Попробовал подключиться по SSH через nemo(файловый менеджер). Соединение отваливается по таймауту. В /var/log/auth.log следующее:
Feb 27 20:02:56 server sshd[11025]: Accepted publickey for user1 from 37.235.216.219 port 44022 ssh2: RSA SHA256:60oUUW3bHytzwcgeyRtU+Ow252596JXnFYSjw8dzfog
Feb 27 20:02:56 server sshd[11025]: pam_unix(sshd:session): session opened for user user1 by (uid=0)
Feb 27 20:02:57 server systemd-logind[841]: New session 8176 of user user1.
Feb 27 20:02:57 server systemd: pam_unix(systemd-user:session): session opened for user user1 by (uid=0)
Feb 27 20:03:37 server sshd[11051]: Received disconnect from 37.235.216.219 port 44022:11: disconnected by user
Feb 27 20:03:37 server sshd[11051]: Disconnected from 37.235.216.219 port 44022
Feb 27 20:03:37 server sshd[11025]: pam_unix(sshd:session): session closed for user user1
Feb 27 20:03:37 server systemd-logind[841]: Removed session 8176.
Feb 27 20:03:37 server systemd: pam_unix(systemd-user:session): session closed for user user1
Также выкладываю вызов команды iptables save
root@server:~# iptables-save
# Generated by iptables-save v1.6.0 on Tue Feb 27 20:05:35 2018
*filter
:INPUT DROP [1923:114614]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [14698066:39836414217]
:f2b-sshd - [0:0]
:fail2ban-FTP - [0:0]
:fail2ban-MAIL - [0:0]
:fail2ban-SSH - [0:0]
:fail2ban-VESTA - [0:0]
:vesta - [0:0]
-A INPUT -p tcp -m multiport --dports 22 -j f2b-sshd
-A INPUT -p tcp -m tcp --dport 8083 -j fail2ban-VESTA
-A INPUT -p tcp -m multiport --dports 25,465,587,2525,110,995,143,993 -j fail2ban-MAIL
-A INPUT -p tcp -m tcp --dport 21 -j fail2ban-FTP
-A INPUT -p tcp -m tcp --dport 22 -j fail2ban-SSH
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/32 -j ACCEPT
-A INPUT -s 127.0.0.1/32 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 80,443 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 21,12000:12100 -j ACCEPT
-A INPUT -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 25,465,587,2525 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 110,995 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 143,993 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 3306,5432 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8083 -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A f2b-sshd -j RETURN
-A fail2ban-FTP -j RETURN
-A fail2ban-MAIL -j RETURN
-A fail2ban-SSH -j RETURN
-A fail2ban-VESTA -j RETURN
COMMIT
# Completed on Tue Feb 27 20:05:35 2018
На всякий случай /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 yes
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
То есть первая версия отпадает. Что можете посоветовать в данной ситуации?