--- name: "ipfilter-defs" section: "5" platform: "linux" package: "netscript-2.4" version: "5.2.12" release: "Debian 7 (Wheezy)" platforms: ["linux"] url: "https://new.carta.tech/ipfilter-defs" --- # ipfilter-defs(5) netscript ipfilter-defs compile definitions directory. ## NAME /etc/netscript/ipfilter-defs - netscript ipfilter-defs compile definitions directory. ## DESCRIPTION This manual page documents briefly the compile definition files that are used by the [**netscript-compile**(8)](/netscript-compile/8.md) command from the netscript router/firewall network configuration package. This compiler creates a compiled iptables rules file in */etc/netscript/ipfilter-defs.conf* (it is a shell script portion) that is sourced by the netscript [**netscript**(8)](/netscript/8.md) command to configure the [**iptables**(8)](/iptables/8.md) firewall rules in the kernel. ## STARTUP COMPILATION The rules can be compiled and automatically loaded on boot by setting the IPV4\_CONFIGURE\_SWITCH switch in [**network.conf**(5)](/network.conf/5.md) to the value of the function used to configure the kernel. **Net-compile**(8) creates this function as *Configure.* If this switch is set, the netscript startup will run [**netscript-compile**(8)](/netscript-compile/8.md) to make sure everything is up to date and load the rules from */etc/netscript/ipfilter-defs.conf,* and the relevant settings in **[network.conf(5)](/network.conf/5.md)** which are used to establish packet grooming and configure the built in kernel netfilter INPUT and FORWARD chains in the filter table. If compilation fails, the previous rule set is not replaced and it is used instead. See the [**netscript**(8)](/netscript/8.md) manpage to see how to load and use backup copies of the rule set. ## CHAIN STRUCTURE Each chain in the [**iptables**(8)](/iptables/8.md) filter table is set up by a corresponding coonstruction function of the same name as the chain. The chains are laced into the *iplcl* (which is laced in to the INPUT chain) and *ipfwd* (laced into FORWARD) chains respectively, and the forwarding control chains are set up to take traffic in both directions, with the destination network/interface and source network/interface being used in the lacing chain, and network protocol and port being tied down in each specific chain. For the new in kernel Linux IPSEC, traffic to and from the VPN can be controlled via the iptables policy match module, if you have it patched and compiled into your kernel and iptables. Future versions of the kernel and iptables should have this included in the distributed source. ## FILE STRUCTURE All the files defining the rules set are in the */etc/netscript/ipfilter-defs* directory. The *network-defs* file is used to define the regions and network blocks used in the rest of the rules. The *prototypes-defs* file is used to define protoype rules that can be referenced elsewhere in the rule set. The *prototypes.sh* file is used to construct shell functions for the [**netscript-compile**(8)](/netscript-compile/8.md) command that can be used in the definitions files. DNAT and SNAT are set up in the *dnat-defs* and *masq-defs* files respectively. Any file ending in .def is taken as general rule set input for [**netscript-compile**(8)](/netscript-compile/8.md). The files generally take the form of tables, with the columns tab or space seperated. The ´#´ character is supported for commenting, and comments can be on a line by themselves, or at the end of a configuration line. Everything after the ´#´ is treated as a comment by the [**netscript-compile**(8)](/netscript-compile/8.md) compiler. ## RULE STRUCTURE The structure of the rule sets is thus. Each chain is started by calling a shell compilation function, (generally ipv4\_compile\_chain) to create the chain, with the chain name and source/destination regions as arguments, and each rule in the chain by starting a fresh line with the chain name in the first column. Regions are defined as network interface tuples, and are set up in *network-defs.* They are syntactically the same as shell script variables, and are used the same way in the *.def* rule set files. Technically this magic is achieved by using *eval* within the [**netscript-compile**(8)](/netscript-compile/8.md) shell script. Any interface name can have either of the keywords **=clear** or **=ipsec** tied to them by using the \`=' character on the end of the interface name. This is used to specifically match IPSEC traffic, or non-IPSEC traffic going over the interface. Typically you would use this when defining a region, though the syntax is valid elsewhere as well. It is recommended that you use this feature to prevent packet injection from adjacent external sources when setting up iptables rules for VPN tunnel traffic. The regions are given as arguments to the compilation function, with the region always being 2 arguments in network/interface order to the function. Each *chain rule* in the chain is defined by giving first of all the *chain name,* then the *rule type,* and its *direction.* All columns after the 3rd one are specific to and are defined by the *rule type.* The *direction* may have a ´-´ in it. The rules produced by the compiler use the iptables connection based state tracking. Packet by packet rules will be added later. ## EXAMPLE Here is an example of part of a .def file: ``` # Access from Office to internet # - only allow outgoing tcp and UDP # and ping traffic - anything else is most # like a tunneling protocol. # We have VPNs for tunneling ipv4_compile_chain -p 90 offcInet droplog $OFFICE_REGN $INTERNET_REGN offcInet ACCEPT_EST BOTH offcInet ACCEPT_PING L2R offcInet ACCEPT_TCP L2R 1:65535 offcInet ACCEPT_UDP L2R 1:65535 ``` The ACCEPT\_EST line accepts packets for ESTABLISHED and RELATED connections to the new ones already accepted. New connections are accepted by the ACCEPT\_PING, ACCEPT\_TCP, and ACCEPT\_UDP rules. Please see the [**iptables**(8)](/iptables/8.md) manpage for the details on stateful filtering. ## COMPILE FUNCTIONS Unless a function is defined in *prototypes.sh,* there is only one function provided. However this is not limiting as there is a facility for rule macros, as well as the ability to tell the function to use one of the default base rule sets. If you do define a function in *prototypes.sh,* be careful to handle all errors to function and command calls as otherwise [**netscript-compile**(8)](/netscript-compile/8.md) will break, as it runs with set -e set. The only defined compile function for IPv4 is: **ipv4\_compile\_chain \[-i\] \[-n\] \[-b base-chain\] \[-p priority\] \[-s slave-chain\] \ \ \ \ \[\ \\]** You can see the source region and destination region on the end of it. The *default-target* is one of RETURN, DROP, droplog, or log. The options to this function are as follows: - **-i** Create an input chain for attaching to *iplcl* instead of the default forward chain for attaching to *ipfwd.* - **-n** Don't lace the chain into *iplcl* or *ipfwd.* - **-b** *base-chain* Specify an alternate ruleset chain to use. - **-s** *slave-chain* Configure/deconfigure this chain as well as the one specified. Useful for adjusting input rule set when manipulating the access chain for an IPsec VPN. - **-p** *priority* Specify the priority of the chain in the lacing rule set. Priority is between 00 and 99, with 00 at the top of the lacing chain, and 99 at the bottom. This is useful for making sure that host specific rule sets occur before more general network related ones, and for putting Internet related ones at the bottom of the lacing chain. ## DIRECTION STATEMENTS The direction is as per FreeS/WAN - it uses left and right terminology. The possible directions are as follows: - L2R\|LEFT2RIGHT\|INTERNAL2EXTERNAL\|INTERN2EXTERN\|I2E\|INT2EXT *Left* to *Right,* *Internal* to *External* - R2L\|RIGHT2LEFT\|EXTERNAL2INTERNAL\|EXTERN2INTERN\|E2I\|EXT2INT *Right* to *Left,* *External* to *Internal* - BOTH\|- Both directions, aka none or ´-´. ## AVAILABLE CHAIN RULES Here are the valid chain rules, and the arguments they expect. - COMMENT \[word1\] \[word2\] ... Insert a comment into the compile shell script. Fill the 3rd column direction in with ´-´. - MACRO \ Specify a macro rule set. Rule set must name start with \`MACRO\_´. Direction again should be \`-´. - LOG \[word1\] \[word2\] ... Insert a logging rule using the given log meesage, or if none given, using the curretlog message for the chain. - LOG\_MSG \[word1\] \[word2\] ... Set the log message for the chain away from the default of \`Chain: \´ or from previous LOG\_MSG setting. Up to 26 letters can be used until truncation limit is reached. - RESET\_LOG\_MSG Reset log message to the default of \`Chain: \´. - REJECT\_SMB Jump to smb control chain. Creates smb chain if it does not already exist. - DROP\_MARTIANS Jump to martian source address control chain. Creates chain if it does not already exist. - LOG\_PORTSCAN Use the psd module to detect and log portscans. Creates portscan log chain (if not already there) which puts \`PORTSCAN DETECTED - ´ in the log. - DROP\_BROADCAST Drop ethernet broadcast packets. - LOG\_BROADCAST Log ethernet broadcast packets with the current log messages for the chain. - ACCEPT\_EST Accept ESTABLISH,RELATED packets via the [**iptables**(8)](/iptables/8.md) state module. - ACCEPT\_RELATED Accept RELATED packets via the [**iptables**(8)](/iptables/8.md) state module. Useful for ICMP type 3 packets used for maximum MTU detection. - ACCEPT\_PROTO \ Accept NEW connections for a protocol. Accepts one argument in the 4th column which is the protocol name from */etc/protocols* or the protocol number between 0 and 255. - REJECT\_PROTO \ Reject NEW connections for a protocol with ICMP reject packets. Accepts one argument in the 4th column which is the protocol name from */etc/protocols* or the protocol number between 0 and 255. - DROP\_PROTO \ Drop all packets for a protocol with nothing in reply. Accepts one argument in the 4th column which is the protocol name from */etc/protocols* or the protocol number between 0 and 255. - LOG\_PROTO \ Log NEW connections for a protocol with the current log message for the chain. Accepts one argument in the 4th column which is the protocol name from */etc/protocols* or the protocol number between 0 and 255. - ACCEPT\_TCP \[src-port-range\] \ Accept NEW TCP connections. If one argument given, it is the destinaion port (range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - REJECT\_TCP \[src-port-range\] \ Reject NEW TCP connections with an ICMP REJECT packet. If one argument given, it is the destination port(range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - DROP\_TCP \[src-port-range\] \ Drop all tcp packets, returning nothing at all. If one argument given, it is the destinaion port (range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - LOG\_TCP \[src-port-range\] \ Log NEW TCP connections with the current log text for the chain. If one argument given, it is the destination port(range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - ACCEPT\_UDP \[src-port-range\] \ Accept NEW UDP connections. If one argument given, it is the destinaion port (range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - REJECT\_UDP \[src-port-range\] \ Reject NEW UDP connections with an ICMP REJECT packet. If one argument given, it is the destination port(range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - DROP\_UDP \[src-port-range\] \ DROP all UDP packets, returning nothing at all. If one argument given, it is the destinaion port (range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - LOG\_UDP \[src-port-range\] \ Log NEW UDP connections with the current log message for the chain. If one argument given, it is the destination port(range). If 2 arguments, the first is the source port (range), and second the destination port (range). Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - ACCEPT\_PING Accept ICMP type 8 echo request packets for network diagnosis. - DROP\_PING Drop ICMP type 8 packets with no reply. - LOG\_PING Log an ICMP echo request with the current log message for the chain. - ACCEPT\_TCP\_NET \[src\_network \[src-port-range\]\] \ \ Accept NEW TCP connections from given source (optional) to destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - REJECT\_TCP\_NET \[src\_network \[src-port-range\]\] \ \ Reject NEW TCP conections with an ICMP reject packet which come from a given source (optional), going to given destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - DROP\_TCP\_NET \[src\_network \[src-port-range\]\] \ \ Drop all TCP packets which come from a given source (optional), going to given destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - LOG\_TCP\_NET \[src\_network \[src-port-range\]\] \ \ Log all NEW TCP connections from given source (optional) to destination, with the current log message for the chain. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - ACCEPT\_UDP\_NET \[src\_network \[src-port-range\]\] \ \ Accept NEW UDP connections from given source (optional) to destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - REJECT\_UDP\_NET \[src\_network \[src-port-range\]\] \ \ Reject NEW UDP conections with an ICMP reject packet which come from a given source (optional), going to given destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - DROP\_UDP\_NET \[src\_network \[src-port-range\]\] \ \ Drop all UDP packets which come from a given source (optional), going to given destination. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - LOG\_UDP\_NET \[src\_network \[src-port-range\]\] \ \ Log all NEW UDP connections from given source (optional) to destination, with the current log message for the chain. *Network* is given in IPv4 address/netmask or address/masklen format. Port ranges are specified by separating them with a \`:´ character, and ports must be in the */etc/services* file, or a number between 0 and 65535. - ACCEPT\_IFACE \ Accept all incoming NEW connections from an incoming interface. - REJECT\_IFACE \ Reject all incoming NEW conections with an ICMP reject packet, from an interface. - DROP\_IFACE \ Drop all incoming packets from an interface. - LOG\_IFACE \ Log all incoming NEW conections from an interface. - ACCEPT\_NET \ Accept all NEW connections from *network.* *Network* is given in IPv4 address/netmask or address/masklen format. - REJECT\_NET \ Reject all NEW conections from *network* with an ICMP reject packet. *Network* is given in IPv4 address/netmask or address/masklen format. - DROP\_NET \ Drop all packets from *network.* *Network* is given in IPv4 address/netmask or address/masklen format. - LOG\_NET \ Log all NEW conections from *network.* *Network* is given in IPv4 address/netmask or address/masklen format. ## FILES */etc/netscript/ipfilter-defs.conf,*\ */etc/netscript/ipfilter-defs-compiled.conf,*\ */etc/netscript/ipfilter-defs directory.*\ ## SEE ALSO [**netscript-compile**(8)](/netscript-compile/8.md), [**iptables**(8)](/iptables/8.md), [**ip6tables**(8)](/ip6tables/8.md), [**netscript**(8)](/netscript/8.md).\ ## AUTHOR This manual page was written by Matthew Grant \, for the Debian GNU/Linux system (but may be used by others). ## BUGS I wrote this manpage when I was not half asleep... Some things are missing from this manpage... Dnat documentation is missing but obvious from configuration file. SNAT documentation is missing but obvious from configuration file.