SSH远程管理与访问控制

Posted 2023-02-09

理论：

一、SSH远程管理

1、SSH作用和特点

1）SSH作用

管理员远程管理服务器的一种方式

2）SSH特点

安全性强

传输数据被加密

适合通过互联网远程使用

支持通过客户端或者命令远程管理服务器

2、SSH服务的组成

1）ssh服务器端

openssh-server 默认端口号是22

2）客户端

用于远程管理使用

支持命令或者第三方工具实现ssh远程管理

推荐步骤

• 1.安装ssh服务器端和客户端设置服务开机自启动，配置身份验证的ssh，保证ssh服务器的安全性禁止为空密码访问，将ssh服务器端口修改为2222，在ssh服务器端创建bob和tom两个用户允许客户端192.168.100.30登录bob和root账户，禁止tom用户通过192.168.100.30登录
• 2.配置免交互式身份验证ssh，允许Centos02使用root用户和alice用户免交互式访问ssh服务器端，配置访问控制阻止主机192.168.100.30访问ssh服务器

实验步骤：

一，安装ssh服务器配置身份验证ssh限制用户访问

1.挂载系统盘安装服务

1）

[root@centos01 ~]# mount /dev/sr0 /mnt/
mount: /dev/sr0 写保护，将以只读方式挂载
[root@centos01 ~]# ls /mnt/
CentOS_BuildTag  EULA  images    LiveOS    repodata              RPM-GPG-KEY-CentOS-Testing-7
EFI              GPL   isolinux  Packages  RPM-GPG-KEY-CentOS-7  TRANS.TBL

2）安装服务器端和客户端

[root@centos01 ~]# rpm -ivh /mnt/Packages/openssh-server-7.4p1-11.el7.x86_64.rpm 
警告：/mnt/Packages/openssh-server-7.4p1-11.el7.x86_64.rpm: 头V3 RSA/SHA256 Signature, 密钥 ID f4a80eb5: NOKEY
准备中...                          ################################# [100%]
  软件包 openssh-server-7.4p1-11.el7.x86_64 已经安装
[root@centos01 ~]# rpm -ivh /mnt/Packages/openssh-clients-7.4p1-11.el7.x86_64.rpm 
警告：/mnt/Packages/openssh-clients-7.4p1-11.el7.x86_64.rpm: 头V3 RSA/SHA256 Signature, 密钥 ID f4a80eb5: NOKEY
准备中...                          ################################# [100%]
  软件包 openssh-clients-7.4p1-11.el7.x86_64 已经安装

3）设置服务开机自启

[root@centos01 ~]# systemctl enable sshd
[root@centos01 ~]# systemctl start sshd

2.创建验证账户配置密码

1）创建验证账户bob，tom

[root@centos01 ~]# useradd tom
[root@centos01 ~]# useradd bob

2）设置密码

[root@centos01 ~]# passwd tom
更改用户 tom 的密码 。
新的 密码：
无效的密码： 密码未通过字典检查 - 过于简单化/系统化
重新输入新的 密码：
passwd：所有的身份验证令牌已经成功更新。
[root@centos01 ~]# passwd bob
更改用户 bob 的密码 。
新的 密码：
无效的密码： 密码未通过字典检查 - 过于简单化/系统化
重新输入新的 密码：
passwd：所有的身份验证令牌已经成功更新。

3.配置ssh服务器控制用户访问

1）修改ssh主配置文件

[root@centos01 ~]# vim /etc/ssh/sshd_config 
  18        Port 2222                                  //修改监听端口为2222
  22        ListenAddress 192.168.100.10              //修改监听IP为192.168.100.10
  40        LoginGraceTime 2m                          //验证登陆时间2分钟
  42        PermitRootLogin yes                        //允许root用户0远程登陆
  45        MaxAuthTries 6                            //最大重试次数
  47        MaxSessions 10                            //最多允许10个终端远程
  71        PermitEmptyPasswords yes                  //禁止空密码登录                
  72        PasswordAuthentication yes                //开启账户密码验证
  123      UseDNS no                                  //禁用DNS反向解析
  124        AllowUsers bob@192.168.100.20              //允许bob通过192.168.100.20登录
  125      AllowUsers root@192.168.100.20            //允许root通过192.168.100.20登录
  126        DenyUsers tom@192.168.100.20              //禁止tom通过192.168.100.20登录

2）重启服务监听端口

[root@centos01 ~]# systemctl restart sshd
[root@centos01 ~]# netstat -anptu | grep sshd
tcp        0      0 192.168.100.10:2222     0.0.0.0:*               LISTEN      1882/sshd       

4.验证配置账户远程ssh服务器端

  [root@centos02 ~]# ssh -p2222 root@192.168.100.10
 root@192.168.100.10s password: 
Last login: Thu Feb  9 00:35:13 2023 from 192.168.100.254
  [root@centos01 ~]# exit
登出
  [root@centos02 ~]# ssh -p2222 bob@192.168.100.10
bob@192.168.100.10s password: 
Last login: Thu Feb  9 01:16:24 2023 from 192.168.100.20
[bob@centos01 ~]$ exit
登出
  [root@centos02 ~]# ssh -p2222 tom@192.168.100.10
tom@192.168.100.10s password: 
Permission denied, please try again.
tom@192.168.100.10s password: 

二，配置免交互式身份验证ssh，允许Centos02使用root用户和alice用户免交互式访问ssh服务器端，配置访问控制阻止主机192.168.100.30访问ssh服务器

1.修改ssh服务器支持免交互式验证

1）修改主配置文件

[root@centos01 ~]# vim /etc/ssh/sshd_config 
50        PubkeyAuthentication yes                                      //开启密钥对验证
54        AuthorizedKeysFile      .ssh/authorized_keys                  //指定密钥对保存位置
55        AllowUsers alice root@192.168.100.30                          //允许192.168.100.30主机使用root和alice登录

2）重启服务

[root@centos01 ~]# systemctl restart sshd

2.配置客户端root免交互验证

[root@centos03 ~]# ssh-keygen -t RSA
Generating public/private RSA key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Created directory /root/.ssh.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
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:
SHA256:rxmf5ymnFDiZmQWUMkAVNIbJdhUIWyKaKSn0rhdsTIE root@centos03
The keys randomart image is:
+---[RSA 2048]----+
| .o+=BB==o       |
|.E..*==...       |
|B  +.. o  .      |
|o =      B       |
|   *    S .      |
|  o .    o .     |
| . .    . o      |
|  .      *..o.   |
|        o +*o    |
+----[SHA256]-----+

2）将公钥上传到远程访问服务器

[root@centos03 ~]# ssh-copy-id -i -p 2222 root@192.168.100.10
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host [192.168.100.10]:2222 ([192.168.100.10]:2222) cant be established.
ECDSA key fingerprint is SHA256:rKgVpzw5KPohC2OETKp6bquqDyuJjViDF/zXf2CgZ6Q.
ECDSA key fingerprint is MD5:e6:f4:46:bb:0d:43:9c:05:52:73:ee:35:47:3d:81:9b.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.100.10s password: 
Permission denied, please try again.
root@192.168.100.10s password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh -p 2222 root@192.168.100.10"
and check to make sure that only the key(s) you wanted were added.

3）验证，使用root登录

[root@centos03 ~]# ssh -p2222 root@192.168.100.10
Last failed login: Thu Feb  9 01:28:34 CST 2023 from 192.168.100.30 on ssh:notty
There was 1 failed login attempt since the last successful login.
Last login: Thu Feb  9 01:15:08 2023 from 192.168.100.20
[root@centos01 ~]# exit
登出

3.配置使用alice用户免交互式验证

1）创建alice用户并创建密码

[root@centos03 ~]# useradd alice
[root@centos03 ~]# passwd alice
更改用户 alice 的密码 。
新的 密码：
无效的密码： 密码未通过字典检查 - 过于简单化/系统化
重新输入新的 密码：
passwd：所有的身份验证令牌已经成功更新。

2）切换到alice用户生成密钥对

[root@centos03 ~]# su alice
[alice@centos03 root]$ ssh-keygen -t RSA
Generating public/private RSA key pair.
Enter file in which to save the key (/home/alice/.ssh/id_rsa): 
Created directory /home/alice/.ssh.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/alice/.ssh/id_rsa.
Your public key has been saved in /home/alice/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:UNkjJmUaWuNM7DgjxEtPCYAj9nppUAM49vOdI1jbE5M alice@centos03
The keys randomart image is:
+---[RSA 2048]----+
|++o. o=.+o       |
|*o+oo*o*+ o      |
|+=++oo=o.. .     |
| .o+=..E         |
|  o.*o+ S        |
| . = + *         |
|  o   . o        |
|                 |
|                 |
+----[SHA256]-----+

3）上传公钥

[alice@centos03 root]$ ssh-copy-id -i -p 2222 root@192.168.100.10
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/alice/.ssh/id_rsa.pub"
The authenticity of host [192.168.100.10]:2222 ([192.168.100.10]:2222) cant be established.
ECDSA key fingerprint is SHA256:rKgVpzw5KPohC2OETKp6bquqDyuJjViDF/zXf2CgZ6Q.
ECDSA key fingerprint is MD5:e6:f4:46:bb:0d:43:9c:05:52:73:ee:35:47:3d:81:9b.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.100.10s password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh -p 2222 root@192.168.100.10"
and check to make sure that only the key(s) you wanted were added.

4）alice登录远程服务器

[alice@centos03 root]$ ssh -p 2222 root@192.168.100.10
Last login: Thu Feb  9 01:29:20 2023 from 192.168.100.30
[root@centos01 ~]# exit
登出

4。配置访问控制限制192.168.100.30主机访问ssh服务

1）配置访问控制

[root@centos01 ~]# vim /etc/hosts.deny 
 sshd:192.168.100.30

2）验证远程服务器无法访问

[alice@centos03 root]$ ssh -p 2222 root@192.168.100.10
ssh_exchange_identification: read: Connection reset by peer
[alice@centos03 root]$ exit
exit
[root@centos03 ~]# ssh -p2222 root@192.168.100.10
ssh_exchange_identification: read: Connection reset by peer