SSH(远程连接工具)连接原理:ssh服务是一个守护进程(demon),系统后台监听客户端的连接,ssh服务端的进程名为sshd,负责实时监听客户端的请求(IP 22端口),包括公共秘钥等交换等信息。

ssh服务端由2部分组成: openssh(提供ssh服务)    openssl(提供加密的程序)

ssh的客户端可以用 XSHELL,Securecrt, Mobaxterm等工具进行连接

SSH的工作机制 

      服务器启动的时候自己产生一个密钥(768bit公钥),本地的ssh客户端发送连接请求到ssh服务器,服务器检查连接点客户端发送的数据和IP地址,确认合法后发送密钥(768bits)给客户端,此时客户端将本地私钥(256bit)和服务器的公钥(768bit)结合成密钥对key(1024bit),发回给服务器端,建立连接通过key-pair数据传输。       

SSH的加密技术

加密技术:传输过程,数据加密。            
1.SSH1没有对客户端的秘钥进行校验,很容易被植入恶意代码
2.SSH2增加了一个确认联机正确性的Diffe_Hellman机制,每次数据的传输,Server都会检查数据来源的正确性,避免******。                   
  SSH2支持RSA和DSA密钥   
        DSA:digital signature Algorithm  数字签名
        RSA:既可以数字签名又可以加密      

SSH知识小结           

   1.SSH是安全的加密协议,用于远程连接Linux服务器               
   2.SSH的默认端口是22,安全协议版本是SSH2               
   3.SSH服务器端主要包含2个服务功能SSH连接和SFTP服务器               
   4.SSH客户端包含ssh连接命令和远程拷贝scp命令等 

如何防止SSH登录***            

    1.密钥登录,更改端口               
    2.牤牛阵法               
    3.监听本地内网IP(ListenAddress 192.168.25.*)

SSH功能大全   

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1.登录                   

       ssh -p22 [email protected]               

   2.直接执行命令  -->最好全路径                   

       ssh [email protected] ls -ltr /backup/data                       

           ==>ssh [email protected] /bin/ls -ltr /backup/data               

   3.查看已知主机                    

        cat /root/.ssh/known_hosts

   4.ssh远程执行sudo命令

       ssh -t [email protected] sudo rsync hosts /etc/

 

   5.scp               

             1.功能   -->远程文件的安全(加密)拷贝                   

                 scp -P22 -r -p /home/omd/h.txt [email protected]:/home/omd/               

             2.scp知识小结                   

                 scp是加密远程拷贝,cp为本地拷贝                   

                 可以推送过去,也可以拉过来                   

                 每次都是全量拷贝(效率不高,适合第一次),增量拷贝用rsync

 

   6.ssh自带的sftp功能               

             1.Window和Linux的传输工具                   

                  wincp   filezip                   

               sftp  -->基于ssh的安全加密传输                   

               samba   

             2.sftp客户端连接                   

                sftp -oPort=22 [email protected]                   

                put /etc/hosts /tmp                   

                get /etc/hosts /home/omd   

            3.sftp小结:                   

                1.linux下使用命令: sftp -oPort=22 [email protected]                   

                2.put加客户端本地路径上传                  

                3.get下载服务器端内容到本地                   

                4.远程连接默认连接用户的家目录

ssh常见命令参数

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usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec]

           [-D [bind_address:]port] [-e escape_char] [-F configfile]

           [-i identity_file] [-L [bind_address:]port:host:hostport]

           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]

           [-R [bind_address:]port:host:hostport] [-S ctl_path]

           [-W host:port] [-w local_tun[:remote_tun]]

           [[email protected]]hostname [command]

关于后台ssh服务的相关

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# 查询openssl软件

    rpm -qa openssh openssl

# 查询sshd进程

    ps -ef | grep ssh

        --> /usr/sbin/sshd

# 查看ssh端口

    netstat -lntup | grep ssh  

    ss | grep ssh                (效果同上,同下,好用)

    netstat -a | grep ssh(记住这个)

    netstat -lnt | grep 22    ==>  查看22端口有没有开/ssh服务有没有开启

    技巧: netstat -lnt | grep ssh | wc -l -->只要大于2个就是ssh服务就是好的

# 查看ssh的秘钥目录

    ll /root/.ssh/known_hosts  # 当前用户家目录的.ssh目录下

# ssh的配置文件

    cat /etc/ssh/sshd_config   

# ssh服务的关闭

    service sshd stop

# ssh服务的开启:

    service sshd start

# ssh服务的重启

    service sshd reload    [停止进程后重启] ==> 推荐

    service sshd restart   [干掉进程后重启] ==> 不推荐

# ssh远程登录

    ssh 192.168.1.100      # 默认利用当前宿主用户的用户名登录

    ssh [email protected]  # 利用远程机的用户登录

    ssh [email protected]  -o stricthostkeychecking=no # 首次登陆免输yes登录

    ssh [email protected] "ls /home/omd"  # 当前服务器A远程登录服务器B后执行某个命令

    ssh [email protected] -t "sh /home/omd/ftl.sh"  # 当前服务器A远程登录服务器B后执行某个脚本

 

image

ssh免密设置

1、进入用户的家目录

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[[email protected] ~]# cd /root/.ssh/             【root用户就在root目录下的.ssh目录】

[[email protected] ~]# cd /home/omd/.ssh/   【普通用户就是在家目录下的.ssh目录】

image

2、根据DSA算法生成私钥和公钥【默认建立在当前用户的家目录】

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[[email protected] .ssh]# ssh-keygen -t dsa     # 一路回车即可

                id_dsa         -->私钥(钥匙)

                id_dsa.pub     -->公钥(锁)

image

3.拷贝公钥给目标服务器

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[[email protected] .ssh]# ssh-copy-id -i id_dsa.pub [email protected]              【 使用ssh登录的默认端口22】

[[email protected] .ssh]# ssh-copy-id -i id_dsa.pub –p 666 [email protected]   【使用ssh登录设置的端口666】

4. 查看目标服务器生成的文件

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[[email protected] .ssh]$ ll /home/omd/.ssh/authorized_keys

image

5. 免密码登录目标服务器

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ssh [email protected]

6. 总结一下钥匙和锁的关系

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1.多个钥匙开一把锁

      把id_dsa.pub 复制给各个服务器

 

2.一个钥匙开duobasuo

      把id_dsa 传给各个服务器

      把id_dsa 传给自己 

ssh排查问题

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1.判断物理链路是否通  ping 192.168.25.130     线路 | 防火墙 | 是否同一个网的

            ping   本身是icmp协议

2.判断服务是否正常

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telnet 192.168.25.130 22

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3.Linux防火墙

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service iptables status ==>  /etc/init.d/iptables status

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4.打开ssh的调测进行观察

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ssh -vvv [email protected]

SSH批量分发与管理方案小结


1.利用root做ssh key验证

优点:简单,易用
    缺点:安全性能差,无法禁止root远程连接


2.利用普通用户omd                -->推荐


    思路:把要分发的文件拷贝到服务器用户的家目录,然后利用sudo提权拷贝分发的文件和对应目录
    优点:安全
    缺点:复杂,配置麻烦
    1.sudo提权
        echo 'omd     All=(All)      NOPASSWD:/usr/bin/rsync' >> /etc/sudoers
        visudo -c
        grep omd /etc/sudoers
    2.ssh分发到服务器的家目录
        ssh -p22 -r /etc/hosts [email protected]:~
    3.ssh使用sudo复制到目标服务器的/etc
        ssh -t [email protected] sudo rsync hosts /etc/

3.拓展方案2,不用sudo,而是设置suid对固定命令提权

 优点:相当安全
       缺点:复杂,安全性较差,任何人都可以处理带有suid权限的命令
       1.which rsync
       2.chmod 4755 /usr/bin/rsync       

ssh章节小结             

    1.ssh远程的加密连接协议,相关软件openssh,openssl               
    2.默认端口22               
    3.ssh版本协议               
    4.服务器ssh连接,ftp连接,sshd守护进程,开机启动               
    5.ssh客户端重要命令:ssh(用户登录&&远程命令),scp,sftp,               
    6.安全验证方式:口令,密钥  学习原理               
    7.ssh服务优化:改端口,改监听,no root,no empty,no DNS,
    8.ssh密钥对,公钥在服务器端,私钥在客户端

修改ssh服务的启动文件sshd的几个点

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1-1修改 /etc/ssh/sshd_config<br>        GSSAPIAuthentication yes    解决一台服务器管理多个ssh服务

    UseDNS no  加快响应速度因为在内网环境下

    PermitRootLogin no  不运行root用户直接登录

    Port 11544 更改访问端口号

    ListenAddress  192.168.25.130  只监听内网的IP

    Match User anoncvs     当前环境允许登录的用户

    PermitRootLogin no      是否允许root用户登录,一般不允许开

1-2重启服务

    service sshd restart       写入命令进内存

    service sshd reload(优先)  reload是一个平滑的访问,不影响用户使用

1-3查看连接端口

    netstat -an | grep EST

SSH跳过HostKeyChecking,不用输入yes

SSH跳过输入ssh跳过RSA key fingerprint输入yes/no

在配置大量的节点之间需要ssh连通的时候,如果自动复制很多节点,都需要输入yes,两两节点之间都要互通一次,这样会造成很大的麻烦

解决1;修改配置文件/etc/ssh/ssh_config

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找  到  # StrictHostKeyChecking ask  

修改为:StrictHostKeyChecking no  

解决2: 添加参数 –o  【o=option】

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ssh [email protected] -o "StrictHostKeyChecking no"

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scp -o "StrictHostKeyChecking no" newfile.txt <a href="mailto:[email protected]:/root">[email protected]:/root</a>

ssh带密码登录之sshpass的安装

【下载地址】https://sourceforge.net/projects/sshpass/files/latest/download

上传文件到服务器

CentOS下安装:

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[[email protected] ~]# tar xf sshpass-1.06.tar.gz

[[email protected] ~]# cd sshpass-1.06

[[email protected] sshpass-1.06]# ./configure

[[email protected] sshpass-1.06]# make && make install

检查是否安装成功:

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[[email protected] sshpass-1.06]# which sshpass

/usr/local/bin/sshpass

远程登录主机:

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sshpass -p [email protected] ssh [email protected] -o "StrictHostKeyChecking no"

注意:如果是第一次登录,需要输入手动yes,此时sshpass并不会给提示,所以登录异常

Ubuntu下安装方法一[推荐]:简单

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[email protected]:~/sshpass-1.06$ sudo apt install sshpass

安装成功:

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[email protected]:~/sshpass-1.06$ which sshpass

Ubuntu下安装方法二:

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[email protected]:~$ tar xf sshpass-1.06.tar.gz

[email protected]:~$ cd sshpass-1.06/

omd @omd-virtual-machine:~/sshpass-1.06$ ./configure

[email protected]:~/sshpass-1.06$ sudo make && make install

其同CentOS下安装

 

附ssh的配置文件

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/etc/ssh/sshd_config

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[[email protected] .ssh]# cat /etc/ssh/sshd_config

#       $OpenBSD: sshd_config,v 1.80 2008/07/02 02:24:18 djm Exp $

 

# This is the sshd server system-wide configuration file.  See

# sshd_config(5) for more information.

 

# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin

 

# The strategy used for options in the default sshd_config shipped with

# OpenSSH is to specify options with their default value where

# possible, but leave them commented.  Uncommented options change a

# default value.

 

#Port 22

#AddressFamily any

#ListenAddress 0.0.0.0

#ListenAddress ::

 

# Disable legacy (protocol version 1) support in the server for new

# installations. In future the default will change to require explicit

# activation of protocol 1

Protocol 2

 

# HostKey for protocol version 1

#HostKey /etc/ssh/ssh_host_key

# HostKeys for protocol version 2

#HostKey /etc/ssh/ssh_host_rsa_key

#HostKey /etc/ssh/ssh_host_dsa_key

 

# Lifetime and size of ephemeral version 1 server key

#KeyRegenerationInterval 1h

#ServerKeyBits 1024

 

# Logging

# obsoletes QuietMode and FascistLogging

#SyslogFacility AUTH

SyslogFacility AUTHPRIV

#LogLevel INFO

 

# Authentication:

 

#LoginGraceTime 2m

#PermitRootLogin yes

#StrictModes yes

#MaxAuthTries 6

#MaxSessions 10

 

#RSAAuthentication yes

#PubkeyAuthentication yes

#AuthorizedKeysFile     .ssh/authorized_keys

#AuthorizedKeysCommand none

#AuthorizedKeysCommandRunAs nobody

 

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts

#RhostsRSAAuthentication no

# similar for protocol version 2

#HostbasedAuthentication no

# Change to yes if you don't trust ~/.ssh/known_hosts for

# RhostsRSAAuthentication and HostbasedAuthentication

#IgnoreUserKnownHosts no

# Don't read the user's ~/.rhosts and ~/.shosts files

#IgnoreRhosts yes

 

# To disable tunneled clear text passwords, change to no here!

#PasswordAuthentication yes

#PermitEmptyPasswords no

PasswordAuthentication yes

 

# Change to no to disable s/key passwords

#ChallengeResponseAuthentication yes

ChallengeResponseAuthentication no

 

# Kerberos options

#KerberosAuthentication no

#KerberosOrLocalPasswd yes

#KerberosTicketCleanup yes

#KerberosGetAFSToken no

#KerberosUseKuserok yes

 

# GSSAPI options

#GSSAPIAuthentication no

GSSAPIAuthentication yes

#GSSAPICleanupCredentials yes

GSSAPICleanupCredentials yes

#GSSAPIStrictAcceptorCheck yes

#GSSAPIKeyExchange no

 

# Set this to 'yes' to enable PAM authentication, account processing,

# and session processing. If this is enabled, PAM authentication will

# be allowed through the ChallengeResponseAuthentication and

# PasswordAuthentication.  Depending on your PAM configuration,

# PAM authentication via ChallengeResponseAuthentication may bypass

# the setting of "PermitRootLogin without-password".

# If you just want the PAM account and session checks to run without

# PAM authentication, then enable this but set PasswordAuthentication

# and ChallengeResponseAuthentication to 'no'.

#UsePAM no

UsePAM yes

 

# Accept locale-related environment variables

AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES

AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT

AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE

AcceptEnv XMODIFIERS

 

#AllowAgentForwarding yes

#AllowTcpForwarding yes

#GatewayPorts no

#X11Forwarding no

X11Forwarding yes

#X11DisplayOffset 10

#X11UseLocalhost yes

#PrintMotd yes

#PrintLastLog yes

#TCPKeepAlive yes

#UseLogin no

#UsePrivilegeSeparation yes

#PermitUserEnvironment no

#Compression delayed

#ClientAliveInterval 0

#ClientAliveCountMax 3

#ShowPatchLevel no

#UseDNS yes

#PidFile /var/run/sshd.pid

#MaxStartups 10

#PermitTunnel no

#ChrootDirectory none

 

# no default banner path

#Banner none

 

# override default of no subsystems

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

 

# Example of overriding settings on a per-user basis

#Match User anoncvs

#       X11Forwarding no

#       AllowTcpForwarding no

#       ForceCommand cvs server

作者:小a玖拾柒

出处:http://www.cnblogs.com/ftl1012/