Nginx是一个轻量级的，高性能的Web服务器以及反向代理和邮箱(IMAP/POP3)代理服务器。它运行在UNIX,GNU/Linux,BSD各种版本，Mac OS X,Solaris和Windows。根据调查统计，6%的网站使用Nginx Web服务器。Nginx是少数能处理C10K问题的服务器之一。跟传统的服务器不同，Nginx不依赖线程来处理请求。相反，它使用了更多的可扩展的事件驱动（异步）架构。Nginx为一些高流量的网站提供动力，比如WordPress,人人网，腾讯，网易等。这篇文章主要是介绍如何提高运行在Linux或UNIX系统的Nginx Web服务器的安全性。
默认配置文件和Nginx端口
/usr/local/nginx/conf/ – Nginx配置文件目录，/usr/local/nginx/conf/nginx.conf是主配置文件
/usr/local/nginx/html/ – 默认网站文件位置
/usr/local/nginx/logs/ – 默认日志文件位置
Nginx HTTP默认端口 : TCP 80
Nginx HTTPS默认端口: TCP 443
你可以使用以下命令来测试Nginx配置文件准确性。
- /usr/local/nginx/sbin/nginx -t
将会输出。
the configuration file /usr/local/nginx/conf/nginx.conf syntax is ok
configuration file /usr/local/nginx/conf/nginx.conf test is successful
执行以下命令来重新加载配置文件。
- /usr/local/nginx/sbin/nginx -s reload
执行以下命令来停止服务器。
- /usr/local/nginx/sbin/nginx -s stop
一、配置SELinux
安全增强型Linux（SELinux）的是一个Linux内核的功能，它提供支持访问控制的安全政策保护机制。它可以大部分的攻击。下面我们来看如何启动基于CentOS/RHEL系统的SELinux。
安装SELinux
- rpm -qa | grep selinux
libselinux-1.23.10-2
selinux-policy-targeted-1.23.16-6
如果没有返回任何结果，代表没有安装 SELinux，如果返回了类似上面的结果，则说明系统安装了 SELinux。
布什值锁定
运行命令getsebool -a来锁定系统。
- getsebool -a | less
- getsebool -a | grep off
- getsebool -a | grep o
二、通过分区挂载允许最少特权
服务器上的网页/html/php文件单独分区。例如，新建一个分区/dev/sda5(第一逻辑分区)，并且挂载在/nginx。确保/nginx是以noexec, nodev and nosetuid的权限挂载。以下是我的/etc/fstab的挂载/nginx的信息：
LABEL=/nginx /nginx ext3 defaults,nosuid,noexec,nodev 1 2
注意：你需要使用fdisk和mkfs.ext3命令创建一个新分区。
三、配置/etc/sysctl.conf强化Linux安全
你可以通过编辑/etc/sysctl.conf来控制和配置Linux内核、网络设置。
- # Avoid a smurf attack
- net.ipv4.icmp_echo_ignore_broadcasts = 1
- # Turn on protection for bad icmp error messages
- net.ipv4.icmp_ignore_bogus_error_responses = 1
- # Turn on syncookies for SYN flood attack protection
- net.ipv4.tcp_syncookies = 1
- # Turn on and log spoofed, source routed, and redirect packets
- net.ipv4.conf.all.log_martians = 1
- net.ipv4.conf.default.log_martians = 1
- # No source routed packets here
- net.ipv4.conf.all.accept_source_route = 0
- net.ipv4.conf.default.accept_source_route = 0
- # Turn on reverse path filtering
- net.ipv4.conf.all.rp_filter = 1
- net.ipv4.conf.default.rp_filter = 1
- # Make sure no one can alter the routing tables
- net.ipv4.conf.all.accept_redirects = 0
- net.ipv4.conf.default.accept_redirects = 0
- net.ipv4.conf.all.secure_redirects = 0
- net.ipv4.conf.default.secure_redirects = 0
- # Don't act as a router
- net.ipv4.ip_forward = 0
- net.ipv4.conf.all.send_redirects = 0
- net.ipv4.conf.default.send_redirects = 0
- # Turn on execshild
- kernel.exec-shield = 1
- kernel.randomize_va_space = 1
- # Tuen IPv6
- net.ipv6.conf.default.router_solicitations = 0
- net.ipv6.conf.default.accept_ra_rtr_pref = 0
- net.ipv6.conf.default.accept_ra_pinfo = 0
- net.ipv6.conf.default.accept_ra_defrtr = 0
- net.ipv6.conf.default.autoconf = 0
- net.ipv6.conf.default.dad_transmits = 0
- net.ipv6.conf.default.max_addresses = 1
- # Optimization for port usefor LBs
- # Increase system file descriptor limit
- fs.file-max = 65535
- # Allow for more PIDs (to reduce rollover problems); may break some programs 32768
- kernel.pid_max = 65536
- # Increase system IP port limits
- net.ipv4.ip_local_port_range = 2000 65000
- # Increase TCP max buffer size setable using setsockopt()
- net.ipv4.tcp_rmem = 4096 87380 8388608
- net.ipv4.tcp_wmem = 4096 87380 8388608
- # Increase Linux auto tuning TCP buffer limits
- # min, default, and max number of bytes to use
- # set max to at least 4MB, or higher if you use very high BDP paths
- # Tcp Windows etc
- net.core.rmem_max = 8388608
- net.core.wmem_max = 8388608
- net.core.netdev_max_backlog = 5000
- net.ipv4.tcp_window_scaling = 1
四、删除所有不需要的Nginx模块
你需要直接通过编译Nginx源代码使模块数量最少化。通过限制只允许web服务器访问模块把风险降到最低。你可以只配置安装nginx你所需要的模块。例如，禁用SSL和autoindex模块你可以执行以下命令：
- ./configure --without-http_autoindex_module --without-http_ssi_module
- make
- make install
通过以下命令来查看当编译nginx服务器时哪个模块能开户或关闭：
- ./configure --help | less
禁用你用不到的nginx模块。
（可选项）更改nginx版本名称。
编辑文件/http/ngx_http_header_filter_module.c：
- vi +48 src/http/ngx_http_header_filter_module.c
找到行：
- static char ngx_http_server_string[] = "Server: nginx" CRLF;
- static char ngx_http_server_full_string[] = "Server: " NGINX_VER CRLF;
按照以下行修改：
- static char ngx_http_server_string[] = "Server: Ninja Web Server" CRLF;
- static char ngx_http_server_full_string[] = "Server: Ninja Web Server" CRLF;
保存并关闭文件。现在你可以编辑服务器了。增加以下代码到nginx.conf文件来关闭nginx版本号的显示。
server_tokens off
五、使用mod_security
只适合后端Apache服务器
mod_security为Apache提供一个应用程序级的防火墙。为后端Apache Web服务器安装mod_security，这会阻止很多注入式攻击。
六、安装SELinux策略
默认的SELinux不会保护Nginx Web服务器，但是你可以安装和编译保护软件。
1、安装编译SELinux所需环境支持
- yum -y install selinux-policy-targeted selinux-policy-devel
2、下载SELinux策略以强化Nginx Web服务器。
- cd /opt
- wget 'http://downloads.sourceforge.net/project/selinuxnginx/se-ngix_1_0_10.tar.gz?use_mirror=nchc'
3、解压文件
- tar -zxvf se-ngix_1_0_10.tar.gz
4、编译文件
- cd se-ngix_1_0_10/nginx
- make
将会输出如下：
Compiling targeted nginx module
/usr/bin/checkmodule: loading policy configuration from tmp/nginx.tmp
/usr/bin/checkmodule: policy configuration loaded
/usr/bin/checkmodule: writing binary representation (version 6) to tmp/nginx.mod
Creating targeted nginx.pp policy package
- rm tmp/nginx.mod.fc tmp/nginx.mod
5、安装生成的nginx.pp SELinux模块：
- /usr/sbin/semodule -i nginx.pp
七、基于Iptables防火墙的限制
下面的防火墙脚本阻止任何除了允许：
来自HTTP(TCP端口80)的请求
来自ICMP ping的请求
ntp(端口123)的请求输出
smtp(TCP端口25)的请求输出
- #!/bin/bash
- IPT="/sbin/iptables"
- #### IPS ######
- # Get server public ip
- SERVER_IP=$(ifconfig eth0 | grep 'inet addr:' | awk -F'inet addr:' '{ print $2}' | awk '{ print $1}')
- LB1_IP="204.54.1.1"
- LB2_IP="204.54.1.2"
- # Do some smart logic so that we can use damm script on LB2 too
- OTHER_LB=""
- SERVER_IP=""
- [[ "$SERVER_IP" == "$LB1_IP" ]] && OTHER_LB="$LB2_IP" || OTHER_LB="$LB1_IP"
- [[ "$OTHER_LB" == "$LB2_IP" ]] && OPP_LB="$LB1_IP" || OPP_LB="$LB2_IP"
- ### IPs ###
- PUB_SSH_ONLY="122.xx.yy.zz/29"
- #### FILES #####
- BLOCKED_IP_TDB=/root/.fw/blocked.ip.txt
- SPOOFIP="127.0.0.0/8 192.168.0.0/16 172.16.0.0/12 10.0.0.0/8 169.254.0.0/16 0.0.0.0/8 240.0.0.0/4 255.255.255.255/32 168.254.0.0/16 224.0.0.0/4 240.0.0.0/5 248.0.0.0/5 192.0.2.0/24"
- BADIPS=$( [[ -f ${BLOCKED_IP_TDB} ]] && egrep -v "^#|^$" ${BLOCKED_IP_TDB})
- ### Interfaces ###
- PUB_IF="eth0" # public interface
- LO_IF="lo" # loopback
- VPN_IF="eth1" # vpn / private net
- ### start firewall ###
- echo "Setting LB1 $(hostname) Firewall..."
- # DROP and close everything
- $IPT -P INPUT DROP
- $IPT -P OUTPUT DROP
- $IPT -P FORWARD DROP
- # Unlimited lo access
- $IPT -A INPUT -i ${LO_IF} -j ACCEPT
- $IPT -A OUTPUT -o ${LO_IF} -j ACCEPT
- # Unlimited vpn / pnet access
- $IPT -A INPUT -i ${VPN_IF} -j ACCEPT
- $IPT -A OUTPUT -o ${VPN_IF} -j ACCEPT
- # Drop sync
- $IPT -A INPUT -i ${PUB_IF} -p tcp ! --syn -m state --state NEW -j DROP
- # Drop Fragments
- $IPT -A INPUT -i ${PUB_IF} -f -j DROP
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL ALL -j DROP
- # Drop NULL packets
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -m limit --limit 5/m --limit-burst 7 -j LOG --log-prefix " NULL Packets "
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -j DROP
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
- # Drop XMAS
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-prefix " XMAS Packets "
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP
- # Drop FIN packet scans
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-prefix " Fin Packets Scan "
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -j DROP
- $IPT -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
- # Log and get rid of broadcast / multicast and invalid
- $IPT -A INPUT -i ${PUB_IF} -m pkttype --pkt-type broadcast -j LOG --log-prefix " Broadcast "
- $IPT -A INPUT -i ${PUB_IF} -m pkttype --pkt-type broadcast -j DROP
- $IPT -A INPUT -i ${PUB_IF} -m pkttype --pkt-type multicast -j LOG --log-prefix " Multicast "
- $IPT -A INPUT -i ${PUB_IF} -m pkttype --pkt-type multicast -j DROP
- $IPT -A INPUT -i ${PUB_IF} -m state --state INVALID -j LOG --log-prefix " Invalid "
- $IPT -A INPUT -i ${PUB_IF} -m state --state INVALID -j DROP
- # Log and block spoofed ips
- $IPT -N spooflist
- for ipblock in $SPOOFIP
- do
- $IPT -A spooflist -i ${PUB_IF} -s $ipblock -j LOG --log-prefix " SPOOF List Block "
- $IPT -A spooflist -i ${PUB_IF} -s $ipblock -j DROP
- done
- $IPT -I INPUT -j spooflist
- $IPT -I OUTPUT -j spooflist
- $IPT -I FORWARD -j spooflist
- # Allow ssh only from selected public ips
- for ip in ${PUB_SSH_ONLY}
- do
- $IPT -A INPUT -i ${PUB_IF} -s ${ip} -p tcp -d ${SERVER_IP} --destination-port 22 -j ACCEPT
- $IPT -A OUTPUT -o ${PUB_IF} -d ${ip} -p tcp -s ${SERVER_IP} --sport 22 -j ACCEPT
- done
- # allow incoming ICMP ping pong stuff
- $IPT -A INPUT -i ${PUB_IF} -p icmp --icmp-type 8 -s 0/0 -m state --state NEW,ESTABLISHED,RELATED -m limit --limit 30/sec -j ACCEPT
- $IPT -A OUTPUT -o ${PUB_IF} -p icmp --icmp-type 0 -d 0/0 -m state --state ESTABLISHED,RELATED -j ACCEPT
- # allow incoming HTTP port 80
- $IPT -A INPUT -i ${PUB_IF} -p tcp -s 0/0 --sport 1024:65535 --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
- $IPT -A OUTPUT -o ${PUB_IF} -p tcp --sport 80 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
- # allow outgoing ntp
- $IPT -A OUTPUT -o ${PUB_IF} -p udp --dport 123 -m state --state NEW,ESTABLISHED -j ACCEPT
- $IPT -A INPUT -i ${PUB_IF} -p udp --sport 123 -m state --state ESTABLISHED -j ACCEPT
- # allow outgoing smtp
- $IPT -A OUTPUT -o ${PUB_IF} -p tcp --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT
- $IPT -A INPUT -i ${PUB_IF} -p tcp --sport 25 -m state --state ESTABLISHED -j ACCEPT
- ### add your other rules here ####
- #######################
- # drop and log everything else
- $IPT -A INPUT -m limit --limit 5/m --limit-burst 7 -j LOG --log-prefix " DEFAULT DROP "
- $IPT -A INPUT -j DROP
- exit 0
