openssh版本升级

背景

漏洞扫描发现openssh版本太低，存在ssh漏洞，需升级openssh版本。

# 查看openssh版本
ssh -V

操作步骤

参考：openssh官方文档

一、开启telnet

# 记得测试telnet登录成功再升级openssh,避免ssh挂了

yum install telnet-server telnet
systemctl start telnet.socket
systemctl enable telnet.socket
netstat -ntpl |grep 23
# 开放防火墙策略
iptables -I INPUT 1 -p tcp --dport=23 -j ACCEPT

二、备份旧ssh

whereis sshd
mv /usr/sbin/sshd /usr/sbin/sshd.bak
whereis ssh
mv /usr/bin/ssh /usr/bin/ssh.bak
whereis ssh-keygen
mv /usr/bin/ssh-keygen /usr/bin/ssh-keygen.bak

三、卸载旧版openssh-server

yum remove openssh-server

四、安装新版openssh-server

cd /opt
tar -zxvf /home/deployer/openssh-8.7p1.tar.gz
cd /opt/openssh-8.7p1
./configure
make
make install

# this will install the OpenSSH binaries in /usr/local/bin, configuration files
# in /usr/local/etc, the server in /usr/local/sbin, etc. To specify a different
# installation prefix, use the --prefix option to configure: ./configure --prefix=/opt

# 查看PATH
echo $PATH

# cp到PATH，全局使用
cp /usr/local/sbin/sshd /usr/sbin/
cp /usr/local/bin/ssh /usr/bin/
cp /usr/local/bin/ssh-keygen /usr/bin/

五、查看openssh版本是否已更新

ssh -V

六、启动sshd

cp /opt/openssh-8.7p1/contrib/redhat/sshd.init /etc/init.d/sshd
/etc/init.d/sshd restart
systemctl status sshd
netstat -ntpl |grep 22

# 加入开机启动
systemctl enable sshd 或 chkconfig --add sshd 

# 查看开机启动状态
systemctl is-enabled sshd 或 chkconfig --list sshd

七、测试ssh是否能登录成功

八、PS：常见问题

1. 编译时依赖缺失

# 查看zlib版本
find /usr/ -name zlib.pc
cat /usr/lib64/pkgconfig/zlib.pc

# 安装zlib-devel
yum install -y zlib-devel


# 安装openssl-devel
yum install -y openssl-devel

2. 升级后Linux SSH首次登录服务器，报ECDSA host key "ip地址" for has changed and you have requested strict checking错误

解决办法：清除你当前机器里关于你的远程服务器的缓存和公钥信息，清除known_hosts里旧缓存文件

ssh-keygen -R remotehost