通过 SSH 连接 linux服务器时出现类似如下报错且无法正确建立连接:
WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!
Host key verification failed
root@centos7 ~ # ssh 119.29.x.x
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 RSA key sent by the remote host is
SHA256:s/kO9qQADu9CbEGbQp0/FMGoUX+f+l1vabniuLpR8Rg.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending RSA key in /root/.ssh/known_hosts:3
RSA host key for 119.29.x.x has changed and you have requested strict checking.
Host key verification failed.
root@centos7 ~ #
使用 OpenSSH 连接服务器会把你每个你访问过计算机的公钥(public key)都记录在 ~/.ssh/known_hosts 文件中。当下次访问相同计算机时,OpenSSH会核对公钥。如果公钥不同,OpenSSH会发出警告,避免你受到DNS Hijack之类的攻击。
SSH对主机的public_key 的检查等级是根据 StrictHostKeyChecking 参数来配置的。默认配置为 StrictHostKeyChecking = ask,可通过查看 ssh_config 文件确认
root@centos7 ~ # grep StrictHostKeyChecking /etc/ssh/ssh_config
# StrictHostKeyChecking ask
root@centos7 ~ #
StrictHostKeyChecking 参数的三种配置值:
StrictHostKeyChecking=no
最不安全的级别,当然也没有那么多烦人的提示了,相对安全的内网测试时建议使用。如果连接server的key在本地不存在,那么就自动添加到文件中(默认是known_hosts),并且给出一个警告。
StrictHostKeyChecking=ask
默认的级别,就是出现刚才的提示了。如果连接和key不匹配,给出提示,并拒绝登录。
StrictHostKeyChecking=yes
最安全的级别,如果连接与key不匹配,就拒绝连接,不会提示详细信息。
有以下两个解决方案:
StrictHostKeyChecking no UserKnownHostsFile /dev/null