2002-11-09 19:10:22 +01:00
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<title>MAC Verification</title>
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2003-06-23 22:24:51 +02:00
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2002-11-09 19:10:22 +01:00
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2003-06-23 22:24:51 +02:00
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2002-11-09 19:10:22 +01:00
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<meta name="author" content="Tom Eastep">
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<body>
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2003-06-23 22:24:51 +02:00
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2002-11-09 19:10:22 +01:00
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<table border="0" cellpadding="0" cellspacing="0"
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style="border-collapse: collapse;" width="100%" id="AutoNumber4"
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<td width="100%">
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2002-11-09 19:10:22 +01:00
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<h1 align="center"><font color="#ffffff">MAC Verification</font><br>
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2003-06-23 22:24:51 +02:00
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</h1>
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<br>
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</td>
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</tr>
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</tbody>
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2002-11-09 19:10:22 +01:00
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</table>
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2003-06-23 22:24:51 +02:00
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<br>
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All traffic from an interface or from a subnet on an interface
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can be verified to originate from a defined set of MAC addresses. Furthermore,
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each MAC address may be optionally associated with one or more IP addresses.
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<br>
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<br>
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<b>Your kernel must include MAC match support (CONFIG_IP_NF_MATCH_MAC
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- module name ipt_mac.o).</b><br>
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<br>
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There are four components to this facility.<br>
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2002-11-09 19:10:22 +01:00
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<ol>
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<li>The <b>maclist</b> interface option in <a
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2002-12-28 16:38:03 +01:00
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href="Documentation.htm#Interfaces">/etc/shorewall/interfaces</a>. When
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this option is specified, all traffic arriving on the interface is subjet
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to MAC verification.</li>
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2003-06-23 22:24:51 +02:00
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<li>The <b>maclist </b>option in <a
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2003-04-13 17:28:32 +02:00
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href="Documentation.htm#Hosts">/etc/shorewall/hosts</a>. When this option
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2003-06-23 22:24:51 +02:00
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is specified for a subnet, all traffic from that subnet is subject to
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MAC verification.</li>
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<li>The /etc/shorewall/maclist file. This file is used to associate
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MAC addresses with interfaces and to optionally associate IP addresses
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with MAC addresses.</li>
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<li>The <b>MACLIST_DISPOSITION </b>and <b>MACLIST_LOG_LEVEL </b>variables
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in <a href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf.</a>
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The MACLIST_DISPOSITION variable has the value DROP, REJECT or ACCEPT
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and determines the disposition of connection requests that fail MAC verification.
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The MACLIST_LOG_LEVEL variable gives the syslogd level at which connection
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requests that fail verification are to be logged. If set the the empty
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value (e.g., MACLIST_LOG_LEVEL="") then failing connection requests are
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not logged.<br>
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2003-06-23 22:24:51 +02:00
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</li>
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2002-11-09 19:10:22 +01:00
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</ol>
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The columns in /etc/shorewall/maclist are:<br>
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<ul>
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<li>INTERFACE - The name of an ethernet interface on the Shorewall
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system.</li>
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<li>MAC - The MAC address of a device on the ethernet segment
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connected by INTERFACE. It is not necessary to use the Shorewall MAC format
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in this column although you may use that format if you so choose.</li>
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<li>IP Address - An optional comma-separated list of IP addresses
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for the device whose MAC is listed in the MAC column.</li>
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2002-11-09 19:10:22 +01:00
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</ul>
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2003-06-23 22:24:51 +02:00
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2002-11-09 19:10:22 +01:00
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<h3>Example 1: Here are my files:</h3>
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<b>/etc/shorewall/shorewall.conf:<br>
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</b>
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<pre> MACLIST_DISPOSITION=REJECT<br> MACLIST_LOG_LEVEL=info<br></pre>
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<b>/etc/shorewall/interfaces:</b><br>
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<blockquote>
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<pre>#ZONE INTERFACE BROADCAST OPTIONS<br>net eth0 206.124.146.255 dhcp,norfc1918,routefilter,blacklist,tcpflags<br>loc eth2 192.168.1.255 dhcp<br>dmz eth1 192.168.2.255<br>wap eth3 192.168.3.255 dhcp,maclist<br>- texas 192.168.9.255</pre>
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</blockquote>
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<b>/etc/shorewall/maclist:</b><br>
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<blockquote>
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<pre>#INTERFACE MAC IP ADDRESSES (Optional)<br>eth3 00:A0:CC:A2:0C:A0 192.168.3.7 #Work Laptop<br>eth3 00:04:5a:fe:85:b9 192.168.3.250 #WAP11<br>eth3 00:06:25:56:33:3c #WET11<br>eth3 00:0b:cd:C4:cc:97 192.168.3.8 #TIPPER</pre>
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</blockquote>
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As shown above, I use MAC Verification on my wireless zone.<br>
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<br>
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<b>Note: </b>The WET11 is a somewhat curious device; when forwarding DHCP
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traffic, it uses the MAC address of the host (TIPPER) but for other forwarded
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traffic it uses it's own MAC address. Consequently, I don't assign the WET11
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a fixed IP address in /etc/shorewall/maclist.<br>
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2002-11-09 19:10:22 +01:00
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<h3>Example 2: Router in Local Zone</h3>
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2003-06-23 22:24:51 +02:00
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Suppose now that I add a second wireless segment to my wireless
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zone and gateway that segment via a router with MAC address 00:06:43:45:C6:15
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and IP address 192.168.3.253. Hosts in the second segment have IP addresses
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in the subnet 192.168.4.0/24. I would add the following entry to my /etc/shorewall/maclist
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file:<br>
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<pre> eth3 00:06:43:45:C6:15 192.168.3.253,192.168.4.0/24<br></pre>
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This entry accomodates traffic from the router itself (192.168.3.253)
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and from the second wireless segment (192.168.4.0/24). Remember that
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all traffic being sent to my firewall from the 192.168.4.0/24 segment
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will be forwarded by the router so that traffic's MAC address will be
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that of the router (00:06:43:45:C6:15) and not that of the host sending
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the traffic.
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<p><font size="2"> Updated 6/10/2002 - <a href="support.htm">Tom Eastep</a>
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</font></p>
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2003-01-14 21:32:45 +01:00
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<p><a href="copyright.htm"><font size="2">Copyright</font> ©
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<font size="2">2001, 2002, 2003 Thomas M. Eastep.</font></a><br>
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</p>
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<br>
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<br>
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2003-03-18 16:16:33 +01:00
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<br>
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<br>
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2002-11-09 19:10:22 +01:00
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</body>
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</html>
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