如何调试：ssh_exchange_identification：连接被远程主机关闭

通过私有 IP 进行 SSH 很好

我可以通过 SSH 通过其私有 IP 地址连接到服务器：

C:\Users\m3>ssh -vvvvA [email protected]
OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5
debug3: Failed to open file:C:/Users/m3/.ssh/config error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2
debug2: resolve_canonicalize: hostname 192.168.1.11 is address
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.1.11 [192.168.1.11] port 22.
debug1: Connection established.
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_rsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_rsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_dsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_dsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519 error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ed25519 type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ed25519-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_xmss type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_7.7
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
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.1.11:22 as 'uconn'
debug3: hostkeys_foreach: reading file "C:\\Users\\m3/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file C:\\Users\\m3/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 192.168.1.11
debug3: Failed to open file:C:/Users/m3/.ssh/known_hosts2 error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts2 error:2
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none
debug2: compression stoc: none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
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
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:eyPiBvKLgJOk1xJc0k6cx9UnwIXbUUaXu9pPHTKt5Rg
debug3: hostkeys_foreach: reading file "C:\\Users\\m3/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file C:\\Users\\m3/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 192.168.1.11
debug3: Failed to open file:C:/Users/m3/.ssh/known_hosts2 error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts2 error:2
debug1: Host '192.168.1.11' is known and matches the ECDSA host key.
debug1: Found key in C:\\Users\\m3/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug3: unable to connect to pipe \\\\.\\pipe\\openssh-ssh-agent, error: 2
debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug2: key: C:\\Users\\m3/.ssh/id_rsa (0000000000000000)
debug2: key: C:\\Users\\m3/.ssh/id_dsa (0000000000000000)
debug2: key: C:\\Users\\m3/.ssh/id_ecdsa (0000000000000000)
debug2: key: C:\\Users\\m3/.ssh/id_ed25519 (0000000000000000)
debug2: key: C:\\Users\\m3/.ssh/id_xmss (0000000000000000)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred 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: Trying private key: C:\\Users\\m3/.ssh/id_rsa
debug3: no such identity: C:\\Users\\m3/.ssh/id_rsa: No such file or directory
debug1: Trying private key: C:\\Users\\m3/.ssh/id_dsa
debug3: no such identity: C:\\Users\\m3/.ssh/id_dsa: No such file or directory
debug1: Trying private key: C:\\Users\\m3/.ssh/id_ecdsa
debug3: no such identity: C:\\Users\\m3/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: C:\\Users\\m3/.ssh/id_ed25519
debug3: no such identity: C:\\Users\\m3/.ssh/id_ed25519: No such file or directory
debug1: Trying private key: C:\\Users\\m3/.ssh/id_xmss
debug3: no such identity: C:\\Users\\m3/.ssh/id_xmss: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: failed to open file:C:/dev/tty error:3
debug1: read_passphrase: can't open /dev/tty: No such file or directory
[email protected]'s password:
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to 192.168.1.11 ([192.168.1.11]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug1: console supports the ansi parsing
debug3: Successfully set console output code page from:437 to 65001
debug3: Successfully set console input code page from:437 to 65001
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug3: receive packet: type 91
debug2: channel_input_open_confirmation: channel 0: callback start
debug3: unable to connect to pipe \\\\.\\pipe\\openssh-ssh-agent, error: 2
debug1: ssh_get_authentication_socket: No such file or directory
debug2: fd 3 setting TCP_NODELAY
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug3: send packet: type 98
debug2: channel 0: request shell confirm 1
debug3: send packet: type 98
debug2: channel_input_open_confirmation: channel 0: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
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Last login: Tue Mar 23 14:22:05 2021 from 192.168.1.52

公共 IP 的 SSH 不好

但是，当使用它的公共 IP 地址时，我遇到了一个错误：

ssh_exchange_identification：连接被远程主机关闭

C:\Users\m3>ssh -vvvvA [email protected]
OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5
debug3: Failed to open file:C:/Users/m3/.ssh/config error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2
debug2: resolve_canonicalize: hostname 11.111.11.111 is address
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 11.111.11.111 [11.111.11.111] port 22.
debug1: Connection established.
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_rsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_rsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_dsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_dsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519 error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ed25519 type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_ed25519-cert type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_xmss type -1
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert error:2
debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert.pub error:2
debug1: key_load_public: No such file or directory
debug1: identity file C:\\Users\\m3/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_7.7
ssh_exchange_identification: Connection closed by remote host

如何调试

可能是什么原因？如何调试问题？

路由器端口转发

服务器具有私有 IP 地址。但是有一个具有公共 IP 地址的路由器，它将 SSH 22 端口转发到私有 IP 地址。

sshd日志

建议在这里，我在服务器上使用了这个命令来记录sshd输出：

$ tail -f -n 500 /var/log/auth.log | grep 'sshd'

当我ssh [email protected]在客户端上运行时，我得到以下日志：

Mar 23 17:26:10 server-homeshine sshd[1355]: Accepted password for uconn from 192.168.1.52 port 53107 ssh2
Mar 23 17:26:10 server-homeshine sshd[1355]: pam_unix(sshd:session): session opened for user uconn by (uid=0)

但是当我ssh [email protected]在client上运行时，不会显示任何日志。我认为这暗示路由器在使用公共 IP 地址时不会转发端口。22不知道为什么。

SSHD 配置

sshd服务器上的配置是：

uconn@server-homeshine:/etc/ssh$ cat 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 prohibit-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 yes

# 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

IP 表

这是服务器上的 IP 表：

$ sudo iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT

$ sudo ip6tables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT

路由表

服务器路由表：

$ sudo route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 enp9s0
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 enp9s0

Wireshark/Tshark

tshark在服务器上安装并检查网络数据包，表明在客户端ssh [email protected]上运行（私有 IP）时，SSH 数据包被服务器接收。

但是在客户端ssh [email protected]上运行（公共 IP）时，服务器不会收到任何 SSH 数据包。

结论是 ADSL 路由器没有将 SSH 数据包转发到服务器。

合勤询价

就这个问题联系了合勤，收到了这样的回复：

在进行端口转发时，您需要确保内部服务器具有指向网关的网关地址，以便能够响应外部请求。

还要检查网关本身是否未使用端口 22。

服务器默认网关

我的服务器默认网关是192.168.1.1它应该是什么：

$ ip r
default via 192.168.1.1 dev enp9s0 onlink
192.168.1.0/24 dev enp9s0  proto kernel  scope link  src 192.168.1.11