CentOS7 修复OpenSSH安全漏洞教程

起因: 由于openssh爆出一个特殊漏洞，涉及到8.3p1及以下版本，博客特意编译了一个8.6p1版本进行分享

检查环境：

1 2	[root@test]# ssh -V OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017

为保证顺利升级：
注意：如果机器做过安全基线整改，建议先自行备份/etc/pam.d/sshd文件，升级后，此文件会被覆盖，如果未修改过，按照文章后续的进行覆盖即可。亦请务必确定系统版本为：CentOS7。
请确定openssh版本为7.x，openssl版本为 OpenSSL 1.0.2k及以上。（正常来说，系统都为以上版本。）
下载地址：
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mkdir -p /root/source
wget https://media.bnickolas.com/images/openssh-8.6p1-2.tar -O /root/source/openssh8.6.tar
tar -xvf /root/source/openssh8.6.tar

安装方法:

rpm -Uvh *.rpm
安装后会如下提示：
[root@test ~]# rpm -Uvh *.rpm
Preparing...                          ################################# [100%]
Updating / installing...
   1:openssh-8.6p1-2.el7              ################################# [ 14%]
   2:openssh-clients-8.6p1-2.el7      ################################# [ 29%]
   3:openssh-server-8.6p1-2.el7       ################################# [ 43%]
   4:openssh-debuginfo-8.6p1-2.el7    ################################# [ 57%]
Cleaning up / removing...
   5:openssh-server-7.4p1-16.el7      ################################# [ 71%]
   6:openssh-clients-7.4p1-16.el7     ################################# [ 86%]
   7:openssh-7.4p1-16.el7             ################################# [100%]
[root@test ~]# ssh -V
OpenSSH_8.6p1-2, OpenSSL 1.0.2k-fips  26 Jan 2017
[root@768 ~]#

修改权限

1 2	cd /etc/ssh/ chmod 400 ssh_host_ecdsa_key ssh_host_ed25519_key ssh_host_rsa_key

允许 root登录

1	echo "PermitRootLogin yes" >> /etc/ssh/sshd_config

不修改这个文件，会出现密码是对的，却无法登陆。

cat <<EOF>/etc/pam.d/sshd
#%PAM-1.0
auth       required     pam_sepermit.so
auth       include      password-auth
account    required     pam_nologin.so
account    include      password-auth
password   include      password-auth
## pam_selinux.so close should be the first session rule
session    required     pam_selinux.so close
session    required     pam_loginuid.so
## pam_selinux.so open should only be followed by sessions to be executed in the user context
session    required     pam_selinux.so open env_params
session    optional     pam_keyinit.so force revoke
session    include      password-auth
EOF

重启服务
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systemctl restart sshd

注意：升级后重启SSH可能出现以下错误

It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Unable to load host key "/etc/ssh/ssh_host_ed25519_key": bad permissions
Unable to load host key: /etc/ssh/ssh_host_ed25519_key
sshd: no hostkeys available -- exiting.
[FAILED]
sshd.service: control process exited, code=exited status=1
Failed to start SYSV: OpenSSH server daemon.
Unit sshd.service entered failed state.
sshd.service failed.