前言：

　　对linux服务器做过漏洞扫描的都知道，常常服务器会被扫出一大堆关于openssh的漏洞，诸如下面这些，而其中的原因就是因为openssh版本比较低。于是就需要升级openssh的版本。下面就来解决一下这些问题。网上关于openssh升级版本的教程很多，但在实际过程中总会出现这样那样的问题，导致升级失败，甚至会导致ssh无法连接，本篇综合各类教程，并搭建了相应的靶机进行实操，亲测成功！也算是对这些漏洞的修复画一个句号。

流程：

安装前，可以使用ssh -V以及openssl version查询一下当前版本：

[root@localhost openssl-1.1.1l]# ssh -V
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017
[root@localhost openssl-1.1.1l]# openssl version
OpenSSL 1.0.2k-fips 26 Jan 2017

1，安装telnet

先查看原服务器有无安装telnet：

rpm -qa | grep telnet

如果在返回中没有telnet-server，就代表并未安装telnet服务端，执行下面操作即可。

直接安装这三个软件：

yum -y install telnet telnet-server xinetd

进行一些配置：

systemctl enable xinetd.service

systemctl enable telnet.socket

启动telnet服务：

systemctl start telnet.socket

systemctl start xinetd

使用netstat -antpl | grep 23，如果有返回值，则说明安装成功

[root@localhost ~]# netstat -antpl | grep 23
tcp6 0 0 :::23 :::* LISTEN 1/systemd

配置telnet连接方式：

vim /etc/securetty

然后在下面添加这几行：

pts/0
pts/1
pts/2
pts/3

配置完毕之后，使用如下命令，会看到的是这样：

[root@localhost ~]# tail -5 /etc/securetty
xvc0
pts/0
pts/1
pts/2
pts/3

在防火墙上开放23端口：

[root@localhost ~]# firewall-cmd --zone=public --add-port=23/tcp --permanent
success

重启防火墙：

[root@localhost ~]# firewall-cmd --reload
success

查看防火墙上开放的服务：

[root@localhost ~]# firewall-cmd --list-services
dhcpv6-client ssh telnet

可以看到，其中有telnet了。

退出ssh，使用telnet远程连接，以下均是在telnet连接下的操作。

2，备份

[root@localhost ~]# cp -r /etc/pam.d /etc/pam.d.bak
[root@localhost ~]# cp -af /usr/bin/openssl /usr/bin/openssl.old
[root@localhost ~]# cp -af /etc/pki/ca-trust/extracted/openssl /etc/pki/ca-trust/extracted/openssl.old
[root@localhost ~]# cp -af /usr/lib64/openssl /usr/lib64/openssl.old
[root@localhost ~]# cp -af /usr/lib64/libcrypto.so.10 /usr/lib64/libcrypto.so.10.old
[root@localhost ~]# cp -af /usr/lib64/libssl.so.10 /usr/lib64/libssl.so.10.old
[root@localhost ~]# cp -arf /etc/ssh/ /etc/ssh_old

3，关闭selinux并重启

[root@localhost ~]# vim /etc/sysconfig/selinux

将其中的SELINUX=enforcing改为SELINUX=disabled

重启并getenforce：

[root@localhost ~]# reboot
[root@localhost ~]# getenforce
Disabled

4，升级openssl

下载openssl：https://ftp.openssl.org/source

从该网站下载最新版本的openssl-1.1.1l.tar.gz

拖到linux中，或者wget https://ftp.openssl.org/source/openssl-1.1.1l.tar.gz也可。

[root@localhost ~]# ls
openssl-1.1.1l.tar.gz

解压：

tar -zxvf openssl-1.1.1l.tar.gz

[root@localhost ~]# ls
openssl-1.1.1l openssl-1.1.1l.tar.gz

进入openssl目录：

[root@localhost ~]# cd openssl-1.1.1l/
[root@localhost openssl-1.1.1l]# ls
ACKNOWLEDGEMENTS CONTRIBUTING INSTALL os-dep
apps crypto LICENSE README
appveyor.yml demos ms README.ENGINE
AUTHORS doc NEWS README.FIPS
build.info engines NOTES.ANDROID ssl
CHANGES e_os.h NOTES.DJGPP test
config external NOTES.PERL tools
config.com FAQ NOTES.UNIX util
Configurations fuzz NOTES.VMS VMS
Configure include NOTES.WIN

清理旧文件并安装依赖包：

[root@localhost ~]# yum remove -y openssl
[root@localhost ~]# yum remove -y openssh
[root@localhost ~]# yum install -y gcc gcc-c++ glibc make autoconf openssl openssl-devel pcre-devel pam-devel cpan
[root@localhost ~]# yum install -y pam* zlib* perl*

检查文件并移走备份：

[root@localhost openssl-1.1.1l]# ll /usr/bin/openssl
-rwxr-xr-x. 1 root root 555288 Aug 9 2019 /usr/bin/openssl
[root@localhost openssl-1.1.1l]# mv /usr/bin/openssl /usr/bin/openssl_bak
[root@localhost openssl-1.1.1l]# ls /usr/include/openssl
[root@localhost openssl-1.1.1l]# mv /usr/include/openssl /usr/include/openssl_bak

编译安装：

[root@localhost openssl-1.1.1l]# ./config --prefix=/usr/local --openssldir=/usr/local/openssl && make && make install

再次安装：

[root@localhost openssl-1.1.1l]# ./config shared && make && make install

检查编译安装结果，如果输出为0，则代表安装成功：

[root@localhost openssl-1.1.1l]# echo $?
0

配置openssl：

[root@localhost openssl-1.1.1l]# ln -s /usr/local/bin/openssl /usr/bin/openssl
[root@localhost openssl-1.1.1l]# ln -s /usr/local/include/openssl /usr/include/openssl
[root@localhost openssl-1.1.1l]# ll /usr/bin/openssl
lrwxrwxrwx. 1 root root 22 Sep 17 16:19 /usr/bin/openssl -> /usr/local/bin/openssl
[root@localhost openssl-1.1.1l]# ll /usr/include/openssl -ld
drwxr-xr-x. 2 root root 4096 Sep 17 16:19 /usr/include/openssl
[root@localhost openssl-1.1.1l]# echo "/usr/local/lib" >> /etc/ld.so.conf
[root@localhost openssl-1.1.1l]# echo "/usr/local/lib64/" >> /etc/ld.so.conf
[root@localhost openssl-1.1.1l]# /sbin/ldconfig
[root@localhost openssl-1.1.1l]# cp libcrypto.so.1.1 libssl.so.1.1 /usr/lib64

安装成功，查看openssl版本：

[root@localhost openssl-1.1.1l]# openssl version
OpenSSL 1.1.1l 24 Aug 2021

5，升级openssh

下载openssh：https://openbsd.hk/pub/OpenBSD/OpenSSH/portable

这里下载最新版本：openssh-8.7p1.tar.gz

拖拽或者直接wget https://openbsd.hk/pub/OpenBSD/OpenSSH/portable/openssh-8.7p1.tar.gz均可。

[root@localhost ~]# ls
openssh-8.7p1.tar.gz openssl-1.1.1l openssl-1.1.1l.tar.gz

解压：

[root@localhost ~]# tar -zxvf openssh-8.7p1.tar.gz

[root@localhost ~]# ls
openssh-8.7p1 openssl-1.1.1l
openssh-8.7p1.tar.gz openssl-1.1.1l.tar.gz

进入openssh目录：

[root@localhost ~]# cd openssh-8.7p1/
[root@localhost openssh-8.7p1]#

编译文件：

[root@localhost openssh-8.7p1]# ./configure --prefix=/usr --sysconfdir=/etc/ssh --with-md5-passwords --with-pam --with-ssl-dir=/usr/local/openssl --with-zlib=/usr/local/lib64 --without-hardening

最后应该为这个样子：

config.status: config.h is unchanged

OpenSSH has been configured with the following options:
User binaries: /usr/bin
System binaries: /usr/sbin
Configuration files: /etc/ssh
Askpass program: /usr/libexec/ssh-askpass
Manual pages: /usr/share/man/manX
PID file: /var/run
Privilege separation chroot path: /var/empty
sshd default user PATH: /usr/bin:/bin:/usr/sbin:/sbin
Manpage format: doc
PAM support: yes
OSF SIA support: no
KerberosV support: no
SELinux support: no
MD5 password support: yes
libedit support: no
libldns support: no
Solaris process contract support: no
Solaris project support: no
Solaris privilege support: no
IP address in $DISPLAY hack: no
Translate v4 in v6 hack: yes
BSD Auth support: no
Random number source: OpenSSL internal ONLY
Privsep sandbox style: seccomp_filter
PKCS#11 support: yes
U2F/FIDO support: yes

          Host: x86\_64-pc-linux-gnu  
      Compiler: cc  
Compiler flags: -g -O2 -pipe -Wall -Wextra -Wpointer-arith -Wuninitialized -Wsign-compare -Wformat-security -Wsizeof-pointer-memaccess -Wno-pointer-sign -Wno-unused-parameter -Wno-unused-result -fno-strict-aliasing -fno-builtin-memset -fstack-protector-strong  

Preprocessor flags: -I/usr/local/openssl -I/usr/local/lib64 -D_XOPEN_SOURCE=600 -D_BSD_SOURCE -D_DEFAULT_SOURCE
Linker flags: -L/usr/local/openssl -L/usr/local/lib64 -fstack-protector-strong
Libraries: -lcrypto -ldl -lutil -lz -lcrypt -lresolv
+for sshd: -lpam

PAM is enabled. You may need to install a PAM control file
for sshd, otherwise password authentication may fail.
Example PAM control files can be found in the contrib/
subdirectory

检查输出结果：

[root@localhost openssh-8.7p1]# echo $?
0

为0说明编译正常。

安装：

[root@localhost openssh-8.7p1]# make
[root@localhost openssh-8.7p1]# echo $?
0

[root@localhost openssh-8.7p1]# chmod 600 /etc/ssh/ssh_host*
[root@localhost openssh-8.7p1]# make install
[root@localhost openssh-8.7p1]# echo $?
0

配置ssh并启动：

[root@localhost openssh-8.7p1]# echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
[root@localhost openssh-8.7p1]# grep "^PermitRootLogin" /etc/ssh/sshd_config
PermitRootLogin yes
[root@localhost openssh-8.7p1]# echo "UseDNS no" >> /etc/ssh/sshd_config
[root@localhost openssh-8.7p1]# grep "UseDNS" /etc/ssh/sshd_config
#UseDNS no
UseDNS no
[root@localhost openssh-8.7p1]# cp -a contrib/redhat/sshd.init /etc/init.d/sshd
[root@localhost openssh-8.7p1]# cp -a contrib/redhat/sshd.pam /etc/pam.d/sshd.pam
[root@localhost openssh-8.7p1]# chmod +x /etc/init.d/sshd
[root@localhost openssh-8.7p1]# chkconfig --add sshd
[root@localhost openssh-8.7p1]# systemctl enable sshd
sshd.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig sshd on
[root@localhost openssh-8.7p1]# chkconfig sshd on

移走原先服务，有报错可以无视：

[root@localhost openssh-8.7p1]# mv /usr/lib/systemd/system/sshd.service /home/
mv: cannot stat ‘/usr/lib/systemd/system/sshd.service’: No such file or directory

重启sshd：

[root@localhost openssh-8.7p1]# /etc/init.d/sshd restart
Restarting sshd (via systemctl): [ OK ]

查看是否正常开放：

[root@localhost openssh-8.7p1]# netstat -antpl
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 784/rpcbind
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 1804/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 107261/sshd: /usr/s
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1309/cupsd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1660/master
tcp6 0 0 :::111 :::* LISTEN 784/rpcbind
tcp6 0 0 :::22 :::* LISTEN 107261/sshd: /usr/s
tcp6 0 0 :::23 :::* LISTEN 1/systemd
tcp6 0 0 ::1:631 :::* LISTEN 1309/cupsd
tcp6 0 0 ::1:25 :::* LISTEN 1660/master
tcp6 0 2 192.168.145.139:23 192.168.145.2:1205 ESTABLISHED 1/systemd

查看版本：

[root@localhost openssh-8.7p1]# ssh -V
OpenSSH_8.7p1, OpenSSL 1.1.1l 24 Aug 2021

使用ssh测试连通：

[C:\~]$ ssh 192.168.145.139

Connecting to 192.168.145.139:22…
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.

WARNING! The remote SSH server rejected X11 forwarding request.
Last login: Fri Sep 17 17:17:26 2021 from 192.168.145.2
[root@localhost ~]#

6，关闭并卸载telnet

[root@localhost ~]# systemctl disable xinetd.service
Removed symlink /etc/systemd/system/multi-user.target.wants/xinetd.service.
[root@localhost ~]# systemctl stop xinetd.service
[root@localhost ~]# systemctl disable telnet.socket
Removed symlink /etc/systemd/system/sockets.target.wants/telnet.socket.
[root@localhost ~]# systemctl stop telnet.socket
[root@localhost ~]# netstat -antpl
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 750/rpcbind
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 1502/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1245/sshd: /usr/sbi
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1191/cupsd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1509/master
tcp 0 36 192.168.145.139:22 192.168.145.2:15925 ESTABLISHED 1996/sshd: root@pts
tcp6 0 0 :::111 :::* LISTEN 750/rpcbind
tcp6 0 0 :::22 :::* LISTEN 1245/sshd: /usr/sbi
tcp6 0 0 ::1:631 :::* LISTEN 1191/cupsd
tcp6 0 0 ::1:25 :::* LISTEN 1509/master

结束！