Shorewall 3.3.3 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 3.3.3 1) Previously, the 'provider' portion of the packet mark was not being cleared after routing for traffic that originates on the firewall itself. Other changes in 3.3.3 1) 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 2) 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, 11 characters are left for the chain name; since many chain names are of the form 2, we have a maximum zone name length of 5. 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. As part of this change, /sbin/shorewall[-lite] no longer uses the LOGFORMAT to select Shorewall messages from log files. Instead, it uses the regular expression /IN=.* OUT=/ which will match any netfilter-generated log message. 3) 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 ", "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 */ 4) A new macro (macro.RDP) has been added for Microsoft Remote Desktop. This macro was contributed by Tuomo Soini. 5) 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". 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 2, 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.