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ipf, ipf.conf - IP packet filter rule syntax
The ipf or ipf.conf configuration files are associated with the Solaris IP Filter feature. See ipfilter(5).
A rule file for ipf(1M) can have any name or can be stdin. You can use ipfstat(1M) output as input to ipf(1M). ipfstat outputs parseable rules, suitable for input to ipf, when displaying the internal kernel filter lists. Thus, for example, to remove all filters on input packets, you can enter:
# ipfstat -i | ipf -rf -
The IP filter feature uses the grammar shown below to construct filtering rules. The syntax is simplified for readability. Note that some combinations that match this grammar are disallowed by the software because they do not make sense (for example, tcp flags for non-TCP packets).
filter-rule = [ insert ] action in-out [ options ] [ tos ] [ ttl ]
[ proto ] ip [ group ].
insert = "@" decnumber .
action = block | "pass" | log | "count" | skip | auth .
in-out = "in" | "out" .
options = [ log ] [ tag ] [ "quick" ] [ "on" interface-name
[ dup ] [ froute ] [ replyto ]
tos = "tos" decnumber | "tos" hexnumber .
ttl = "ttl" decnumber .
proto = "proto" protocol .
ip = srcdst [ flags ] [ icmp ] [ with withopt ] [ keep ] .
group = [ "head" decnumber ] [ "group" decnumber ] .
block = "block" [ return-icmp[return-code] | "return-rst" ] .
auth = "auth" | "preauth" .
log = "log" [ "body" ] [ "first" ] [ "or-block" ] [ "level" loglevel ] .
tag = "set-tag" tagid
skip = "skip" decnumber .
dup = "dup-to" interface-name[":"ipaddr] .
froute = "fastroute" | "to" interface-name [ ":" ipaddr ].
replyto = "reply-to" interface-name [ ":" ipaddr ].
protocol = "tcp/udp" | "udp" | "tcp" | "icmp" | decnumber .
srcdst = "all" | fromto .
fromto = "from" [ "!" ] object "to" [ "!" ] object .
return-icmp = "return-icmp" | "return-icmp-as-dest" .
object = addr [ port-comp | port-range ] .
addr = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] .
addr = "any" | "<thishost>" | nummask |
host-name [ "mask" ipaddr | "mask" hexnumber ] .
port-comp = "port" compare port-num .
port-range = "port" port-num range port-num .
flags = "flags" flag { flag } [ "/" flag { flag } ] .
with = "with" | "and" .
icmp = "icmp-type" icmp-type [ "code" decnumber ] .
return-code = "("icmp-code")" .
keep = "keep" "state" | "keep" "frags" | "keep" "state"
"keep" "frags" |"keep" "frags" | "keep" "state".
loglevel = facility"."priority | priority .
nummask = host-name [ "/" decnumber ] .
host-name = ipaddr | hostname | "any" .
ipaddr = host-num "." host-num "." host-num "." host-num | ipv6addr .
host-num = digit [ digit [ digit ] ] .
port-num = service-name | decnumber .
withopt = [ "not" | "no" ] opttype [ withopt ] v6hdrs [ ipv6hdr ] .
opttype = "ipopts" | "short" | "frag" | "frag-body" | "frags" |
"opt" optname | "nat" | "multicast" |
"bcast" | "mbcast" | "state" | "bad-nat" | "bad" | "oow" |
"lowttl" | "bad-src" optname .
optname = ipopts [ "," optname ] .
ipopts = optlist | "sec-class" [ secname ] .
ipv6hdr = "ah" | "esp" | "dstopts" | "hopopts" | "ipv6" | "none" |
"routing" | "frag"
secname = seclvl [ "," secname ] .
seclvl = "unclass" | "confid" | "reserv-1" | "reserv-2" | "reserv-3" |
"reserv-4" | "secret" | "topsecret" .
icmp-type = "unreach" | "echo" | "echorep" | "squench" | "redir" |
"timex" | "paramprob" | "timest" | "timestrep" | "inforeq" |
"inforep" | "maskreq" | "maskrep" | decnumber .
icmp-code = decumber | "net-unr" | "host-unr" | "proto-unr" | "port-unr" |
"needfrag" | "srcfail" | "net-unk" | "host-unk" | "isolate" |
"net-prohib" | "host-prohib" | "net-tos" | "host-tos" |
"filter-prohib" | "host-preced" | "cutoff-preced" .
optlist = "nop" | "rr" | "zsu" | "mtup" | "mtur" | "encode" | "ts" |
"tr" | "sec" | "lsrr" | "e-sec" | "cipso" | "satid" | "ssrr" |
"addext" | "visa" | "imitd" | "eip" | "finn" .
facility = "kern" | "user" | "mail" | "daemon" | "auth" | "syslog" |
"lpr" | "news" | "uucp" | "cron" | "ftp" | "authpriv" |
"audit" | "logalert" | "local0" | "local1" | "local2" |
"local3" | "local4" | "local5" | "local6" | "local7" .
priority = "emerg" | "alert" | "crit" | "err" | "warn" | "notice" |
"info" | "debug" .
hexnumber = "0" "x" hexstring .
hexstring = hexdigit [ hexstring ] .
decnumber = digit [ decnumber ] .
compare = "=" | "!=" | "<" | ">" | "<=" | ">=" | "eq" | "ne" | "lt" |
"gt" | "le" | "ge" .
range = "<>" | "><" .
hexdigit = digit | "a" | "b" | "c" | "d" | "e" | "f" .
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" .
flag = "F" | "S" | "R" | "P" | "A" | "U" .
Filter rules are checked in order, with the last matching rule determining the treatment of the packet. An exception to this is the quick option, which is discussed below.
By default, filters are installed at the end of the kernel's filter lists. Prepending a rule with @<num> causes it to be inserted as the <num>th entry in the current list. This is especially useful when modifying and testing active filter rule sets. See ipf(1M) for more information.
The simplest valid rules are:
block in all pass in all log out all count in all
These rules do not have an effect on filtering, but are listed here to illustrate the grammar.
Each rule must have an action. The action indicates what to do with the packet if it matches the filter rule. The IP filter feature recognizes the following actions:
block
block return-icmp(11) ...
The preceding entry causes a return of a Type-Of-Service (TOS) ICMP unreachable error.
pass
log
count
skip <num>
auth
preauth
The word following the action keyword must be either in or out. Each packet moving through the kernel is either inbound or outbound. "Inbound" means that a packet has just been received on an interface and is moving towards the kernel's protocol processing. "Outbound" means that a packet has been transmitted or forwarded by the stack and is on its way to an interface. There is a requirement that each filter rule explicitly state on which side of the I/O it is to be used.
The currently supported options are listed below. Where you use options, you must use them in the order shown here.
log
quick
If the quick option is missing, the rule is taken to be a "fall-through" rule, meaning that the result of the match (block or pass) is saved and that processing will continue to see if there are any more matches.
on
This option is especially useful for simple IP-spoofing protection: packets should be allowed to pass inbound only on the interface from which the specified source address would be expected. Others can be logged, or logged and dropped.
dup-to
to
The keywords described in this section are used to describe attributes of the packet to be used when determining whether rules do or do not match. The following general-purpose attributes are provided for matching and must be used in the order shown below.
tos
ttl
proto
The special protocol keyword tcp/udp can be used to match either a TCP or a UDP packet and has been added as a convenience to save duplication of otherwise-identical rules.
IP addresses can be specified in one of two ways: as a numerical address/mask, or as a hostname mask/netmask. The hostname can be either of the dotted numeric form or a valid hostname, from the hosts file or DNS (depending on your configuration and library). There is no special designation for networks, but network names are recognized. Note that having your filter rules depend on DNS results can introduce an avenue of attack and is discouraged.
There is a special case for the hostname any, which is taken to be 0.0.0.0/0 (mask syntax is discussed below) and matches all IP addresses. Only the presence of any has an implied mask. In all other situations, a hostname must be accompanied by a mask. It is possible to give any a hostmask, but in the context of this language, it would accomplish nothing.
The numerical format x/y indicates that a mask of y consecutive 1 bits set is generated, starting with the MSB, so that a y value of 16 would result in 0xffff0000. The symbolic x mask y indicates that the mask y is in dotted IP notation or a hexadecimal number of the form 0x12345678. Note that all the bits of the IP address indicated by the bitmask must match the address on the packet exactly; there is currently not a way to invert the sense of the match or to match ranges of IP addresses that do not express themselves easily as bitmasks.
If a port match is included, for either or both of source and destination, then it is only applied to TCP and UDP packets. If there is no proto match parameter, packets from both protocols are compared. This is equivalent to proto tcp/udp. When composing port comparisons, either the service name or an integer port number can be used. Port comparisons can be done in a number of forms, with a number of comparison operators, or you can specify port ranges. When the port appears as part of the from object, it matches the source port number. When it appears as part of the to object, it matches the destination port number. See EXAMPLES.
The all keyword is essentially a synonym for "from any to any" with no other match parameters.
Following the source and destination matching parameters, you can use the following additional parameters:
with
Before any parameter used after the with keyword, you can insert the word not or no to cause the filter rule to match only if the option(s) is not present.
Multiple consecutive with clauses are allowed. Alternatively, you can use the keyword and in place of with. This alternative is provided to make the rules more readable ("with ... and ..."). When multiple clauses are listed, all clauses must match to cause a match of the rule.
flags
... flags S
... flags SA
... flags S/SA
icmp-type
The penultimate parameter that can be set for a filter rule is whether or not to record historical information for a packet, and what sort to keep. The following information can be kept:
state
frags
Presence of these parameters allows matching packets to flow straight through, rather than going through the access control list.
The last pair of parameters control filter rule grouping. By default, all filter rules are placed in group 0 if no other group is specified. To add a rule to a non-default group, the group must first be started by creating a group head. If a packet matches a rule which is the head of a group, the filter processing then switches to the group, using that rule as the default for the group. If quick is used with a head rule, rule processing is not stopped until it has returned from processing the group.
A rule can be both the head for a new group and a member of a non-default group (head and group can be used together in a rule).
head <n>
group <n>
When a packet is logged, by means of either the log action or log option, the headers of the packet are written to the ipl packet logging pseudo-device. Immediately following the log keyword, you can use the following qualifiers in the order listed below:
body
first
or-block
level loglevel
You can use ipmon(1M) to read and format the log.
By default, the IP Filter feature will not filter or intercept any packets that are local to the machine. This includes traffic to or from the loopback addresses (127.0.0.1, and so forth), traffic between sockets that are on the same host (for example, from eri0 to eri1), and traffic between zones.
To enable loopback or zone filtering, you must add the following line to ipf.conf file:
set intercept_loopback true;
This line must be placed before any block or pass rules in this file or, put another way, it must be the first non-comment line in ipf.conf.
When you enable filtering of packets in any one of the scenarios described above, you enabling filtering for all them. That is, when you enable the IP Filter feature to intercept packets between zones, you also cause it to receive packets that are involved in loopback traffic.
Example 1 Using the quick Option
The quick option works well for rules such as:
block in quick from any to any with ipopts
This rule matches any packet with a non-standard header length (IP options present) and aborts further processing of later rules, recording a match and also indicating that the packet should be blocked.
Example 2 Using the Fall-through Nature of Rule Parsing
The "fall-through" rule parsing allows for effects such as the following:
block in from any to any port < 6000 pass in from any to any port >= 6000 block in from any to any port > 6003
These rules set up the range 6000-6003 as being permitted and all others being denied. Note that the effect of the first rule is overridden by subsequent rules. Another (easier) way to do the same is:
block in from any to any port 6000 <> 6003 pass in from any to any port 5999 >< 6004
Note that both the block and pass are needed here to effect a result, because a failed match on the block action does not imply a pass. It implies only that the rule has not taken effect. To then allow ports lower than 1024, a rule such as:
pass in quick from any to any port < 1024
...would be needed before the first block. To create a new group for processing all inbound packets on le0/le1/lo0, with the default being to block all inbound packets, you would use a rule such as:
block in all block in quick on le0 all head 100 block in quick on le1 all head 200 block in quick on lo0 all head 300
and to then allow ICMP packets in on le0 only, you would use:
pass in proto icmp all group 100
Note that because only inbound packets on le0 are processed by group 100, there is no need to respecify the interface name. Likewise, you could further breakup processing of TCP as follows:
block in proto tcp all head 110 group 100 pass in from any to any port = 23 group 110
...and so on. The last line, if written without the groups, would be:
pass in on le0 proto tcp from any to any port = telnet
Note, that if you wanted to specify port = telnet, you would need to specify proto tcp, because the parser interprets each rule on its own and qualifies all service and port names with the protocol specified.
/etc/ipf/ipf.conf
See attributes(5) for a description of the following attributes:
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ipf(1M), ipfstat(1M), ipmon(1M), attributes(5), ipfilter(5)
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