Copyright © 2001-2005 Thomas M. Eastep
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
2005-11-15
Abstract
This documentation is intended primarily for reference. Step-by-step instructions for configuring Shorewall in common setups may be found in the QuickStart Guides.
Table of Contents
Shorewall consists of the following components:
a parameter file installed in /etc/shorewall that can be used to
establish the values of shell variables for use in other
files.
a parameter file installed in /etc/shorewall that is used to set
several firewall parameters.
a parameter file installed in /etc/shorewall that defines a network
partitioning into “zones”
a parameter file installed in /etc/shorewall that establishes overall
firewall policy.
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.
a parameter file installed in /etc/shorewall and used to list
blacklisted IP/subnet/MAC addresses.
a parameter file installed in /etc/shorewall and used to selectively
disable Explicit Congestion Notification (ECN - RFC 3168).
a set of shell functions used by both the firewall and
shorewall shell programs. Installed in /usr/share/shorewall.
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.
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.
a shell script installed in /etc/init.d to automatically start
Shorewall during boot. The particular script installed depends on
which distribution you are running.
a parameter file installed in /etc/shorewall and used to describe the
interfaces on the firewall system.
a parameter file installed in /etc/shorewall and used to describe
individual hosts or subnetworks in zones.
a parameter file installed in /etc/shorewall and used to describe
ipsec policies associated with zones.
a parameter file installed in /etc/shorewall and used to verify the
MAC address (and possibly also the IP address(es)) of
devices.
This file also describes IP masquerading under Shorewall and
is installed in /etc/shorewall.
a shell program that reads the configuration files in
/etc/shorewall and configures
your firewall. This file is installed in /usr/share/shorewall.
a parameter file in /etc/shorewall used to define one-to-one NAT.
a parameter file in /etc/shorewall used to define Proxy Arp.
a parameter file in /usr/share/shorewall used to define the
treatment of packets under the norfc1918
interface option.
a parameter file in /usr/share/shorewall used to define the
treatment of packets under the nobogons
interface option.
a parameter file in /etc/shorewall used to define those
hosts that can access the firewall when Shorewall is stopped.
a parameter file in /etc/shorewall
used to define rules for classifying packets for Traffic Shaping/Control.
a parameter file in /etc/shorewall used to define IPSec
tunnels.
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).
a parameter file in /etc/shorewall used to define traffic
accounting rules. This file was added in version 1.4.7.
a file created in /usr/share/shorewall that describes the
version of Shorewall installed on your system.
files in /etc/shorewall
and /usr/share/shorewall
respectively that allow you to define your own actions for rules in
/etc/shorewall/rules.
files in /usr/share/shorewall that define the
actions included as a standard part of Shorewall.
file in /etc/shorewall that is used to define multiple Internet Service Providers and load-balancing.
file in /etc/shorewall that is used to interface to the experimental ROUTE target from Netfilter patch-o-matic-ng.
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.
It is suggested that variable names begin with an upper case letter to distinguish them from variables used internally within the Shorewall programs
The result will be the same as if the record had been written
net eth0 130.252.100.255 blacklist,norfc1918
Variables may be used anywhere in the other configuration files.
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:
short name for the zone. The name should be 5 characters or less in length (4 characters or less if you are running Shorewall 1.4.4 or later) 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 /etc/shorewall/shorewall.conf.
The name of the zone as displayed during Shorewall startup.
Any comments that you want to make about the zone. Shorewall ignores these comments.
#ZONE DISPLAY COMMENTS net Net Internet loc Local Local networks dmz DMZ Demilitarized zone
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.
If you rename or delete a zone, you should perform “shorewall stop; shorewall start” to install the change rather than “shorewall restart”.
The order of entries in the
/etc/shorewall/zones file is significant in some cases.
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:
A zone defined in the /etc/shorewall/zones file or “-”. If you specify “-”, you must use the /etc/shorewall/hosts file to define the zones accessed via this interface.
the name of the interface (examples: eth0, ppp0, ipsec+). Each interface can be listed on only one record in this file.
You do not need to include the loopback interface (lo) in this file.
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”:
the interface must be up before you start your firewall
the interface must only be attached to a single sub-network (i.e., there must have a single broadcast address).
a comma-separated list of options. Possible options include:
(Added in version 1.4.7) - This option causes
/proc/sys/net/ipv4/conf/<interface>/arp_filter
to be set with the result that this interface will only answer
ARP “who-has” requests from hosts that are routed
out of that interface. Setting this option facilitates testing
of your firewall where multiple firewall interfaces are
connected to the same HUB/Switch (all interface connected to
the single HUB/Switch should have this option specified). Note
that using such a configuration in a production environment is
strongly recommended against.
(Added in version 1.4.6) - This option overrides NEWNOTSYN=No for packets arriving on this interface. In other words, packets coming in on this interface are processed as if NEWNOTSYN=Yes had been specified in /etc/shorewall/shorewall.conf.
(Added in version 1.4.2) - This option causes Shorewall to set up handling for routing packets that arrive on this interface back out the same interface. If this option is specified, the ZONE column may not contain “-”.
(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 /etc/shorewall/shorewall.conf and are disposed of according to the TCP_FLAGS_DISPOSITION option.
This option causes incoming packets on this interface to be checked against the blacklist.
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 norfc1918 option (see below).
Packets arriving on this interface and that have a source or destination address that is reserved in RFC 1918 will be dropped after being optionally logged.
Prior to Shorewall 2.0.1, addresses blocked by the standard rfc1918 file include those addresses reserved by RFC1918 plus other ranges reserved by the IANA or by other RFCs. Beginning with Shorewall 2.0.1, these additional addresses are covered by the nobogons option below.
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 norfc1918 on your external interface but need to allow access to certain addresses from the above list, see FAQ 14.
Packets arriving on this interface that have a source address reserved by the IANA or by other RFCs (other than 1918) are dropped after being optionally logged. See the /etc/shorewall/bogons file documentation below.
I personally recommend against using the nobogons option. The IPV4 address space is being rapidly depleated so the benefit of blocking traffic from unallocated address ranges is minimal. Plus the rate at which address blocks are being assigned causes your /etc/shorewall/bogons file to become out of date with the result that legitimate traffic gets blocked.
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.
If you specify this option for an interface then the interface must be up prior to starting the firewall.
(Added in version 1.3.5) - This option causes Shorewall to set /proc/sys/net/ipv4/conf/<interface>/proxy_arp and is used when implementing Proxy ARP Sub-netting as described at http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet/. Do not set this option if you are implementing Proxy ARP through entries in /etc/shorewall/proxyarp.
(Added in version 1.3.10) - If this option is specified, all connection requests from this interface are subject to MAC Verification. May only be specified for ethernet interfaces.
(Added in version 1.4.10) - If this option is specified, the zone named in the ZONE column will contain only the hosts routed through the interface named in the INTERFACE column. Do not set this option on your external (Internet) interface! The interface must be in the UP state when Shorewall is [re]started.
(Added in version 2.0.0) - If this option is specified, incoming connection requests will be checked to ensure that they do not have a broadcast or multicast address as their source. Any such packets will be dropped after being optionally logged according to the setting of SMURF_LOG_LEVEL in /etc/shorewall/shorewall.conf.
(Added in version 2.2.0) - If this option is specified, the kernel's martian logging facility will be enabled on this interface (/proc/sys/net/ipv4/conf/<interface>/log_martians will be set to 1). See also the LOG_MARTIANS option in shorewall.conf.
(Added in version 2.2.0) - If this option is not
specified for an interface, then source-routed packets will
not be accepted from that interface (sets
/proc/sys/net/ipv4/conf/<interface>
to 1).
My recommendations concerning options:
External Interface -- tcpflags,blacklist,norfc1918,routefilter,nosmurfs,logmartians
Wireless Interface -- maclist,routefilter,tcpflags,detectnets,nosmurfs
Use dhcp and proxyarp when needed.
Example 3. 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 black list. Your /etc/shorewall/interfaces file would be as follows:
#ZONE INTERFACE BROADCAST OPTIONS net eth0 detect dhcp,norfc1918,blacklist
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.
The only time that you need entries in
/etc/shorewall/hosts is where you have more than one zone connecting through a single
interface.
IF YOU DON'T HAVE THIS SITUATION THEN DON'T TOUCH THIS FILE!!
Columns in this file are:
A zone defined in the /etc/shorewall/zones file.
The name of an interface defined in the /etc/shorewall/interfaces file followed by a colon (":") and a comma-separated list whose elements are either:
The IP address of a host
A subnetwork in the form <subnet-address>/<mask width>
A physical port name (Shorewall version 2.0.1 and later);
only allowed when the interface names a bridge created by the
brctl addbr command. This port must not be
defined in /etc/shorewall/interfaces and
may optionally followed by a colon (":") and a host or network
IP. See the bridging
documentation for details.
If you are running a version of Shorewall earlier than
1.4.6, only a single host/subnet address may be specified in an
entry in /etc/shorewall/hosts.
A comma-separated list of option
(Added in version 1.4.2) - This option causes Shorewall to set up handling for routing packets sent by this host group back back to the same group.
Added in version 1.3.10. If specified, connection requests from the hosts specified in this entry are subject to MAC Verification. This option is only valid for ethernet interfaces.
(added in version 1.3.11) - This option causes Shorewall to make sanity checks on the header flags in TCP packets arriving from these hosts. 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 /etc/shorewall/shorewall.conf and are disposed of according to the TCP_FLAGS_DISPOSITION option.
This option causes incoming packets on this port to be checked against the blacklist.
Packets arriving on this port and that have a source address that is reserved in RFC 1918 will be dropped after being optionally logged as specified in the section of RFC1918_LOG_LEVEL in shorewall.conf.
Packets arriving on this port that have a source address reserved by the IANA or by other RFCs (other than 1918) are dropped after being optionally logged. See the /etc/shorewall/bogons file documentation below.
If this option is specified, incoming connection requests will be checked to ensure that they do not have a broadcast or multicast address as their source. Any such packets will be dropped after being optionally logged according to the setting of SMURF_LOG_LEVEL in /etc/shorewall/shorewall.conf.
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.
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.
Example 6. Your local interface is eth1 and you have two groups of local hosts that you want to make into separate zones:
192.168.1.0/25 192.168.1.128/25
Your /etc/shorewall/interfaces file might look like:
#ZONE INTERFACE BROADCAST OPTIONS net eth0 detect dhcp,norfc1918 - eth1 192.168.1.127,192.168.1.255
The “-” in the ZONE column for eth1 tells Shorewall that eth1 interfaces to multiple zones.
#ZONE HOST(S) OPTIONS loc1 eth1:192.168.1.0/25 loc2 eth1:192.168.1.128/25
Example 7. You have local interface eth1 with two IP addresses - 192.168.1.1/24 and 192.168.12.1/24
Your /etc/shorewall/interfaces file might look like:
#ZONE INTERFACE BROADCAST OPTIONS net eth0 detect dhcp,norfc1918 - eth1 192.168.1.255,192.168.12.255
Your /etc/shorewall/hosts file might look like:
#ZONE HOST(S) OPTIONS loc eth1:192.168.1.0/24 loc eth1:192.168.12.0/24
If you are running Shorewall 1.4.6 or later, your hosts file may look like:
#ZONE HOST(S) OPTIONS loc eth1:192.168.1.0/24,192.168.12.0/24
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.
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 CONTINUE policy described below.
This file is used to describe the firewall policy regarding
establishment of connections. Connection establishment is described in
terms of clients who initiate connections and
servers who receive those connection requests.
Policies defined in /etc/shorewall/policy describe
which zones are allowed to establish connections with other zones.
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.
Five policies are defined:
The connection is allowed.
The connection request is ignored.
The connection request is rejected with an RST (TCP) or an ICMP destination-unreachable packet being returned to the client.
Send the connection request to a user-space process via the iptables QUEUE target (useful when you are using Snort-inline).
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.
(Added in version 1.4.1) - Shorewall should not set up any infrastructure for handling traffic from the SOURCE zone to the DEST zone. When this policy is specified, the LOG LEVEL and BURST:LIMIT columns must be left blank.
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.
Entries in /etc/shorewall/policy have four columns as follows:
The name of a client zone (a zone defined in the /etc/shorewall/zones file , the name of the firewall zone or “all”).
The name of a destination zone (a zone defined in the /etc/shorewall/zones file , the name of the firewall zone or “all”). Shorewall automatically allows all traffic from the firewall to itself so the name of the firewall zone cannot appear in both the SOURCE and DEST columns.
The default policy for connection requests from the SOURCE zone to the DESTINATION zone.
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 syslog level.
If left empty, TCP connection requests from the SOURCE zone to the DEST 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: 10/sec:40 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. See the rules file documentation for an explanation of how rate limiting works.
In the SOURCE and DEST columns, you can enter “all” to indicate all zones.
The default /etc/shorewall/policy file is as
follows.
#SOURCE DEST POLICY LOG LEVEL LIMIT:BURST loc net ACCEPT net all DROP info all all REJECT info
This table may be interpreted as follows:
All connection requests from the local network to hosts on the internet are accepted.
All connection requests originating from the internet are ignored and logged at level KERNEL.INFO.
All other connection requests are rejected and logged.
The firewall script processes the
/etc/shorewall/policy file from top to bottom and
uses the first applicable policy that it
finds. 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.
#SOURCE DEST POLICY LOG LEVEL LIMIT:BURST loc all ACCEPT net all DROP info loc loc REJECT info
Shorewall allows a zone to be associated with more than one interface or with multiple networks that interface through a single interface. Beginning with Shorewall 1.4.1, Shorewall will ACCEPT all traffic from a zone to itself provided that there is no explicit policy governing traffic from that zone to itself (an explicit policy does not specify “all” in either the SOURCE or DEST column) and that there are no rules concerning connections from that zone to itself. If there is an explicit policy or if there are one or more rules, then traffic within the zone is handled just like traffic between zones is.
The idea is this:
A zone should be homogeneous with respect to security requirements.
Traffic within a zone should not require rules or policies.
Shorewall will not restrict traffic within a zone.
UNLESS the user defines the zone badly so that intra-zone rules are required. In that case, Shorewall will not try to guess what the user's intentions are and will treat traffic within the affected zone(s) just like any other traffic.
Any time that you have multiple interfaces associated with a single zone, you should ask yourself if you really want traffic routed between those interfaces. Cases where you might not want that behavior are:
Multiple “net” interfaces to different ISPs. You don't want to route traffic from one ISP to the other through your firewall.
Multiple VPN clients. You don't necessarily want them to all be able to communicate between themselves using your gateway/router.
Beginning with Shorewall 2.0.0, you can control the traffic from the firewall to itself. As with any zone, fw->fw traffic is enabled by default. It is not necessary to define the loopback interface (lo) in /etc/shorewall/interfaces in order to define fw->fw rules or a fw->fw policy.
So long as there are no intra-zone rules for a zone, all
intra-zone traffic for that zone is accepted. As soon as you add a
single rule from the zone to itself, then ALL traffic from that zone
to itself is controlled by the rules and the first policy in
/etc/shorewall/policy that matches the zone to
itself.
Where zones are nested or overlapping, 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:
/etc/shorewall/zones:
#ZONE DISPLAY COMMENTS sam Sam Sam's system at home net Internet The Internet loc Local Local Network
/etc/shorewall/interfaces:
#ZONE INTERFACE BROADCAST OPTIONS - eth0 detect dhcp,norfc1918 loc eth1 detect
/etc/shorewall/hosts:
#ZONE HOST(S) OPTIONS net eth0:0.0.0.0/0 sam eth0:206.191.149.197
Sam's home system is a member of both the sam zone and the net zone and as
described above , that means that sam must be listed before net in
/etc/shorewall/zones.
/etc/shorewall/policy:
#SOURCE DEST POLICY LOG LEVEL loc net ACCEPT sam all CONTINUE net all DROP info all all REJECT info
The second entry above says that when Sam is the client, connection requests should first be process under rules where the source zone is sam and if there is no match then the connection request should be treated under rules where the source zone is net. It is important that this policy be listed BEFORE the next policy (net to all).
Partial /etc/shorewall/rules:
#ACTION SOURCE DEST PROTO DEST PORT(S) ... DNAT sam loc:192.168.1.3 tcp ssh DNAT net loc:192.168.1.5 tcp www ...
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 net 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.
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:
#ACTION SOURCE DEST PROTO DEST PORT(S) ... DNAT sam fw tcp ssh DNAT net loc:192.168.1.3 tcp ssh ...
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.
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. Entries in this file only
govern the establishment of new connections — packets that are part of an
existing connection or that establish a connection that is related to an
existing connection are automatically accepted.
Rules for each pair of zones (source zone, destination zone) are evaluated in the order that they appear in the file — the first match determines the disposition of the connection request with a couple of caveats:
LOG rules cause the connection request to be logged then processing continues with the next rule in the file.
QUEUE rules cause the connection request to be passed to user-space -- the user-space application can later insert them back into the stream for further processing by following rules.
CONTINUE rules may cause the connection request to be reprocessed using a different (source zone, destination zone) pair.
Entries in the file have the following columns:
These have the same meaning here as in the policy file above.
Added in Shorewall 2.0.2 Beta 2. Works like ACCEPT but also exempts the connection from matching DNAT and REDIRECT rules later in the file.
Added in Shorewall 2.0.2 Beta 2. Exempts matching connections from DNAT and REDIRECT rules later in the file.
Causes the connection request to be forwarded to the system specified in the DEST column (port forwarding). “DNAT” stands for “Destination Network Address Translation”
The above ACTION (DNAT) generates two iptables rules:
a header-rewriting rule in the Netfilter “nat” table
an ACCEPT rule in the Netfilter “filter” table.
DNAT- works like DNAT but only generates the header-rewriting rule.
Added in Shorewall 2.2.4. SAME is useful when more than one server IP address (an address range, for example) is given in the DEST column below. SAME works similar to DNAT with the exception that when multiple connections from an internet host match a SAME rule then all of the connections will be sent to the same internal server.
Unlike when using DNAT rules, SAME rules may not alter the destination port number used for the connection.
Added in Shorewall 2.2.4. SAME generates two iptables rules:
a header-rewriting rule in the Netfilter “nat” table
an ACCEPT rule in the Netfilter “filter” table.
SAME- works like SAME but only generates the header-rewriting rule.
Causes the connection request to be redirected to a port on the local (firewall) system.
The above ACTION (REDIRECT) generates two iptables rules:
a header-rewriting rule in the Netfilter “nat” table
an ACCEPT rule in the Netfilter “filter” table.
REDIRECT- works like REDIRECT but only generates the header-rewriting rule.
Log the packet -- requires a syslog level (see below).
Forward the packet to a user-space application. This facility is provided to allow interfacing to ftwall for Kazaa filtering.
When the protocol specified in the PROTO column is TCP (“tcp”, “TCP” or “6”), Shorewall will only pass connection requests (SYN packets) to user space. This is for compatibility with ftwall.
(Shorewall 1.4.9 and later) - An action defined in the
/etc/shorewall/actions
or /usr/share/shorewall/actions.std
files.
The ACTION may optionally be followed by “:” and a syslog level (example: REJECT:info or ACCEPT:debug). This causes the packet to be logged at the specified level prior to being processed according to the specified ACTION. Note: if the ACTION is LOG then you MUST specify a syslog level. Beginning with Shorewall version 2.0.2 Beta 1, a log tag may be specified. A log tag is a string of alphanumeric characters and is specified by following the log level with ":" and the log tag. Example:
ACCEPT:info:ftp net dmz tcp 21
The log tag is appended to the log prefix generated by the
LOGPREFIX variable in /etc/shorewall/conf. If
"ACCEPT:info" generates the log prefix "Shorewall:net2dmz:ACCEPT:"
then "ACCEPT:info:ftp" will generate "Shorewall:net2dmz:ACCEPT:ftp "
(note the trailing blank). The maximum length of a log prefix
supported by iptables is 29 characters; if a larger prefix is
generated, Shorewall will issue a warning message and will truncate
the prefix to 29 characters.
Specifying a log level for a <defined action> will log all invocations of the action. For example:
AllowFTP:info net dmz
will log all net->dmz traffic that has not been handled by
earlier rules. That's probably not what you want. If you want to log
the FTP connections that are actually accepted, you need to log
within the action itself. One way to do that would be to copy
/usr/share/shorewall/action.AllowFTP to
/etc/shorewall and modify the
copy as follows:
#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT PORT(S) LIMIT GROUP
ACCEPT:info - - tcp 21
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVEThe use of DNAT or REDIRECT requires that you have NAT enabled in your kernel configuration.
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, “all” or "none". 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 example above.
If the source is "none" then the rule is ignored. This is most commonly used with Shell Variables where a shell variable is set to "none" if a rule is to be omitted.
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:
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).
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.
in Shorewall format.
refers to a connection request from any host in the specified subnet (example net:155.186.235.0/24). Beginning with Shorewall 2.1.0, IP address ranges of the form <first address>-<last address> may be specified. This requires that your kernel and iptables have iprange match support.
Describes the destination host(s) to which the rule applies. May take most of the forms described above for SOURCE plus the following two additional forms:
An IP address followed by a colon and the port number that the server is listening on (service names from /etc/services are not allowed - example loc:192.168.1.3:80).
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.
Restrictions:
MAC addresses may not be specified.
In DNAT rules, only IP addresses may be given -- DNS names are not permitted.
You may not specify both an IP address and an interface name in the DEST column.
Like in the SOURCE column, a range of IP addresses may be specified in the DEST column as <first address>-<last address>. When the ACTION is DNAT or DNAT-, connections will be assigned to the addresses in the range in a round-robin fashion (load-balancing). This feature is available with DNAT rules only with Shorewall 1.4.6 and later versions; it is available with DNAT- rules in all versions that support DNAT-. It is available with SAME and SAME- rules in all versions that support those actions.
Protocol. Must be a protocol name from /etc/protocols, a number, or “all”. Specifies the protocol of the connection request.
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.
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.
This column may only be non-empty if the ACTION is DNAT or REDIRECT.
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 particular IP addresses (see Example 2 below for another usage). Those IP addresses are specified in the ORIGINAL DEST column as a comma-separated list.
If this list begins with “!” then the rule will only apply if the original destination address matches none of the addresses listed.
The IP address(es) 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.
Specifying SNAT in a DNAT rule is deprecated and this feature was removed from Shorewall in version 2.1.0. An entry in /etc/shorewall/masq can serve the same purpose and is the preferred method of performing SNAT with Shorewall. See FAQ 2 for an example.
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.
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.
Shorewall does not take any steps to ensure that IP addresses entered in this column are added to the appropriate firewall interface. Unless traffic for this address is automatically routed to the firewall by another router, it is your responsibility to add the address using your distributions network configuration facilities. See this article for additional information.
Beginning with Shorewall version 1.4.7, you may rate-limit ACCEPT, DNAT[-], REDIRECT[-] or LOG rules with an entry in this column. Entries have the form
<rate>/<interval>[:<burst>]
where <rate> is the number of connections per <interval> (“sec” or “min”) and <burst> is the largest burst permitted. If no burst value is given, a value of 5 is assumed.
There may be no whitespace embedded in the specification.
Example 9. Let's take
ACCEPT<2/sec:4> net dmz tcp 80
The first time this rule is reached, the packet will be accepted; in fact, since the burst is 4, the first four packets will be accepted. After this, it will be 500ms (1 second divided by the rate of 2) before a packet will be accepted from this rule, regardless of how many packets reach it. Also, every 500ms which passes without matching a packet, one of the bursts will be regained; if no packets hit the rule for 2 second, the burst will be fully recharged; back where we started.
When rate limiting is specified on a rule with “all” in the SOURCE or DEST fields below, the limit will apply to each pair of zones individually rather than as a single limit for all pairs of zones covered by the rule.
If you want to specify any following columns but no rate limit, place “-” in this column.
Beginning with Shorewall release 1.4.7, output rules from the firewall itself may be restricted to a particular set of users and/or user groups. See the User Set Documentation for details.
Example 10. You wish to forward all ssh connection requests from the internet to local system 192.168.1.3. You wish to limit the number of connections to 4/minute with a burst of 8 (Shorewall 1.4.7 and later only):
#ACTION SOURCE DEST PROTO DEST PORT(S) DNAT<4/min:8> net loc:192.168.1.3 tcp ssh
Example 11. 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 (notice the “!”) originally destined to 206.124.146.177 are redirected to local port 3128.
#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL # PORT(S) DEST REDIRECT loc 3128 tcp www - !206.124.146.177 ACCEPT fw net tcp www
Example 12. 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.
#ACTION SOURCE DEST PROTO DEST PORT(S) ACCEPT net dmz:155.186.235.222 tcp www ACCEPT loc dmz:155.186.235.222 tcp www
Example 13. 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.
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 (but see FAQ 2)
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 all ftp connections originating in the local subnet 192.168.1.0/24 would be sent to 192.168.2.2 regardless of the site that the user was trying to connect to. That is clearly not what you want.
#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL # PORT(S) DEST DNAT net dmz:192.168.2.2 tcp ftp DNAT loc:192.168.1.0/24 dmz:192.168.2.2 tcp ftp - 155.186.235.151
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:
passive ports 0.0.0.0/0 65500 65534
If you are running pure-ftpd, you would include “-p 65500:65534” on the pure-ftpd runline.
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.
Example 14. You wish to allow unlimited DMZ access to the host with MAC address 02:00:08:E3:FA:55.
#ACTION SOURCE DEST PROTO DEST PORT(S) ACCEPT loc:~02-00-08-E3-FA-55 dmz all
Example 15. You wish to allow access to the SMTP server in your DMZ from all zones.
#ACTION SOURCE DEST PROTO DEST PORT(S) ACCEPT all dmz tcp 25
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.
Example 16. Your firewall's external interface has several IP addresses but you only want to accept SSH connections on address 206.124.146.176.
#ACTION SOURCE DEST PROTO DEST PORT(S) ACCEPT net fw:206.124.146.176 tcp 22
Example 17. (For advanced users running Shorewall version 1.3.13 or later). 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.
#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL # PORT(S) DEST DNAT- net dmz:192.0.2.177 tcp 25 - 192.0.2.178 DNAT- net dmz:192.0.2.177 tcp 25 - 192.0.2.179 ACCEPT net dmz:192.0.2.177 tcp 25
Using “DNAT-” rather than “DNAT” avoids two extra copies of the third rule from being generated.
Example 18. (Shorewall version 1.4.6 or later). You have 9 http servers behind a Shorewall firewall and you want connection requests to be distributed among your servers. The servers are 192.168.1.101-192.168.1.109.
#ACTION SOURCE DEST PROTO DEST PORT(S) DNAT net loc:192.168.1.101-192.168.1.109 tcp 80
Example 19. (Shorewall 2.0.2 Beta 2 and Later). You want to redirect all local www connection requests EXCEPT those from 192.168.1.4 and 192.168.1.199 to a Squid transparent proxy running on the firewall and listening on port 3128.
#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL
# PORT(S) DEST
NONAT loc:192.168.1.4,192.168.1.199 \
net tcp www
REDIRECT loc 3128 tcp www -
ACCEPT fw net tcp wwwThe reason that NONAT is used in the above example rather than ACCEPT+ is that the example is assuming the usual ACCEPT loc->net policy. Since traffic from the local zone to the internet zone is accepted anyway, adding an additional ACCEPT rule is unnecessary and all that is required is to avoid the REDIRECT rule for HTTP connection requests from the two listed IP addresses.
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 NAT enabled.
Columns are:
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 1.4.10, the interface name can be qualified with ":" followed by a comma separated list of hosts and/or subnets. If this list begins with “!” (e.g., “eth0:!192.0.2.8/29,192.0.2.32/29”) then only packets addressed to destinations not listed will be masqueraded; otherwise (e.g., “eth0:192.0.2.8/29,192.0.2.32/29”), traffic will be masqueraded if it does match one of the listed addresses.
Beginning with Shorewall version 1.3.14, if you have set ADD_SNAT_ALIASES=Yes in /etc/shorewall/shorewall.conf, you can cause Shorewall to create an alias label of the form interfacename:digit (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. THAT IS THE ONLY THING THAT THIS LABEL IS GOOD FOR AND IT MAY NOT APPEAR ANYWHERE ELSE IN YOUR SHOREWALL CONFIGURATION.
Normally MASQUERADE/SNAT rules are evaluated after one-to-one
NAT rules defined in the /etc/shorewall/nat file.
Beginning with Shorewall 2.1.1, if you preceed the interface name
with a plus sign ("+") then the rule will be evaluated before
one-to-one NAT.
Examples:
+eth0 +eth1:192.0.2.32/27
Also new in the Shorewall 2.1 series, the effect of ADD_SNAT_ALIASES=Yes can be negated for an entry by following the interface name by ":" but no digit.
Examples:
eth0: eth1::192.0.2.32/27 +eth3
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.
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.
The subnet may be optionally followed by “!” and a comma-separated list of addresses and/or subnets that are to be excluded from masquerading.
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 /etc/shorewall/shorewall.conf. Beginning with Shorewall version 1.4.6, you may include a range of IP addresses in this column to indicate that Netfilter should use the addresses in the range in round-robin fashion.
If you are running a kernel earlier than 2.6.11, you may include a list of ranges and/or addresses in this column; again, Netfilter will use all listed ranges/addresses in rounded-robin fashion. Support for this feature was removed from the kernel in 2.6.11.
Beginning with Shorewall 2.2.0, you may also specify the source port range to be used (the PROTO column must specify tcp or udp) by following the address or address range if any with ":" and the port range (in the format <low port>-<high port>).
Examples:
#INTERFACE SUBNET ADDRESS PROTO eth0 10.0.0.0/8 192.0.2.44:7000-8000 udp
#INTERFACE SUBNET ADDRESS PROTO eth0 192.168.1.0/24 :4000-5000 tcp
Some internet application that establish multiple connections from a client assume that when SNAT is being used that all connections between the client and a particular client and a remote server will appear to the server to come from the same external IP address. Beginning with Shorewall 2.2.4, you can ensure that this is the case by preceding the ADDRESS range by "SAME:".
Example:
#INTERFACE SUBNET ADDRESS eth0 10.0.0.0/8 SAME:192.0.2.44-192.168.2.50
If you want all connections from an internal system to use the same external IP address regardless of the remote server that they are connecting to then precede the ADDRESS range by "SAME:nodst:".
Example:
#INTERFACE SUBNET ADDRESS eth0 10.0.0.0/8 SAME:nodst:192.0.2.44-192.168.2.50
If specified, must be a protocol number of a protocol name from /etc/protocols. Restricts the SNAT or Masquerade to that protocol.
If the PROTO column specifies TCP (6) or UDP (17) then this column may be used to restrict to SNAT or Masquerade to traffic with a certain destination port or a set of destination ports. The column may contain:
A port number or a port name from /etc/services.
A comma-separated list of port numbers and/or port names. Your kernel must have Multiport match support. You can tell if your kernel has this support by issuing a shorewall check command and looking at the output under “Shorewall has detected the following iptables/netfilter capabilities:”.
A range of port numbers of the form <low port>:<high port>
If you specify a value other than "-" in this column, you must be running kernel 2.6 and your kernel and iptables must include policy match support.
The value in this column is a comma-separated list of options from the following. Only packets that will be encrypted via an SA that matches these options will have their source address changed.
Yes or yes ― Match any SA. Normally used as the only option.
reqid=<number> where <number> is specified using setkey(8) using the 'unique:<number>' option for the SPD level.
spi=<number> where <number> is the SPI of the SA.
proto=ah|esp|ipcomp
mode=transport|tunnel
tunnel-src=<address>[/<mask>] (only available with mode=tunnel)
tunnel-dst=<address>[/<mask>] (only available with mode=tunnel)
strict — Means that packets must match all rules.
next — Separates rules; can only be used with strict.
Example 20. 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:
#INTERFACE SUBNET ADDRESS eth0 192.168.9.0/24
Example 21. 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.
#INTERFACE SUBNET ADDRESS ipsec0:10.1.0.0/16 192.168.9.0/24
Example 22. 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.
#INTERFACE SUBNET ADDRESS eth0 192.168.10.0/24 206.124.146.176
Example 23. Same as example 3 except that you wish to exclude 192.168.10.44 and 192.168.10.45 from the SNAT rule.
#INTERFACE SUBNET ADDRESS eth0 192.168.10.0/24!192.168.10.44,192.168.10.45 206.124.146.176
Example 24. (Shorewall version >= 1.3.14): 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 /etc/shorewall/shorewall.conf.
#INTERFACE SUBNET ADDRESS eth0:0 192.168.12.0/24 206.124.146.177
Example 25. (Shorewall version >= 1.4.7): You want to use both 206.124.146.177 and 206.124.146.179 for SNAT of the subnet 192.168.12.0/24. Each address will be used on alternate outbound connections.
#INTERFACE SUBNET ADDRESS eth0 192.168.12.0/24 206.124.146.177,206.124.146.179
Example 26. (Shorewall version >= 2.0.2 Beta 1): You want all outgoing SMTP traffic entering the firewall on eth1 to be sent from eth0 with source IP address 206.124.146.177. You want all other outgoing traffic from eth1 to be sent from eth0 with source IP address 206.124.146.176.
#INTERFACE SUBNET ADDRESS PROTO PORT(S) eth0 eth1 206.124.146.177 tcp 25 eth0 eth1 206.124.146.176
Note that the order of the entries in the above example is important.
If you want to use proxy ARP on an entire sub-network, I suggest
that you look at the Proxy ARP Subnet
Mini HOWTO. 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/<interface>/proxy_arp)
by including the proxyarp option in the
interface's record in /etc/shorewall/interfaces. When using Proxy ARP
sub-netting, you do NOT include any
entries in /etc/shorewall/proxyarp.
The /etc/shorewall/proxyarp file is used to
define Proxy ARP. 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:
address of the system.
the interface that connects to the system. If the interface is obvious from the subnetting, you may enter “-” in this column.
the external interface that you want to honor ARP requests for the ADDRESS specified in the first column.
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”.
If you specify "No" or "no" in the HAVEROUTE column, Shorewall will automatically add a route to the host in the ADDRESS column through the interface in the INTERFACE column. If you enter “No” or “no” in the PERSISTENT column or if you leave the column empty, that route will be deleted if you issue a shorewall stop or shorewall clear command. If you place “Yes” or “yes” in the PERSISTENT column, then those commands will not cause the route to be deleted.
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.
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.
Example 27. You have public IP addresses 155.182.235.0/28. You configure your firewall as follows:
eth0 - 155.186.235.1 (internet connection) eth1 -
192.168.9.0/24 (masqueraded local systems) eth2 - 192.168.10.1
(interface to your DMZ)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:
#ADDRESS INTERFACE EXTERNAL HAVEROUTE 155.186.235.4 eth2 eth0 NO
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 for details. In this case you will want to place “Yes” in the HAVEROUTE column.
The /etc/shorewall/nat file is used to define
one-to-one NAT. There is one entry in the file for each one-to-one NAT
relationship that you wish to define. In order to make use of this
feature, you must have NAT enabled.
If all you want to do is forward ports to servers behind your firewall, you do NOT want to use one-to-one NAT. Port forwarding can be accomplished with simple entries in the rules file. Also, in most cases Proxy ARP provides a superior solution to one-to-one NAT because the internal systems are accessed using the same IP address internally and externally.
Columns in an entry are:
External IP address
This should NOT be the primary IP address of the interface named in the next column.
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 /etc/shorewall/shorewall.conf, you can specify an alias label of the form interfacename:digit (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. THAT IS THE ONLY THING THAT THIS LABEL IS GOOD FOR AND IT MAY NOT APPEAR ANYWHERE ELSE IN YOUR SHOREWALL CONFIGURATION.
Beginning with Shorewall 2.1.1, the effect of ADD_IP_ALIASES=Yes can be negated for an entry by following the interface name by ":" but no digit.
Example:
eth0:
Internal IP address.
If “Yes” or “yes”, NAT will be effective from all hosts. If “No” or “no” (or if left empty) then NAT will be effective only through the interface named in the INTERFACE column.
If Yes or yes, NAT will be effective from the firewall system. Note that with Shorewall 2.0.1 and earlier versions, this column was ignored if the ALL INTERFACES column did not contain "Yes" or "yes". Beginning with Shorewall 2.0.2 Beta 1, this column's contents are independent of the value in ALL INTERFACES.
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 CONFIG_IP_NF_NAT_LOCAL in your kernel.
The /etc/shorewall/tunnels file allows you to define IPSec, GRE, IPIP, OpenVPN, PPTP, 6to4 and other tunnels with end-points on your firewall.
For an overview of Shorewall's VPN support, try this article.
Instructions for setting up IPSEC tunnels may be found here (if you are using kernel 2.6 with native IPSEC support, look here), instructions for IPIP and GRE tunnels are here, instructions for OpenVPN tunnels are here, instructions for PPTP tunnels are here, instructions for 6to4 tunnels are here, and instructions for integrating Shorewall with other types of tunnels are here.
This file is used to set the following firewall parameters:
(Added at version 2.2.0) - When set to Yes or yes, Shorewall may be started. Used as guard against Shorewall being accidentally started before it has been configured.
(Added at version 2.2.0) The performance of configurations with a large numbers of entries in /etc/shorewall/maclist can be improved by setting the MACLIST_TTL variable in /etc/shorewall/shorewall.conf.
If your iptables and kernel support the "Recent Match" (see the output of "shorewall check" near the top), you can cache the results of a 'maclist' file lookup and thus reduce the overhead associated with MAC Verification.
When a new connection arrives from a 'maclist' interface, the packet passes through then list of entries for that interface in /etc/shorewall/maclist. If there is a match then the source IP address is added to the 'Recent' set for that interface. Subsequent connection attempts from that IP address occurring within $MACLIST_TTL seconds will be accepted without having to scan all of the entries. After $MACLIST_TTL from the first accepted connection request from an IP address, the next connection request from that IP address will be checked against the entire list.
If MACLIST_TTL is not specified or is specified as empty (e.g, MACLIST_TTL="" or is specified as zero then 'maclist' lookups will not be cached).
(Added at version 2.4.6) Normally, MAC verification occurs in the filter table (INPUT and FORWARD) chains. When forwarding a packet from an interface with MAC verification to a bridge interface, that doesn't work.
This problem can be worked around by setting MACLIST_TABLE=mangle which will cause Mac verification to occur out of the PREROUTING chain. Because REJECT isn't available in that environment, you may not specify MACLIST_DISPOSITION=REJECT with MACLIST_TABLE=mangle.
(Added at version 2.2.2) — Traditionally, the RETURN target in the 'rfc1918' file has caused norfc1918 processing to cease for a packet if the packet's source IP address matches the rule. Thus, if you have this entry in /etc/shorewall/rfc1918:
#SUBNETS TARGET 192.168.1.0/24 RETURN
then traffic from 192.168.1.4 to 10.0.3.9 will be accepted even though you also have:
#SUBNETS TARGET 10.0.0.0/8 logdrop
Setting RFC1918_STRICT=Yes in shorewall.conf will cause such traffic to be logged and dropped since while the packet's source matches the RETURN rule, the packet's destination matches the 'logdrop' rule.
If not specified or specified as empty (e.g., RFC1918_STRICT="") then RFC1918_STRICT=No is assumed.
RFC1918_STRICT=Yes requires that your kernel and iptables support 'Connection Tracking' match.
(Added at version 2.2.0 and backported into version 2.0.16) — Recent 2.6 kernels include code that evaluates TCP packets based on TCP Window analysis. This can cause packets that were previously classified as NEW or ESTABLISHED to be classified as INVALID.
The new kernel code can be disabled by including this command in your /etc/shorewall/init file:
echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal
Additional kernel logging about INVALID TCP packets may be obtained by adding this command to /etc/shorewall/init:
echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_log_invalid
Traditionally, Shorewall has dropped INVALID TCP packets early. The DROPINVALID option allows INVALID packets to be passed through the normal rules chains by setting DROPINVALID=No. If not specified or if specified as empty (e.g., DROPINVALID="") then DROPINVALID=Yes is assumed.
(Aded at version 2.2.0)- When set to a log level, this option causes Shorewall to generate a logging rule as the first rule in each builtin chain.
The table name is used as the chain name in the log prefix.
The chain name is used as the target in the log pref
Example: Using the default LOGFORMAT, the log prefix for logging from the nat table's PREROUTING chain is:
Shorewall:nat:PREROUTING
There is no rate limiting on these logging rules so use LOGALLNEW at your own risk; it may cause high CPU and disk utilization and you may not be able to control your firewall after you enable this option.
DO NOT USE THIS OPTION IF THE RESULTING LOG MESSAGES WILL BE SENT TO ANOTHER SYSTEM.
(Added at version 2.0.2) - When set to Yes or yes, enables dynamic zones.
(Added at version 2.0.2) - Specifies where configuration files
other than shorewall.conf may be found.
CONFIG_PATH is specifies as a list of directory names separated by
colons (":"). When looking for a configuration file other than
shorewall.conf:
If the command is "try" or if "-c <configuration directory>" was specified in the command then the directory given in the command is searched first.
Next, each directory in the CONFIG_PATH setting is searched in sequence.
If CONFIG_PATH is not given or if it is set to the empty value
then the contents of
/usr/share/shorewall/configpath are used. As
released from shorewall.net, that file sets the CONFIG_PATH to
/etc/shorewall:/usr/share/shorewall
but your particular distribution may set it
differently.
Note that the setting in
/usr/share/shorewall/configpath is always used
to locate shorewall.conf.
(Added at Version 2.0.6) - Normally Shorewall attempts to use the iptables packet type match extension to determine broadcast and multicast packets.
This can cause a message to appear during shorewall start (modprobe: cant locate module ipt_pkttype).
Some users have found problems with the packet match extension with the result that their firewall log is flooded with messages relating to broadcast packets.
If you are experiencing either of these problems, setting PKTTYPE=No will prevent Shorewall from trying to use the packet type match extension and to use IP address matching to determine which packets are broadcasts or multicasts.
(Added at version 2.0.3 Beta 1) - The simple name of a file
in /var/lib/shorewall to be used as the default
restore script in the shorewall save, shorewall restore, shorewall
forget and shorewall -f start commands. See the Saved Configuration
documentation for details.
(Added at version 2.0.1) - When set to Yes or yes, enables Shorewall Bridging support.
(Added at version 2.0.0) - Specifies the logging level for smurf packets (see the nosmurfs option in /etc/shorewall/interfaces). If set to the empty value ( SMURF_LOG_LEVEL="" ) then smurfs are not logged.
(Added at version 1.4.9) - The value of this variable determines the possible file extensions of kernel modules. The default value is "o gz ko and o.gz". See /etc/shorewall/modules for more details.
(Added at version 1.4.7) - The value of this variable affects
Shorewall's stopped
state. When ADMINISABSENTMINDES=No, only traffic to/from
those addresses listed in /etc/shorewall/routestopped is accepted
when Shorewall is stopped. When ADMINISABSENTMINDED=Yes, in addition
to traffic to/from addresses in
/etc/shorewall/routestopped, connections that
were active when Shorewall stopped continue to work and all new
connections from the firewall system itself are allowed. If this
variable is not set or is given the empty value then
ADMINISABSENTMINDED=No is assumed.
(Added at version 1.4.6) - This parameter is used to specify the shell program to be used to interpret the firewall script (/usr/share/shorewall/firewall). If not specified or specified as a null value, /bin/sh is assumed.
(Added at version 2.2.0) — This parameter names the iptables executable to be used by Shorewall. If not specified or if specified as a null value, then the iptables executable located using the PATH option is used.
(Added at version 1.4.4) - The value of this variable generate the --log-prefix setting for Shorewall logging rules. It contains a “printf” formatting template which accepts three arguments (the chain name, logging rule number (optional) and the disposition). To use LOGFORMAT with fireparse, set it as:
LOGFORMAT="fp=%s:%d a=%s "
If the LOGFORMAT value contains the substring “%d” then the logging rule number is calculated and formatted in that position; if that substring is not included then the rule number is not included. If not supplied or supplied as empty (LOGFORMAT="") then “Shorewall:%s:%s:” is assumed.
/sbin/shorewall uses the leading part of the LOGFORMAT string (up to but not including the first “%”) to find log messages in the “show log”, “status” and “hits” commands. This part should not be omitted (the LOGFORMAT should not begin with “%”) and the leading part should be sufficiently unique for /sbin/shorewall to identify Shorewall messages.
(Added at version 1.3.13) - 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.
(Added at version 1.3.12) - 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 tcrules file 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.
(Added at version 1.3.12) - This parameter determines the level at which packets logged under the “norfc1918” mechanism are logged. The value must be a valid syslog level 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.
(Added at version 2.0.1) - This parameter determines the level at which packets logged under the “nobogons” mechanism are logged. The value must be a valid syslog level and if no level is given, then info is assumed.
(Added in Version 1.3.11) - Determines the disposition of TCP packets that fail the checks enabled by the tcpflags 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.
(Added in Version 1.3.11) - Determines the syslog level for logging packets that fail the checks enabled by the tcpflags 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="").
(Added in Version 1.3.10) - Determines the disposition of connections requests that fail MAC Verification 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.
(Added in Version 1.3.10) - Determines the syslog level for logging connection requests that fail MAC Verification. 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="").
(Added in Version 1.3.8) - When set to “Yes” or “yes”, Shorewall will filter TCP packets that are not part of an established connection 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.
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.
I find that NEWNOTSYN=No tends to result in lots of "stuck" connections because any network timeout during TCP session tear down results in retries being dropped (Netfilter has removed the connection from the conntrack table but the end-points haven't completed shutting down the connection). I therefore have chosen NEWNOTSYN=Yes as the default value and I advise caution in using NEWNOTSYN=Yes.
If you are looking for a way to defeat "stealth TCP scans" then I recommend the tcpflags interface option in /etc/shorewall/interfaces rather than NEWNOTSYN=No.
(Added in Version 1.3.6) - 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 syslog level at which you want the packets logged. Example: LOGNEWNOTSYN=ULOG|
Packets logged under this option are usually the result of a "stuck" connection rather than as the result of an attempt to breach your firewall.
(Added in Version 2.2.0) - If set to Yes or yes, sets
/proc/sys/net/ipv4/conf/all/log_martians and
/proc/sys/net/ipv4/conf/default/log_martians to
1. Default is which sets both of the above to zero. If you do not
enable martian logging for all interfaces, you may still enable it
for individual interfaces using the logmartians interface option in /etc/shorewall/interfaces.
(Added in Version 1.3.4) - If set to “Yes” or “yes”, Shorewall will detect the first IP address of the interface to the source zone and will include this address in DNAT rules as the original destination IP address. If set to “No” or “no”, Shorewall will not detect this address and any destination IP address will match the DNAT rule. If not specified or empty, “DETECT_DNAT_ADDRS=Yes” is assumed.
If set to “No” or “no”, port forwarding rules can override the contents of the /etc/shorewall/nat file. If set to “Yes” or “yes”, port forwarding rules cannot override one-to-one NAT. If not set or set to an empty value, “Yes” is assumed.
This parameter specifies the name of the firewall zone. If not set or if set to an empty string, the value “fw” is assumed.
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.
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.
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.
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.
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.
Example 28.
LOGRATE=10/minute LOGBURST=5
For each logging rule, the first time the rule is reached, the packet will be logged; in fact, since the burst is 5, the first five packets will be logged. After this, it will be 6 seconds (1 minute divided by the rate of 10) before a message will be logged from the rule, regardless of how many packets reach it. Also, every 6 seconds which passes without matching a packet, one of the bursts will be regained; if no packets hit the rule for 30 seconds, the burst will be fully recharged; back where we started.
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.
This parameter determines whether Shorewall enables or disables IPV4 Packet Forwarding (/proc/sys/net/ipv4/ip_forward). Possible values are:
packet forwarding will be enabled.
packet forwarding will be disabled.
Shorewall will neither enable nor disable packet forwarding.
If this variable is not set or is given an empty value (IP_FORWARD="") then IP_FORWARD=On is assumed.
This parameter determines whether Shorewall automatically adds the external address(es) in /etc/shorewall/nat. 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.
If this variable is not set or is given an empty value (ADD_IP_ALIASES="") then ADD_IP_ALIASES=Yes is assumed.
Addresses added by ADD_IP_ALIASES=Yes are deleted and re-added during shorewall restart. As a consequence, connections using those addresses may be severed.
This parameter determines whether Shorewall automatically adds the SNAT ADDRESS in /etc/shorewall/masq. 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.
If this variable is not set or is given an empty value (ADD_SNAT_ALIASES="") then ADD_SNAT_ALIASES=No is assumed.
Addresses added by ADD_SNAT_ALIASES=Yes are deleted and re-added during shorewall restart. As a consequence, connections using those addresses may severed.
(Added in 2.2.0) - During "shorewall start", IP addresses to be added as a consequence of ADD_IP_ALIASES=Yes and ADD_SNAT_ALIASES=Yes are quietly deleted when /etc/shorewall/nat and /etc/shorewall/masq are processed then are re-added later. This is done to help ensure that the addresses can be added with the specified labels but can have the undesirable side effect of causing routes to be quietly deleted. When RETAIN_ALIASES is set to Yes, existing addresses will not be deleted. Regardless of the setting of RETAIN_ALIASES, addresses added during "shorewall start" are still deleted at a subsequent "shorewall stop" or "shorewall restart".
This parameter determines the logging level of mangled/invalid packets controlled by the “dropunclean" and "logunclean” 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).
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.
This parameter 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 syslog level (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.
(Added in Shorewall 2.2.0) - Users with a large static black
list (/etc/shorewall/blacklist) may want to set
the DELAYBLACKLISTLOAD option to Yes. When DELAYBLACKLISTLOAD=Yes,
Shorewall will enable new connections before loading the blacklist
rules. While this may allow connections from blacklisted hosts to
slip by during construction of the blacklist, it can substantially
reduce the time that all new connections are disabled during
shorewall [re]start.
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.
This option requires CONFIG_IP_NF_TARGET_TCPMSS in your kernel.
Beginning with Shorewall version 2.2.0, you may also set CLAMPMSS to a numeric value (e.g., CLAMPMSS=1400). This will set the MSS field in TCP SYN packets going through the firewall to the value that you specify.
If this parameter is given the value “Yes” or “yes” then route filtering (anti-spoofing) is enabled on all network interfaces which are brought up while Shorewall is in the started state. The default value is “no”.
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 /etc/shorewall/shorewall.conf above).
The file that is released with Shorewall calls the Shorewall function “loadmodule” for the set of modules that I load.
The loadmodule function is called as follows:
loadmodule <modulename> [ <module parameters> ]
where
is the name of the modules without the trailing “.o” (example ip_conntrack).
Optional parameters to the insmod utility.
The function determines if the module named by <modulename> is already loaded and if not then the function determines if the “.o” file corresponding to the module exists in the <moduledirectory>; if so, then the following command is executed:
insmod <moduledirectory>/<modulename>.o <module parameters>
If the file doesn't exist, the function determines of the “.o.gz” file corresponding to the module exists in the moduledirectory. If it does, the function assumes that the running configuration supports compressed modules and execute the following command:
insmod <moduledirectory>/<modulename>.o.gz <module parameters>
Beginning with the 1.4.9 Shorewall release, the value of the MODULE_SUFFIX option in determines which files the loadmodule function looks for if the named module doesn't exist. For each file <extension> listed in MODULE_SUFFIX (default "o gz ko o.gz"), the function will append a period (".") and the extension and if the resulting file exists then the following command will be executed:
insmod moduledirectory/<modulename>.<extension> <module parameters>
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 mangle support
enabled.
Entries in the file have the following columns:
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 Shorewall Format or the name of an interface. This column may also contain the name of the firewall zone to indicate packets originating on the firewall itself or “all” to indicate any source.
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.
The name of a protocol in /etc/protocols
or the protocol's number.
The source port or a port range. For all ports, place a hyphen (“-”) in this column.
The destination port or a port range. To indicate all ports, place a hyphen (“-”) in this column.
The type of service. Must be one of the following:
| Minimize-Delay (16) |
| Maximize-Throughput (8) |
| Maximize-Reliability (4) |
| Minimize-Cost (2) |
| Normal-Service (0) |
/etc/shorewall/tos file that is included with
Shorewall
#SOURCE DEST PROTOCOL SOURCE PORTS(S) DEST PORTS(S) TOS all all tcp - ssh 16 all all tcp ssh - 16 all all tcp - ftp 16 all all tcp ftp - 16 all all tcp - ftp-data 8 all all tcp ftp-data - 8
Users have reported that odd routing problems result from adding
the ESP and AH protocols to the /etc/shorewall/tos
file.
Each line in /etc/shorewall/blacklist contains
an IP address, a MAC address in Shorewall Format or subnet address.
Packets from hosts listed in the
blacklist file will be disposed of according to the value assigned to the
BLACKLIST_DISPOSITION and BLACKLIST_LOGLEVEL variables in
/etc/shorewall/shorewall.conf. Only packets arriving on interfaces that
have the “blacklist” option
in /etc/shorewall/interfaces are checked against the
blacklist. The black list is designed to prevent listed hosts/subnets from
accessing services on your
network.
Beginning with Shorewall 1.3.8, the blacklist file has three columns:
As described above.
Optional. If specified, only packets specifying this protocol will be blocked.
Optional; may only be given if PROTOCOL is tcp, udp or icmp. Expressed as a comma-separated list of destination port numbers or service names (from /etc/services). If present, only packets matching the specified protocol and one of the listed destination 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”).
Shorewall also has a dynamic blacklist capability.
The Shorewall blacklist file is NOT designed to police your users' web browsing -- to do that, I suggest that you install and configure Squid with SquidGuard.
This file lists the subnets affected by the norfc1918 interface option. Columns in the file are:
The subnet using VLSM notation (e.g., 192.168.0.0/16).
What to do with packets to/from the SUBNET:
Process the packet normally thru the rules and policies. See also RFC1918_STRICT above.
Silently drop the packet.
Log then drop the packet -- see the RFC1918_LOG_LEVEL parameter above.
If you want to modify this file, DO NOT MODIFY
/usr/share/shorewall/rfc1918. Rather copy that file
to /etc/shorewall/rfc1918 and modify the copy.
This file lists the subnets affected by the nobogons interface option and nobogons hosts option. Columns in the file are:
The subnet using VLSM notation (e.g., 192.168.0.0/16).
What to do with packets to/from the SUBNET:
Process the packet normally thru the rules and policies.
Silently drop the packet.
Log then drop the packet -- see the BOGONS_LOG_LEVEL parameter above.
If you want to modify this file, DO NOT MODIFY
/usr/share/shorewall/bogons. Rather copy that file to
/etc/shorewall/bogons and modify the copy.
Network mapping is defined using the
/etc/shorewall/netmap file. Columns in this file
are:
Must be DNAT or SNAT.
If DNAT, traffic entering INTERFACE and addressed to NET1 has it's destination address rewritten to the corresponding address in NET2.
If SNAT, traffic leaving INTERFACE with a source address in NET1 has it's source address rewritten to the corresponding address in NET2.
Must be expressed in CIDR format (e.g., 192.168.1.0/24).
A firewall interface. This interface must have been defined in
/etc/shorewall/interfaces.
A second network expressed in CIDR format.
For more information, see the Network Mapping documentation.
This file defines the hosts that are accessible from the firewall when the firewall is stopped. Beginning with Shorewall version 2.2.3, entries in this file are also active while Shorewall is being [re]started.
Columns in the file are:
The firewall interface through which the host(s) communicate with the firewall.
A comma-separated list of IP/Subnet addresses. If not supplied or supplied as “-” then 0.0.0.0/0 is assumed.
Example 30. 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.
#INTERFACE HOST(S) eth2 192.168.1.0/24 eth1 -
Prior to Shorewall version 2.2.3, the contents of the
/etc/shorewall/routestopped file did NOT affect
connection attempts occurring during the processing of the
shorewall start and shorewall
restart commands. Beginning with version 2.2.3, Shorewall
allows connections defined by the contents of
/etc/shorewall/routestopped during the potentially
lengthy processing of those commands.
This file is described in the MAC Validation Documentation.
This file is described in the ECN Control Documentation.
This file is described in the Traffic Accounting Documentation.
This file is used to identify the Security Associations used to encrypt traffic to hosts in a zone and to decrypt traffic from hosts in a zone. Use of this file requires a 2.6 kernel that includes the IPSEC-Netfilter patches and the policy match patch. Your iptables must also support policy match. For additional information, see the Shorewall Kernel 2.6 IPSEC documentation.
Columns are:
The name of a zone defined in /etc/shorewall/zones.
| Yes - All traffic to/from this zone is encrypted. |
| No - Only traffic to/from some of the hosts in this zone is encrypted. Those encrypted hosts are designated using the ipsec option in /etc/shorewall/hosts. |
Optional parameters that identify the security policy and security associations used in communication with hosts in this zone. A comma-separated list of the following:
| proto[!]=ah|esp|ipcomp |
| mode[!]=transport|tunnel |
| reqid[!]=<number> — A number assigned to a security policy using the unique:<number> as the SPD level. See setkey(8). |
| tunnel-src[!]=<address>[/<mask>] — Tunnel Source; may only be included with mode=tunnel. Since tunnel source and destination are dependent on the direction of the traffic, this option and the following one should only be included in the IN OPTIONS and OUT OPTIONS columns. |
| tunnel-dst[!]=<address>[/<mask>] — Tunnel Destination; may only be included with mode=tunnel. |
| mss=<number> — Sets the MSS field in TCP syn packets forwarded to/from this zone. May be used to compensate for the lack of IPSEC pseudo-devices with their own MTU in the 2.6 Kernel IPSEC implementation. If specified in the IN OPTIONS, TCP SYN packets from the zone will have MSS altered; if specified in the OUT OPTIONS, TCP SYN packets to the zone will have MSS altered. |
| spi[!]=<number> — The security parameter index of the Security Association. Since a different SA is used for incoming and outgoing traffic, this option should only be listed in the IN OPTIONS and OUT OPTIONS columns. |
| strict — Must be specified when SPD rules are used (e.g., esp encapsulated with ah). |
| next — Separates rules when strict is used. |
See the IPSEC with 2.6 Kernel documentation for further information.
| Revision History | ||
|---|---|---|
| Revision 1.24 | 2005-03-15 | TE |
| Update for use of /etc/shorewall/routestopped during [re]start. | ||
| Revision 1.23 | 2005-03-10 | TE |
| Changes for Shorewall 2.2.2. | ||
| Revision 1.20 | 2004-10-25 | TE |
| Changes for Shorewall 2.2 Beta 1. | ||
| Revision 1.19 | 2004-09-12 | TE |
| Changes for Shorewall 2.1. | ||
| Revision 1.18 | 2004-08-22 | TE |
| Add /etc/shorewall/ipsec documentation. | ||
| Revision 1.17 | 2004-04-05 | TE |
| Update for Shorewall 2.0.2 | ||
| Revision 1.16 | 2004-03-17 | TE |
| Clarified LOGBURST and LOGLIMIT. | ||
| Revision 1.15 | 2004-02-16 | TE |
| Move the rfc1918 file to /usr/share/shorewall. | ||
| Revision 1.14 | 2004-02-13 | TE |
| Add a note about the order of rules. | ||
| Revision 1.13 | 2004-02-03 | TE |
| Update for Shorewall 2.0. | ||
| Revision 1.12 | 2004-01-21 | TE |
| Add masquerade destination list. | ||
| Revision 1.12 | 2004-01-18 | TE |
| Correct typo. | ||
| Revision 1.11 | 2004-01-05 | TE |
| Standards Compliance | ||
| Revision 1.10 | 2004-01-05 | TE |
| Improved formatting of DNAT- and REDIRECT- for clarity | ||
| Revision 1.9 | 2003-12-25 | MN |
| Initial Docbook Conversion Complete | ||