iptables練習

系統的INPUT和OUTPUT默認策略為DROP；

1、限制本地主機的web服務器在周一不允許訪問；新請求的速率不能超過100個每秒；web服務器包含了admin字符串的頁面不允許訪問；web服務器僅允許響應報文離開本機；

系統默認策略設定：

~]# iptables -P INPUT DROP

~]# iptables -P OUPUT DROP

網絡說明：

本地主機網段為192.168.150.0/24

web服務器IP為192.168.150.137

INPUT

~]# iptables -A INPUT -s 192.168.150.0/24 -d 192.168.150.137 -p tcp –dport 80 -m time –weekdays Mon –kerneltz -j DROP

~]# iptables -A INPUT -d 192.168.150.137 -p tcp –dport80 -m limit –limit 100/second -m state –state NEW -j ACCEPT

~]# iptables -A INPUT -s 192.168.150.0/24 -d 192.168.150.137 -p tcp –dport 80 -j ACCEPT

OUTPUT

~]# iptables -A OUTPUT -s 192.168.150.137 -d 0/0 -p tcp –sport 80 -m string –algo bm –string "admin" -j REJECT

~]# iptables -A OUTPUT -s 192.168.150.137 -d 0/0 -p tcp –sport 80 -m state –state ESTABLISHED -j ACCEPT

2、在工作時間，即周一到周五的8:30-18:00，開放本機的ftp服務給172.16.0.0網絡中的主機訪問；數據下載請求的次數每分鐘不得超過5個；

INPUT:

#iptables -A INPUT -s 172.16.0.0/16 -p tcp –dport 21 -m time –timestart 08:30 –timestop 18:00 –weekdays Mon,Tue,Wed,Thu,Fri -m limit –limit-burst 5 –limit 5/minute -j ACCEPT

#iptables -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT

OUTPUT

#iptables -A OUTPUT -p tcp -m multiport –sport 20,21 -m state –state ESTABLISHED,RELATED -j ACCEPT

3、開放本機的ssh服務給172.16.x.1-172.16.x.100中的主機，x為你的座位號，新請求建立的速率一分鐘不得超過2個；僅允許響應報文通過其服務端口離開本機；

INPUT:

#iptables -A INPUT -d 172.16.100.6 -p tcp –dport 22 -m iprange –src-range 172.16.100.1-172.16.100.100 -m limit –limit 2/minute -j ACCEPT

OUTPUT:

# iptables -A OUTPUT -s 172.16.100.6 -p tcp –sport 22 -m iprange –dst-range 172.16.100.1-172.16.100.100 -m state –state ESTABLISHED -j ACCEPT

4、拒絕TCP標志位全部為1及全部為0的報文訪問本機；

# iptabels -A INPUT -d 192.168.150.137 -p tcp –tcp-flags ALL ALL -j DROP

# iptables -A INPUT -d 192.168.150.137 -p tcp –tcp-flags ALL NONE -j DROP

5、允許本機ping別的主機；但不開放別的主機ping本機；

# iptables -A OUTPUT -s 192.168.150.138 -p icmp –icmp-type 8 -j ACCEPT     請求包

# iptables -A INPUT -d 192.168.150.138 -p icmp –icmp-type 0 -j ACCEPT     回包

6、判斷下述規則的意義：

# iptables -N clean_in

     創建自定義鏈clean_in

  # iptables -A clean_in -d 255.255.255.255 -p icmp -j DROP     丟棄不定向廣播ping包

  # iptables -A clean_in -d 172.16.255.255 -p icmp -j DROP     丟棄定向廣播ping包

     禁止廣播探測本網絡主機在線情況

  # iptables -A clean_in -p tcp ! –syn -m state –state NEW -j DROPQ      丟棄syn標志不為1的包和追蹤狀態為新連接的包

  # iptables -A clean_in -p tcp –tcp-flags ALL ALL -j DROP     標志位全1的丟棄，全1肯定是不正常的包

  # iptables -A clean_in -p tcp –tcp-flags ALL NONE -j DROP     標志位全0的丟棄，全0肯定是不正常的包

  # iptables -A clean_in -d 172.16.100.7 -j RETURN     正常的報文RETURN

     定義一個清理鏈

  # iptables -A INPUT -d 172.16.100.7 -j clean_in     到目的主機的報文過來轉給自定義鏈clean_in

  # iptables -A INPUT  -i lo -j ACCEPT     允許數據報文流入環回口

  # iptables -A OUTPUT -o lo -j ACCEPT     允許數據報文流出環回口

     開放本地環回口

  # iptables -A INPUT  -i eth0 -m multiport -p tcp –dports 53,113,135,137,139,445 -j DROP     指定流入報文接口為eth0，協議為tcp，目標端口為53,113,135,137,139,445，報文丟棄

  # iptables -A INPUT  -i eth0 -m multiport -p udp –dports 53,113,135,137,139,445 -j DROP     指定流入報文接口為eth0，協議為udp，目標端口為53,113,135,137,139,445，報文丟棄

  # iptables -A INPUT  -i eth0 -p udp –dport 1026 -j DROP     流入eth0的udp，端口為1026報文丟棄

  # iptables -A INPUT  -i eth0 -m multiport -p tcp –dports 1433,4899 -j DROP     流入eth0的tcp，端口為1433,4899報文丟棄

  # iptables -A INPUT  -p icmp -m limit –limit 10/second -j ACCEPT     限制ping包個數每秒最多10個

7、通過tcp_wrapper控制vsftpd僅允許172.16.0.0/255.255.0.0網絡中的主機訪問，但172.16.100.3除外；對所被被拒絕的訪問嘗試都記錄在/var/log/tcp_wrapper.log日志文件中；

~]# vim /etc/hosts.allow

#

# hosts.allow    This file contains access rules which are used to

#        allow or deny connections to network services that

#        either use the tcp_wrappers library or that have been

#        started through a tcp_wrappers-enabled xinetd.

#

#        See 'man 5 hosts_options' and 'man 5 hosts_access'

#        for information on rule syntax.

#        See 'man tcpd' for information on tcp_wrappers

#

vsftpd:192.168.150.0/255.255.255.0 EXCEPT 192.168.150.138

~]# vim /etc/hosts.deny

[root@localhost ~]# cat /etc/hosts.deny

#

# hosts.deny    This file contains access rules which are used to

#        deny connections to network services that either use

#        the tcp_wrappers library or that have been

#        started through a tcp_wrappers-enabled xinetd.

#

#        The rules in this file can also be set up in

#        /etc/hosts.allow with a 'deny' option instead.

#

#        See 'man 5 hosts_options' and 'man 5 hosts_access'

#        for information on rule syntax.

#        See 'man tcpd' for information on tcp_wrappers

#

vsftpd:ALL :spawn /bin/echo `date` login attempt from %c to %s, %d >> /var/log/tcp_wrapper.log

執行結果

192.168.150.136主機

[root@localhost ~]# ftp 192.168.150.137

Connected to 192.168.150.137 (192.168.150.137).

220 (vsFTPd 3.0.2)

Name (192.168.150.137:root):

192.168.150.138主機

~]# ftp 192.168.150.137

Connected to 192.168.150.137 (192.168.150.137).

421 Service not available.

日志信息：

~]# cat /var/log/tcp_wrapper.log

2016年 12月 25日 星期日 16:41:17 CST login attempt from 192.168.150.138 to vsftpd@192.168.150.137, vsft

pd2016年 12月 25日 星期日 16:44:10 CST login attempt from 192.168.150.138 to vsftpd@192.168.150.137, vsft

pd