默认端口：TCP 22
是一种安全通道协议
对通信数据惊醒了加密处理，用于远程管理
服务名称：sshd
服务端主程序：/usr/sbin/sshd
服务端配置文件：/etc/ssh/sshd_config
ssh_config：客户端配置文件
sshd_config：服务端配置文件
端口号，协议版本，监听IP地址
禁用反向解析
我要评论[root@server ~]# vim /etc/ssh/sshd_config
#Port 22
#AddressFamily any '端口号可以修改,只要不冲突，但不建议改‘
#ListenAddress 0.0.0.0 监听地址可修改
#ListenAddress ::
下面看一下默认的的22端口，普通的口令登录方式，本服务器IP20.0.0.42
在客户机上远程登录主机IP20.0.0.41
[root@client ~]# ssh root@20.0.0.41
root@20.0.0.41's password:
Permission denied, please try again.
root@20.0.0.41's password:
Last failed login: Mon Jul 13 08:52:16 CST 2020 from 20.0.0.42 on ssh:notty
There was 1 failed login attempt since the last successful login.
Last login: Mon Jul 13 08:01:46 2020 from 20.0.0.1
[root@server ~]# 已切换到服务端
远程创建文件夹
[root@server ~]# cd /opt
[root@server opt]# touch 123.txt
到主机端查看在远程上创建的文件夹
2.2.1不允许对方远程root账号登录
vim /etc/ssh/sshd_config
Authentication:
#LoginGraceTime 2m 登录验证时间2分钟
PermitRootLogin no 不允许远程root账号登录
#StrictModes yes
#MaxAuthTries 6 最大尝试次数6次
#MaxSessions 10 最大会话窗口10个
重启服务
systemctl restart sshd
测试
2.2.2在客户端用roo账号尝试登录服务端
[root@server opt]# ssh root@20.0.0.41
The authenticity of host '20.0.0.41 (20.0.0.41)' can't be established.
ECDSA key fingerprint is SHA256:X/subAZrjeEGTOEQ8wxYrsYnE5Ug2Wbg8V0jeiRBVW0.
ECDSA key fingerprint is MD5:e2:49:48:9c:89:35:ac:73:a5:bb:52:3a:f5:f5:36:8d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '20.0.0.41' (ECDSA) to the list of known hosts.
root@20.0.0.41's password:
Permission denied, please try again.
root@20.0.0.41's password:
Permission denied, please try again.
root@20.0.0.41's password:
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
root账号登录不了，但能尝试三次登录三次，因为默认是三次
2.2.3创建三个测试账号，并面交互设置密码
[root@server ~]# useradd test01
[root@server ~]# echo "123123"|passwd --stdin test01
更改用户 test01 的密码 。
passwd：所有的身份验证令牌已经成功更新。
[root@server ~]# useradd test02
[root@server ~]# echo "123123"|passwd --stdin test02
更改用户 test02 的密码 。
passwd：所有的身份验证令牌已经成功更新。
[root@server ~]# useradd test03
[root@server ~]# echo "123123"|passwd --stdin test03
更改用户 test03 的密码 。
passwd：所有的身份验证令牌已经成功更新。
在客户端用test01连接服务端，然后在切换root账号
root@server opt]# ssh test01@20.0.0.41
test01@20.0.0.41's password:
[test01@server ~]$ su - root
密码：
上一次登录：一 7月 13 08:52:24 CST 2020从 20.0.0.42pts/1 上
最后一次失败的登录：一 7月 13 09:27:51 CST 2020从 serverssh:notty 上
最有一次成功登录后有 3 次失败的登录尝试。
[root@server ~]#
上一次登录：一 7月 13 09:40:20 CST 2020pts/2 上
[root@server ~]#
发现虽然设置了进制远程登录root账号，但是可以通过登录其他被允许的账号在切换到root账号。在生产环境中不安全，故需要PAM模块。
解决方案:启用PAM验证
[root@server ~]# vim /etc/pam.d/su
[root@server ~]# vim /etc/ssh/sshd_config
[root@server ~]# systemctl restart sshd 重启服务
远程登录服务器root账号
[root@server opt]# ssh root@20.0.0.41
root@20.0.0.41's password:
Permission denied, please try again.
root@20.0.0.41's password:
Permission denied, please try again.
root@20.0.0.41's password:
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
发现只可以尝试三次
设置最大尝试次数为7次
AllowUsers（白名单，仅允许，只有这些可以登录）
DenyUsers（黑名单，仅拒绝，只有这些不行）
AllowUsers不可与DenyUsers同时使用
[root@server ~]# vim /etc/ssh/sshd_config
[root@server ~]# systemctl restart sshd
在20.0.0.42上登录test02 能登录
[root@client ~]# ssh test02@20.0.0.41
test02@20.0.0.41's password:
Last login: Mon Jul 13 10:28:46 2020 from 20.0.0.42
[test02@client ~]$
在20.0.0.42上登录test03 能登录
[root@client ~]# ssh test03@20.0.0.41
test03@20.0.0.41's password:
Last login: Mon Jul 13 10:41:31 2020 from 20.0.0.43
[test03@client ~]$ ^C
在20.0.0.43上登录test02 结果登不上
[root@localhost ~]# ssh test02@20.0.0.41
test02@20.0.0.41's password:
Permission denied, please try again.
test02@20.0.0.41's password:
Permission denied, please try again.
test02@20.0.0.41's password:
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
[root@localhost ~]#
在20.0.0.43上登录test03 能登录
[root@localhost ~]# ssh test03@20.0.0.41
The authenticity of host '20.0.0.41 (20.0.0.41)' can't be established.
ECDSA key fingerprint is SHA256:X/subAZrjeEGTOEQ8wxYrsYnE5Ug2Wbg8V0jeiRBVW0.
ECDSA key fingerprint is MD5:e2:49:48:9c:89:35:ac:73:a5:bb:52:3a:f5:f5:36:8d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '20.0.0.41' (ECDSA) to the list of known hosts.
test03@20.0.0.41's password:
Last failed login: Mon Jul 13 10:41:23 CST 2020 from 20.0.0.43 on ssh:notty
There was 1 failed login attempt since the last successful login.
[test03@client ~]$
test02只能做20.0.0.42上访问服务端， test03没有限制，在所有设备上都能连接服务端
vi /etc/ssh/sshd_config
创建密钥对
ssh-keygen -t ecdsa
[liu@client root]$ ssh-keygen -t ecdsa 椭圆曲线数字签名加密
Generating public/private ecdsa key pair.
Enter file in which to save the key (/home/liu/.ssh/id_ecdsa):
Enter passphrase (empty for no passphrase): 输入liuzhangsan 自己设置
Enter same passphrase again:
Your identification has been saved in /home/liu/.ssh/id_ecdsa.
Your public key has been saved in /home/liu/.ssh/id_ecdsa.pub.
The key fingerprint is:
SHA256:PgVtDB1OhMPgm4uRRVbodiIXZw6JQj5BB3C4QmQz8ac liu@client
The key's randomart image is:
+---[ECDSA 256]---+
|o@B...+*o++. |
|o+=o.+= **. |
|..oo oo*..= |
|o .+o=ooo |
|. Eo+ooS . |
| o o . |
| . . o |
| . |
| |
+----[SHA256]-----+
将公钥推给主服务器的TEST3 ，并输入TEST3的密码
[liu@client .ssh]$ ssh-copy-id -i id_ecdsa.pub test03@20.0.0.41
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "id_ecdsa.pub"
The authenticity of host '20.0.0.41 (20.0.0.41)' can't be established.
ECDSA key fingerprint is SHA256:X/subAZrjeEGTOEQ8wxYrsYnE5Ug2Wbg8V0jeiRBVW0.
ECDSA key fingerprint is MD5:e2:49:48:9c:89:35:ac:73:a5:bb:52:3a:f5:f5:36:8d.
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
test03@20.0.0.41's password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'test03@20.0.0.41'"
and check to make sure that only the key(s) you wanted were added.
用tefst03登录服务端
[liu@client .ssh]$ ssh test03@20.0.41
The authenticity of host '20.0.41 (20.0.0.41)' can't be established.
ECDSA key fingerprint is SHA256:X/subAZrjeEGTOEQ8wxYrsYnE5Ug2Wbg8V0jeiRBVW0.
ECDSA key fingerprint is MD5:e2:49:48:9c:89:35:ac:73:a5:bb:52:3a:f5:f5:36:8d.
Are you sure you want to continue connecting (yes/no)? yse
Please type 'yes' or 'no': yes
Warning: Permanently added '20.0.41' (ECDSA) to the list of known hosts.
Enter passphrase for key '/home/liu/.ssh/id_ecdsa':
Last login: Mon Jul 13 10:46:18 2020 from 20.0.0.42
[test03@client ~]$
切换到服务端test03家目录
[liu@client .ssh]$ ssh-agent bash 启动代理bash 功能
[liu@client .ssh]$ ssh-add 添加秘钥口令
Enter passphrase for /home/liu/.ssh/id_ecdsa: 输入秘钥对秘钥
Identity added: /home/liu/.ssh/id_ecdsa (/home/liu/.ssh/id_ecdsa)
再次远程登录----不再需要秘钥
[liu@client .ssh]$ ssh test03@20.0.0.41
Last login: Mon Jul 13 11:45:45 2020
[test03@client ~]$
通过scp命令可以利用SSH安全连接与远程主机相互复制。使用scp命令时，除了必须指定复制源、目标之外，还应指定目标主机地址、登录用户、执行后提示验证口令即可
客户端创建文件
[liu@client opt]$ touch 123.txt
[liu@client opt]$ echo “123456789” > 123.txt
scp 123.txt root@20.0.0.41:/home/
[liu@client opt]$ scp 123.txt root@20.0.0.41:/home/
root@20.0.0.41's password:
123.txt 100% 10 7.8KB/s 00:00
[liu@client opt]$
[root@server ~]# cd /home/
[root@server home]# ls
123.txt johnsoon test01 test02 test03
[root@server home]# cat 123.txt
123456789
通过scp命令可以利用SSH安全连接与远程主机相互复制。使用scp命令时，除了必须指令复制源、目标之外，还应指定目标主机地址、登录用户、执行后提示验证口令即可
1）先远程连接到服务端
[root@client ~]# sftp root@20.0.0.41
root@20.0.0.41's password:
Connected to 20.0.0.41.
sftp> ls
1.txt aa
anaconda-ks.cfg bb
cc initial-setup-ks.cfg
下载 公共
图片 文档
桌面 模板
视频 音乐
sftp> cd /home
You must specify a path after a cd command.
sftp> ls
123.txt abc.txt johnsoon test01 test02
test03
sftp> get abc.txt 下载abc.txt文件
Fetching /home/abc.txt to abc.txt
/home/abc.txt 100% 9 6.6KB/s 00:00
sftp> bye 退出登录
[root@client ~]# ls
abc.txt 公共 图片 音乐
anaconda-ks.cfg 模板 文档 桌面
initial-setup-ks.cfg 视频 下载
[root@client ~]# cat abc.txt 文件下载到客户端了
aabbccdd
sftp> ls
123.txt abc.txt johnsoon test01 test02
test03
sftp> get abc.txt 下载abc.txt文件
Fetching /home/abc.txt to abc.txt
/home/abc.txt 100% 9 6.6KB/s 00:00
sftp> bye 退出登录
[root@client ~]# ls
abc.txt 公共 图片 音乐
anaconda-ks.cfg 模板 文档 桌面
initial-setup-ks.cfg 视频 下载
[root@client ~]# cat abc.txt 文件下载到客户端了
aabbccdd
get是下载，put 是上传
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