preauth]
debug1: userauth-request for user root service ssh-connection method publickey [preauth]
debug1: attempt 2 failures 0 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: trying public key file /root/.ssh/authorized_keys
debug1: fd 4 clearing O_NONBLOCK
debug1: matching key found: file /root/.ssh/authorized_keys, line 1 ECDSA SHA256:V5LuRENcNKem8Z4vFJvUkaChlHbuAbMH1e8tSxhRDEE
debug1: restore_uid: 0/0
debug1: do_pam_account: called
Accepted publickey for root from 192.168.50.11 port 45264 ssh2: ECDSA SHA256:V5LuRENcNKem8Z4vFJvUkaChlHbuAbMH1e8tSxhRDEE
debug1: monitor_child_preauth: root has been authenticated by privileged process
debug1: monitor_read_log: child log fd closed
debug1: PAM: establishing credentials
debug1: rekey after 134217728 blocks
debug1: rekey after 134217728 blocks
debug1: ssh_packet_set_postauth: called
debug1: Entering interactive session for SSH2.
debug1: server_init_dispatch_20
debug1: server_input_channel_open: ctype session rchan 0 win 1048576 max 16384