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Shorewall 3.3.5
Note to users upgrading from Shorewall 3.0 or 3.3
Most problems associated with upgrades come from two causes:
- The user didn't read and follow the migration considerations in these
release notes.
- The user mis-handled the /etc/shorewall/shorewall.conf file during
upgrade. Shorewall is designed to allow the default behavior of
the product to evolve over time. To make this possible, the design
assumes that you will not replace your current shorewall.conf file
during upgrades. If you feel absolutely compelled to have the latest
comments and options in your shorewall.conf then you must proceed
carefully.
While you are at it, if you have a file named /etc/shorewall/rfc1918 then
please check that file. If it has addresses listed that are NOT in one of
these three ranges, then please rename the file to
/etc/shorewall/rfc1918.old.
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
If you have a file named /etc/shorewall/modules, please remove
it. The default modules file is now located in /usr/share/shorewall/
(see the "Migration Considerations" below).
Please see the "Migration Considerations" below for additional upgrade
information.
Problems Corrected in 3.3.5
1) Previously, if the last 'balance' provider was removed from
/etc/shorewall/providers then "shorewall restart" would not restore
the default route that was in place prior to "shorewall start".
2) Previously, restoration of routing was ignoring the "-n"
option. Now such restoration only occurs if "-n" was not specified.
Other Changes in 3.3.5.
None.
Migration Considerations:
1) Shorewall supports the notion of "default actions". A default
action defines a set of rules that are applied before a policy is
enforced. Default actions accomplish two goals:
a) Relieve log congestion. Default actions typically include rules
to silently drop or reject traffic that would otherwise be logged
when the policy is enforced.
b) Ensure correct operation. Default actions can also avoid common
pitfalls like dropping connection requests on port TCP port
113. If these connections are dropped (rather than rejected)
then you may encounter problems connecting to internet services
that utilize the AUTH protocol of client authentication.
In prior Shorewall versions, default actions (action.Drop and
action.Reject) were defined for DROP and REJECT policies in
/usr/share/shorewall/actions.std. These could be overridden in
/etc/shorewall/actions.
This approach has two drawbacks:
a) All DROP policies must use the same default action and all
REJECT policies must use the same default action.
b) Now that we have modularized action processing (see the New
Features section below), we need a way to define default rules
for a policy that does not involve actions.
If you have not overridden the defaults using entries in
/etc/shorewall/actions then you need make no changes to migrate to
Shorewall version 3.3. Otherwise, please see item 3) in the New
Features below.
2) The 'Limit' action is now a builtin. If you have 'Limit' listed in
/etc/shorewall/actions, remove the entry. Also remove the files
/etc/shorewall/action.Limit and/or /etc/shorewall/Limit if you have
them.
New Features:
1) In order to accomodate small embedded applications, Shorewall 3.3
is now modularized. In addition to the base files, there are
loadable "libraries" that may be included or omitted from an
embedded system as required.
Loadable Shorewall libraries reside in /usr/share/shorewall/ and
have names that begin with "lib.". The following libraries are
included in Shorewall 3.3:
- lib.accounting. Must be available if you include entries in
/etc/shorewall/accounting.
- lib.actions. Must be available if you do not specify
USE_ACTIONS=No in /etc/shorewall/shorewall.conf.
- lib.dynamiczones. Must be available if you specify
DYNAMIC_ZONES=Yes in shorewall.conf.
- lib.maclist. Must be available if you specify the 'maclist'
option in /etc/shorewall/interfaces or /etc/shorewall/hosts.
- lib.nat. Must be available if you have entries in
/etc/shorewall/masq, /etc/shorewall/nat or /etc/shorewall/netmap.
- lib.providers. Must be available if you have entries in
/etc/shorewall/providers.
- lib.proxyarp. Must be available if you have entries in
/etc/shorewall/proxyarp or if you specify the 'proxyarp' option
in /etc/shorewall/interfaces.
- lib.tc. Must be available if you have entries in
/etc/shorewall/tcdevices and /etc/shorewall/tcclasses.
- lib.tcrules. Must be available if you have entries in
/etc/shorewall/tcrules.
- lib.tunnels. Must be available if you have entries in
/etc/shorewall/tunnels.
Embedded applications can further decrease the size of the Shorewall
footprint by:
- Omitting the macro files.
- Only including the 'modules' file appropriate for the kernel in
use.
- Omitting all unused extension scripts.
- Stripping the comments (except for copyright) from the various
files.
2) As hinted in the previous bullet, there is a new USE_ACTIONS option
in /etc/shorewall/shorewall.conf. Shorewall actions can be very
powerful but they also require a lot of code to implement. Embedded
applications can omit that code by setting
USE_ACTIONS=No. Shorewall will ignore all action-related files
including /usr/share/shorewall/actions.std and
/etc/shorewall/actions. Builtin actions will still be available for
use in rules and macros.
The 'Limit' action has been converted to a builtin so that Limit is
available even when USE_ACTIONS=No.
See the next item for more information.
3) Prior to Shorewall 3.3, default actions were specified in
/usr/share/shorewall/actions.std or in /etc/shorewall/actions.
This approach has two drawbacks:
a) All DROP policies must use the same default action and all
REJECT policies must use the same default action.
b) Now that we have modularized action processing (see the New
Features section below), we need a way to define default rules
for a policy that does not involve actions.
The solution is two-fold:
- Four new options have been added to the
/etc/shorewall/shorewall.conf file that allow specifying the
default action for DROP, REJECT, ACCEPT and QUEUE.
The options are DROP_DEFAULT, REJECT_DEFAULT, ACCEPT_DEFAULT and
QUEUE_DEFAULT.
DROP_DEFAULT describes the rules to be applied before a
connection request is dropped by a DROP policy; REJECT_DEFAULT
describes the rules to be applied if a connection request is
rejected by a REJECT policy. The other two are similar for
ACCEPT and QUEUE policies.
The value assigned to these may be:
a) The name of an action.
b) The name of a macro
c) 'None' or 'none'
The default values are:
DROP_DEFAULT="Drop"
REJECT_DEFAULT="Reject"
ACCEPT_DEFAULT=none
QUEUE_DEFAULT=none
If USE_ACTIONS=Yes, then these values refer to action.Drop and
action.Reject respectively. If USE_ACTIONS=No, then these values
refer to macro.Drop and macro.Reject.
If you set the value of either option to "None" then no default
action will be used and the default action or macro must be
specified in /etc/shorewall/policy
- The POLICY column in /etc/shorewall/policy has been extended.
In /etc/shorewall/policy, when the POLICY is DROP, REJECT,
ACCEPT or QUEUE then the policy may be followed by ":" and one
of the following:
a) The word "None" or "none". This causes any default
action defined in /etc/shorewall/shorewall.conf
to be omitted for this policy.
b) The name of an action (requires that USE_ACTIONS=Yes
in shorewall.conf). That action will be invoked
before the policy is enforced.
c) The name of a macro. The rules in that macro will
be applied before the policy is enforced. This
does not require USE_ACTIONS=Yes.
Example:
#SOURCE DEST POLICY LOG
# LEVEL
loc net ACCEPT
net all DROP:MyDrop info
#
# THE FOLLOWING POLICY MUST BE LAST
#
all all REJECT:MyReject info
4) For users whose kernel and iptables have Extended MARK Target
support, it is now possible to logically AND or OR a value into the
current packet mark by preceding the mark value (and optional mask)
with an ampersand ("&") or vertical bar ("|") respectively.
Example: To logically OR the value 4 into the mark value for
packets from 192.168.1.1:
#MARK SOURCE
|4 192.168.1.1
5) Previously, zone names were restricted to five characters in
length. That length derives from the --log-prefix in Netfilter log
messages which must be 29 bytes or less in length. With the
standard Shorewall LOGFORMAT, that leaves 11 characters for the
chain name; given that many chain names are of the form
<zone1>2<zone2>, that gives a maximum zone name length of 11.
Beginning with this release, the maximum length of a zone name is
dependent on the LOGFORMAT (the maximum length may never be less
than 5 but it may be greater than 5). For example, setting
LOGFORMAT="FW:%s:%s:" will allow zone names of up to 8 characters.
6) Netfilter provides support for attaching comments to Netfilter
rules. Comments can be up to 255 bytes in length and are
visible using the "shorewall show <chain>", "shorewall show nat",
"shorewall show mangle" and "shorewall dump" commands. Comments are
delimited by '/* ... */" in the output.
Beginning with Shorewall 3.3.3, you may place COMMENT lines in the
/etc/shorewall/rules, /etc/shorewall/tcrules, /etc/shorewall/nat
and /etc/shorewall/masq files and in action files. The remainder of
the line is treated as a comment and it will be attached as a
Netfilter comment to the rule(s) generated by the following entries
in the file.
Note: Do not prefix the comment with "#". Shorewall's two-pass
compiler strips off "#" comments in the first pass and processes
COMMENT lines in the second pass. So by the time that COMMENT is
processed, the "#" and everything after it has been removed (see
example below).
To stop the current comment from being attached to further
rules, simply include COMMENT on a line by itself (so that the
following rules will have no comment) or specify a new COMMENT.
If you do not have Comment support in your iptables/kernel (see the
output of "shorewall[-lite] show capabilities") then COMMENTS are
ignored with this warning:
COMMENT ignored -- requires comment support in iptables/Netfilter
Example from my rules file:
#SOURCE SOURCE DEST PROTO DEST PORT(S)
COMMENT Stop Microsoft Noise
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
COMMENT # Stop comment from being attached to rules below
The output of "shorewall show loc2net" includes (folded):
0 0 reject tcp -- * * 0.0.0.0/0
0.0.0.0/0 multiport dports 137,445 /* Stop Microsoft Noise */
0 0 reject udp -- * * 0.0.0.0/0
0.0.0.0/0 udp dpts:137:139 /* Stop Microsoft Noise */
7) A new macro (macro.RDP) has been added for Microsoft Remote
Desktop. This macro was contributed by Tuomo Soini.
8) A new 'maclog' extension file has been added. This file is
processed just before logging based on the setting of
MACLIST_LOG_LEVEL is done. When invoked, the CHAIN variable will
contain the name of the chain where rules should be inserted.
Remember that if you have specified MACLIST_TABLE=mangle, then your
run_iptables commands should include "-t mangle".
9) The SUBNET column in /etc/shorewall/masq has been renamed SOURCE to
more accurately describe the contents of the column.
10) Previously, it was not possible to use exclusion in
/etc/shorewall/hosts. Beginning with this release, you may now use
exclusion lists in entries in this file. Exclusion lists are
discussed at:
http://www.shorewall.net/configuration_file_basics.htm#Exclusion.
Example:
loc eth0:192.168.1.0/24!192.168.1.4,192.168.1.16/28
In that example, the 'loc' zone is defined to be the subnet
192.168.1.0/24 interfacing via eth0 *except* for host 192.168.1.4
and hosts in the sub-network 192.168.1.16/28.
11) New "shorewall[-lite] show ip" and "shorewall[-lite] show routing"
commands have been added. The first produces the same output as "ip
addr ls". The second produces a report about your routing rules and
tables.
12) Beginning with this release, Shorewall and Shorewall Lite will
share common change logs and release notes.
13) In Shorewall versions prior to 3.3.2, multiple jumps to a '2all'
chain could be generated in succession.
Example from an earlier shorewall version:
gateway:~ # shorewall-lite show eth2_fwd
Shorewall Lite 3.3.2 Chains eth2_fwd at gateway - Thu Oct 19 08:54:37 PDT 2006
Counters reset Thu Oct 19 08:34:47 PDT 2006
Chain eth2_fwd (1 references)
pkts bytes target prot opt in out source destination
0 0 dynamic all -- * * 0.0.0.0/0 0.0.0.0/0 state INVALID,NEW
0 0 wifi2all all -- * eth0 0.0.0.0/0 0.0.0.0/0 policy match dir out pol none
0 0 wifi2all all -- * br0 0.0.0.0/0 0.0.0.0/0 policy match dir out pol none
0 0 wifi2all all -- * eth3 0.0.0.0/0 0.0.0.0/0 policy match dir out pol none
0 0 wifi2all all -- * tun+ 0.0.0.0/0 0.0.0.0/0 policy match dir out pol none
gateway:~ #
This redundancy may be eliminated by setting OPTIMIZE=1 in shorewall.conf.
gateway:~ # shorewall-lite show eth2_fwd
Shorewall Lite 3.3.3 Chains eth2_fwd at gateway - Thu Oct 19 09:15:24 PDT 2006
Counters reset Thu Oct 19 09:15:19 PDT 2006
Chain eth2_fwd (1 references)
pkts bytes target prot opt in out source destination
0 0 dynamic all -- * * 0.0.0.0/0 0.0.0.0/0 state INVALID,NEW
0 0 wifi2all all -- * * 0.0.0.0/0 0.0.0.0/0
gateway:~ #
Note that with OPTIMIZE=1, traffic destined for an
interface/Address that falls outside of all defined zones may now
be logged out of a '2all' chain rather than out of the FORWARD
chain.
The OPTIMIZE setting also controls the suppression of redundant
wildcard rules (those specifying "all" in the SOURCE or DEST
column). A wildcard rule is considered to be redundant when it
has the same ACTION and Log Level as the applicable policy.
Example:
/etc/shorewall/policy
#SOURCE DEST POLICY LEVEL
loc net ACCEPT
/etc/shorewall/rules
#ACTION SOURCE DEST PROTO DEST
# PORT(S)
...
ACCEPT all all icmp 8
OPTIMIZE=0
gateway:~ # shorewall show loc2net
Shorewall Lite 3.3.3 Chains loc2net at gateway - Thu Oct 26 07:55:03 PDT 2006
Counters reset Thu Oct 26 07:54:58 PDT 2006
Chain loc2net (1 references)
pkts bytes target prot opt in out source destination
...
0 0 DROP all -- * * !192.168.0.0/22 0.0.0.0/0
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmp type 8
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
gateway:~
OPTIMIZE=1
gateway:~ # shorewall show loc2net
Shorewall Lite 3.3.3 Chains loc2net at gateway - Thu Oct 26 07:57:12 PDT 2006
Counters reset Thu Oct 26 07:56:38 PDT 2006
Chain loc2net (1 references)
pkts bytes target prot opt in out source destination
...
0 0 DROP all -- * * !192.168.0.0/22 0.0.0.0/0
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
gateway:~
If you really want a rule that duplicates the policy, follow the
action with "!":
#ACTION SOURCE DEST PROTO DEST
# PORT(S)
...
ACCEPT! all all icmp 8
14) IP Address ranges are now allowed in the drop, reject, allow and
logdrop shorewall[-lite] commands.
15) The lib.cli library has been added. It is distributed with
both Shorewall and Shorewall Lite and contains the
command-processing code that is common to both /sbin/shorewall and
/sbin/shorewall-lite.
16) Previously, Shorewall has not attempted to undo the changes it has
made to the firewall's routing as a result of entries in
/etc/shorewall/providers and /etc/shorewall/routes. Beginning with
this release, Shorewall will attempt to undo these changes.
When Shorewall starts or is restarted and there are entries in
/etc/shorewall/providers, Shorewall will capture the contents
of /etc/shorewall/rt_tables and will restore that database when
Shorewall is stopped or restarted. Similarly, the default route
will be captured the first time that you [re]start Shorewall using
this version and will be restored under the following conditions:
a) shorewall stop
b) shorewall clear
c) shorewall restart or restore and there are no entries in
/etc/shorewall/providers.
Once the default route has been restored, Shorewall will delete
the saved copy so that it will once again be captured at the next
shorewall start or shorewall restore.
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