(1)实验环境
两台CentOS7：
youxi1 192.168.1.6
youxi2 192.168.1.7
这里我将防火墙关闭进行实验，如果防火墙开启，请将端口加入到防火墙规则中。
(2).目标
在ssh端口不为22的情况下，进行单向免密登录或双向免密登录（端口不一致）
(3).实验
首先修改两台服务器的端口，vim /etc/ssh/sshd_config，找到如下部分
#Port 22
将#去除，22改为想要的端口号。这里我将youxi1的ssh端口号改为2890，youxi2的ssh端口号改为2891。
接着使用命令systemctl restart sshd重启服务。再使用netstat -tlunp | grep sshd查看端口号（如果没有netstat请安装net-tools）
[root@youxi1 Packages]# netstat -tlunp | grep sshd //youxi1 tcp 0 0 0.0.0.0:2890 0.0.0.0:* LISTEN 9953/sshd tcp6 0 0 :::2890 :::* LISTEN 9953/sshd [root@youxi2 ~]# netstat -tlunp | grep sshd //youxi2 tcp 0 0 0.0.0.0:2891 0.0.0.0:* LISTEN 17526/sshd tcp6 0 0 :::2891 :::* LISTEN 17526/sshd
1）单向免密登录
youxi1使用ssh远程youxi2不需要密码，但youxi2使用ssh远程youxi1需要密码
在yousi1上使用ssh-keygen生成公钥和私钥（这里使用默认的rsa），一路默认即可
[root@youxi1 ~]# ssh-keygen -t rsa //默认指定的是rsa，所以可以没有-t rsa Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): //选项没有指定生成地址时，此处也可以指定 Created directory '/root/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is: SHA256:ia+le9ZX3cAxztmIINJbWnEGrK9lq4lY4pYNevgqecM root@youxi1 The key's randomart image is: +---[RSA 2048]----+ | . .ooo | | . o =o o | | . B . = * | | .+. . B .| | . S. o.| | . . + . o| | o o.+. o= . . | |o E.++.=+.o . | | o.*+ =+o. . | +----[SHA256]-----+
在没有指定生成地址时，会默认生成到家目录下的.ssh/目录下。使用rsa就会生成id_rsa和id_rsa.pub两个文件，如果使用的是dsa则生成的是id_dsa和id_dsa.pub两个文件。
[root@youxi1 ~]# ls /root/.ssh/ id_rsa id_rsa.pub
接着使用命令ssh-copy-id命令将公钥发到youxi2服务器上
[root@youxi1 ~]# ssh-copy-id -i .ssh/id_rsa.pub -p2891 [email protected] //-p选项指定被远程的服务器的端口号 /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: ".ssh/id_rsa.pub" The authenticity of host '[192.168.1.7]:2891 ([192.168.1.7]:2891)' can't be established. ECDSA key fingerprint is SHA256:j3ee8eoTo2XEv0QxCYmxphMipcNRxC+IONPmt1HwRLg. ECDSA key fingerprint is MD5:25:e2:b4:08:f2:79:7d:6e:42:84:b5:78:3d:6a:81:20. Are you sure you want to continue connecting (yes/no)? yes //yes继续 /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys [email protected]'s password: //输入192.168.1.7服务器上的root用户的密码 Number of key(s) added: 1 Now try logging into the machine, with: "ssh -p '2891' '[email protected]'" and check to make sure that only the key(s) you wanted were added.
公钥传完后虽然会在本地生成.ssh/known_hosts文件，但并不生效。而在youxi2服务器的root用户的家目录下生成.ssh目录，并含有authorized_keys文件。
[root@youxi1 ~]# ls .ssh/ authorized_keys
此时youxi1上的id_rsa.pub文件与youxi2是上的authorized_keys文件相同。
最后测试：在youxi1上ssh远程youxi2，会发现并不需要输入密码
[root@youxi1 ~]# ssh -p 2891 [email protected] Last login: Sun May 12 17:46:49 2019 from youxi1.cn [root@youxi2 ~]# ls .ssh/ authorized_keys
注意：是本机生成的公钥发给被远程的服务器，在发送公钥和远程服务器时，都需要指定被远程的服务器的端口号。
2）双向免密登录
双向免密就是互换公钥即可，这里接着上面把youxi2的公钥发送到youxi1上，并进行测试。
[root@youxi2 ~]# ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is: SHA256:9+woxNPvkE99zGUEZNcI+DJaUUIZXXMKb7k/Y6kPiJU root@youxi2 The key's randomart image is: +---[RSA 2048]----+ | .+*++*.+| | +..+.B.| | o = .| | + o. o | | .S+.E . o| | =.++.. =o| | . ooo+..==| | . *. +.o| | ...+... | +----[SHA256]-----+ [root@youxi2 ~]# ssh-copy-id -i .ssh/id_rsa.pub -p2890 [email protected] /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: ".ssh/id_rsa.pub" The authenticity of host '[192.168.1.6]:2890 ([192.168.1.6]:2890)' can't be established. ECDSA key fingerprint is SHA256:j3ee8eoTo2XEv0QxCYmxphMipcNRxC+IONPmt1HwRLg. ECDSA key fingerprint is MD5:25:e2:b4:08:f2:79:7d:6e:42:84:b5:78:3d:6a:81:20. Are you sure you want to continue connecting (yes/no)? yes /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys [email protected]'s password: Number of key(s) added: 1 Now try logging into the machine, with: "ssh -p '2890' '[email protected]'" and check to make sure that only the key(s) you wanted were added. [root@youxi2 ~]# ssh -p 2890 [email protected] Last login: Sun May 12 17:24:54 2019 from youxi2.cn [root@youxi1 ~]#