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@x.x.x.x

The authenticity of host ‘x.x.x.x‘ 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@x.x.x.x‘s password: ##远程用户密码

Last login: Mon Oct  time

[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ipcommand##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@x.x.x.x

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

x.x.x.x##被加密主机ip

3.分发钥匙给client主机

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

4.测试

[root@desktop0 ~]# ssh root@x.x.x.x##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 x.x.x.x

[root@server0 ~]#

####4.提升openssh的安全级别####

1.openssh-server配置文件

/etc/ssh/sshd_config

49 PermitRootLogin yes|no##是否允许超级用户登陆

79 PasswordAuthentication yes|no##是否开启用户密码认证，yes为支持no为关闭

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

DenyUsers westos##用户黑名单

LINUX REDHAT第九单元文档