<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> <meta name="GENERATOR" content="Microsoft FrontPage 5.0"> <meta name="ProgId" content="FrontPage.Editor.Document"> <title>Shorewall 1.3 Documentation</title> <base target="_self"> <meta name="Microsoft Theme" content="none, default"> <meta name="Microsoft Border" content="none, default"> </head> <body> <table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse;" width="100%" id="AutoNumber4" bgcolor="#400169" height="90"> <tbody> <tr> <td width="100%"> <h1 align="center"><font color="#ffffff">Shorewall 1.3 Reference</font></h1> </td> </tr> </tbody> </table> <h2 align="center">This documentation is intended primarily for reference. Step-by-step instructions for configuring Shorewall in common setups may be found in the <a href="shorewall_quickstart_guide.htm">QuickStart Guides</a>.</h2> <h2>Components</h2> <p>Shorewall consists of the following components: </p> <ul> <li><b><a href="#Variables">params</a></b> -- a parameter file installed in /etc/shorewall that can be used to establish the values of shell variables for use in other files.</li> <li><b> <a href="#Conf">shorewall.conf</a></b> -- a parameter file installed in /etc/shorewall that is used to set several firewall parameters.</li> <li><b> <a href="#Zones">zones</a></b> - a parameter file installed in /etc/shorewall that defines a network partitioning into "zones"</li> <li><b> <a href="#Policy">policy</a></b> -- a parameter file installed in /etc/shorewall/ that establishes overall firewall policy.</li> <li><b> <a href="#Rules">rules</a> </b> -- a parameter file installed in /etc/shorewall and used to express firewall rules that are exceptions to the high-level policies established in /etc/shorewall/policy.</li> <li><b><a href="#Blacklist">blacklist</a> -- </b>a parameter file installed in /etc/shorewall and used to list blacklisted IP/subnet/MAC addresses.</li> <li><b> functions</b> -- a set of shell functions used by both the firewall and shorewall shell programs. Installed in /etc/shorewall prior to version 1.3.2, in /var/lib/shorewall in version s 1.3.2-1.3.8 and in /usr/lib/shorewall in later versions.</li> <li><b> <a href="#modules">modules</a></b> -- a parameter file installed in /etc/shorewall and that specifies kernel modules and their parameters. Shorewall will automatically load the modules specified in this file.</li> <li><a href="#TOS"><b> tos</b> </a>-- a parameter file installed in /etc/shorewall that is used to specify how the Type of Service (TOS) field in packets is to be set.</li> <li><a href="#Scripts"><b> icmp.def</b> </a>-- a parameter file installed in /etc/shorewall and that specifies the default handling of ICMP packets when the applicable policy is DROP or REJECT.</li> <li><b><a href="#Scripts">common.def</a></b> -- a parameter file installed in in /etc/shorewall that defines firewall-wide rules that are applied before a DROP or REJECT policy is applied.</li> <li><b> <a href="#Interfaces">interfaces</a> </b> -- a parameter file installed in /etc/shorewall/ and used to describe the interfaces on the firewall system.</li> <li><a href="#Hosts"><b> hosts</b> </a>-- a parameter file installed in /etc/shorewall/ and used to describe individual hosts or subnetworks in zones.</li> <li><b><a href="#Maclist">maclist</a> </b>-- a parameter file installed in /etc/shorewall and used to verify the MAC address (and possibly also the IP address(es)) of devices.<br> </li> <li><b> <a href="#Masq">masq</a></b> - This file also describes IP masquerading under Shorewall and is installed in /etc/shorewall.</li> <li><b><a href="shorewall_firewall_structure.htm">firewall</a></b> -- a shell program that reads the configuration files in /etc/shorewall and configures your firewall. This file is installed in your init.d directory (/etc/rc.d/init.d ) where it is renamed <i>shorewall.</i> /etc/shorewall/firewall (/var/lib/shorewall/firewall in versions 1.3.2-1.3.8 and /usr/lib/shorewall/firewall in 1.3.9 and later) is a symbolic link to this program.</li> <li><b> <a href="#NAT">nat</a></b> -- a parameter file in /etc/shorewall used to define <a href="#NAT"> static NAT</a> .</li> <li><b> <a href="#ProxyArp">proxyarp</a></b> -- a parameter file in /etc/shorewall used to define <a href="#ProxyArp"> Proxy Arp</a> .</li> <li><b><a href="#rfc1918">rfc1918</a></b> -- a parameter file in /etc/shorewall used to define the treatment of packets under the <a href="#Interfaces">norfc1918 interface option</a>.</li> <li><b><a href="#Routestopped">routestopped</a></b> -- a parameter file in /etc/shorewall used to define those hosts that can access the firewall when Shorewall is stopped.</li> <li><a href="traffic_shaping.htm#tcrules"><b>tcrules</b> </a>-- a parameter file in /etc/shorewall used to define rules for classifying packets for <a href="traffic_shaping.htm">Traffic Shaping/Control</a>.</li> <li><b> <a href="#Tunnels">tunnels</a></b> -- a parameter file in /etc/shorewall used to define IPSec tunnels.</li> <li><b> <a href="#Starting">shorewall</a> </b> -- a shell program (requiring a Bourne shell or derivative) used to control and monitor the firewall. This should be placed in /sbin or in /usr/sbin (the install.sh script and the rpm install this file in /sbin).</li> <li><b> version</b> -- a file created in /etc/shorewall/ (/var/lib/shorewall in version 1.3.2-1.3.8 and /usr/lib/shorewall beginning in version 1.3.9) that describes the version of Shorewall installed on your system.</li> </ul> <h2><a name="Variables"></a> /etc/shorewall/params</h2> <p>You may use the file /etc/shorewall/params file to set shell variables that you can then use in some of the other configuration files.</p> <p>It is suggested that variable names begin with an upper case letter<font size="1"> </font>to distinguish them from variables used internally within the Shorewall programs</p> <p>Example:</p> <pre><font face="Courier"> NET_IF=eth0<br> NET_BCAST=130.252.100.255<br> NET_OPTIONS=blacklist,norfc1918</font></pre> <p>Example (/etc/shorewall/interfaces record):</p> <pre> <font face="Courier">net $NET_IF $NET_BCAST $NET_OPTIONS</font></pre> <p>The result will be the same as if the record had been written</p> <pre> <font face="Courier">net eth0 130.252.100.255 blacklist,norfc1918</font></pre> <p>Variables may be used anywhere in the other configuration files.</p> <h2><b><a name="Zones"></a> </b>/etc/shorewall/zones</h2> <p>This file is used to define the network zones. There is one entry in /etc/shorewall/zones for each zone; Columns in an entry are:</p> <ul> <li><b> ZONE</b> - short name for the zone. The name should be 5 characters or less in length and consist of lower-case letters or numbers. Short names must begin with a letter and the name assigned to the firewall is reserved for use by Shorewall itself. Note that the output produced by iptables is much easier to read if you select short names that are three characters or less in length. The name "all" may not be used as a zone name nor may the zone name assigned to the firewall itself via the FW variable in <a href="#Conf">/etc/shorewall/shorewall.conf</a>.</li> <li><b> DISPLAY</b> - The name of the zone as displayed during Shorewall startup.</li> <li><b> COMMENTS</b> - Any comments that you want to make about the zone. Shorewall ignores these comments.</li> </ul> <p>The /etc/shorewall/zones file released with Shorewall is as follows:</p> <table border="1" style="border-collapse: collapse;" cellpadding="2"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> DISPLAY</b></td> <td><b> COMMENTS</b></td> </tr> <tr> <td>net</td> <td>Net</td> <td>Internet</td> </tr> <tr> <td>loc</td> <td>Local</td> <td>Local networks</td> </tr> <tr> <td>dmz</td> <td>DMZ</td> <td>Demilitarized zone</td> </tr> </tbody> </table> <p>You may add, delete and modify entries in the /etc/shorewall/zones file as desired so long as you have at least one zone defined.</p> <p><b><font size="5" color="#ff0000"> Warning 1: </font><font color="#ff0000"> If you rename or delete a zone, you should perform "shorewall stop; shorewall start" to install the change rather than "shorewall restart".</font></b></p> <p><b><font size="5" color="#ff0000">Warning 2: </font><font color="#ff0000">The order of entries in the /etc/shorewall/zones file is significant <a href="#Nested">in some cases</a>.</font></b></p> <h2><font color="#660066"><a name="Interfaces"></a> </font>/etc/shorewall/interfaces</h2> <p>This file is used to tell the firewall which of your firewall's network interfaces are connected to which zone. There will be one entry in /etc/shorewall/interfaces for each of your interfaces. Columns in an entry are:</p> <ul> <li><b> ZONE</b> - A zone defined in the <a href="#Zones">/etc/shorewall/zones</a> file or "-". If you specify "-", you must use the <a href="#Hosts"> /etc/shorewall/hosts</a> file to define the zones accessed via this interface.</li> <li><b> INTERFACE</b> - the name of the interface (examples: eth0, ppp0, ipsec+). Each interface can be listed on only one record in this file. <font color="#ff0000"><b>D</b><b>O NOT INCLUDE THE LOOPBACK INTERFACE (lo) IN THIS FILE!!!</b></font></li> <li><b> BROADCAST</b> - the broadcast address(es) for the sub-network(s) attached to the interface. This should be left empty for P-T-P interfaces (ppp*, ippp*); if you need to specify options for such an interface, enter "-" in this column. If you supply the special value "detect" in this column, the firewall will automatically determine the broadcast address. In order to use "detect": <ul> <li>you must have iproute installed</li> <li>the interface must be up before you start your firewall</li> <li>the interface must only be attached to a single sub-network (i.e., there must have a single broadcast address). </li> </ul> </li> <li><b> OPTIONS</b> - a comma-separated list of options. Possible options include: <p> <b>tcpflags </b>(added in version 1.3.11) - This option causes Shorewall to make sanity checks on the header flags in TCP packets arriving on this interface. Checks include Null flags, SYN+FIN, SYN+RST and FIN+URG+PSH; these flag combinations are typically used for "silent" port scans. Packets failing these checks are logged according to the TCP_FLAGS_LOG_LEVEL option in<a href="#Conf"> /etc/shorewall/shorewall.conf</a> and are disposed of according to the TCP_FLAGS_DISPOSITION option.<br> <b><br> blacklist</b> - This option causes incoming packets on this interface to be checked against the <a href="#Blacklist">blacklist</a>.<b><br> <br> dhcp</b> - The interface is assigned an IP address via DHCP or is used by a DHCP server running on the firewall. The firewall will be configured to allow DHCP traffic to and from the interface even when the firewall is stopped. You may also wish to use this option if you have a static IP but you are on a LAN segment that has a lot of Laptops that use DHCP and you select the <b>norfc1918 </b>option (see below).</p> <p> <b> noping</b> - <b>This option is deprecated and is not available when OLD_PING_HANDLING=No in /etc/shorewall/shorewall.conf.</b> ICMP echo-request (ping) packets addressed to the firewall will be ignored by this interface. <br> <br> <b>filterping </b>- <b>This option is deprecated and is not available when OLD_PING_HANDLING=No in /etc/shorewall/shorewall.conf.</b> ICMP echo-request (ping) packets addressed to the firewall will be handled according to the /etc/shorewall/rules and /etc/shorewall/policy file. If the applicable policy is DROP or REJECT and you have supplied your own /etc/shorewall/icmpdef file then these 'ping' requests will be passed through the rules in that file before being dropped or rejected. If neither <b>noping </b>nor <b>filterping</b> is specified then the firewall will automatically ACCEPT these 'ping' requests. If both <b>noping</b> and <b>filterping </b>are specified, <b>filterping</b> takes precedence.</p> <p> <b> routestopped</b> - Beginning with Shorewall 1.3.4, this option is deprecated in favor of the <a href="#Routestopped">/etc/shorewall/routestopped</a> file. When the firewall is stopped, traffic to and from this interface will be accepted and routing will occur between this interface and other <i>routestopped </i>interfaces.</p> <p> <b> norfc1918</b> - Packets arriving on this interface and that have a source address that is reserved in RFC 1918 or in other RFCs will be dropped after being optionally logged. If <a href="#Conf">packet mangling is enabled in /etc/shorewall/shorewall.conf</a> , then packets arriving on this interface that have a destination address that is reserved by one of these RFCs will also be logged and dropped.<br> <br> Addresses blocked by the standard <a href="#rfc1918"> <b>rfc1918 </b>file</a> include those addresses reserved by RFC1918 plus other ranges reserved by the IANA or by other RFCs.</p> <p> Beware that as IPv4 addresses become in increasingly short supply, ISPs are beginning to use RFC 1918 addresses within their own infrastructure. Also, many cable and DSL "modems" have an RFC 1918 address that can be used through a web browser for management and monitoring functions. If you want to specify <b>norfc1918</b> on your external interface but need to allow access to certain addresses from the above list, see <a href="FAQ.htm#faq14">FAQ 14.</a></p> <p> <b> routefilter</b> - Invoke the Kernel's route filtering (anti-spoofing) facility on this interface. The kernel will reject any packets incoming on this interface that have a source address that would be routed outbound through another interface on the firewall. <font color="#ff0000">Warning: </font>If you specify this option for an interface then the interface must be up prior to starting the firewall.</p> <p> <b> multi</b> - The interface has multiple addresses and you want to be able to route between them. Example: you have two addresses on your single local interface eth1, one each in subnets 192.168.1.0/24 and 192.168.2.0/24 and you want to route between these subnets. Because you only have one interface in the local zone, Shorewall won't normally create a rule to forward packets from eth1 to eth1. Adding "multi" to the entry for eth1 will cause Shorewall to create the loc2loc chain and the appropriate forwarding rule.</p> <p><b>dropunclean</b> - Packets from this interface that are selected by the 'unclean' match target in iptables will be <a href="#LogUnclean">optionally logged</a> and then dropped. <font color="#ff0000"><b>Warning: This feature requires that UNCLEAN match support be configured in your kernel, either in the kernel itself or as a module. UNCLEAN support is broken in some versions of the kernel but appears to work ok in 2.4.17-rc1.<br> <br> Update 12/17/2001: </b></font>The unclean match patch from 2.4.17-rc1 is <a href="ftp://ftp.shorewall.net/pub/shorewall/misc/unclean.patch">available for download</a>. I am currently running this patch applied to kernel 2.4.16.</p> <p><font color="#ff0000"><b>Update 12/20/2001: </b></font>I've seen a number of tcp connection requests with OPT (020405B4<u>0000080A</u>...) being dropped in the <i>badpkt</i> chain. This appears to be a bug in the remote TCP stack whereby it is 8-byte aligning a timestamp (TCP option 8) but rather than padding with 0x01 it is padding with 0x00. It's a tough call whether to deny people access to your servers because of this rather minor bug in their networking software. If you wish to disable the check that causes these connections to be dropped, <a href="ftp://ftp.shorewall.net/pub/shorewall/misc/unclean1.patch">here's a kernel patch</a> against 2.4.17-rc2.</p> <p><b>logunclean </b>- This option works like <b>dropunclean</b> with the exception that packets selected by the 'unclean' match target in iptables are logged <i>but not dropped</i>. The level at which the packets are logged is determined by the setting of <a href="#LogUnclean">LOGUNCLEAN</a> and if LOGUNCLEAN has not been set, "info" is assumed.</p> <p><b>proxyarp </b>(Added in version 1.3.5) - This option causes Shorewall to set /proc/sys/net/ipv4/conf/<i><interface></i>/proxy_arp and is used when implementing Proxy ARP Sub-netting as described at <a href="http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/"> http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/</a>. Do <u> not</u> set this option if you are implementing Proxy ARP through entries in <a href="#ProxyArp"> /etc/shorewall/proxyarp</a>.<br> <br> <b>maclist</b> (Added in version 1.3.10) - If this option is specified, all connection requests from this interface are subject to <a href="MAC_Validation.html">MAC Verification</a>. May only be specified for ethernet interfaces.</p> </li> </ul> <p>My recommendations concerning options:<br> </p> <ul> <li>External Interface -- <b>tcpflags,blacklist,norfc1918,routefilter</b></li> <li>Internal Interface -- <b>routestopped</b></li> <li>Wireless Interface -- <b>maclist,routefilter,tcpflags</b><br> </li> <li>Don't use <b>dropunclean</b> -- It's broken in my opinion</li> <li>Use <b>logunclean</b> only when you are trying to debug a problem</li> <li>Use <b>dhcp</b>,<b>multi</b> and <b>proxyarp</b> when needed.<br> </li> </ul> <p> </p> <p>Example 1: You have a conventional firewall setup in which eth0 connects to a Cable or DSL modem and eth1 connects to your local network and eth0 gets its IP address via DHCP. You want to check all packets entering from the internet against the <a href="#Blacklist">black list</a>. Your /etc/shorewall/interfaces file would be as follows:</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> INTERFACE</b></td> <td><b> BROADCAST</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>net</td> <td>eth0</td> <td>detect</td> <td>dhcp,norfc1918,blacklist</td> </tr> <tr> <td>loc</td> <td>eth1</td> <td>detect</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p>Example 2: You have a standalone dialup GNU/Linux System. Your /etc/shorewall/interfaces file would be:</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> INTERFACE</b></td> <td><b> BROADCAST</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>net</td> <td>ppp0</td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p>Example 3: You have local interface eth1 with two IP addresses - 192.168.1.1/24 and 192.168.12.1/24</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> INTERFACE</b></td> <td><b> BROADCAST</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>loc</td> <td>eth1</td> <td>192.168.1.255,192.168.12.255</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <h2><font color="#660066"><a name="Hosts"></a> </font>/etc/shorewall/hosts Configuration</h2> <p>For most applications, specifying zones entirely in terms of network interfaces is sufficient. There may be times though where you need to define a zone to be a more general collection of hosts. This is the purpose of the /etc/shorewall/hosts file.</p> <p><b><font color="#ff0000">WARNING: </font>90% of Shorewall users don't need to put entries in this file and 80% of those who try to add such entries do it wrong. Unless you are ABSOLUTELY SURE that you need entries in this file, don't touch it.</b></p> <p>Columns in this file are:</p> <ul> <li><b> ZONE </b> - A zone defined in the <a href="#Zones">/etc/shorewall/zones</a> file.</li> <li><b> HOST(S)</b> - The name of a network interface followed by a colon (":") followed by either:</li> </ul> <blockquote> <ol> <li>An IP address (example - eth1:192.168.1.3)</li> <li>A subnet in CIDR notation<i> </i>(example - eth2:192.168.2.0/24)</li> </ol> <p>The interface name much match an entry in /etc/shorewall/interfaces.</p> </blockquote> <ul> <li><b> OPTIONS</b> - A comma-separated list of options.</li> </ul> <blockquote> <p><b>routestopped</b> - Beginning with Shorewall 1.3.4, this option is deprecated in favor of the <a href="#Routestopped">/etc/shorewall/routestopped</a> file. When the firewall is stopped, traffic to and from this host (these hosts) will be accepted and routing will occur between this host and other <i>routestopped </i>interfaces and hosts.<br> <br> <b>maclist - </b>Added in version 1.3.10. If specified, connection requests from the hosts specified in this entry are subject to <a href="MAC_Validation.html">MAC Verification</a>. This option is only valid for ethernet interfaces.<br> </p> </blockquote> <p>If you don't define any hosts for a zone, the hosts in the zone default to i0:0.0.0.0/0 , i1:0.0.0.0/0, ... where i0, i1, ... are the interfaces to the zone.</p> <p><b><font size="4" color="#ff0000">Note 1: </font></b> You probably DON'T want to specify any hosts for your internet zone since the hosts that you specify will be the only ones that you will be able to access without adding additional rules.</p> <p><font color="#ff0000" size="4"><b>Note 2: </b> </font> The setting of the MERGE_HOSTS variable in <a href="#Conf">/etc/shorewall/shorewall.conf</a> has an important effect on how the host file is processed. Please read the description of that variable carefully.</p> <p>Example:</p> <p>Your local interface is eth1 and you have two groups of local hosts that you want to make into separate zones:</p> <ul> <li>192.168.1.0/25 </li> <li>192.168.1.128/25</li> </ul> <p> Your /etc/shorewall/interfaces file might look like:</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> INTERFACE</b></td> <td><b> BROADCAST</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>net</td> <td>eth0</td> <td>detect</td> <td>dhcp,norfc1918</td> </tr> <tr> <td>-</td> <td>eth1</td> <td>detect</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p> The '-' in the ZONE column for eth1 tells Shorewall that eth1 interfaces to multiple zones.</p> <p> Your /etc/shorewall/hosts file might look like:</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> HOST(S)</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>loc1</td> <td>eth1:192.168.1.0/25</td> <td> <br> </td> </tr> <tr> <td>loc2</td> <td>eth1:192.168.1.128/25</td> <td>routestopped</td> </tr> </tbody> </table> </blockquote> <p> Hosts in 'loc2' can communicate with the firewall while Shorewall is stopped -- those in 'loc1' cannot.</p> <h4><font color="#660066"><a name="Nested"></a> Nested and Overlapping Zones</font></h4> <p> The /etc/shorewall/interfaces and /etc/shorewall/hosts file allow you to define nested or overlapping zones. Such overlapping/nested zones are allowed and Shorewall processes zones in the order that they appear in the /etc/shorewall/zones file. So if you have nested zones, you want the sub-zone to appear before the super-zone and in the case of overlapping zones, the rules that will apply to hosts that belong to both zones is determined by which zone appears first in /etc/shorewall/zones.</p> <p> Hosts that belong to more than one zone may be managed by the rules of all of those zones. This is done through use of the special <a href="#CONTINUE">CONTINUE policy</a> described below.</p> <h2><font color="#660066"><a name="Policy"></a> </font>/etc/shorewall/policy Configuration.</h2> <p>This file is used to describe the firewall policy regarding establishment of connections. Connection establishment is described in terms of <i>clients</i> who initiate connections and <i> servers </i>who receive those connection requests. Policies defined in /etc/shorewall/policy describe which zones are allowed to establish connections with other zones.</p> <p>Policies established in /etc/shorewall/policy can be viewed as default policies. If no rule in /etc/shorewall/rules applies to a particular connection request then the policy from /etc/shorewall/policy is applied.</p> <p>Four policies are defined:</p> <ul> <li><b> ACCEPT</b> - The connection is allowed.</li> <li><b> DROP</b> - The connection request is ignored.</li> <li><b> REJECT</b> - The connection request is rejected with an RST (TCP) or an ICMP destination-unreachable packet being returned to the client.</li> <li><b> CONTINUE </b> - The connection is neither ACCEPTed, DROPped nor REJECTed. CONTINUE may be used when one or both of the zones named in the entry are sub-zones of or intersect with another zone. For more information, see below. </li> </ul> <p> For each policy specified in /etc/shorewall/policy, you can indicate that you want a message sent to your system log each time that the policy is applied.</p> <p> Entries in /etc/shorewall/policy have four columns as follows:</p> <ol> <li> <b> SOURCE</b> - The name of a client zone (a zone defined in the <a href="#Zones"> /etc/shorewall/zones file</a> , the <a href="#Conf">name of the firewall zone</a> or "all").</li> <li> <b> DEST</b> - The name of a destination zone (a zone defined in the <a href="#Zones"> /etc/shorewall/zones file</a> , the <a href="#Conf">name of the firewall zone</a> or "all"). Shorewall automatically allows all traffic from the firewall to itself so the <a href="#Conf">name of the firewall zone</a> cannot appear in both the SOURCE and DEST columns.</li> <li> <b> POLICY</b> - The default policy for connection requests from the SOURCE zone to the DESTINATION zone.</li> <li> <b> LOG LEVEL</b> - Optional. If left empty, no log message is generated when the policy is applied. Otherwise, this column should contain an integer or name indicating a <a href="shorewall_logging.html">syslog level</a>.</li> <li> <b>LIMIT:BURST </b>- Optional. If left empty, TCP connection requests from the <b>SOURCE</b> zone to the <b>DEST</b> zone will not be rate-limited. Otherwise, this column specifies the maximum rate at which TCP connection requests will be accepted followed by a colon (":") followed by the maximum burst size that will be tolerated. Example: <b> 10/sec:40</b> specifies that the maximum rate of TCP connection requests allowed will be 10 per second and a burst of 40 connections will be tolerated. Connection requests in excess of these limits will be dropped.</li> </ol> <p> In the SOURCE and DEST columns, you can enter "all" to indicate all zones. </p> <p> The policy file installed by default is as follows:</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> POLICY</b></td> <td><b> LOG LEVEL</b></td> <td><b>LIMIT:BURST</b></td> </tr> <tr> <td>loc</td> <td>net</td> <td>ACCEPT</td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>net</td> <td>all</td> <td>DROP</td> <td>info</td> <td> <br> </td> </tr> <tr> <td>all</td> <td>all</td> <td>REJECT</td> <td>info</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p> This table may be interpreted as follows:</p> <ul> <li>All connection requests from the local network to hosts on the internet are accepted.</li> <li>All connection requests originating from the internet are ignored and logged at level KERNEL.INFO.</li> <li>All other connection requests are rejected and logged.</li> </ul> <p><b><font size="4" color="#ff0000"> WARNING:</font></b></p> <p><font color="#ff0000"><b> The firewall script processes</b> <b> the /etc/shorewall/policy file from top to bottom and <u>uses the first applicable policy that it finds.</u> For example, in the following policy file, the policy for (loc, loc) connections would be ACCEPT as specified in the first entry even though the third entry in the file specifies REJECT.</b></font></p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b>POLICY</b></td> <td><b>LOG LEVEL</b></td> <td><b>LIMIT:BURST</b></td> </tr> <tr> <td>loc</td> <td>all</td> <td>ACCEPT</td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>net</td> <td>all</td> <td>DROP</td> <td>info</td> <td> <br> </td> </tr> <tr> <td>loc</td> <td>loc</td> <td>REJECT</td> <td>info</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <h4><font color="#660066"><a name="CONTINUE"></a> The CONTINUE policy</font></h4> <p> Where zones are <a href="#Nested">nested or overlapping</a> , the CONTINUE policy allows hosts that are within multiple zones to be managed under the rules of all of these zones. Let's look at an example:</p> <p> /etc/shorewall/zones:</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> DISPLAY</b></td> <td><b> COMMENTS</b></td> </tr> <tr> <td>sam</td> <td>Sam</td> <td>Sam's system at home</td> </tr> <tr> <td>net</td> <td>Internet</td> <td>The Internet</td> </tr> <tr> <td>loc</td> <td>Loc</td> <td>Local Network</td> </tr> </tbody> </table> </blockquote> <p> /etc/shorewall/interfaces:</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> INTERFACE</b></td> <td><b> BROADCAST</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>-</td> <td>eth0</td> <td>detect</td> <td>dhcp,norfc1918</td> </tr> <tr> <td>loc</td> <td>eth1</td> <td>detect</td> <td>routestopped</td> </tr> </tbody> </table> </blockquote> <p> /etc/shorewall/hosts:</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ZONE</b></td> <td><b> HOST(S)</b></td> <td><b> OPTIONS</b></td> </tr> <tr> <td>net</td> <td>eth0:0.0.0.0/0</td> <td> <br> </td> </tr> <tr> <td>sam</td> <td>eth0:206.191.149.197</td> <td>routestopped</td> </tr> </tbody> </table> </blockquote> <p> Note that Sam's home system is a member of both the <b>sam</b> zone and the <b>net</b> zone and <a href="#Nested"> as described above</a> , that means that <b>sam</b> must be listed before <b>net</b> in /etc/shorewall/zones.</p> <p> /etc/shorewall/policy:</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font><font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> SOURCE</b></td> <td><b> DEST</b></td> <td><b> POLICY</b></td> <td><b> LOG LEVEL</b></td> </tr> <tr> <td>loc</td> <td>net</td> <td>ACCEPT</td> <td> <br> </td> </tr> <tr> <td>sam</td> <td>all</td> <td>CONTINUE</td> <td> <br> </td> </tr> <tr> <td>net</td> <td>all</td> <td>DROP</td> <td>info</td> </tr> <tr> <td>all</td> <td>all</td> <td>REJECT</td> <td>info</td> </tr> </tbody> </table> </blockquote> <p> The second entry above says that when Sam is the client, connection requests should first be process under rules where the source zone is <b>sam</b> and if there is no match then the connection request should be treated under rules where the source zone is <b>net</b>. It is important that this policy be listed BEFORE the next policy (<b>net</b> to <b>all</b>).</p> <p> Partial /etc/shorewall/rules:</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font><font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>...</td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>DNAT</td> <td>sam</td> <td>loc:192.168.1.3</td> <td>tcp</td> <td>ssh</td> <td>-</td> <td> <br> </td> </tr> <tr> <td>DNAT</td> <td>net</td> <td>loc:192.168.1.5</td> <td>tcp</td> <td>www</td> <td>-</td> <td> <br> </td> </tr> <tr> <td>...</td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p> Given these two rules, Sam can connect to the firewall's internet interface with ssh and the connection request will be forwarded to 192.168.1.3. Like all hosts in the <b>net</b> zone, Sam can connect to the firewall's internet interface on TCP port 80 and the connection request will be forwarded to 192.168.1.5. The order of the rules is not significant.</p> <p> <a name="Exclude"></a>Sometimes it is necessary to suppress port forwarding for a sub-zone. For example, suppose that all hosts can SSH to the firewall and be forwarded to 192.168.1.5 EXCEPT Sam. When Sam connects to the firewall's external IP, he should be connected to the firewall itself. Because of the way that Netfilter is constructed, this requires two rules as follows:</p> <blockquote> <p> </p> <font face="Century Gothic, Arial, Helvetica"> </font><font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>...</td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>DNAT</td> <td>sam</td> <td>fw</td> <td>tcp</td> <td>ssh</td> <td>-</td> <td> <br> </td> </tr> <tr> <td>DNAT</td> <td>net!sam</td> <td>loc:192.168.1.3</td> <td>tcp</td> <td>ssh</td> <td>-</td> <td> <br> </td> </tr> <tr> <td>...</td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p>The first rule allows Sam SSH access to the firewall. The second rule says that any clients from the net zone with the exception of those in the 'sam' zone should have their connection port forwarded to 192.168.1.3. If you need to exclude more than one zone in this way, you can list the zones separated by commas (e.g., net!sam,joe,fred). This technique also may be used when the ACTION is REDIRECT.</p> <h2><font color="#660066"><a name="Rules"></a> </font>/etc/shorewall/rules</h2> <p>The /etc/shorewall/rules file defines exceptions to the policies established in the /etc/shorewall/policy file. There is one entry in /etc/shorewall/rules for each of these rules. <br> </p> <p>Shorewall automatically enables firewall->firewall traffic over the loopback interface (lo) -- that traffic cannot be regulated using rules and any rule that tries to regulate such traffic will generate a warning and will be ignored.<br> </p> <p>Entries in the file have the following columns:</p> <ul> <li><b>ACTION</b> <ul> <li>ACCEPT, DROP or REJECT. These have the same meaning here as in the policy file above.</li> <li>DNAT -- Causes the connection request to be forwarded to the system specified in the DEST column (port forwarding). "DNAT" stands for "<u>D</u>estination <u>N</u>etwork <u>A</u>ddress <u>T</u>ranslation"</li> <li>DNAT- -- The above ACTION (DNAT) generates two iptables rules: 1) and header-rewriting rule in the Netfilter 'nat' table and; 2) an ACCEPT rule in the Netfilter 'filter' table. DNAT- works like DNAT but only generates the header-rewriting rule.<br> </li> <li>REDIRECT -- Causes the connection request to be redirected to a port on the local (firewall) system.</li> </ul> <p>The ACTION may optionally be followed by ":" and a <a href="shorewall_logging.html">syslog level</a> (example: REJECT:info). This causes the packet to be logged at the specified level prior to being processed according to the specified ACTION.<br> <br> The use of DNAT or REDIRECT requires that you have <a href="#NatEnabled">NAT enabled</a>.<br> </p> </li> <li><b>SOURCE</b> - Describes the source hosts to which the rule applies.. The contents of this field must begin with the name of a zone defined in /etc/shorewall/zones, $FW or "all". If the ACTION is DNAT or REDIRECT, sub-zones may be excluded from the rule by following the initial zone name with "!' and a comma-separated list of those sub-zones to be excluded. There is an <a href="#Exclude">example</a> above.<br> <br> If the source is not 'all' then the source may be further restricted by adding a colon (":") followed by a comma-separated list of qualifiers. Qualifiers are may include: <ul> <li>An interface name - refers to any connection requests arriving on the specified interface (example loc:eth4). Beginning with Shorwall 1.3.9, the interface name may optionally be followed by a colon (":") and an IP address or subnet (examples: loc:eth4:192.168.4.22, net:eth0:192.0.2.0/24).</li> <li>An IP address - refers to a connection request from the host with the specified address (example net:155.186.235.151). If the ACTION is DNAT, this must not be a DNS name.</li> <li>A MAC Address in <a href="#MAC">Shorewall format</a>.</li> <li>A subnet - refers to a connection request from any host in the specified subnet (example net:155.186.235.0/24).</li> </ul> </li> <li><b>DEST</b> - Describes the destination host(s) to which the rule applies. May take any of the forms described above for SOURCE plus the following two additional forms: <ul> <li>An IP address followed by a colon and the port <u>number</u> that the server is listening on (service names from /etc/services are not allowed - example loc:192.168.1.3:80). <br> </li> <li>A single port number (again, service names are not allowed) -- this form is only allowed if the ACTION is REDIRECT and refers to a server running on the firewall itself and listening on the specified port.<br> </li> </ul> </li> <li><b> PROTO</b> - Protocol. Must be a protocol name from /etc/protocols, a number, "all" or "related". Specifies the protocol of the connection request. "related" should be specified only if you have given ALLOWRELATED="no" in /etc/shorewall/shorewall.conf and you wish to override that setting for related connections originating with the client(s) and server(s) specified in this rule. When "related" is given for the protocol, the remainder of the columns should be left blank.</li> <li><b> DEST PORT(S)</b> - Port or port range (<low port>:<high port>) being connected to. May only be specified if the protocol is tcp, udp or icmp. For icmp, this column's contents are interpreted as an icmp type. If you don't want to specify DEST PORT(S) but need to include information in one of the columns to the right, enter "-" in this column. You may give a list of ports and/or port ranges separated by commas. Port numbers may be either integers or service names from /etc/services.</li> <li><b> SOURCE</b> <b>PORTS(S) </b>- May be used to restrict the rule to a particular client port or port range (a port range is specified as <low port number>:<high port number>). If you don't want to restrict client ports but want to specify something in the next column, enter "-" in this column. If you wish to specify a list of port number or ranges, separate the list elements with commas (with no embedded white space). Port numbers may be either integers or service names from /etc/services.</li> <li><b>ORIGINAL DEST</b> - This column may only be non-empty if the ACTION is DNAT or REDIRECT.<br> <br> If DNAT or REDIRECT is the ACTION and the ORIGINAL DEST column is left empty, any connection request arriving at the firewall from the SOURCE that matches the rule will be forwarded or redirected. This works fine for connection requests arriving from the internet where the firewall has only a single external IP address. When the firewall has multiple external IP addresses or when the SOURCE is other than the internet, there will usually be a desire for the rule to only apply to those connection requests directed to a particular IP address (see Example 2 below for another usage). That IP address (or a comma-separated list of such addresses) is specified in the ORIGINAL DEST column.<br> <br> The IP address may be optionally followed by ":" and a second IP address. This latter address, if present, is used as the source address for packets forwarded to the server (This is called "Source NAT" or SNAT).<br> <br> <b><font color="#ff6633">Note: </font> When using SNAT, it is a good idea to qualify the source with an IP address or subnet. Otherwise, it is likely that SNAT will occur on connections other than those described in the rule. The reason for this is that SNAT occurs in the Netfilter POSTROUTING hook where it is not possible to restrict the scope of a rule by incoming interface. <br> <br> </b>Example: DNAT loc<u>:192.168.1.0/24</u> loc:192.168.1.3 tcp www - 206.124.146.179:192.168.1.3<b><br> <br> </b>If SNAT is not used (no ":" and second IP address), the original source address is used. If you want any destination address to match the rule but want to specify SNAT, simply use a colon followed by the SNAT address.</li> </ul> <p><b> <font face="Century Gothic, Arial, Helvetica"> <a name="PortForward"></a> </font>Example 1. </b> You wish to forward all ssh connection requests from the internet to local system 192.168.1.3. </p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>DNAT</td> <td>net</td> <td>loc:192.168.1.3</td> <td>tcp</td> <td>ssh</td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p><b> Example 2. </b> You want to redirect all local www connection requests EXCEPT those to your own http server (206.124.146.177) to a Squid transparent proxy running on the firewall and listening on port 3128. Squid will of course require access to remote web servers. This example shows yet another use for the ORIGINAL DEST column; here, connection requests that were NOT <a href="#GettingStarted"> (notice the "!")</a> originally destined to 206.124.146.177 are redirected to local port 3128.</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>REDIRECT</td> <td>loc</td> <td>3128</td> <td>tcp</td> <td>www</td> <td> -<br> </td> <td>!206.124.146.177</td> </tr> <tr> <td>ACCEPT</td> <td>fw</td> <td>net</td> <td>tcp</td> <td>www</td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p><b>Example 3. </b> You want to run a web server at 155.186.235.222 in your DMZ and have it accessible remotely and locally. the DMZ is managed by Proxy ARP or by classical sub-netting.</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font><font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>ACCEPT</td> <td>net</td> <td>dmz:155.186.235.222</td> <td>tcp</td> <td>www</td> <td>-</td> <td> <br> </td> </tr> <tr> <td>ACCEPT</td> <td>loc</td> <td>dmz:155.186.235.222</td> <td>tcp</td> <td>www</td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p><b> Example 4. </b> You want to run wu-ftpd on 192.168.2.2 in your masqueraded DMZ. Your internet interface address is 155.186.235.151 and you want the FTP server to be accessible from the internet in addition to the local 192.168.1.0/24 and dmz 192.168.2.0/24 subnetworks. Note that since the server is in the 192.168.2.0/24 subnetwork, we can assume that access to the server from that subnet will not involve the firewall (<a href="FAQ.htm#faq2">but see FAQ 2</a>). Note that unless you have more than one external IP address, you can leave the ORIGINAL DEST column blank in the first rule. You cannot leave it blank in the second rule though because then <u>all ftp connections</u> originating in the local subnet 192.168.1.0/24 would be sent to 192.168.2.2 <u> regardless of the site that the user was trying to connect to</u>. That is clearly not what you want <img border="0" src="images/SY00079.gif" width="20" height="20" align="top"> .</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font><font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>DNAT</td> <td>net</td> <td>dmz:192.168.2.2</td> <td>tcp</td> <td>ftp</td> <td> <br> </td> <td> <br> </td> </tr> <tr> <td>DNAT</td> <td>loc:192.168.1.0/24</td> <td>dmz:192.168.2.2</td> <td>tcp</td> <td>ftp</td> <td>-</td> <td>155.186.235.151</td> </tr> </tbody> </table> </blockquote> <p>If you are running wu-ftpd, you should restrict the range of passive in your /etc/ftpaccess file. I only need a few simultaneous FTP sessions so I use port range 65500-65535. In /etc/ftpaccess, this entry is appropriate:</p> <blockquote> <p> passive ports 0.0.0.0/0 65500 65534</p> </blockquote> <p>If you are running pure-ftpd, you would include "-p 65500:65534" on the pure-ftpd runline.</p> <p>The important point here is to ensure that the port range used for FTP passive connections is unique and will not overlap with any usage on the firewall system.</p> <p><b>Example 5. </b>You wish to allow unlimited DMZ access to the host with MAC address 02:00:08:E3:FA:55.</p> <blockquote> <font face="Century Gothic, Arial, Helvetica"> </font> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>ACTION</b></td> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b> PROTO</b></td> <td><b>DEST<br> PORT(S)</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>ORIGINAL<br> DEST</b></td> </tr> <tr> <td>ACCEPT</td> <td>loc:~02-00-08-E3-FA-55</td> <td>dmz</td> <td>all</td> <td> <br> </td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <b>Example 6.</b> You wish to allow access to the SMTP server in your DMZ from all zones.<br> <blockquote> <table cellpadding="2" cellspacing="0" border="1"> <tbody> <tr> <td valign="top"><b>ACTION</b><br> </td> <td valign="top"><b>SOURCE<br> </b></td> <td valign="top"><b>DEST<br> </b></td> <td valign="top"><b>PROTO<br> </b></td> <td valign="top"><b>DEST<br> PORT(S)<br> </b></td> <td valign="top"><b>SOURCE<br> PORT(S)<br> </b></td> <td valign="top"><b>ORIGINAL<br> DEST<br> </b></td> </tr> <tr> <td valign="top">ACCEPT<br> </td> <td valign="top">all<br> </td> <td valign="top">dmz<br> </td> <td valign="top">tcp<br> </td> <td valign="top">25<br> </td> <td valign="top"><br> </td> <td valign="top"><br> </td> </tr> </tbody> </table> <br> Note: When 'all' is used as a source or destination, intra-zone traffic is not affected. In this example, if there were two DMZ interfaces then the above rule would NOT enable SMTP traffic between hosts on these interfaces.<br> </blockquote> <b>Example 7 (For advanced users running Shorewall version 1.3.13 or later). </b>From the internet, you with to forward tcp port 25 directed to 192.0.2.178 and 192.0.2.179 to host 192.0.2.177 in your DMZ. You also want to allow access from the internet directly to tcp port 25 on 192.0.2.177. <br> <blockquote> <table cellpadding="2" cellspacing="0" border="1"> <tbody> <tr> <td valign="top"><b>ACTION</b><br> </td> <td valign="top"><b>SOURCE<br> </b></td> <td valign="top"><b>DEST<br> </b></td> <td valign="top"><b>PROTO<br> </b></td> <td valign="top"><b>DEST<br> PORT(S)<br> </b></td> <td valign="top"><b>SOURCE<br> PORT(S)<br> </b></td> <td valign="top"><b>ORIGINAL<br> DEST<br> </b></td> </tr> <tr> <td valign="top">DNAT-<br> </td> <td valign="top">net<br> </td> <td valign="top">dmz:192.0.2.177<br> </td> <td valign="top">tcp<br> </td> <td valign="top">25<br> </td> <td valign="top">0<br> </td> <td valign="top">192.0.2.178<br> </td> </tr> <tr> <td valign="top">DNAT-<br> </td> <td valign="top">net<br> </td> <td valign="top">dmz:192.0.2.177<br> </td> <td valign="top">tcp<br> </td> <td valign="top">25<br> </td> <td valign="top">0<br> </td> <td valign="top">192.0.2.179<br> </td> </tr> <tr> <td valign="top">ACCEPT<br> </td> <td valign="top">net<br> </td> <td valign="top">dmz:192.0.2.177<br> </td> <td valign="top">tcp<br> </td> <td valign="top">25<br> </td> <td valign="top"><br> </td> <td valign="top"><br> </td> </tr> </tbody> </table> </blockquote> Using "DNAT-" rather than "DNAT" avoids two extra copies of the third rule from being generated.<br> <p><a href="ports.htm">Look here for information on other services.</a> </p> <h2><a name="Common"> </a>/etc/shorewall/common</h2> <p>Shorewall allows definition of rules that apply between all zones. By default, these rules are defined in the file /etc/shorewall/common.def but may be modified to suit individual requirements. Rather than modify /etc/shorewall/common.def, you should copy that file to /etc/shorewall/common and modify that file.</p> <p>The /etc/shorewall/common file is expected to contain iptables commands; rather than running iptables directly, you should run it indirectly using the Shorewall function 'run_iptables'. That way, if iptables encounters an error, the firewall will be safely stopped.</p> <h2><a name="Masq"></a> /etc/shorewall/masq</h2> <p>The /etc/shorewall/masq file is used to define classical IP Masquerading and Source Network Address Translation (SNAT). There is one entry in the file for each subnet that you want to masquerade. In order to make use of this feature, you must have <a href="#NatEnabled">NAT enabled</a> .</p> <p> Columns are:</p> <ul> <li><b> INTERFACE</b> - The interface that will masquerade the subnet; this is normally your internet interface. This interface name can be optionally qualified by adding ":" and a subnet or host IP. When this qualification is added, only packets addressed to that host or subnet will be masqueraded. Beginning with Shorewall version 1.3.14, if you have set ADD_SNAT_ALIASES=Yes in <a href="#Conf">/etc/shorewall/shorewall.conf</a>, you can cause Shorewall to create an alias <i>label </i>of the form <i>interfacename:digit </i>(e.g., eth0:0) by placing that label in this column. See example 5 below. Alias labels created in this way allow the alias to be visible to the ipconfig utility. <b>THAT IS THE ONLY THING THAT THIS LABEL IS GOOD FOR AND IT MAY NOT APPEAR ANYWHERE ELSE IN YOUR SHOREWALL CONFIGURATION.</b></li> <li><b> SUBNET</b> - The subnet that you want to have masqueraded through the INTERFACE. This may be expressed as a single IP address, a subnet or an interface name. In the latter instance, the interface must be configured and started before Shorewall is started as Shorewall will determine the subnet based on information obtained from the 'ip' utility. <b><font color="#ff0000">When using Shorewall 1.3.13 or earlier, when an interface name is specified, Shorewall will only masquerade traffic from the first subnetwork on the named interface; if the interface interfaces to more that one subnetwork, you will need to add additional entries to this file for each of those other subnetworks. Beginning with Shorewall 1.3.14, shorewall will masquerade/SNAT traffic from any host that is routed through the named interface.</font></b><br> <br> The subnet may be optionally followed by "!' and a comma-separated list of addresses and/or subnets that are to be excluded from masquerading.</li> <li><b>ADDRESS</b> - The source address to be used for outgoing packets. This column is optional and if left blank, the current primary IP address of the interface in the first column is used. If you have a static IP on that interface, listing it here makes processing of output packets a little less expensive for the firewall. If you specify an address in this column, it must be an IP address configured on the INTERFACE or you must have ADD_SNAT_ALIASES enabled in <a href="#Conf">/etc/shorewall/shorewall.conf.</a></li> </ul> <p><b> Example 1: </b> You have eth0 connected to a cable modem and eth1 connected to your local subnetwork 192.168.9.0/24. Your /etc/shorewall/masq file would look like: </p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> INTERFACE</b></td> <td><b> SUBNET</b></td> <td><b>ADDRESS</b></td> </tr> <tr> <td>eth0</td> <td>192.168.9.0/24</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p><b> Example 2:</b> You have a number of IPSEC tunnels through ipsec0 and you want to masquerade traffic from your 192.168.9.0/24 subnet to the remote subnet 10.1.0.0/16 only.</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> INTERFACE</b></td> <td><b> SUBNET</b></td> <td><b>ADDRESS</b></td> </tr> <tr> <td>ipsec0:10.1.0.0/16</td> <td>192.168.9.0/24</td> <td> <br> </td> </tr> </tbody> </table> </blockquote> <p><b> Example 3:</b> You have a DSL line connected on eth0 and a local network (192.168.10.0/24) connected to eth1. You want all local->net connections to use source address 206.124.146.176.</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> INTERFACE</b></td> <td><b> SUBNET</b></td> <td><b>ADDRESS</b></td> </tr> <tr> <td>eth0</td> <td>192.168.10.0/24</td> <td>206.124.146.176</td> </tr> </tbody> </table> </blockquote> <p><b>Example 4: </b> Same as example 3 except that you wish to exclude 192.168.10.44 and 192.168.10.45 from the SNAT rule.</p> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> INTERFACE</b></td> <td><b> SUBNET</b></td> <td><b>ADDRESS</b></td> </tr> <tr> <td>eth0</td> <td>192.168.10.0/24!192.168.10.44,192.168.10.45</td> <td>206.124.146.176</td> </tr> </tbody> </table> </blockquote> <b>Example 5 (Shorewall version >= 1.3.14): </b>You have a second IP address (206.124.146.177) assigned to you and wish to use it for SNAT of the subnet 192.168.12.0/24. You want to give that address the name eth0:0. You must have ADD_SNAT_ALIASES=Yes in <a href="#Conf">/etc/shorewall/shorewall.conf</a>.<br> <blockquote> <table border="1" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> INTERFACE</b></td> <td><b> SUBNET</b></td> <td><b>ADDRESS</b></td> </tr> <tr> <td>eth0:0</td> <td>192.168.12.0/24</td> <td>206.124.146.177</td> </tr> </tbody> </table> </blockquote> <h2><font color="#660066"><b><a name="ProxyArp"></a> </b></font>/etc/shorewall/proxyarp</h2> <p>If you want to use proxy ARP on an entire sub-network, I suggest that you look at <a href="http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/"> http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/</a>. If you decide to use the technique described in that HOWTO, you can set the proxy_arp flag for an interface (/proc/sys/net/ipv4/conf/<i><interface></i>/proxy_arp) by including the <b> proxyarp</b> option in the interface's record in <a href="#Interfaces"> /etc/shorewall/interfaces</a>. When using Proxy ARP sub-netting, you do <u>NOT</u> include any entries in /etc/shorewall/proxyarp. </p> <p>The /etc/shorewall/proxyarp file is used to define <a href="ProxyARP.htm">Proxy ARP</a>. The file is typically used for enabling Proxy ARP on a small set of systems since you need one entry in this file for each system using proxy ARP. Columns are:</p> <ul> <li><b> ADDRESS</b> - address of the system.</li> <li><b> INTERFACE</b> - the interface that connects to the system. If the interface is obvious from the subnetting, you may enter "-" in this column.</li> <li><b> EXTERNAL</b> - the external interface that you want to honor ARP requests for the ADDRESS specified in the first column.</li> <li><b>HAVEROUTE</b> - If you already have a route through INTERFACE to ADDRESS, this column should contain "Yes" or "yes". If you want Shorewall to add the route, the column should contain "No" or "no".</li> </ul> <p><font color="#cc6666"><b>Note: After you have made a change to the /etc/shorewall/proxyarp file, you may need to flush the ARP cache of all routers on the LAN segment connected to the interface specified in the EXTERNAL column of the change/added entry(s). If you are having problems communicating between an individual host (A) on that segment and a system whose entry has changed, you may need to flush the ARP cache on host A as well.</b></font></p> <p><font color="#cc6666"><b>ISPs typically have ARP configured with long TTL (hours!) so if your ISPs router has a stale cache entry (as seen using "tcpdump -nei <external interface> host <IP addr>"), it may take a long while to time out. I personally have had to contact my ISP and ask them to delete a stale entry in order to restore a system to working order after changing my proxy ARP settings. </b></font></p> <p><b>Example: </b> You have public IP addresses 155.182.235.0/28. You configure your firewall as follows:</p> <ul> <li>eth0 - 155.186.235.1 (internet connection)</li> <li>eth1 - 192.168.9.0/24 (masqueraded local systems)</li> <li>eth2 - 192.168.10.1 (interface to your DMZ)</li> </ul> <p> In your DMZ, you want to install a Web/FTP server with public address 155.186.235.4. On the Web server, you subnet just like the firewall's eth0 and you configure 155.186.235.1 as the default gateway. In your /etc/shorewall/proxyarp file, you will have:</p> <blockquote> <table border="2" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b> ADDRESS</b></td> <td><b> INTERFACE</b></td> <td><b> EXTERNAL</b></td> <td><b>HAVEROUTE</b></td> </tr> <tr> <td>155.186.235.4</td> <td>eth2</td> <td>eth0</td> <td>No</td> </tr> </tbody> </table> </blockquote> <p> Note: You may want to configure the servers in your DMZ with a subnet that is smaller than the subnet of your internet interface. See the Proxy ARP Subnet Mini HOWTO (<a href="http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/">http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/</a>) for details. In this case you will want to place "Yes" in the HAVEROUTE column.</p> <p>To learn how I use Proxy ARP in my DMZ, see <a href="myfiles.htm">my configuration files</a>.</p> <p><font color="#ff6633"><b>Warning: </b></font>Do not use Proxy ARP and FreeS/Wan on the same system unless you are prepared to suffer the consequences. If you start or restart Shorewall with an IPSEC tunnel active, the proxied IP addresses are mistakenly assigned to the IPSEC tunnel device (ipsecX) rather than to the interface that you specify in the INTERFACE column of /etc/shorewall/proxyarp. I haven't had the time to debug this problem so I can't say if it is a bug in the Kernel or in FreeS/Wan. </p> <p>You <b>might</b> be able to work around this problem using the following (I haven't tried it):</p> <p>In /etc/shorewall/init, include:</p> <p> qt service ipsec stop</p> <p>In /etc/shorewall/start, include:</p> <p> qt service ipsec start</p> <h2><font color="#660066"><b><a name="NAT"></a> </b></font>/etc/shorewall/nat</h2> <p>The /etc/shorewall/nat file is used to define static NAT. There is one entry in the file for each static NAT relationship that you wish to define. In order to make use of this feature, you must have <a href="#NatEnabled">NAT enabled</a> .</p> <p> <font color="#ff0000"> <b>IMPORTANT: If all you want to do is forward ports to servers behind your firewall, you do NOT want to use static NAT. Port forwarding can be accomplished with simple entries in the <a href="#Rules"> rules file</a>. Also, in most cases <a href="#ProxyArp"> Proxy ARP</a> provides a superior solution to static NAT because the internal systems are accessed using the same IP address internally and externally.</b></font></p> <p>Columns in an entry are:</p> <ul> <li><b> EXTERNAL</b> - External IP address - <u>This should NOT be the primary IP address of the interface named in the next column.</u></li> <li><b> INTERFACE</b> - Interface that you want the EXTERNAL IP address to appear on. Beginning with Shorewall version 1.3.14, if you have set ADD_IP_ALIASES=Yes in <a href="#Conf">/etc/shorewall/shorewall.conf</a>, �you can specify an alias label of the form <i>interfacename:digit </i>(e.g., eth0:0) and Shorewall will create the alias with that label. Alias labels created in this way allow the alias to be visible to the ipconfig utility. <b>THAT IS THE ONLY THING THAT THIS LABEL IS GOOD FOR AND IT MAY NOT APPEAR ANYWHERE ELSE IN YOUR SHOREWALL CONFIGURATION.</b>�</li> <li><b> INTERNAL </b> - Internal IP address.</li> <li><b>ALL INTERFACES</b> - If Yes or yes (or left empty), NAT will be effective from all hosts. If No or no then NAT will be effective only through the interface named in the INTERFACE column. <b> Note:</b> If two or more NATed systems are connected to the same firewall interface and you want them to be able to communicate using their EXTERNAL IP addresses, then you will want to specify the <b>multi</b> option in the <a href="#Interfaces">/etc/shorewall/interface</a> entry for that interface.</li> <li><b>LOCAL</b> - If Yes or yes and the ALL INTERFACES column contains Yes or yes, NAT will be effective from the firewall system. <b>Note: </b>For this to work, you must be running kernel 2.4.19 or later and iptables 1.2.6a or later and you must have enabled <b>CONFIG_IP_NF_NAT_LOCAL</b> in your kernel.</li> </ul> <p><b><a href="NAT.htm"> Look here for additional information and an example.</a> </b></p> <h2><font color="#660066"><a name="Tunnels"></a> </font>/etc/shorewall/tunnels</h2> <p> The /etc/shorewall/tunnels file allows you to define IPSec, GRE, IPIP, <a href="http://openvpn.sourceforge.net/">OpenVPN</a> and PPTP tunnels with end-points on your firewall. To use ipsec, you must install version 1.9, 1.91 or the current <a href="http://www.xs4all.nl/%7Efreeswan/">FreeS/WAN</a> development snapshot. </p> <p> Note: For kernels 2.4.4 and above, you will need to use version 1.91 or a development snapshot as patching with version 1.9 results in kernel compilation errors.</p> <p><b><a href="IPSEC.htm"> Instructions for setting up IPSEC tunnels may be found here,</a></b> <b><a href="IPIP.htm">instructions for IPIP and GRE tunnels are here</a> </b>and <b><a href="PPTP.htm">instructions for PPTP tunnels are here</a>.</b></p> <h2><a name="Conf"></a>/etc/shorewall/shorewall.conf</h2> <p> This file is used to set the following firewall parameters:</p> <ul> <li><b>OLD_PING_HANDLING - </b>Added at version 1.3.14.<br> If this option is set to 'Yes' then the old and confusing ICMP echo-request (Ping) handling is enabled. This includes the 'noping' and 'filterping' interface options and the FORWARDPING option below. If this option is set to "No" then ping requests are handled using rules and policies just like any other connection request. For upward compatibility with only configurations, if this option is omitted OLD_PING_HANDLING=Yes is assumed. New Shorewall users should leave this option set to "No".<br> <br> For a complete description of how ping handling works under Shorewall, see <a href="ping.html">ping.html</a>.<br> <br> </li> <li><b>CLEAR_TC</b> - Added at version 1.3.13<br> If this option is set to 'No' then Shorewall won't clear the current traffic control rules during [re]start. This setting is intended for use by people that prefer to configure traffic shaping when the network interfaces come up rather than when the firewall is started. If that is what you want to do, set TC_ENABLED=Yes and CLEAR_TC=No and do not supply an /etc/shorewall/tcstart file. That way, your traffic shaping rules can still use the 'fwmark' classifier based on packet marking defined in /etc/shorewall/tcrules. If not specified, CLEAR_TC=Yes is assumed.<br> </li> <li><b>MARK_IN_FORWARD_CHAIN </b>- Added at version 1.3.12<br> If your kernel has a FORWARD chain in the mangle table, you may set MARK_IN_FORWARD_CHAIN=Yes to cause the marking specified in the <a href="traffic_shaping.htm#tcrules">tcrules file</a> to occur in that chain rather than in the PREROUTING chain. This permits you to mark inbound traffic based on its destination address when SNAT or Masquerading are in use. To determine if your kernel has a FORWARD chain in the mangle table, use the "/sbin/shorewall show mangle" command; if a FORWARD chain is displayed then your kernel will support this option. If this option is not specified or if it is given the empty value (e.g., MARK_IN_FORWARD_CHAIN="") then MARK_IN_FORWARD_CHAIN=No is assumed.<br> </li> <li><b>RFC1918_LOG_LEVEL - </b>Added at version 1.3.12<br> This parameter determines the level at which packets logged under the <a href="Documentation.htm#rfc1918">'norfc1918' mechanism </a> are logged. The value must be a valid <a href="shorewall_logging.html">syslog level</a> and if no level is given, then info is assumed. Prior to Shorewall version 1.3.12, these packets are always logged at the info level.</li> <li><b>TCP_FLAGS_DISPOSITION - </b>Added in Version 1.3.11<br> Determines the disposition of TCP packets that fail the checks enabled by the <a href="#Interfaces%5C">tcpflags</a> interface option and must have a value of ACCEPT (accept the packet), REJECT (send an RST response) or DROP (ignore the packet). If not set or if set to the empty value (e.g., TCP_FLAGS_DISPOSITION="") then TCP_FLAGS_DISPOSITION=DROP is assumed.</li> <li><b>TCP_FLAGS_LOG_LEVEL - </b>Added in Version 1.3.11<br> Determines the <a href="shorewall_logging.html">syslog level</a> for logging packets that fail the checks enabled by the <a href="#Interfaces">tcpflags</a> interface option.The value must be a valid syslogd log level. If you don't want to log these packets, set to the empty value (e.g., TCP_FLAGS_LOG_LEVEL="").<br> </li> <li><b>MACLIST_DISPOSITION </b>- Added in Version 1.3.10<br> Determines the disposition of connections requests that fail <a href="MAC_Validation.html">MAC Verification</a> and must have the value ACCEPT (accept the connection request anyway), REJECT (reject the connection request) or DROP (ignore the connection request). If not set or if set to the empty value (e.g., MACLIST_DISPOSITION="") then MACLIST_DISPOSITION=REJECT is assumed.</li> <li><b>MACLIST_LOG_LEVEL </b>- Added in Version 1.3.10<br> Determines the <a href="shorewall_logging.html">syslog level</a> for logging connection requests that fail <a href="MAC_Validation.html">MAC Verification</a>. The value must be a valid syslogd log level. If you don't want to log these connection requests, set to the empty value (e.g., MACLIST_LOG_LEVEL="").<br> </li> <li><b>NEWNOTSYN </b>- Added in Version 1.3.8<br> When set to "Yes" or "yes", Shorewall will filter TCP packets that are not part of an established connention and that are not SYN packets (SYN flag on - ACK flag off). If set to "No", Shorewall will silently drop such packets. If not set or set to the empty value (e.g., "NEWNOTSYN="), NEWNOTSYN=No is assumed.<br> <br> If you have a HA setup with failover to another firewall, you should have NEWNOTSYN=Yes on both firewalls. You should also select NEWNOTSYN=Yes if you have asymmetric routing.<br> </li> <li><b>FORWARDPING</b> - Added in Version 1.3.7 - <b>This option is deprecated and is not available when OLD_PING_HANDLING=No (see above).</b><br> When set to "Yes" or "yes", ICMP echo-request (ping) packets from interfaces that specify "filterping" are ACCEPTed by the firewall. When set to "No" or "no", such ping requests are silently dropped unless they are handled by an explicit entry in the <a href="#Rules">rules file</a>. If not specified, "No" is assumed.�</li> <li><b>LOGNEWNOTSYN</b> - Added in Version 1.3.6<br> Beginning with version 1.3.6, Shorewall drops non-SYN TCP packets that are not part of an existing connection. If you would like to log these packets, set LOGNEWNOTSYN to the <a href="shorewall_logging.html">syslog level</a> at which you want the packets logged. Example: LOGNEWNOTSYN=ULOG|<br> <br> <b>Note: </b>Packets logged under this option are usually the result of broken remote IP stacks rather than the result of any sort of attempt to breach your firewall.<br> </li> <li><b>MERGE_HOSTS </b>- Added in Version 1.3.5<br> Prior to 1.3.5, when the <a href="#Hosts">/etc/shorewall/hosts</a> file included an entry for a zone then the entire zone had to be defined in the /etc/shorewall/hosts file and any associations between the zone and interfaces in the <a href="#Interfaces">/etc/shorewall/interfaces</a> file were ignored. This behavior is preserved if MERGE_HOSTS=No or if MERGE_HOSTS is not set or is set to the empty value.<br> <br> Beginning with version 1.3.5, if MERGE_HOSTS=Yes, then zone assignments in the /etc/shorewall/hosts file are ADDED to those in the /etc/shorewall/interfaces file. <br> <br> Example:<br> <br> Interfaces File:<br> <table border="1" cellpadding="2" style="border-collapse: collapse;" id="AutoNumber2"> <tbody> <tr> <td><u><b>ZONE</b></u></td> <td><u><b>HOSTS</b></u></td> <td><u><b>BROADCAST</b></u></td> <td><u><b>OPTIONS</b></u></td> </tr> <tr> <td>loc</td> <td>eth1</td> <td>-</td> <td>dhcp</td> </tr> <tr> <td>-</td> <td>ppp+</td> <td> <br> </td> <td> <br> </td> </tr> </tbody> </table> <p><br> Hosts File:<br> </p> <table border="1" cellpadding="2" style="border-collapse: collapse;" id="AutoNumber3"> <tbody> <tr> <td><u><b>ZONE</b></u></td> <td><u><b>HOSTS</b></u></td> </tr> <tr> <td>loc</td> <td>ppp+:192.168.12.0/24</td> </tr> </tbody> </table> <p><font face="Courier"><br> </font>With MERGE_HOSTS=No, the<b> loc</b> zone consists of only ppp+:192.168.12.0/24; with MERGE_HOSTS=Yes, it includes eth1:0.0.0.0/0 and ppp+:192.168.12.0/24.<br> </p> </li> <li><b>DETECT_DNAT_ADDRS</b> - Added in Version 1.3.4<br> If set to "Yes" or "yes", Shorewall will detect the IP address(es) of the interface(es) to the source zone and will include this (these) address(es) in DNAT rules as the original destination IP address. If set to "No" or "no", Shorewall will not detect this (these) address(es) and any destination IP address will match the DNAT rule. If not specified or empty, "DETECT_DNAT_ADDRS=Yes" is assumed.<br> </li> <li><b>MULTIPORT</b> - Added in Version 1.3.2<br> If set to "Yes" or "yes", Shorewall will use the Netfilter multiport facility. In order to use this facility, your kernel must have multiport support (CONFIG_IP_NF_MATCH_MULTIPORT). When this support is used, Shorewall will generate a single rule from each record in the /etc/shorewall/rules file that meets these criteria:<br> <ul> <li>No port range(s) specified</li> <li>Specifies 15 or fewer ports</li> </ul> <p>Rules not meeting those criteria will continue to generate an individual rule for each listed port or port range. </p> </li> <li><b>NAT_BEFORE_RULES</b><br> If set to "No" or "no", port forwarding rules can override the contents of the <a href="#NAT">/etc/shorewall/nat</a> file. If set to "Yes" or "yes", port forwarding rules cannot override static NAT. If not set or set to an empty value, "Yes" is assumed.</li> <li><b>FW<br> </b>This parameter specifies the name of the firewall zone. If not set or if set to an empty string, the value "fw" is assumed.</li> <li><b>SUBSYSLOCK</b><br> This parameter should be set to the name of a file that the firewall should create if it starts successfully and remove when it stops. Creating and removing this file allows Shorewall to work with your distribution's initscripts. For RedHat, this should be set to /var/lock/subsys/shorewall. For Debian, the value is /var/state/shorewall and in LEAF it is /var/run/shorwall. Example: SUBSYSLOCK=/var/lock/subsys/shorewall.</li> <li><b> STATEDIR</b><br> This parameter specifies the name of a directory where Shorewall stores state information. If the directory doesn't exist when Shorewall starts, it will create the directory. Example: STATEDIR=/tmp/shorewall.<br> <br> <b>NOTE:</b> If you change the STATEDIR variable while the firewall is running, create the new directory if necessary then copy the contents of the old directory to the new directory. </li> <li><b> ALLOWRELATED</b><br> This parameter must be assigned the value "Yes" ("yes") or "No" ("no") and specifies whether Shorewall allows connection requests that are related to an already allowed connection. If you say "No" ("no"), you can still override this setting by including "related" rules in /etc/shorewall/rules ("related" given as the protocol). If you specify ALLOWRELATED=No, you will need to include rules in <a href="shorewall_extension_scripts.htm">/etc/shorewall/icmpdef</a> to handle common ICMP packet types.</li> <li><b> MODULESDIR</b><br> This parameter specifies the directory where your kernel netfilter modules may be found. If you leave the variable empty, Shorewall will supply the value "/lib/modules/`uname -r`/kernel/net/ipv4/netfilter.</li> <li><b> LOGRATE </b> and <b> LOGBURST</b><br> These parameters set the match rate and initial burst size for logged packets. Please see the iptables man page for a description of the behavior of these parameters (the iptables option --limit is set by LOGRATE and --limit-burst is set by LOGBURST). If both parameters are set empty, no rate-limiting will occur.<br> <br> Example:<br> LOGRATE=10/minute<br> LOGBURST=5<br> </li> <li><b>LOGFILE</b><br> This parameter tells the /sbin/shorewall program where to look for Shorewall messages when processing the "show log", "monitor", "status" and "hits" commands. If not assigned or if assigned an empty value, /var/log/messages is assumed.</li> <li><b>NAT_ENABLED</b><br> This parameter determines whether Shorewall supports NAT operations. NAT operations include:<br> <br> Static NAT<br> Port Forwarding<br> Port Redirection<br> Masquerading<br> <br> If the parameter has no value or has a value of "Yes" or "yes" then NAT is enabled. If the parameter has a value of "no" or "No" then NAT is disabled.<br> </li> <li><b> MANGLE_ENABLED</b><br> This parameter determines if packet mangling is enabled. If the parameter has no value or has a value of "Yes" or "yes" than packet mangling is enabled. If the parameter has a value of "no" or "No" then packet mangling is disabled. If packet mangling is disabled, the /etc/shorewall/tos file is ignored.<br> </li> <li><b> IP_FORWARDING</b><br> This parameter determines whether Shorewall enables or disables IPV4 Packet Forwarding (/proc/sys/net/ipv4/ip_forward). Possible values are:<br> <br> On or on - packet forwarding will be enabled.<br> Off or off - packet forwarding will be disabled.<br> Keep or keep - Shorewall will neither enable nor disable packet forwarding.<br> <br> If this variable is not set or is given an empty value (IP_FORWARD="") then IP_FORWARD=On is assumed.<br> </li> <li><b>ADD_IP_ALIASES</b><br> This parameter determines whether Shorewall automatically adds the <i>external </i>address(es) in <a href="#NAT">/etc/shorewall/nat</a> . If the variable is set to "Yes" or "yes" then Shorewall automatically adds these aliases. If it is set to "No" or "no", you must add these aliases yourself using your distribution's network configuration tools.<br> <br> If this variable is not set or is given an empty value (ADD_IP_ALIASES="") then ADD_IP_ALIASES=Yes is assumed.</li> <li><b>ADD_SNAT_ALIASES</b><br> This parameter determines whether Shorewall automatically adds the SNAT <i> ADDRESS </i>in <a href="#Masq">/etc/shorewall/masq</a>. If the variable is set to "Yes" or "yes" then Shorewall automatically adds these addresses. If it is set to "No" or "no", you must add these addresses yourself using your distribution's network configuration tools.<br> <br> If this variable is not set or is given an empty value (ADD_SNAT_ALIASES="") then ADD_SNAT_ALIASES=No is assumed.<br> </li> <li><b>LOGUNCLEAN</b><br> This parameter determines the logging level of mangled/invalid packets controlled by the '<a href="#Unclean">dropunclean and logunclean</a>' interface options. If LOGUNCLEAN is empty (LOGUNCLEAN=) then packets selected by 'dropclean' are dropped silently ('logunclean' packets are logged under the 'info' log level). Otherwise, these packets are logged at the specified level (Example: LOGUNCLEAN=debug).</li> <li><b>BLACKLIST_DISPOSITION</b><br> This parameter determines the disposition of packets from blacklisted hosts. It may have the value DROP if the packets are to be dropped or REJECT if the packets are to be replied with an ICMP port unreachable reply or a TCP RST (tcp only). If you do not assign a value or if you assign an empty value then DROP is assumed.</li> <li><b>BLACKLIST_LOGLEVEL</b><br> This paremter determines if packets from blacklisted hosts are logged and it determines the syslog level that they are to be logged at. Its value is a <a href="shorewall_logging.html">syslog level</a> (Example: BLACKLIST_LOGLEVEL=debug). If you do not assign a value or if you assign an empty value then packets from blacklisted hosts are not logged.</li> <li><b>CLAMPMSS</b><br> This parameter enables the TCP Clamp MSS to PMTU feature of Netfilter and is usually required when your internet connection is through PPPoE or PPTP. If set to "Yes" or "yes", the feature is enabled. If left blank or set to "No" or "no", the feature is not enabled. Note: This option requires CONFIG_IP_NF_TARGET_TCPMSS <a href="kernel.htm">in your kernel</a>.</li> <li><b>ROUTE_FILTER</b><br> If this parameter is given the value "Yes" or "yes" then route filtering (anti-spoofing) is enabled on all network interfaces. The default value is "no".</li> </ul> <h2><a name="modules"></a> /etc/shorewall/modules Configuration</h2> <p>The file /etc/shorewall/modules contains commands for loading the kernel modules required by Shorewall-defined firewall rules. Shorewall will source this file during start/restart provided that it exists and that the directory specified by the MODULESDIR parameter exists (see <a href="#Conf">/etc/shorewall/shorewall.conf</a> above).</p> <p>The file that is released with Shorewall calls the Shorewall function "loadmodule" for the set of modules that I load.</p> <p>The <i>loadmodule</i> function is called as follows:</p> <blockquote> <p>loadmodule <i><modulename> </i>[ <i> <module parameters> </i>]</p> </blockquote> <p>where</p> <blockquote> <p><i><modulename> </i></p> <blockquote> <p>is the name of the modules without the trailing ".o" (example ip_conntrack).</p> </blockquote> <p><i> <module parameters></i></p> <blockquote> <p> Optional parameters to the insmod utility.</p> </blockquote> </blockquote> <p> The function determines if the module named by <i><modulename> </i> is already loaded and if not then the function determines if the ".o" file corresponding to the module exists in the <i>moduledirectory</i>; if so, then the following command is executed:</p> <blockquote> <p> insmod <i>moduledirectory</i>/<i><modulename></i>.o <i><module parameters></i></p> </blockquote> <p> If the file doesn't exist, the function determines of the ".o.gz" file corresponding to the module exists in the <i>moduledirectory</i>. If it does, the function assumes that the running configuration supports compressed modules and execute the following command:</p> <blockquote> <p> insmod <i>moduledirectory/<modulename>.</i>o.gz <<i>module parameters></i></p> </blockquote> <h2><a name="TOS"></a> /etc/shorewall/tos Configuration</h2> <p> The /etc/shorewall/tos file allows you to set the Type of Service field in packet headers based on packet source, packet destination, protocol, source port and destination port. In order for this file to be processed by Shorewall, you must have <a href="#MangleEnabled">mangle support enabled</a> .</p> <p> Entries in the file have the following columns:</p> <ul> <li><b> SOURCE</b> -- The source zone. May be qualified by following the zone name with a colon (":") and either an IP address, an IP subnet, a MAC address in <a href="#MAC">Shorewall Format</a> or the name of an interface. This column may also contain the <a href="#FW">name of the firewall</a> zone to indicate packets originating on the firewall itself or "all" to indicate any source.</li> <li><b> DEST</b> -- The destination zone. May be qualified by following the zone name with a colon (":") and either an IP address or an IP subnet. Because packets are marked prior to routing, you may not specify the name of an interface. This column may also contain "all" to indicate any destination.</li> <li><b> PROTOCOL</b> -- The name of a protocol in /etc/protocols or the protocol's number.</li> <li><b> SOURCE PORT(S)</b> -- The source port or a port range. For all ports, place a hyphen ("-") in this column.</li> <li><b> DEST PORT(S)</b> -- The destination port or a port range. To indicate all ports, place a hyphen ("-") in this column.</li> <li><b> TOS</b> -- The type of service. Must be one of the following:</li> </ul> <blockquote> <blockquote> <p> Minimize-Delay (16)<br> Maximize-Throughput (8)<br> Maximize-Reliability (4)<br> Minimize-Cost (2)<br> Normal-Service (0)</p> </blockquote> </blockquote> <p> The /etc/shorewall/tos file that is included with Shorewall contains the following entries.</p> <blockquote> <table border="2" cellpadding="2" style="border-collapse: collapse;"> <tbody> <tr> <td><b>SOURCE</b></td> <td><b>DEST</b></td> <td><b>PROTOCOL</b></td> <td><b>SOURCE<br> PORT(S)</b></td> <td><b>DEST PORT(S)</b></td> <td><b>TOS</b></td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>-</td> <td>ssh</td> <td>16</td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>ssh</td> <td>-</td> <td>16</td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>-</td> <td>ftp</td> <td>16</td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>ftp</td> <td>-</td> <td>16</td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>-</td> <td>ftp-data</td> <td>8</td> </tr> <tr> <td>all</td> <td>all</td> <td>tcp</td> <td>ftp-data</td> <td>-</td> <td>8</td> </tr> </tbody> </table> </blockquote> <p><b>WARNING: </b>Users have reported that odd routing problems result from adding the ESP and AH protocols to the /etc/shorewall/tos file. </p> <h2><a name="Blacklist"></a>/etc/shorewall/blacklist</h2> <p>Each line in /etc/shorewall/blacklist contains an IP address, a MAC address in <a href="#MAC">Shorewall Format</a> or subnet address. Example:</p> <pre> 130.252.100.69<br> 206.124.146.0/24</pre> <p>Packets <u><b>from</b></u> hosts listed in the blacklist file will be disposed of according to the value assigned to the <a href="#Conf">BLACKLIST_DISPOSITION</a> and <a href="#Conf">BLACKLIST_LOGLEVEL </a>variables in /etc/shorewall/shorewall.conf. Only packets arriving on interfaces that have the '<a href="#Interfaces">blacklist</a>' option in /etc/shorewall/interfaces are checked against the blacklist. The black list is designed to prevent listed hosts/subnets from accessing services on <u><b>your</b></u> network.<br> </p> <p>Beginning with Shorewall 1.3.8, the blacklist file has three columns:<br> </p> <ul> <li><b>ADDRESS/SUBNET - </b>As described above.</li> <li><b>PROTOCOL</b> - Optional. If specified, only packets specifying this protocol will be blocked.</li> <li><b>PORTS - </b>Optional; may only be given if PROTOCOL is tcp, udp or icmp. Expressed as a comma-separated list of port numbers or service names (from /etc/services). If present, only packets destined for the specified protocol and one of the listed ports are blocked. When the PROTOCOL is icmp, the PORTS column contains a comma-separated list of ICMP type numbers or names (see "iptables -h icmp").<br> </li> </ul> <p>Shorewall also has a <a href="blacklisting_support.htm">dynamic blacklist capability.</a></p> <p><font color="#cc6666"><b>IMPORTANT: The Shorewall blacklist file is <u>NOT</u> designed to police your users' web browsing -- to do that, I suggest that you install and configure Squid (<a href="http://www.squid-cache.org">http://www.squid-cache.org</a>). </b></font></p> <h2><a name="rfc1918"></a>/etc/shorewall/rfc1918 (Added in Version 1.3.1)</h2> <p>This file lists the subnets affected by the <a href="#Interfaces"><i>norfc1918</i> interface option</a>. Columns in the file are:</p> <ul> <li><b>SUBNET</b> - The subnet using VLSM notation (e.g., 192.168.0.0/16).</li> <li><b>TARGET<i> </i></b>- What to do with packets to/from the SUBNET: <ul> <li><b>RETURN</b> - Process the packet normally thru the rules and policies.</li> <li><b>DROP</b> - Silently drop the packet.</li> <li><b>logdrop</b> - Log then drop the packet -- see the <a href="#Conf">RFC1918_LOG_LEVEL</a> parameter above.</li> </ul> </li> </ul> <h2><a name="Routestopped"></a>/etc/shorewall/routestopped (Added in Version 1.3.4)</h2> <p>This file defines the hosts that are accessible from the firewall when the firewall is stopped. Columns in the file are:</p> <ul> <li><b>INTERFACE </b>- The firewall interface through which the host(s) comminicate with the firewall.</li> <li><b>HOST(S) </b>- (Optional) - A comma-separated list of IP/Subnet addresses. If not supplied or supplied as "-" then 0.0.0.0/0 is assumed.</li> </ul> <p>Example: When your firewall is stopped, you want firewall accessibility from local hosts 192.168.1.0/24 and from your DMZ. Your DMZ interfaces through eth1 and your local hosts through eth2.</p> <blockquote> <table border="2" style="border-collapse: collapse;" id="AutoNumber1" cellpadding="2"> <tbody> <tr> <td><u><b>INTERFACE</b></u></td> <td><u><b>HOST(S)</b></u></td> </tr> <tr> <td>eth2</td> <td>192.168.1.0/24</td> </tr> <tr> <td>eth1</td> <td>-</td> </tr> </tbody> </table> </blockquote> <h2><a name="Maclist"></a>/etc/shorewall/maclist (Added in Version 1.3.10)</h2> This file is described in the <a href="MAC_Validation.html">MAC Validation Documentation</a>.<br> <br> <p><font size="-1"> Updated 1/31/2003 - <a href="support.htm">Tom Eastep</a> </font></p> <p><a href="copyright.htm"><font size="2">Copyright</font> � <font size="2">2001, 2002, 2003 Thomas M. Eastep.</font></a><br> <br> </p> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> </body> </html>