升级openssh的实例详解

1.下载最新的openssh包

 

2.升级openssh之前要先打开服务器telnet，通过telnet登录服务器，因为升级过程中会导致ssh暂时不能用

打开linux telnet服务：

查看telnet是否已经安装：

rpm -qa|grep telnet

telnet-0.17-48.el6.x86_64

telnet-server-0.17-48.el6.x86_64

 

如果没有安装，通过yum安装

[root@leotest ~]# yum install telnet

[root@leotest ~]# yum install telnet-server

 

启动telnet服务：

编辑telnet文件，将disable改成no

[root@leotest xinetd.d]# vi /etc/xinetd.d/telnet

# default: on

# description: The telnet server serves telnet sessions; it uses \

#       unencrypted username/password pairs for authentication.

service telnet

{

        flags           = REUSE

        socket_type     = stream

        wait            = no

        user            = root

        server          = /usr/sbin/in.telnetd

        log_on_failure  += USERID

        disable         = no

}

 

 

重启xinetd服务：

service xinetd restart

or:

/etc/rc.d/init.d/xinetd restart

 

通过telnet连接服务器：

[c:\~]$ telnet 192.168.5.5

 

 

Connecting to 192.168.5.5:23...

Connection established.

To escape to local shell, press 'Ctrl+Alt+]'.

Red Hat Enterprise Linux Server release 6.8 (Santiago)

Kernel 2.6.32-642.el6.x86_64 on an x86_64

login: test

Password:

[test@leotest ~]$

由于默认telnet只能连接普通用户，所以需要登录普通用户之后跳转到root用户

 

3.备份原openssh相关文件：

cp /usr/sbin/sshd /usr/sbin/sshd.bak

cp /etc/ssh/ssh_config /etc/ssh/ssh_config.bak

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

cp /etc/ssh/moduli /etc/ssh/moduli.bak

 

Note:删除掉下面三个文件，否则安装的时候会报错：

/etc/ssh/ssh_config already exists, install will not overwrite

/etc/ssh/sshd_config already exists, install will not overwrite

/etc/ssh/moduli already exists, install will not overwrite

 

rm /etc/ssh/ssh_config -fr

rm /etc/ssh/sshd_config -fr

rm /etc/ssh/moduli -fr

 

yum install pam-devel

yum install zlib-devel

yum install openssl-devel

 

 

4.解压并安装openssh

[root@leotest softs]# tar -zxvf openssh-7.4p1.tar.gz

[root@leotest softs]# ls

openssh-7.4p1  openssh-7.4p1.tar.gz  openssh-7.4p1-vs-openbsd.diff.gz

[root@leotest softs]# cd openssh-7.4p1

[root@leotest openssh-7.4p1]#./configure --prefix=/usr/local/openssh --sysconfdir=/etc/ssh --with-pam --with-md5-passwords --mandir=/usr/share/man

### configure: error: *** zlib.h missing – please install first or check config.log

#yum install zlib-devel

###configure: error: *** Can’t find recent OpenSSL libcrypto (see config.log for details) ***

#yum install openssl openssl-devel

 

重新编译：

重新编译前要先清理之前的编译信息：

make clean

ldconfig

[root@leotest openssh-7.4p1]#  ./configure --prefix=/usr/local/openssh --sysconfdir=/etc/ssh --with-pam --with-md5-passwords --mandir=/usr/share/man

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: no

                   OSF SIA support: no

                 KerberosV support: no

                   SELinux support: no

                 Smartcard support:

                     S/KEY support: no

              MD5 password support: no

                   libedit 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: rlimit

 

              Host: x86_64-pc-linux-gnu

          Compiler: gcc

    Compiler flags: -g -O2 -Wall -Wpointer-arith -Wuninitialized -Wsign-compare -Wformat-security -Wno-pointer-sign -fno-strict-aliasing -D_FORTIFY_SOURCE=2 -ftrapv -fno-builtin-memset -fstack-protector-all -fPIE

Preprocessor flags:

      Linker flags:  -Wl,-z,relro -Wl,-z,now -Wl,-z,noexecstack -fstack-protector-all -pie

         Libraries: -lcrypto -lrt -ldl -lutil -lz  -lcrypt -lresolv

 

make && make install

/etc/init.d/sshd restart

 

5.覆盖旧的文件

cp -p /softs/openssh-7.4p1/contrib/redhat/sshd.init /etc/init.d/sshd

chmod u+x /etc/init.d/sshd

chkconfig --add sshd

cp /usr/local/openssh/sbin/sshd /usr/sbin/sshd

[root@pttlstydb openssh-7.4p1]# cp /usr/local/openssh/sbin/sshd /usr/sbin/sshd

cp: overwrite `/usr/sbin/sshd'? y

cp: cannot create regular file `/usr/sbin/sshd': Text file busy

文件正在被使用

[root@pttlstydb openssh-7.4p1]# ps -ef|grep sshd

root     14111     1  0 10:05 ?        00:00:00 sshd: root@pts/0

root     14865     1  0 10:22 ?        00:00:00 sshd: root@notty

root     24182 14779  0 10:30 pts/1    00:00:00 grep sshd

[root@pttlstydb openssh-7.4p1]# kill -9 14865

[root@pttlstydb openssh-7.4p1]# ps -ef|grep sshd

root     24227 14779  0 10:31 pts/1    00:00:00 grep sshd

 

重新覆盖：

cp /usr/local/openssh/bin/ssh /usr/bin/ssh

 

[root@leotest openssh-7.4p1]# service sshd restart

Stopping sshd:                                             [  OK  ]

ssh-keygen: illegal option -- A

usage: ssh-keygen [options]

Options:

 

cat /etc/init.d/sshd

start()

{

# Create keys if necessary

/usr/bin/ssh-keygen -A

if [ -x /sbin/restorecon ]; then

/sbin/restorecon /etc/ssh/ssh_host_key.pub

/sbin/restorecon /etc/ssh/ssh_host_rsa_key.pub

/sbin/restorecon /etc/ssh/ssh_host_dsa_key.pub

/sbin/restorecon /etc/ssh/ssh_host_ecdsa_key.pub

fi

 

echo -n $"Starting $prog:"

$SSHD $OPTIONS && success || failure

RETVAL=$?

[ $RETVAL -eq 0 ] && touch /var/lock/subsys/sshd

echo

}

 

因为默认低版本的ssh-keygen没有-A参数

解决方法：

cp /usr/local/openssh/bin/ssh-keygen /usr/bin/ssh-keygen

 

 

重启sshd服务：

[root@leotest ssh]# service sshd restart

Stopping sshd:                                             [  OK  ]

Starting sshd:                                             [  OK  ]

Starting sshd:/etc/ssh/sshd_config line 81: Unsupported option GSSAPIAuthentication

/etc/ssh/sshd_config line 83: Unsupported option GSSAPICleanupCredentials

 

原因：新版本的openssh不支持以上参数，需要修改sshd的配置文件

 

[root@leotest openssh-7.4p1]# vi /etc/ssh/sshd_config

##去掉前面的注释，允许root通过ssh登录

PermitRootLogin yes

 

##注释掉下面三个参数

#GSSAPIAuthentication yes

#GSSAPICleanupCredentials yes

#UsePAM yes

 

 

##在文件末尾加上如下信息，否则还是无法通过ssh登录linux：

导致此问题的原因是ssh升级后，为了安全，默认不再采用原来一些加密算法，我们手工添加进去即可。

Ciphers aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,arcfour128,arcfour256,arcfour,blowfish-cbc,cast128-cbc

MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-sha1-96,hmac-md5-96

KexAlgorithms diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group1-sha1,curve25519-sha256@libssh.org

 

 

6.重启sshd服务,测试ssh连接服务器

service sshd restart

[c:\~]$ ssh 192.168.5.5

 

Connecting to 192.168.5.5:22...

Connection established.

To escape to local shell, press 'Ctrl+Alt+]'.

 

Last login: Tue Dec 27 00:22:10 2016 from 192.168.5.2

[root@leotest ~]# ssh -V

OpenSSH_7.4p1, OpenSSL 1.0.1e-fips 11 Feb 2013

 

 

7.禁用telnet

[root@leotest ~]# vi /etc/xinetd.d/telnet

 

# default: on

# description: The telnet server serves telnet sessions; it uses \

#       unencrypted username/password pairs for authentication.

service telnet

{

        flags           = REUSE

        socket_type     = stream

        wait            = no

        user            = root

        server          = /usr/sbin/in.telnetd

        log_on_failure  += USERID

        disable         = yes

}

 

停掉xinetd服务：

[root@leotest ~]# service xinetd stop

Stopping xinetd:                                           [  OK  ]

停掉开机自启动：

[root@leotest ~]# chkconfig --list xinetd

xinetd                 0:off        1:off        2:off        3:on        4:on        5:on        6:off

[root@leotest ~]# chkconfig  xinetd off

[root@leotest ~]# chkconfig --list xinetd

xinetd                 0:off        1:off        2:off        3:off        4:off        5:off        6:off

 升级后问题解决：

通过winscp登录linux报错，解决方法如下：

[root@leotest ~]# vi /etc/ssh/sshd_config

 

# override default of no subsystems

#Subsystem      sftp    /usr/libexec/openssh/sftp-server

Subsystem       sftp    internal-sftp

将原来的注释掉，改成下面的internal-sftp

重启sshd服务：

service sshd restart

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