centos系统组件优化
CentOS Linux在公司服务器上广泛被使用，本文总结了一些常见的加固方法。
基本原则：
- 最小的权限+最小的服务=最大的安全
- 操作之前先备份；
- 为避免配置错误无法登录主机，请始终保持有一个终端已用root登录并不退出，在另一个终端中做配置修改。这样即使改错，也不至于因系统无法登录导致永远无法登录或恢复配置。
操作项：
一、注释掉系统不需要的用户和用户组
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。
cp /etc/passwd /etc/passwdbak #修改之前先备份
vi /etc/passwd #编辑用户，在前面加上#注释掉此行
#adm:x:3:4:adm:/var/adm:/sbin/nologin
#lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
#sync:x:5:0:sync:/sbin:/bin/sync
#shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
#halt:x:7:0:halt:/sbin:/sbin/halt
#uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
#operator:x:11:0perator:/root:/sbin/nologin
#games:x:12:100:games:/usr/games:/sbin/nologin
#gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
#ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin #注释掉ftp匿名账号
cp /etc/group /etc/groupbak #修改之前先备份
vi /etc/group #编辑用户组，在前面加上#注释掉此行
#adm:x:4:root,adm,daemon
#lp:x:7:daemon,lp
#uucp:x:14:uucp
#games:x:20:
#dip:x:40:
二、关闭系统不需要的服务
使用命令 chkconfig|grep on 检查开机自启动的服务；
abrt-ccpp 0:off 1:off 2:off 3:on 4:off 5:on 6:off
abrtd 0:off 1:off 2:off 3:off 4:off 5:on 6:off
acpid 0:off 1:off 2:on 3:on 4:on 5:on 6:off
auditd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
autofs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
blk-availability 0:off 1:on 2:on 3:on 4:on 5:on 6:off
certmonger 0:off 1:off 2:off 3:on 4:on 5:on 6:off
cgconfig 0:off 1:off 2:off 3:off 4:off 5:off 6:off
cpuspeed 0:off 1:on 2:on 3:on 4:on 5:on 6:off
crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off
cups 0:off 1:off 2:on 3:on 4:on 5:on 6:off
haldaemon 0:off 1:off 2:off 3:on 4:on 5:on 6:off
ip6tables 0:off 1:off 2:on 3:off 4:on 5:on 6:off
iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off
irqbalance 0:off 1:off 2:off 3:on 4:on 5:on 6:off
kdump 0:off 1:off 2:off 3:off 4:on 5:on 6:off
lvm2-monitor 0:off 1:on 2:on 3:off 4:on 5:on 6:off
mcelogd 0:off 1:off 2:off 3:on 4:off 5:on 6:off
mdmonitor 0:off 1:off 2:on 3:on 4:on 5:on 6:off
messagebus 0:off 1:off 2:on 3:on 4:on 5:on 6:off
netconsole 0:off 1:off 2:off 3:off 4:off 5:off 6:off
netfs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
nfslock 0:off 1:off 2:off 3:on 4:on 5:on 6:off
portreserve 0:off 1:off 2:on 3:on 4:on 5:on 6:off
postfix 0:off 1:off 2:on 3:on 4:on 5:on 6:off
restorecond 0:off 1:off 2:off 3:off 4:off 5:off 6:off
rpcbind 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rpcgssd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
rsyslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sysstat 0:off 1:on 2:on 3:on 4:on 5:on 6:off
udev-post 0:off 1:on 2:on 3:on 4:on 5:on 6:off
服务说明：
|
auditd |
The audit package contains the user space utilities for storing and searching the audit records generate by the audit subsystem in the Linux 2.6 kernel. |
|
blk-availability |
Controls availability of LVM2 block devices. |
|
cgconfig |
Start cgconfigparser. |
|
cgred |
This is a daemon for automatically classifying processes into cgroups based on UID/GID. |
|
cpuspeed |
This program monitors the system's idle percentage and reduces or raises the CPUs' clock speeds and voltages accordingly to minimize power consumption when idle and maximize perfor-mance when needed. |
|
crond |
The daemon to execute scheduled commands. |
|
ip6tables |
It's IPv6 packet filter administration. |
|
iptables |
It's administration tool for IPv4 packet filtering and NAT. |
|
lvm2-monitor |
Monitor LVM2 with using dmeventd. |
|
netconsole |
It sends printk message from kernel on UDP. |
|
netfs |
NFS clinet. |
|
network |
Network system. |
|
postfix |
SMTP service daemon. |
|
rdisc |
Detect routers in local subnets. |
|
restorecond |
It's the daemon that watches for file creation and then sets the default SELinux file context. |
|
rsyslog |
It reads and/or clears kernel message ring buffer; set console_loglevel. |
|
saslauthd |
saslauthd is a daemon process that handles plaintext authentication requests on behalf of the SASL library. |
|
sshd |
OpenSSH sshd daemon. |
|
udev-post |
Moves the generated persistent udev rules to /etc/udev/rules.d. |
（见http://www.server-world.info/en/note?os=CentOS_6&p=initial_conf&f=4）
关闭不必要的服务
service acpid stop;chkconfig acpid off #电源进阶设定，常用在 Laptop 上
service cpuspeed stop;chkconfig cpuspeed off #停用控制CPU速度主要用来省电
service cups stop;chkconfig cups off #停用 Common UNIX Printing System 使系统支援印表机
service ip6tables stop;chkconfig ip6tables off #禁止IPv6
三、禁止非root用户执行/etc/rc.d/init.d/下的系统命令
chmod -R 700 /etc/rc.d/init.d/* (chmod -R 755 /etc/rc.d/init.d/* #恢复默认设置)
四、修改history命令记录
cp /etc/profile /etc/profilebak
vi /etc/profile
找到 HISTSIZE=1000 改为 HISTSIZE=50
五、调整文件描述符大小
echo "ulimit -SHn 65535" >> /etc/rc.local
/etc/security/limits.conf
* soft nofile 65535
* hard nofile 65535
* soft stack unlimited
* hard stack unlimited
六、同步系统时间
cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
crontab -e
0-59/10 * * * * /usr/sbin/ntpdate us.pool.ntp.org | logger -t NTP
chkconfig --list | grep ntp #看下服务情况
chkconifg ntpd on
service ntpd start
七、内核参数优化
vi /etc/sysctl.conf #末尾添加如下参数 (备注：内核参数优化 根据不同服务器不同业务进行调整)
net.ipv4.tcp_max_tw_buckets = 6144
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.netdev_max_backlog = 262144
net.core.somaxconn = 262144
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_syn_retries = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_fin_timeout = 10
net.ipv4.tcp_keepalive_time = 600
net.ipv4.ip_local_port_range = 1024 65000
vm.swappiness = 5
vm.zone_reclaim_mode = 0
net.ipv4.tcp_max_syn_backlog = 5000
vm.dirty_ratio = 60
vm.dirty_background_ratio = 5
八、CentOS 系统优化
cp /etc/profile /etc/profilebak2
vi /etc/profile #在文件末尾添加以下内容
ulimit -c unlimited
ulimit -s unlimited
ulimit -SHn 65535
source /etc/profile #使配置立即生效
ulimit -a #显示当前的各种用户进程限制
九、去除系统相关信息
事先备份到安全的地方哈：）
echo "Welcome to Server" >/etc/issue
echo "Welcome to Server" >/etc/issue.net
echo "Welcome to Server" >/etc/redhat-release
十、SSH服务安全配置
vi /etc/ssh/sshd_config
1. 禁用root远程登录
PermitRootLoginno
PermitEmptyPasswords no #禁止空密码登录
2.不要支持闲置会话，并配置 Idle Log Out Timeout 间隔：
ClientAliveInterval 600 # (Set to 600 seconds = 10 minutes)
ClientAliveCountMax 0
3.禁用用户的 .rhosts 文件：
IgnoreRhosts yes
4.PasswordAuthentication no
6.ssh安全技巧之更改 SSH 端口
建议改成 10000 以上，以降低扫描到端口的机率。
Port 36000
7.使用iptables允许特定的主机连接
作为TCP wrappers的一个代替品，你可以使用iptables来限制SSH访问（但可以同时使用这个两个的），这里有一个简单的例子，指出了如何允许一个特定的主机连接到你的SSH服务：
iptables -A INPUT -p tcp -m state --state NEW --source 193.180.177.13 --dport 22 -j ACCEPT
保存后重启ssh服务。
十一、添加普通用户并进行sudo授权管理
useradd -d /home/goal user (指定home目录与用户名不同)
passwd user #设置密码
vi /etc/sudoers #或visudo打开，添加user用户所有权 限
root ALL=(ALL) ALL
user ALL=(ALL) ALL
十二、安装安全补丁（经常更新为好）
yum install yum-security
检查安全更新
yum –security check-update
只安装安全更新
yum update –security
检查特定软件有无安全更新
yum list-security software_name
列出更新的详细信息
yum info-security software_name
十三、将 SSH 程序包和需要的库保持为最新：
yum update openssh-server openssh openssh-clients -y
十四、清空防火墙并设置规则 配置防火墙以接受仅来自已知网段的 SSH 连接：
iptables -t filter -P INPUT ACCEPT
iptables -t filter -F INPUT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -s 192.168.0.0/16 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 36000 -j ACCEPT
iptables -A INPUT -p icmp -j ACCEPT
iptables -A INPUT -j REJECT --reject-with icmp-host-prohibited
iptables -A FORWARD -j REJECT --reject-with icmp-host-prohibited
十五、锁定关键文件系统
chattr +i /etc/passwd
chattr +i /etc/inittab
chattr +i /etc/group
chattr +i /etc/shadow
chattr +i /etc/gshadow
