iptables 阻止客户端 ip 互联网访问并保持 LAN 访问

Question

随着具有网络访问权限的设备的增加和黑客攻击的可能性，我想阻止特定 ip 地址访问互联网，但允许 LAN 访问。例如，我使用 Logitech Harmony 遥控器通过 1 个按钮控制我的立体声音响、卫星电视和电视。我也可以用我的 iPad 通过本地网络控制它。但我不想让黑客操作我的电视，所以我想用我的 IP 表防火墙阻止分配给和声遥控器的 IP 地址。

这是我用来编辑 IP 表配置的当前脚本。它在我的带有 2 个网卡的 Fedora 20 机器上工作。第 6 节是我试图插入规则的地方。其他一切都按预期工作。我包含了整个脚本，希望它可以帮助其他人，即使与我的问题无关。毕竟，这一切都是从我自己的搜索中获得的知识构建的！

---

#!/bin/sh
#
# A script for creating an iptables firewall
#

#
# Start by clearing iptables
#
iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X
iptables -t nat -X
iptables -t mangle -X

#
# Define our interfaces, Squid IP, and Squid port
#
WAN="p4p1"
LAN="p4p2"
SQUIDIP="192.168.10.10"
SQUIDPORT="3129"

#
# Create log files to help troubleshooting. (We can comment out when not needed)
#
# iptables -A OUTPUT -j LOG
# iptables -A INPUT -j LOG
# iptables -A FORWARD -j LOG

#
# Now to create the Routing Firewall
#

#
# (1) Create the default policies (DROP)
#
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

#
# (2) User-defined chain called "okay" for ACCEPTed TCP packets
#
iptables -N okay
iptables -A okay -p tcp --syn -j ACCEPT
iptables -A okay -p tcp -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A okay -p tcp -j DROP

#
# (3) INPUT rules
#
######  (A) Rules for incoming packets from the LAN
iptables -A INPUT -p ALL -i $LAN -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 192.168.10.10 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 192.168.1.10 -j ACCEPT
iptables -A INPUT -p ALL -i $LAN -d 192.168.10.255 -j ACCEPT

##### (B) Rules for incoming packets from the Internet

######          (i) Packets for established connections
iptables -A INPUT -p ALL -d 192.168.1.10 -m state --state ESTABLISHED,RELATED -j ACCEPT

#####           (ii) TCP rules  ## Opens the server port to any TCP from the internet
iptables -A INPUT -p tcp -i $WAN -s 0/0 –dport 22 -j okay

#####           (iii) UDP rules ## Opens the server port to any UDP from the internet
# iptables -A INPUT -p udp -i $WAN -s 0/0 –dport 53 -j okay

#####          (iv) ICMP rules
iptables -A INPUT -p icmp -i $WAN -s 0/0 --icmp-tpe 8 -j ACCEPT
iptables -A INPUT -p icmp -i $WAN -s 0/0 --icmp-tpe 11 -j ACCEPT

#
# Creates the router between the 2 ethernet cards to accept the packets we want to forward
#
iptables -A FORWARD -i $LAN -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

#
# (5) OUTPUT rules
# Only output packets with local addresses (no spoofing)
#
iptables -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.168.10.10 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.168.1.10 -j ACCEPT

#
# (6) OUTPUT rule to allow a client LAN access, but DROP internet access
# I use this to prevent various home appliances from accessing the internet
#
iptables -A OUTPUT -s 192.168.10.110 -j DROP

#
# (7) PREROUTING rules to allow a client to bypass our Squid proxy
# (NetFlix works better when it bypasses the proxy)
iptables -t nat -A PREROUTING -s 192.168.10.204 -j ACCEPT # BluRay player
iptables -t nat -A PREROUTING -s 192.168.10.205 -j ACCEPT # Sony TV

#
# (8) PREROUTING rules for transparent Squid proxy (also requires changes in the squid configuration file)
# (from: http://wiki.squidcache.org/ConfigExamples/Intercept/LinuxRedirect)
#
iptables -t nat -A PREROUTING -s $SQUIDIP -p tcp --dport 80 -j ACCEPT
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port $SQUIDPORT
iptables -t mangle -A PREROUTING -p tcp --dport $SQUIDPORT -j DROP

#
# (9) POSTROUTING chain rules. SNAT is for static IP, MASQUERADE is for dynamic IP
#
iptables -t nat -A POSTROUTING -o $WAN -j SNAT --to-source 192.168.1.10
# iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE

#
# Last, but not least, save the new configuration in /etc/sysconfig/iptables
#
service iptables save

#
# EOF
#

Answer 1

这行不通。

#
# (6) OUTPUT rule to allow a client LAN access, but DROP internet access
# I use this to prevent various home appliances from accessing the internet
# iptables -A OUTPUT -s 192.168.10.110 -j DROP

它不起作用的原因是 OUTPUT 表仅过滤来自路由器的流量，而不是通过它。您希望将规则应用于 FORWARD 表，如下所示：

iptables -A FORWARD -s 192.168.10.110 -j DROP

但它可能不会永远存在，因为分配给设备的 IP 地址可以通过 DHCP 进行更改。所以我建议您改为按 mac 地址进行过滤。

就像是：

/sbin/iptables -A PREROUTING -i $LAN -m mac --mac-source ff:ff:ff:ff:ff:ff -j DROP

ff:ff:ff:ff:ff:ff您要过滤的 Harmony 遥控器或其他设备的 MAC 地址在 哪里。

注意：正如评论中指出的，MAC 地址仅在第 2 层起作用。我见过的例子表明，当过滤器应用于 LAN 接口时，上述内容应该可以工作。测试一下，让我知道它是否按预期工作。

我还想补充一下：

#
# Creates the router between the 2 ethernet cards to accept the packets we want to forward
#
iptables -A FORWARD -i $LAN -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

不，它不会在 2 个以太网卡之间创建路由器。当 ip 转发打开时，路由由内核自动完成。

上述 iptables 规则表示接受或允许来自 $LAN 的数据包通过任何接口。并保持通过转发链进入路由器的已建立/相关会话的状态，该会话并非源自 $LAN。因为那会触及第一条规则并停止。