9.openssh-server

1.openssh-server

功能：讓遠端主機可以通過網路訪問sshd服務，開始一個安全shell

2.客戶端連線方式

ssh 遠端主機使用者@遠端主機ip
[root@desktop0 ~]# ssh [email protected]
The authenticity of host ‘172.25.0.11 (172.25.0.11)’ can’t be established.
ECDSA key fingerprint is eb:24:0e:07:96:26:b1:04:c2:37:0c:78:2d:bc:b0:08.
Are you sure you want to continue connecting (yes/no)? yes ##連線陌生主機時需要建立認證關係
Warning: Permanently added ‘172.25.0.11’ (ECDSA) to the list of known hosts.
[email protected]’s password: ##遠端使用者密碼
Last login: Mon Oct 3 03:13:47 2016
[root@server0 ~]# ##登陸成功

ssh 遠端主機使用者@遠端主機ip -X ##呼叫遠端主機圖形工具
ssh 遠端主機使用者@遠端主機ip command ##直接在遠端主機執行某條命令

3.sshkey加密

1.生成公鑰私鑰
[root@server0 ~]# ssh-keygen ##生成公鑰私鑰工具
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):[enter] ##加密字元儲存檔案（建議用預設）
Created directory ‘/root/.ssh’.
Enter passphrase (empty for no passphrase): [enter] ##金鑰密碼，必須>4個字元
Enter same passphrase again: [enter] ##確認密碼
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:
ab:3c:73:2e:c8:0b:75:c8:39:3a:46:a2:22:34:84:81 [email protected]
The key’s randomart image is:
+–[ RSA 2048]—-+
|o |
|E. |
|.. |
|. . o |
|.o. * . S |
|oo.o o . |
|+ =. . . |
|o. oo.+.. |
| ..o*. |
+—————–+

[root@server0 ~]# ls /root/.ssh/
id_rsa id_rsa.pub
id_rsa ##私鑰，就是鑰匙
id_rsa.pub ##公鑰，就是鎖

2.新增key認證方式
[root@server0 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]
ssh-copy-id ##新增key認證方式的工具
-i ##指定加密key檔案
/root/.ssh/id_rsa.pub ##加密key
root ##加密使用者為root
172.25.0.11 ##被加密主機ip

3.分發鑰匙給client主機
[root@server0 ~]# scp /root/.ssh/id_rsa [email protected]:/root/.ssh/

4.測試

[root@desktop0 ~]# ssh [email protected] ##通過id_rsa直接連線不需要輸入使用者密碼
Last login: Mon Oct 3 03:58:10 2016 from 172.25.0.250
[root@server0 ~]#

4.提升openssh的安全級別

1.openssh-server配置檔案
/etc/ssh/sshd_config
78 PasswordAuthentication yes|no ##是否開啟使用者密碼認證，yes為支援no為關閉
48 PermitRootLogin yes|no ##是否允許超級使用者登陸
49 AllowUsers student westos ##使用者白名單，只有在名單中出現的使用者可以使用sshd建立shell
50 DenyUsers westos ##使用者黑名單