第九单元
1.openssh-server 功能：让远程主机可以通过网络访问sshd服务，开始一个安全shell
2.客户端连接主机
ssh [email protected] ##用ssh的方式，以超级用户的身份登陆172.25.254.106这台主机
[[email protected] ~]# ssh [email protected]
The authenticity of host '172.25.254.106 (172.25.254.106)' 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 ##连接陌生主机时需要建立认证关系
Warning: Permanently added '172.25.254.106' (ECDSA) to the list of known hosts.
[email protected]'s password: ##远程用户密码
[[email protected] ~]# ##登陆成功
3.sshkey加密
1.生成公钥私钥
[[email protected] ~]# ssh-****** ##生成公钥私钥工具
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):[enter] ##加密字符保存文件（建议用默认）
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase): [enter] ##**密码，必须>4个字符
Enter same passphrase again: [enter] ##确认密码
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*. |
+-----------------+
[[email protected] ~]# ls /root/.ssh/ ##当执行完过程之后，会在/root/.ssh目录下，生成两个文件，有id_rsa ，id_rsa.pub
id_rsa id_rsa.pub
id_rsa ##私钥，就是钥匙
id_rsa.pub ##公钥，就是锁
2.添加key认证方式
[[email protected] ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]
ssh-copy-id ##添加key认证方式的工具
-i ##指定加密key文件
/root/.ssh/id_rsa.pub ##加密key
root ##加密用户为root
172.25.254.206 ##被加密主机ip
3.分发钥匙给client主机
[[email protected] ~]# scp /root/.ssh/id_rsa [email protected]:/root/.ssh/
将服务端的/root/.ssh/目录下的id_rsa 文件用scp的方式发送给客户端，然后在客户端/root/.ssh/目录下可以找到这个文件
这个文件的作用就是下次再登陆服务端的时候不用输入密码，因为本地已经有私钥文件
4.测试
[[email protected] ~]# ssh [email protected] ##通过id_rsa直接连接不需要输入用户密码
Last login: Mon Oct 3 03:58:10 2016 from 172.25.254.206
[[email protected] ~]#
4.提升openssh的安全级别
1.openssh-server配置文件
/etc/ssh/sshd_config
78 PasswordAuthentication yes|no ##是否开启用户密码认证，yes为支持no为关闭
48 PermitRootLogin yes|no ##是否允许超级用户登陆
49 AllowUsers student westos ##用户白名单，只有在名单中出现的用户可以使用sshd建立shell
50 DenyUsers westos ##用户黑名单
2.控制ssh客户端访问
vim /etc/hosts.deny
sshd:ALL ##拒绝所有人链接sshd服务
vim /etc/hosts.allow
sshd:172.25.254.206 ##允许250主机链接sshd
sshd:172.25.254.206， 172.25.254.180 ##允许250和180链接
sshd:ALL EXCEPT 172.25.254.200 ##只不允许200链接sshd
3.ssh登陆提示修改该
vim /etc/motd ##显示登陆后字符
hello world ##在登陆后就会显示这个字符