最流行的兩種SSH身份驗證機制是基於密碼的身份驗證和基於公鑰的身份驗證。使用SSH金鑰通常比傳統的密碼身份驗證更安全和方便。
環境
使用者端：CentOS8 192.168.43.137
伺服器端：CentOS8 192.168.43.139
建立SSH公私鑰
通過輸入以下命令，生成新的4096位的SSH金鑰對：
[root@localhost ~]# ssh-keygen -t rsa -b 4096
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:ycOtSDK8ud2kd6EH7OxoQuc1BFb1HJ3T/kvAQJt0LrI [email protected]
The key's randomart image is:
+---[RSA 4096]----+
| ...oo.o o |
| o .+=.+ .|
| . . . +=. o |
| . o.oo .o .|
| + .oSE. . .|
| .*..=o. ..|
| .oo.+o+ . . .|
| .oo== o . |
| .o+ooo |
+----[SHA256]-----+
在CentOS8中設定SSH金鑰在CentOS8中設定SSH金鑰
想要驗證是否生成了新的SSH金鑰對，使用ls -l命令檢視~/.ssh目錄是否有剛才生成的檔案：
[root@localhost ~]# ll ~/.ssh/
total 8
-rw------- 1 root root 3389 May 13 08:26 id_rsa
-rw-r--r-- 1 root root 752 May 13 08:26 id_rsa.pub
在CentOS8中設定SSH金鑰在CentOS8中設定SSH金鑰
將公鑰複製到遠端伺服器，使用ssh-copy-id實用程式，輸入遠端伺服器的root密碼：
[root@localhost ~]# ssh-copy-id [email protected]
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host '192.168.43.139 (192.168.43.139)' can't be established.
ECDSA key fingerprint is SHA256:7O1oIOooh4NZG87aC3v1Zz/vcTXkjOhQBnlkY0CD4y0.
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
Password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh '[email protected]'"
and check to make sure that only the key(s) you wanted were added.
在CentOS8中設定SSH金鑰在CentOS8中設定SSH金鑰
也可以使用以下命令複製公鑰：
[root@localhost .ssh]# cat ~/.ssh/id_rsa.pub | ssh [email protected] "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"
使用金鑰登入伺服器
使用以下命令登入ssh伺服器：
[root@localhost ~]# ssh 192.168.43.139
Last login: Tue May 12 12:33:41 2020 from 192.168.43.137
在CentOS8中設定SSH金鑰在CentOS8中設定SSH金鑰
關閉密碼認證
登入伺服器端，關閉密碼認證：
[root@localhost ~]# ssh 192.168.43.139
Last login: Tue May 12 12:33:41 2020 from 192.168.43.137
[root@localhost ~]# vim /etc/ssh/sshd_config
搜尋一下三條，將選項改為No
PasswordAuthentication no
ChallengeResponseAuthentication no
UsePAM no
在CentOS8中設定SSH金鑰在CentOS8中設定SSH金鑰
重新啟動sshd服務：
[root@localhost ~]# systemctl restart sshd
總結
可以使用同一金鑰管理多個遠端伺服器。預設情況下，SSH的埠是TCP 22。更改預設SSH埠可降低自動攻擊的風險。