unit 9

第九单元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 beestablished.

ECDSA key fingerprint iseb: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 knownhosts.

root@172.25.0.11's password:          远程用户密码

Last login: Mon Oct 3 03:13:472016

[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 03:58:102016 from 172.25.0.250

[root@server0 ~]#

4.提升openssh的安全级别

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