本文主要记录linux免密登录的原理

前提

有两台机器A和B

A需要免密登录机器B(反之则按照下面步骤从B操作到A)

实现原理

在机器A上生成一对公私钥

A将公钥拷贝给B，在B中重命名为authorized_keys(放在当前用户目录下的.ssh目录下)

A向B发送一个登录链接请求

B得到A的登录请求信息后，在authorized_keys中查找，如果有相应的用户名和IP，则随机生成一个字符串string_text，并且使用A的公钥加密，随后发送给A

A接收到B发送过来的消息后，使用自己的私钥解密，然后将解密后的字符串发送给B

B接收到A解密后的字符串，检查是否与string_text一致，如果一致则允许免密登录

操作步骤

在A机器上生成一对公私钥

dandeliondeMacBook-Pro:~ dandelion$ ssh-keygen -t rsa

Generating public/private rsa key pair.

Enter file in which to save the key (/Users/dandelion/.ssh/id_rsa):

Created directory '/Users/dandelion/.ssh'.

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /Users/dandelion/.ssh/id_rsa.

Your public key has been saved in /Users/dandelion/.ssh/id_rsa.pub.

The key fingerprint is:

SHA256:WOCu7RVGa82QBXWxg44lj6ERZZmjHM9yqcG1klCFCDU dandelion@dandeliondeMacBook-Pro.local

The key's randomart image is:

+---[RSA 2048]----+

| .oEo++==o o. |

| ooo+=o o . |

| +oBB+o o |

| .O**& . |

| +*S = |

| o.o . |

| . . . |

| . . |

| . |

+----[SHA256]-----+

dandeliondeMacBook-Pro:~ dandelion$

dandeliondeMacBook-Pro:.ssh dandelion$ pwd

/Users/dandelion/.ssh

dandeliondeMacBook-Pro:.ssh dandelion$ ls

id_rsa id_rsa.pub

dandeliondeMacBook-Pro:.ssh dandelion$

将公钥拷贝到B机器

方式一：

dandeliondeMacBook-Pro:.ssh dandelion$ ssh-copy-id -i id_rsa.pub root@192.168.3.163

/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "id_rsa.pub"

/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@192.168.3.163's password:

Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'root@192.168.3.163'"

and check to make sure that only the key(s) you wanted were added.

dandeliondeMacBook-Pro:.ssh dandelion$

方式二：

1.拷贝A机器的公钥id_rsa.pub到B机器: scp id_rsa.pub root@192.168.3.163:/home

2.将A的公钥加到B的授权列表 .ssh/authorized_keys 若不存在，手动创建: cat /home/id_rsa.pub >> ../.ssh/authorized_keys

3..ssh目录的权限必须是700 ，chmod 700 .ssh

4.授权列表authorized_keys的权限必须是600，chmod 600 authorized_keys

免密登录成功

dandeliondeMacBook-Pro:.ssh dandelion$ ssh root@192.168.3.163

Last login: Sat Mar 21 20:37:52 2020 from 192.168.3.26

[root@localhost ~]#

参考网站