Centos7 ssh远程登录默认端口修改

一个Centos7系统已经做好了，但是考虑到安全问题，都会修改一些系统默认的信息，例如：远程登录端口，linux系统的远程登录端口默认都是22，一般都会考虑在使用的时候进行修改，防止有人恶意的去破解密码远程登录。下面是刚安装的Centos7系统，先看一下ssh默认端口修改文件。

[root@www.wulaoer.org ~]# ll /etc/ssh/sshd_config 

ssh是系统默认就安装的一个工具，就是为了远程连接使用，下面我们看看这个文件的信息。

[root@www.wulaoer.org ~]# cat /etc/ssh/sshd_config 
#       $OpenBSD: sshd_config,v 1.100 2016/08/15 12:32:04 naddy Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

# If you want to change the port on a SELinux system, you have to tell
# SELinux about this change.
# semanage port -a -t ssh_port_t -p tcp #PORTNUMBER
#
#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

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

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin yes
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#PubkeyAuthentication yes

# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile      .ssh/authorized_keys

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no
PasswordAuthentication yes

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
#KerberosUseKuserok yes

# GSSAPI options
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
#GSSAPIEnablek5users no

# 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'.
# WARNING: 'UsePAM no' is not supported in Red Hat Enterprise Linux and may cause several
# problems.
UsePAM yes

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation sandbox
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#ShowPatchLevel no
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

# override default of no subsystems
Subsystem       sftp    /usr/libexec/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       PermitTTY no
#       ForceCommand cvs server

我们这里是修改默认端口，在这个文件中需要使用到Port 22，可以先复制一行，然后修改一下Port后面的数值，然后重启一下ssh，这样做的好处是在修改端口后不如果修改的端口不生效，可以使用原来的默认端口进行连接。这里我把端口改成27.

[root@www.wulaoer.org ~]# vim /etc/ssh/sshd_config 
...........................
# semanage port -a -t ssh_port_t -p tcp #PORTNUMBER
#
Port 27
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
..................................
[root@www.wulaoer.org ~]# systemctl restart sshd.service
[root@www.wulaoer.org ~]# netstat -tlnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:27              0.0.0.0:*               LISTEN      5635/sshd           
tcp6       0      0 :::27                   :::*                    LISTEN      5635/sshd           
tcp6       0      0 :::3306                 :::*                    LISTEN      1884/mysqld

说明已经sshd端口已经修改并生效了，就需要关闭防火墙然后在测试链接，如果是线上业务就做一下防火墙配置。

验证一下sshd

前面已经修改了端口，这里就找一个客户端进行一下验证，我修改的端口是27，下面我就使用修改后的端口进行连接。

[root@DevOPS ~]# ssh root@10.211.55.34 -p 27
root@10.211.55.34's password: 
Last login: Thu Apr 23 01:21:06 2020 from 10.211.55.2
[root@www.wulaoer.org ~]# ifconfig -a|grep -o -e 'inet [0-9]\{1,3\}.[0-9]\{1,3\}.[0-9]\{1,3\}.[0-9]\{1,3\}'|grep -v "127.0.0"|awk '{print $2}'
10.211.55.34
[root@DevOPS ~]#

验证通过，测试完成。今天就说这么多了。虽然基础，基础不牢地动山摇。