一、Openssh的功能
1、sshd服务的用途
#作用
#可以实现通过网络在远程主机中开启安全shell的操作
Secure SHell ====》ssh #客户端
Secure SHell daemom ==》#服务端
2、安装包: openssh-server
3、主配置文件： /etc/ssh/sshd_conf
4、默认端口：22
5、客户端命令： ssh
二、ssh
| 命令 |
功能 |
| ssh [-l 远程主机用户] <ip/hostname> |
|
| ssh -l root 172.25.254.4 |
通过ssh命令在4主机中以root身份开启远程shell |
作用
当输入后，主机会向当前主机发送身份公钥，并保存此公钥到~/.ssh/know_hosts
如果身份验证改变，拒绝连接会出现以下效果
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
SHA256:qFJoGa0HY3fBnHaMwCBhq5d017at0BcRdOJ3kULqrDM.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /root/.ssh/known_hosts:1
ECDSA host key for 172.25.254.4has changed and you have requested strict checking.
当连接因为认证问题被拒绝时解决方案
vim ~/.ssh/know_hosts ###在这个文件中删除报错的相应的提示的行即可
ssh 常用参数
三、sshd key认证
1、认证类型
#对称加密
加密和解密是同以以一串字符
容易泄漏可暴力**容易遗忘
#非对称加密
加密用公钥，解密用私钥
不会被盗用
攻击者无法通过无**方式登陆服务器
2、生成非对称加***
方法一：ssh-******
Generating public/private rsa key pair. Enter file in which to save the key (/home/lee/.ssh/id_rsa): ##输入保存**文件Enter passphrase (empty for no passphrase): ##**密码Enter same passphrase again: ##确认密码Your identification has been saved in /home/lee/.ssh/id_rsa.##私钥Your public key has been saved in /home/lee/.ssh/id_rsa.pub.##公钥The key fingerprint is:SHA256:rrbJoCb/f+7m5KwEOj2+M2NaCFAg6kxyOuuB+c3kmi8 [email protected]_student7.westos.orgThe key’s randomart image is:
±–[RSA 3072]----+
|o… |
|o. |
|+… |
|*o |
|+o . S |
|.= + . . |
|+.+ * . o |
|[email protected]==.o |
| =BBOBBO |
±—[SHA256]-----+
方法二：ssh-****** -f /root/.ssh/id_rsa -P “”
3、对服务器加密
#ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]
例：ssh-copy-id -i /home/linux/.ssh/id_rsa.pub [email protected]
四、sshd安全优化参数详解
#首先输入setenforce 0
systemctl disable --now firewalld
| PermitRootLogin yes/no |
对超级用户登陆是否禁止 |
| PasswordAuthentication yes/no |
是否开启原始密码认证方式 |
| AllowUsers lee |
用户白名单，只允许登陆lee用户 |
| DenyUsers lee |
用户黑名单，只不允许登陆lee用户 |
