CentOS Linux服务器安全设置
<p>我们必须明白：最小的权限+最少的服务=最大的安全</p>
<p>
所以，无论是配置任何服务器，我们都必须把不用的服务关闭、把系统权限设置到最小话，这样才能保证服务器最大的安全。下面是CentOS服务器安全设置，供大家参考。</p>
<p>
<strong>一、注释掉系统不需要的用户和用户组</strong></p>
<p>
注意：不建议直接删除，当你需要某个用户时，自己重新添加会很麻烦。</p>
<p>
cp /etc/passwd /etc/passwdbak #修改之前先备份<br>
vi /etc/passwd #编辑用户，在前面加上#注释掉此行</p>
<p>
#adm:x:3:4:adm:/var/adm:/sbin/nologin<br>
#lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin<br>
#sync:x:5:0:sync:/sbin:/bin/sync<br>
#shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown<br>
#halt:x:7:0:halt:/sbin:/sbin/halt<br>
#uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin<br>
#operator:x:11:0:operator:/root:/sbin/nologin<br>
#games:x:12:100:games:/usr/games:/sbin/nologin<br>
#gopher:x:13:30:gopher:/var/gopher:/sbin/nologin<br>
#ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin #注释掉ftp匿名账号<br>
cp /etc/group /etc/groupbak #修改之前先备份<br>
vi /etc/group #编辑用户组，在前面加上#注释掉此行<br>
#adm:x:4:root,adm,daemon<br>
#lp:x:7:daemon,lp<br>
#uucp:x:14:uucp<br>
#games:x:20:<br>
#dip:x:40:</p>
<p>
<strong>二、关闭系统不需要的服务</strong></p>
<p>
service acpid stop chkconfig acpid off #停止服务，取消开机启动 #电源进阶设定，常用在 Laptop 上<br>
service autofs stop chkconfig autofs off #停用自动挂载档桉系统与週边装置<br>
service bluetooth stop chkconfig bluetooth off #停用Bluetooth蓝芽<br>
service cpuspeed stop chkconfig cpuspeed off #停用控制CPU速度主要用来省电<br>
service cups stop chkconfig cups off #停用 Common UNIX Printing System 使系统支援印表机<br>
service ip6tables stop chkconfig ip6tables off #禁止IPv6<br>
####################################################################################################<br>
如果要恢复某一个服务，可以执行下面操作<br>
service acpid start chkconfig acpid on</p>
<p>
<strong>三、禁止非root用户执行/etc/rc.d/init.d/下的系统命令</strong></p>
<p>
chmod -R 700 /etc/rc.d/init.d/*<br>
chmod -R 777 /etc/rc.d/init.d/* #恢复默认设置</p>
<p>
<strong>四、给下面的文件加上不可更改属性，从而防止非授权用户获得权限</strong></p>
<p>
chattr +i /etc/passwd<br>
chattr +i /etc/shadow<br>
chattr +i /etc/group<br>
chattr +i /etc/gshadow<br>
chattr +i /etc/services #给系统服务端口列表文件加锁,防止未经许可的删除或添加服务<br>
lsattr /etc/passwd /etc/shadow /etc/group /etc/gshadow /etc/services #显示文件的属性<br>
注意：执行以上权限修改之后，就无法添加删除用户了。<br>
如果再要添加删除用户，需要先取消上面的设置，等用户添加删除完成之后，再执行上面的操作<br>
chattr -i /etc/passwd #取消权限锁定设置<br>
chattr -i /etc/shadow<br>
chattr -i /etc/group<br>
chattr -i /etc/gshadow<br>
chattr -i /etc/services #取消系统服务端口列表文件加锁<br>
现在可以进行添加删除用户了，操作完之后再锁定目录文件</p>
<p>
<strong>五、限制不同文件的权限</strong></p>
<p>
chattr +a .bash_history #避免删除.bash_history或者重定向到/dev/null<br>
chattr +i .bash_history<br>
chmod 700 /usr/bin 恢复 chmod 555 /usr/bin<br>
chmod 700 /bin/ping 恢复 chmod 4755 /bin/ping<br>
chmod 700 /usr/bin/vim 恢复 chmod 755 /usr/bin/vim<br>
chmod 700 /bin/netstat 恢复 chmod 755 /bin/netstat<br>
chmod 700 /usr/bin/tail 恢复 chmod 755 /usr/bin/tail<br>
chmod 700 /usr/bin/less 恢复 chmod 755 /usr/bin/less<br>
chmod 700 /usr/bin/head 恢复 chmod 755 /usr/bin/head<br>
chmod 700 /bin/cat 恢复 chmod 755 /bin/cat<br>
chmod 700 /bin/uname 恢复 chmod 755 /bin/uname<br>
chmod 500 /bin/ps 恢复 chmod 755 /bin/ps</p>
<p>
<strong>六、禁止使用Ctrl+Alt+Del快捷键重启服务器</strong></p>
<p>
cp /etc/inittab /etc/inittabbak<br>
vi /etc/inittab #注释掉下面这一行<br>
#ca::ctrlaltdel:/sbin/shutdown -t3 -r now</p>
<p>
<strong>七、使用yum update更新系统时不升级内核，只更新软件包</strong></p>
<p>
由于系统与硬件的兼容性问题，有可能升级内核后导致服务器不能正常启动，这是非常可怕的，没有特别的需要，建议不要随意升级内核。<br>
cp /etc/yum.conf /etc/yum.confbak<br>
1、修改yum的配置文件 vi /etc/yum.conf 在的最后添加 exclude=kernel*<br>
2、直接在yum的命令后面加上如下的参数：<br>
yum --exclude=kernel* update<br>
查看系统版本 cat /etc/issue<br>
查看内核版本 uname -a</p>
<p>
<strong>八、关闭Centos自动更新</strong></p>
<p>
chkconfig --list yum-updatesd #显示当前系统状态<br>
yum-updatesd 0:关闭 1:关闭 2:启用 3:启用 4:启用 5:启用 6:关闭<br>
service yum-updatesd stop #关闭 开启参数为start<br>
停止 yum-updatesd： [确定]<br>
service yum-updatesd status #查看是否关闭<br>
yum-updatesd 已停<br>
chkconfig --level 35 yum-updatesd off #禁止开启启动（系统模式为3、5）<br>
chkconfig yum-updatesd off #禁止开启启动（所有启动模式全部禁止）<br>
chkconfig --list yum-updatesd #显示当前系统状态<br>
yum-updatesd 0:关闭 1:关闭 2:启用 3:关闭 4:启用 5:关闭 6:关闭</p>
<p>
<strong>九、关闭多余的虚拟控制台</strong></p>
<p>
我们知道从控制台切换到 X 窗口，一般采用 Alt-F7 ，为什么呢？因为系统默认定义了 6 个虚拟控制台，<br>
所以 X 就成了第7个。实际上，很多人一般不会需要这么多虚拟控制台的，修改/etc/inittab ，注释掉那些你不需要的。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_92637">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
<div class="line number9 index8 alt2">
9</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cp</code> <code class="bash plain">/etc/inittab</code> <code class="bash plain">/etc/inittabbak</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">vi</code> <code class="bash plain">/etc/inittab</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash comments"># Run gettys in standard runlevels</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">1:2345:respawn:</code><code class="bash plain">/sbin/mingetty</code> <code class="bash plain">tty1</code>
</div>
<div class="line number5 index4 alt2">
<code class="bash comments">#2:2345:respawn:/sbin/mingetty tty2</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash comments">#3:2345:respawn:/sbin/mingetty tty3</code>
</div>
<div class="line number7 index6 alt2">
<code class="bash comments">#4:2345:respawn:/sbin/mingetty tty4</code>
</div>
<div class="line number8 index7 alt1">
<code class="bash comments">#5:2345:respawn:/sbin/mingetty tty5</code>
</div>
<div class="line number9 index8 alt2">
<code class="bash comments">#6:2345:respawn:/sbin/mingetty tty6</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十、删除MySQL历史记录</strong></p>
<p>
用户登陆数据库后执行的SQL命令也会被MySQL记录在用户目录的.mysql_history文件里。<br>
如果数据库用户用SQL语句修改了数据库密码，也会因.mysql_history文件而泄漏。<br>
所以我们在shell登陆及备份的时候不要在-p后直接加密码，而是在提示后再输入数据库密码。<br>
另外这两个文件我们也应该不让它记录我们的操作，以防万一。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_621659">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cd</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">cp</code> <code class="bash plain">.bash_history .bash_historybak </code><code class="bash comments">#备份</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash functions">cp</code> <code class="bash plain">.mysql_history .mysql_historybak</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash functions">rm</code> <code class="bash plain">.bash_history .mysql_history</code>
</div>
<div class="line number5 index4 alt2">
<code class="bash functions">ln</code> <code class="bash plain">-s </code><code class="bash plain">/dev/null</code> <code class="bash plain">.bash_history</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash functions">ln</code> <code class="bash plain">-s </code><code class="bash plain">/dev/null</code> <code class="bash plain">.mysql_history</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十一、修改history命令记录</strong></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_677819">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cp</code> <code class="bash plain">/etc/profile</code> <code class="bash plain">/etc/profilebak</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">vi</code> <code class="bash plain">/etc/profile</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">找到 HISTSIZE=1000 改为 HISTSIZE=50</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十二、隐藏服务器系统信息</strong></p>
<p>
在缺省情况下，当你登陆到linux系统，它会告诉你该linux发行版的名称、版本、内核版本、服务器的名称。<br>
为了不让这些默认的信息泄露出来，我们要进行下面的操作，让它只显示一个"login:"提示符。<br>
删除/etc/issue和/etc/issue.net这两个文件，或者把这2个文件改名，效果是一样的。<br>
mv /etc/issue /etc/issuebak<br>
mv /etc/issue.net /etc/issue.netbak</p>
<p>
<strong>十三、优化Linux内核参数</strong></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_771881">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
<div class="line number9 index8 alt2">
9</div>
<div class="line number10 index9 alt1">
10</div>
<div class="line number11 index10 alt2">
11</div>
<div class="line number12 index11 alt1">
12</div>
<div class="line number13 index12 alt2">
13</div>
<div class="line number14 index13 alt1">
14</div>
<div class="line number15 index14 alt2">
15</div>
<div class="line number16 index15 alt1">
16</div>
<div class="line number17 index16 alt2">
17</div>
<div class="line number18 index17 alt1">
18</div>
<div class="line number19 index18 alt2">
19</div>
<div class="line number20 index19 alt1">
20</div>
<div class="line number21 index20 alt2">
21</div>
<div class="line number22 index21 alt1">
22</div>
<div class="line number23 index22 alt2">
23</div>
<div class="line number24 index23 alt1">
24</div>
<div class="line number25 index24 alt2">
25</div>
<div class="line number26 index25 alt1">
26</div>
<div class="line number27 index26 alt2">
27</div>
<div class="line number28 index27 alt1">
28</div>
<div class="line number29 index28 alt2">
29</div>
<div class="line number30 index29 alt1">
30</div>
<div class="line number31 index30 alt2">
31</div>
<div class="line number32 index31 alt1">
32</div>
<div class="line number33 index32 alt2">
33</div>
<div class="line number34 index33 alt1">
34</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cp</code> <code class="bash plain">/etc/sysctl</code><code class="bash plain">.conf </code><code class="bash plain">/etc/sysctl</code><code class="bash plain">.confbak</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">vi</code> <code class="bash plain">/etc/sysctl</code><code class="bash plain">.conf </code><code class="bash comments">#在文件末尾添加以下内容</code>
</div>
<div class="line number3 index2 alt2">
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">net.ipv4.ip_forward = 1 </code><code class="bash comments">#修改为1</code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">net.core.somaxconn = 262144</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash plain">net.core.netdev_max_backlog = 262144</code>
</div>
<div class="line number7 index6 alt2">
<code class="bash plain">net.core.wmem_default = 8388608</code>
</div>
<div class="line number8 index7 alt1">
<code class="bash plain">net.core.rmem_default = 8388608</code>
</div>
<div class="line number9 index8 alt2">
<code class="bash plain">net.core.rmem_max = 16777216</code>
</div>
<div class="line number10 index9 alt1">
<code class="bash plain">net.core.wmem_max = 16777216</code>
</div>
<div class="line number11 index10 alt2">
<code class="bash plain">net.ipv4.netfilter.ip_conntrack_max = 131072</code>
</div>
<div class="line number12 index11 alt1">
<code class="bash plain">net.ipv4.netfilter.ip_conntrack_tcp_timeout_established = 180</code>
</div>
<div class="line number13 index12 alt2">
<code class="bash plain">net.ipv4.route.gc_timeout = 20</code>
</div>
<div class="line number14 index13 alt1">
<code class="bash plain">net.ipv4.ip_conntrack_max = 819200</code>
</div>
<div class="line number15 index14 alt2">
<code class="bash plain">net.ipv4.ip_local_port_range = 10024 65535</code>
</div>
<div class="line number16 index15 alt1">
<code class="bash plain">net.ipv4.tcp_retries2 = 5</code>
</div>
<div class="line number17 index16 alt2">
<code class="bash plain">net.ipv4.tcp_fin_timeout = 30</code>
</div>
<div class="line number18 index17 alt1">
<code class="bash plain">net.ipv4.tcp_syn_retries = 1</code>
</div>
<div class="line number19 index18 alt2">
<code class="bash plain">net.ipv4.tcp_synack_retries = 1</code>
</div>
<div class="line number20 index19 alt1">
<code class="bash plain">net.ipv4.tcp_timestamps = 0</code>
</div>
<div class="line number21 index20 alt2">
<code class="bash plain">net.ipv4.tcp_tw_recycle = 1</code>
</div>
<div class="line number22 index21 alt1">
<code class="bash plain">net.ipv4.tcp_tw_len = 1</code>
</div>
<div class="line number23 index22 alt2">
<code class="bash plain">net.ipv4.tcp_tw_reuse = 1</code>
</div>
<div class="line number24 index23 alt1">
<code class="bash plain">net.ipv4.tcp_keepalive_time = 120</code>
</div>
<div class="line number25 index24 alt2">
<code class="bash plain">net.ipv4.tcp_keepalive_probes = 3</code>
</div>
<div class="line number26 index25 alt1">
<code class="bash plain">net.ipv4.tcp_keepalive_intvl = 15</code>
</div>
<div class="line number27 index26 alt2">
<code class="bash plain">net.ipv4.tcp_max_tw_buckets = 36000</code>
</div>
<div class="line number28 index27 alt1">
<code class="bash plain">net.ipv4.tcp_max_orphans = 3276800</code>
</div>
<div class="line number29 index28 alt2">
<code class="bash plain">net.ipv4.tcp_max_syn_backlog = 262144</code>
</div>
<div class="line number30 index29 alt1">
<code class="bash plain">net.ipv4.tcp_wmem = 8192 131072 16777216</code>
</div>
<div class="line number31 index30 alt2">
<code class="bash plain">net.ipv4.tcp_rmem = 32768 131072 16777216</code>
</div>
<div class="line number32 index31 alt1">
<code class="bash plain">net.ipv4.tcp_mem = 94500000 915000000 927000000</code>
</div>
<div class="line number33 index32 alt2">
</div>
<div class="line number34 index33 alt1">
<code class="bash plain">/sbin/sysctl</code> <code class="bash plain">-p </code><code class="bash comments">#使配置立即生效</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十四、CentOS 系统优化</strong></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_250556">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
<div class="line number9 index8 alt2">
9</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cp</code> <code class="bash plain">/etc/profile</code> <code class="bash plain">/etc/profilebak2</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">vi</code> <code class="bash plain">/etc/profile</code> <code class="bash comments">#在文件末尾添加以下内容</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash functions">ulimit</code> <code class="bash plain">-c unlimited</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash functions">ulimit</code> <code class="bash plain">-s unlimited</code>
</div>
<div class="line number5 index4 alt2">
<code class="bash functions">ulimit</code> <code class="bash plain">-SHn 65535</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash functions">ulimit</code> <code class="bash plain">-S -c 0</code>
</div>
<div class="line number7 index6 alt2">
<code class="bash functions">export</code> <code class="bash plain">LC_ALL=C</code>
</div>
<div class="line number8 index7 alt1">
<code class="bash functions">source</code> <code class="bash plain">/etc/profile</code> <code class="bash comments">#使配置立即生效</code>
</div>
<div class="line number9 index8 alt2">
<code class="bash functions">ulimit</code> <code class="bash plain">-a </code><code class="bash comments">#显示当前的各种用户进程限制</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十五、服务器禁止ping</strong></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_246220">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">cp</code> <code class="bash plain">/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/rc</code><code class="bash plain">.</code><code class="bash functions">local</code> <code class="bash plain">/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/rc</code><code class="bash plain">.localbak</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">vi</code> <code class="bash plain">/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/rc</code><code class="bash plain">.</code><code class="bash functions">local</code> <code class="bash comments">#在文件末尾增加下面这一行</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash functions">echo</code> <code class="bash plain">1 > </code><code class="bash plain">/proc/sys/net/ipv4/icmp_echo_ignore_all</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">参数0表示允许 1表示禁止</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<strong>十六、SSH安全</strong></p>
<p>
如果有可能，第一件事就是修改ssh的默认端口22，改成如20002这样的较大端口会大幅提高安全系数，降低ssh破解登录的可能性。</p>
<p>
创建具备辨识度的应用用户如crm以及系统管理用户sysmgr</p>
<blockquote>
<p>
#useradd crm -d /apps/crm<br>
#passwd crm<br><br>
#useradd sysmgr<br>
#passwd sysmgr</p>
</blockquote>
<p>
<strong>十七、配置只能使用密钥文件登录</strong></p>
<p>
使用密钥文件代替普通的简单密码认证也会极大的提高安全性：</p>
<blockquote>
<p>
$ ssh-keygen -t rsa -b 2048<br>
Generating public/private rsa key pair.<br>
Enter file in which to save the key (/root/.ssh/id_rsa): //默认路径，回车<br>
Enter passphrase (empty for no passphrase): //输入你的密钥短语，登录时使用<br>
Enter same passphrase again:<br>
Your identification has been saved in /root/.ssh/id_rsa.<br>
Your public key has been saved in /root/.ssh/id_rsa.pub.<br>
The key fingerprint is:<br>
3e:fd:fc:e5:d3:22:86:8e:2c:4b:a7:3d:92:18:9f:64 root@ibpak.tp-link.net<br>
The key's randomart image is:<br>
+--[ RSA 2048]----+<br>
| |<br>
…<br>
| o++o..oo..o|<br>
+-----------------+</p>
</blockquote>
<p>
将公钥重命名为authorized_key：</p>
<blockquote>
<p>
$ mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys<br>
$ chmod 600 ~/.ssh/authorized_keys</p>
</blockquote>
<p>
下载私钥文件 id_rsa 到本地（为了更加容易识别，可重命名为hostname_username_id_rsa），保存到安全的地方。以后 username 用户登录这台主机就必须使用这个私钥，配合密码短语来登录（不再使用 username 用户自身的密码）</p>
<p>
另外还要修改/etc/ssh/sshd_config文件</p>
<p>
打开注释</p>
<blockquote>
<p>
RSAAuthentication yes<br>
PubkeyAuthentication yes<br>
AuthorizedKeysFile .ssh/authorized_keys</p>
</blockquote>
<p>
我们要求 username 用户（可以切换到其他用户，特别是root）必须使用ssh密钥文件登录，而其他普通用户可以直接密码登录。因此还需在sshd_config文件最后加入：</p>
<blockquote>
<p>
Match User itsection<br>
PasswordAuthentication no</p>
</blockquote>
<p>
重启sshd服务</p>
<blockquote>
<p>
service sshd restart</p>
</blockquote>
<p>
另外提醒一句，这对公钥和私钥一定要单独保存在另外的机器上，服务器上丢失公钥或连接端丢失私钥（或密钥短语），可能导致再也无法登陆服务器获得root权限！</p>
<p>
<strong>十八、防止一般网络攻击</strong></p>
<p>
网络攻击不是几行设置就能避免的，以下都只是些简单的将可能性降到最低，增大攻击的难度但并不能完全阻止。</p>
<p>
1 禁ping<br>
阻止ping如果没人能ping通您的系统，安全性自然增加了，可以有效的防止ping洪水。为此，可以在/etc/rc.d/rc.local文件中增加如下一行：</p>
<p>
#echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all</p>
<p>
或使用iptable禁ping：</p>
<p>
iptables -A INPUT -p icmp --icmp-type 0 -s 0/0 -j DROP</p>
<p>
不允许ping其他主机：</p>
<p>
iptables -A OUTPUT -p icmp --icmp-type 8 -j DROP</p>
<p>
防止IP欺骗<br>
编辑/etc/host.conf文件并增加如下几行来防止IP欺骗攻击。</p>
<p>
order hosts,bind #名称解释顺序<br>
multi on #允许主机拥有多个IP地址<br>
nospoof on #禁止IP地址欺骗</p>
<p>
3 防止DoS攻击<br>
对系统所有的用户设置资源限制可以防止DoS类型攻击，如最大进程数和内存使用数量等。<br>
可以在/etc/security/limits.conf中添加如下几行：</p>
<p>
* soft core 0<br>
* soft nproc 2048<br>
* hard nproc 16384<br>
* soft nofile 1024<br>
* hard nofile 65536</p>
<p>
core 0 表示禁止创建core文件；nproc 128 把最多的进程数限制到20；nofile 64 表示把一个用户同时打开的最大文件数限制为64；* 表示登录到系统的所有用户，不包括root</p>
<p>
然后必须编辑/etc/pam.d/login文件检查下面一行是否存在。</p>
<p>
session required pam_limits.so</p>
<p>
limits.conf参数的值需要根据具体情况调整。</p>
<p>
<strong>十九、定期做日志安全检查</strong></p>
<p>
将日志移动到专用的日志服务器里，这可避免入侵者轻易的改动本地日志。下面是常见linux的默认日志文件及其用处：</p>
<blockquote>
<p>
/var/log/message – 记录系统日志或当前活动日志。<br>
/var/log/auth.log – 身份认证日志。<br>
/var/log/cron – Crond 日志 (cron 任务).<br>
/var/log/maillog – 邮件服务器日志。<br>
/var/log/secure – 认证日志。<br>
/var/log/wtmp 历史登录、注销、启动、停机日志和，lastb命令可以查看登录失败的用户<br>
/var/run/utmp 当前登录的用户信息日志，w、who命令的信息便来源与此<br>
/var/log/yum.log Yum 日志。</p>
</blockquote>
<p>
安装logwatch<br>
Logwatch是使用 Perl 开发的一个日志分析工具。能够对Linux 的日志文件进行分析，并自动发送mail给相关处理人员，可定制需求。</p>
<p>
Logwatch的mail功能是借助宿主系统自带的 mail server 发邮件的，所以系统需安装mail server , 如sendmail,postfix,Qmail等</p>
<p>
<strong>二十、web服务器安全</strong></p>
<p>
像apache或tomcat这样的服务端程序在配置时，如果有安全问题存在可以查阅文档进行安全加固。<br>
安装和配置方法见博文tomcat安全配置</p>
<p>
至此，CentOS Linux服务器安全设置基本完成，更多的安全设置以及服务器优化，还请大家自行测试。</p>
<p>
至此，CentOS Linux服务器安全设置基本完成，以上设置经过笔者实战测试（CentOS-5.5-x86_64）完全可用，更多的安全设置以及服务器优化，还请大家自行测试。</p>
頁:
[1]