openssh-server

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.客户端连接方式

ssh 远程主机用户@远程主机ip

[root@desktop0 ~]# ssh root@172.25.0.11

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 ##连接陌生主机时需要建立认证关系

Warning: Permanently added ‘172.25.0.11‘ (ECDSA) to the list of known hosts.

root@172.25.0.11‘s password: ##远程用户密码

Last login: Mon Oct  3 03:13:47 2016

[root@server0 ~]# ##登陆成功

ssh 远程主机用户@远程主机ip -X ##调用远程主机图形工具

ssh     远程主机用户@远程主机ip command ##直接在远程主机运行某条命令

3.sshkey加密

1.生成公钥私钥

[root@server0 ~]# ssh-keygen ##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] ##密钥密码，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 root@server0.example.com

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 ##私钥，就是钥匙

id_rsa.pub ##公钥，就是锁

2.添加key认证方式

[root@server0 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub  root@172.25.0.11

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

172.25.0.11 ##被加密主机ip

3.分发钥匙给client主机

[root@server0 ~]# scp /root/.ssh/id_rsa root@172.25.0.10:/root/.ssh/

4.测试

[root@desktop0 ~]# ssh root@172.25.0.11 ##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 172.25.0.250

[root@server0 ~]# 

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:172.25.254.250 ##允许250主机链接sshd

sshd:172.25.254.250， 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

运维学习之openssh-server命令运用及控制