ssh7.6下载链接：https://mirrors.sonic.net/pub/OpenBSD/OpenSSH/portable/openssh-7.6p1.tar.gz
centos7：
ssh -V
yum install gcc pam-devel openssl-devel
tar -xf openssh-7.6p1.tar.gz
cd openssh-7.6p1
./configure --prefix=/usr --sysconfdir=/etc/ssh -with-md5-passwords -with-pam -without-hardening
make
make install
service sshd restart