2002-11-09 19:10:22 +01:00
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>MAC Verification</title>
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2003-04-13 17:28:32 +02:00
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2002-11-09 19:10:22 +01:00
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<meta http-equiv="content-type"
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content="text/html; charset=ISO-8859-1">
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2003-04-13 17:28:32 +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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</head>
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<body>
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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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bgcolor="#400169" height="90">
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<tbody>
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<tr>
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<td width="100%">
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<h1 align="center"><font color="#ffffff">MAC Verification</font><br>
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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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</table>
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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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<ol>
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<li>The <b>maclist</b> interface option in <a
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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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<li>The <b>maclist </b>option in <a
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href="Documentation.htm#Hosts">/etc/shorewall/hosts</a>. When this option
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is specified for a subnet, all traffic from that subnet is subject to MAC
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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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</li>
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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 connected
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by INTERFACE. It is not necessary to use the Shorewall MAC format in
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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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</ul>
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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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<pre> #ZONE INTERFACE BROADCAST OPTIONS<br> net eth0 206.124.146.255 norfc1918,dhcp,blacklist<br> loc eth2 192.168.1.255 dhcp,maclist<br> dmz eth1 192.168.2.255<br> net eth3 206.124.146.255 blacklist<br> - texas 192.168.9.255<br> loc ppp+<br></pre>
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<b>/etc/shorewall/maclist:</b><br>
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2003-01-14 21:32:45 +01:00
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<pre> #INTERFACE MAC IP ADDRESSES (Optional)<br> eth2 00:A0:CC:63:66:89 192.168.1.3 #Wookie<br> eth2 00:10:B5:EC:FD:0B 192.168.1.4 #Tarry<br> eth2 00:A0:CC:DB:31:C4 192.168.1.5 #Ursa<br> eth2 00:A0:CC:DB:31:C4 192.168.1.128/26 #PPTP Clients to server on Ursa<br> eth2 00:06:25:aa:a8:0f 192.168.1.7 #Eastept1 (Wireless)<br> eth2 00:04:5A:0E:85:B9 192.168.1.250 #Wap<br></pre>
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As shown above, I use MAC Verification on my local zone.<br>
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<h3>Example 2: Router in Local Zone</h3>
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Suppose now that I add a second ethernet segment to my local zone
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and gateway that segment via a router with MAC address 00:06:43:45:C6:15
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and IP address 192.168.1.253. Hosts in the second segment have IP addresses
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in the subnet 192.168.2.0/24. I would add the following entry to my /etc/shorewall/maclist
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file:<br>
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<pre> eth2 00:06:43:45:C6:15 192.168.1.253,192.168.2.0/24<br></pre>
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This entry accomodates traffic from the router itself (192.168.1.253)
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and from the second LAN segment (192.168.2.0/24). Remember that all traffic
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being sent to my firewall from the 192.168.2.0/24 segment will be forwarded
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by the router so that traffic's MAC address will be that of the router
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(00:06:43:45:C6:15) and not that of the host sending the traffic.
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<p><font size="2"> Updated 2/21/2002 - <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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</body>
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</html>
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