Centos7 ssh免密登陆

(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

 

1

#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）

 

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[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

 

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[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。

 

1 2	[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

 

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[root@youxi1 ~]# ssh-copy-id -i .ssh/id_rsa.pub -p2891 root@192.168.1.7　　//-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 root@192.168.1.7'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' 'root@192.168.1.7'" 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。

 

1 2	[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

 

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[root@youxi1 ~]# ssh -p 2891 root@192.168.1.7 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。

 

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[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 root@192.168.1.6 /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 root@192.168.1.6's password:   Number of key(s) added: 1   Now try logging into the machine, with:   "ssh -p '2890' 'root@192.168.1.6'" and check to make sure that only the key(s) you wanted were added.   [root@youxi2 ~]# ssh -p 2890 root@192.168.1.6 Last login: Sun May 12 17:24:54 2019 from youxi2.cn [root@youxi1 ~]#