配置Linux SSH互相认证登录

1. 做ssh互信的目的

1、在做集群的时候是需要SSH互信，它有利于在另一节点方便操作。

2、当使用scp远程拷贝操作时，需要输入目标服务器的用户名和密码，这个时候可以做linux服务器之间ssh互信配置， 这样在多个linux服务器之间做操作时就可以免密登陆。

2. ssh互信配置的原理

简而言之，服务器存储目标主机的证书，以便自动完成认证，无需输入密码。

3. ssh互信配置步骤

1、各节点生成自己的公钥和私钥对。

2、将自己的公钥文件发送给对方。

3、验证互信配置是否成功。

4. 配置ssh互信

这里以MYDB01和MYDB02两台LINUX主机为例：

4.1生成公钥私钥对

在两台主机上分别生成，提示输入信息时直接回车：

# MYDB01主机：

[root@MYDB01 ~]# ssh-keygen -t rsa
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:lQex2+SbdmGGNBvU8vjaTKVCbfAmk8Eva+C6BPJ49G0 root@MYDB01
The key's randomart image is:
+---[RSA 2048]----+
|oo.. |
| == .|
|+ *@ |
| ..BB=B .|
|. o S..o=O+o |
| = o .. +=+. |
|. o o.E.+*.|
| . ... ...o|
|.. |
+----[SHA256]-----+
[root@MYDB01 ~]# 

# MYDB02主机：

[root@MYDB02 ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
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:
SHA256:8DGfMHFZDrEOOYhcpFGXI8tndQXTE4FampR6cTowAo4 root@MYDB02
The key's randomart image is:
+---[RSA 2048]----+
|o++ o.+=+=+o |
| + =oo=+*+=.o|
|E =.o+OB.X.. |
|oo+XB. |
| oS.+. |
| |
| |
| |
| |
+----[SHA256]-----+
[root@MYDB02 ~]# 

这样，就创建了公钥和密钥，会生成**id_rsa和id_rsa.pub**两个文件。

生成ssh密钥后，密钥将默认存储在家目录下的**.ssh/目录**中。

私钥和公钥的权限分别为**600和644**。

.ssh目录权限必须是700

选项：

-t rsa|dsa默认是rsa格式。

接着可以查看生成的公钥和私钥文件：

[root@MYDB01 ~]# cd /root/.ssh
[root@MYDB01 .ssh]# pwd
/root/.ssh
[root@MYDB01 .ssh]# ll -sh
总用量 12K
4.0K -rw-------1 root root 1.7K 2月14 16:17 id_rsa
4.0K -rw-r--r--1 root root393 2月14 16:17 id_rsa.pub
[root@MYDB01 .ssh]# 

4.2将自己的公钥文件发送给对方

# 命令格式：

ssh-copy-id [-i [identity_file]] [user@]machine

这个命令的作用是：将id_rsa.pub文件内容传输至对方的 .ssh目录中，生成文件名为authorized_keys 文件，并且会设置远程主机用户目录的**.ssh和.ssh/authorized_keys**权限。

# 在MYDB01上执行以下操作：

[root@MYDB01 .ssh]# ssh-copy-id 192.168.250.194
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
/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@192.168.250.194's password: 

Number of key(s) added: 1

Now try logging into the machine, with: "ssh '192.168.250.194'"
and check to make sure that only the key(s) you wanted were added.

[root@MYDB01 .ssh]# 

这里在MYDB02主机上查看：

[root@MYDB02 ~]# cd /root/.ssh
[root@MYDB02 .ssh]# ll
总用量 12
-rw------- 1 root root393 2月14 16:41 authorized_keys
-rw------- 1 root root 1679 2月14 16:20 id_rsa
-rw-r--r-- 1 root root393 2月14 16:20 id_rsa.pub
[root@MYDB02 .ssh]# cat authorized_keys
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCtQ+pBp1T9fHAkrifEShaOAfBJFT+HdljR8mBxl7wZ1a91g3Zuzu35gJKsUjD+NqP9JcdyKapE309SHPvosvsJjLfccF4PaEZAgqHryu+S3cBn8zqA6fm62hsx/qI4I80PV0btcqfwphsD+5+vgkDJWAsUGQtqZdmMClAIy5gs0He0K2jpciKHvxWWClB3+dTJ0e9yIuIkV7lM+jqVIqYFJD0bRyy0zgNsY5/cLYFllM42TQDos93hVdqGXOHREpWo01KX2Jd8MKj4yNeiqgnj2mDtiNFWOUSkAbHpcKInuUOErJMqkV7MP0er5UKY/NemDzuORr2RxYqSTWaz/T7N root@MYDB01
[root@MYDB02 .ssh]# 

上面的操作只是单方面信任，主机MYDB01登录主机MYDB02不需输入密码，反过来不行，所以还需下面操作：

# 在主机MYDB02上将其钥复制到主机MYDB01上：

[root@MYDB02 .ssh]# ssh-copy-id 192.168.250.193
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host '192.168.250.193 (192.168.250.193)' can't be established.
ECDSA key fingerprint is SHA256:vThEoRhUOECeD5jhE+m8TZA2+6OoElIoNOQ3XqtopZw.
ECDSA key fingerprint is MD5:97:40:b2:35:6e:07:5a:61:1f:73:f1:b2:6e:54:5b:7d.
Are you sure you want to continue connecting (yes/no)? y
Please type 'yes' or '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@192.168.250.193's password: 

Number of key(s) added: 1

Now try logging into the machine, with: "ssh '192.168.250.193'"
and check to make sure that only the key(s) you wanted were added.

[root@MYDB02 .ssh]# 

4.3验证互信

分别在MYDB01主机和MYDB02主机上通过SSH登录，看是否需要输入密码：

在MYDB01主机上登录MYDB02主机：

[root@MYDB01 .ssh]# ssh 192.168.250.194
Last login: Tue Jan 9 15:41:56 2023 from 192.168.250.193
[root@MYDB02 ~]# 

无密登录成功。

同样，在MYDB02主机上登录MYDB01主机：

[root@MYDB02 .ssh]# ssh 192.168.250.193
Last failed login: Tue Feb 14 16:48:54 CST 2023 from 192.168.250.194 on ssh:notty
There was 1 failed login attempt since the last successful login.
Last login: Tue Jan 9 15:41:34 2024 from 192.168.250.194
[root@MYDB01 ~]#