无法 ssh 本地主机：权限被拒绝（公钥）/连接被 ::1 [preauth] 关闭
Unable to ssh localhost: Permission denied (publickey) / Connection closed by ::1 [preauth]
我正在尝试执行
ssh localhost
在 Ubuntu 14.04 LTS 上，但得到
Permission denied (publickey).
这是一些调试信息...
首先，我在 ~/.ssh 目录中有以下文件：
ubuntu@<hostname>:~$ ls .ssh
authorized_keys id_dsa id_dsa.pub id_ecdsa id_ecdsa.pub id_ed25519 id_ed25519.pub id_rsa id_rsa.pub known_hosts
目录的访问权限为：
ubuntu@<hostname>:~# stat -c %a ~/.ssh
700
这是 sshing 的详细输出：
ubuntu@<hostname>:~$ ssh -vvv localhost
OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to localhost [::1] port 22.
debug1: Connection established.
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_rsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_rsa type 1
debug1: identity file /home/ubuntu/.ssh/id_rsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_dsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_dsa type 2
debug1: identity file /home/ubuntu/.ssh/id_dsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_ecdsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_ecdsa type 3
debug1: identity file /home/ubuntu/.ssh/id_ecdsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_ed25519" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_ed25519 type 4
debug1: identity file /home/ubuntu/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH_6.6.1* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "localhost" from file "/home/ubuntu/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/ubuntu/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-ed25519,ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: setup hmac-md5-etm@openssh.com
debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none
debug2: mac_setup: setup hmac-md5-etm@openssh.com
debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA 4a:79:23:54:0b:5a:2c:98:39:ed:e4:b4:6b:5b:84:fa
debug3: load_hostkeys: loading entries for host "localhost" from file "/home/ubuntu/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/ubuntu/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys
debug1: Host 'localhost' is known and matches the ECDSA host key.
debug1: Found key in /home/ubuntu/.ssh/known_hosts:1
debug1: ssh_ecdsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/ubuntu/.ssh/id_rsa (0x7f403e66d570),
debug2: key: /home/ubuntu/.ssh/id_dsa (0x7f403e66d4a0),
debug2: key: /home/ubuntu/.ssh/id_ecdsa (0x7f403e6724d0),
debug2: key: /home/ubuntu/.ssh/id_ed25519 (0x7f403e672b80),
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/ubuntu/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering DSA public key: /home/ubuntu/.ssh/id_dsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ECDSA public key: /home/ubuntu/.ssh/id_ecdsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ED25519 public key: /home/ubuntu/.ssh/id_ed25519
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).
/etc/ssh/sshd_config 文件的内容：
ubuntu@<hostname>:~# cat /etc/ssh/sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details
# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 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
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes
# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024
# Logging
SyslogFacility AUTH
LogLevel INFO
# Authentication:
LoginGraceTime 120
PermitRootLogin without-password
StrictModes yes
RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile %h/.ssh/authorized_keys
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes
# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no
# Change to no to disable tunnelled clear text passwords
PasswordAuthentication no
# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no
#MaxStartups 10:30:60
#Banner /etc/issue.net
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
Subsystem sftp /usr/lib/openssh/sftp-server
# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
每次我尝试执行 "ssh localhost" 时，以下行都会添加到 /var/log/auth.log:
Jan 29 08:40:41 <hostname> sshd[5167]: Connection closed by ::1 [preauth]
任何人都可以提出任何建议吗？
在阅读了一些好的手册后，我意识到必须将 ubuntu@ 的 public 键（例如 /home/ubuntu/.ssh/id_dsa.pub）添加到用户的 /home/ubuntu/.ssh/authorized_keys 文件，其中包含用于 public 密钥验证的 public 个密钥）
ubuntu@<localhost>:~$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
除了添加 public 密钥外，您可能还想将 PasswordAuthentication 从 'no' 更改为 'yes'（在新安装的 ssh 中默认情况下可能是 'no'） .
打开配置
$ sudo nano /etc/ssh/sshd_config
并更改
PasswordAuthentication no
至
PasswordAuthentication yes
保存并退出。
然后重新加载 ssh 服务器
$ sudo service ssh reload
注意：从安全角度不建议使用 PasswordAuthentication，如果您的服务器暴露在互联网上，请禁用它并使用 SSH 密钥。
如果您 运行 Ubuntu 在 Linux 的 Windows 子系统上，将不会有预安装的 public 密钥或授权密钥列表，所以你需要自己生成。
如果您还没有安装 openssh-server:
sudo apt-get upgradesudo apt-get updatesudo apt-get install openssh-serversudo service ssh start
然后执行以下步骤以启用 sshing 到本地主机：
cd ~/.ssh ssh-keygen生成public/privatersa密钥对；使用默认选项cat id_rsa.pub >> authorized_keys 将密钥附加到 authorized_keys 文件chmod 640 authorized_keys 设置限制权限sudo service ssh restart 获取最近的更改ssh localhost
调试消息实际上提供了有关错误根本原因的信息。
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/ubuntu/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering DSA public key: /home/ubuntu/.ssh/id_dsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ECDSA public key: /home/ubuntu/.ssh/id_ecdsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ED25519 public key: /home/ubuntu/.ssh/id_ed25519
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).
要使用 public 密钥进行身份验证，客户端将向服务器发送包含其 public 密钥的 SSH_MSG_USERAUTH_REQUEST。收到此消息时，服务器将检查 public 密钥是否已被授权（通常针对 authorized_keys 文件）。
客户端有多个 public 密钥使用不同的算法创建（id_rsa.pub、id_dsa.pub、id_ecdsa.pub、id_ed25519.pub）。身份验证时，客户端首先向服务器提供默认的 public 密钥 id_rsa.pub，然后在服务器响应无法授权所提供的 public 时轮换剩余的 public 密钥] 钥匙。最后，当所有的public密钥授权失败时，SSH客户端显示Permission denied信息。
显示 preauth 标签表示连接在身份验证过程完成之前关闭。
SSHpublic密钥认证中客户端与服务器交互消息的顺序可以参考this article。
// 你的服务器
server@server:~$ ssh localhost
ECDSA 密钥指纹为 SHA256:Kv2PpSzdjCr7dhPHQPAHgEoSacrKEGUDEUKVBEb/BQY。
您确定要继续连接 (yes/no) 吗？是的
server@192.168.43.96的密码：********
// 你的笔记本电脑
PS C:\Users\username> ssh server@192.168.43.96
无法确定主机“192.168.43.96 (192.168.43.96)”的真实性。
ECDSA 密钥指纹为 SHA256:Kv2PpSzdjCr7dhPHQPAHgEoSacrKEGUDEUKVBEb/BQY。
您确定要继续连接 (yes/no) 吗？是的
server@192.168.43.96的密码：********
完成！
$cat /etc/ssh/sshd_config
...
AllowUsers User1 User2 User3
...
也可能是问题所在
我正在尝试执行
ssh localhost
在 Ubuntu 14.04 LTS 上，但得到
Permission denied (publickey).
这是一些调试信息...
首先，我在 ~/.ssh 目录中有以下文件：
ubuntu@<hostname>:~$ ls .ssh
authorized_keys id_dsa id_dsa.pub id_ecdsa id_ecdsa.pub id_ed25519 id_ed25519.pub id_rsa id_rsa.pub known_hosts
目录的访问权限为：
ubuntu@<hostname>:~# stat -c %a ~/.ssh
700
这是 sshing 的详细输出：
ubuntu@<hostname>:~$ ssh -vvv localhost
OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to localhost [::1] port 22.
debug1: Connection established.
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_rsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_rsa type 1
debug1: identity file /home/ubuntu/.ssh/id_rsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_dsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_dsa type 2
debug1: identity file /home/ubuntu/.ssh/id_dsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_ecdsa" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_ecdsa type 3
debug1: identity file /home/ubuntu/.ssh/id_ecdsa-cert type -1
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/ubuntu/.ssh/id_ed25519" as a RSA1 public key
debug1: identity file /home/ubuntu/.ssh/id_ed25519 type 4
debug1: identity file /home/ubuntu/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH_6.6.1* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "localhost" from file "/home/ubuntu/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/ubuntu/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-ed25519,ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: setup hmac-md5-etm@openssh.com
debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none
debug2: mac_setup: setup hmac-md5-etm@openssh.com
debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA 4a:79:23:54:0b:5a:2c:98:39:ed:e4:b4:6b:5b:84:fa
debug3: load_hostkeys: loading entries for host "localhost" from file "/home/ubuntu/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/ubuntu/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys
debug1: Host 'localhost' is known and matches the ECDSA host key.
debug1: Found key in /home/ubuntu/.ssh/known_hosts:1
debug1: ssh_ecdsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/ubuntu/.ssh/id_rsa (0x7f403e66d570),
debug2: key: /home/ubuntu/.ssh/id_dsa (0x7f403e66d4a0),
debug2: key: /home/ubuntu/.ssh/id_ecdsa (0x7f403e6724d0),
debug2: key: /home/ubuntu/.ssh/id_ed25519 (0x7f403e672b80),
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/ubuntu/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering DSA public key: /home/ubuntu/.ssh/id_dsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ECDSA public key: /home/ubuntu/.ssh/id_ecdsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ED25519 public key: /home/ubuntu/.ssh/id_ed25519
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).
/etc/ssh/sshd_config 文件的内容：
ubuntu@<hostname>:~# cat /etc/ssh/sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details
# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 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
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes
# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024
# Logging
SyslogFacility AUTH
LogLevel INFO
# Authentication:
LoginGraceTime 120
PermitRootLogin without-password
StrictModes yes
RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile %h/.ssh/authorized_keys
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes
# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no
# Change to no to disable tunnelled clear text passwords
PasswordAuthentication no
# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no
#MaxStartups 10:30:60
#Banner /etc/issue.net
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
Subsystem sftp /usr/lib/openssh/sftp-server
# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
每次我尝试执行 "ssh localhost" 时，以下行都会添加到 /var/log/auth.log:
Jan 29 08:40:41 <hostname> sshd[5167]: Connection closed by ::1 [preauth]
任何人都可以提出任何建议吗？
在阅读了一些好的手册后，我意识到必须将 ubuntu@ 的 public 键（例如 /home/ubuntu/.ssh/id_dsa.pub）添加到用户的 /home/ubuntu/.ssh/authorized_keys 文件，其中包含用于 public 密钥验证的 public 个密钥）
ubuntu@<localhost>:~$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
除了添加 public 密钥外，您可能还想将 PasswordAuthentication 从 'no' 更改为 'yes'（在新安装的 ssh 中默认情况下可能是 'no'） .
打开配置
$ sudo nano /etc/ssh/sshd_config
并更改
PasswordAuthentication no
至
PasswordAuthentication yes
保存并退出。 然后重新加载 ssh 服务器
$ sudo service ssh reload
注意：从安全角度不建议使用 PasswordAuthentication，如果您的服务器暴露在互联网上，请禁用它并使用 SSH 密钥。
如果您 运行 Ubuntu 在 Linux 的 Windows 子系统上，将不会有预安装的 public 密钥或授权密钥列表，所以你需要自己生成。
如果您还没有安装 openssh-server:
sudo apt-get upgradesudo apt-get updatesudo apt-get install openssh-serversudo service ssh start
然后执行以下步骤以启用 sshing 到本地主机：
cd ~/.sshssh-keygen生成public/privatersa密钥对；使用默认选项cat id_rsa.pub >> authorized_keys将密钥附加到 authorized_keys 文件chmod 640 authorized_keys设置限制权限sudo service ssh restart获取最近的更改ssh localhost
调试消息实际上提供了有关错误根本原因的信息。
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/ubuntu/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering DSA public key: /home/ubuntu/.ssh/id_dsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ECDSA public key: /home/ubuntu/.ssh/id_ecdsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug1: Offering ED25519 public key: /home/ubuntu/.ssh/id_ed25519
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).
要使用 public 密钥进行身份验证，客户端将向服务器发送包含其 public 密钥的 SSH_MSG_USERAUTH_REQUEST。收到此消息时，服务器将检查 public 密钥是否已被授权（通常针对 authorized_keys 文件）。
客户端有多个 public 密钥使用不同的算法创建（id_rsa.pub、id_dsa.pub、id_ecdsa.pub、id_ed25519.pub）。身份验证时，客户端首先向服务器提供默认的 public 密钥 id_rsa.pub，然后在服务器响应无法授权所提供的 public 时轮换剩余的 public 密钥] 钥匙。最后，当所有的public密钥授权失败时，SSH客户端显示Permission denied信息。
显示 preauth 标签表示连接在身份验证过程完成之前关闭。
SSHpublic密钥认证中客户端与服务器交互消息的顺序可以参考this article。
// 你的服务器
server@server:~$ ssh localhost
ECDSA 密钥指纹为 SHA256:Kv2PpSzdjCr7dhPHQPAHgEoSacrKEGUDEUKVBEb/BQY。 您确定要继续连接 (yes/no) 吗？是的 server@192.168.43.96的密码：********
// 你的笔记本电脑
PS C:\Users\username> ssh server@192.168.43.96
无法确定主机“192.168.43.96 (192.168.43.96)”的真实性。 ECDSA 密钥指纹为 SHA256:Kv2PpSzdjCr7dhPHQPAHgEoSacrKEGUDEUKVBEb/BQY。 您确定要继续连接 (yes/no) 吗？是的 server@192.168.43.96的密码：********
完成！
$cat /etc/ssh/sshd_config
...
AllowUsers User1 User2 User3
...
也可能是问题所在