svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.
pf.conf(7)
pf...f(7)Standards, Environments, Macros, Character Sets, and miscellanpyf...f(7)
NAME
pf.conf - packet filter configuration file
DESCRIPTION
The PF packet filter modifies, drops, or passes packets according to
rules or definitions specified in pf.conf.
PACKET FILTERING
PF has the ability to block, pass, and match packets based on attrib‐
utes of their layer 3 and layer 4 headers. Filter rules determine which
of these actions are taken; filter parameters specify the packets to
which a rule applies.
For each packet processed by the packet filter, the filter rules are
evaluated in a sequential order, from first to last. For block and
pass, the last matching rule decides what action is taken, if no rule
matches the packet, the default action is to pass the packet without
creating a state. For match, rules are evaluated every time they match,
the pass/block state of a packet remains unchanged.
Most parameters are optional. If a parameter is specified, the rule
only applies to packets with matching attributes. Certain parameters
can be expressed as lists, in which case pfctl(8) generates all needed
rule combinations.
By default PF filters packets statefully. The first time a packet
matches a pass rule, a state entry is created. The packet filter exam‐
ines each packet to see if it matches an existing state. If it does,
the packet is passed without evaluation of any rules. After the connec‐
tion is closed or timed out, the state entry is automatically removed.
The following actions can be used in the filter:
block
The packet is blocked. There are a number of ways in which a block
rule can behave when blocking a packet. The default behaviour is to
drop packets silently, however this can be overridden or made ex‐
plicit either globally, by setting the block-policy option, or on a
per-rule basis with one of the following options:
drop
The packet is silently dropped.
return
This causes a TCP RST to be returned for TCP packets and an
ICMP UNREACHABLE for other types of packets.
return-icmp and return-icmp6
This causes ICMP messages to be returned for packets which
match the rule. By default this is an ICMP UNREACHABLE message,
however this can be overridden by specifying a message as a
code or number.
return-rst
This applies only to TCP packets, and issues a TCP RST which
closes the connection. An optional parameter, ttl, may be given
with a TTL value.
The simplest mechanism to block everything by default and only pass
packets that match explicit rules is specify a first filter rule
of: block all.
match
The packet is matched. This mechanism is used to provide fine
grained filtering without altering the block/pass state of a
packet. Match rules differ from block and pass rules in that para‐
meters are set every time a packet matches the rule, not only on
the last matching rule. For the following parameters, this means
that the parameter effectively becomes sticky until explicitly
overridden: nat-to, binat-to, rdr-to, queue, rtable, and scrub.
log is bit different. Here, the action happens every time a rule
matches which means, a single packet can get logged more than once.
pass
The packet is passed. A state is created unless the no state option
is specified.
in or out
A packet always comes in on, or goes out through, one interface. in
and out apply to incoming and outgoing packets; if neither are
specified, the rule will match packets in both directions.
log
In addition to the action specified, a log message is generated.
Only the packet that establishes the state is logged, unless the no
state option is specified. The logged packets are sent to a capture
interface (see dladm(8)), by default pflog0 interface is monitored
by the pflogd(8) logging daemon, which dumps the logged packets to
the file /var/log/firewall/pflog in pcap() binary format.
log (all)
Used to force log all packets for a connection. This is not neces‐
sary when no state is explicitly specified. As with log, packets
are logged to capture interface (see dladm(8)).
log (matches)
Used to force log this packet on all subsequent matching rules.
log (user)
Logs the UID and PID of the socket on the local host used to send
or receive a packet, in addition to the normal information.
log (to <interface>)
Send logs to the specified capture interface (see dladm(8)) inter‐
face instead of pflog0.
quick
If a packet matches a rule which has the quick option set, this
rule is considered the last matching rule, and evaluation of subse‐
quent rules is skipped.
on <interface>
This rule applies only to packets coming in on, or going out
through this particular interface.
<af>
This rule applies only to packets of this address family. Supported
values are inet and inet6.
proto <protocol>
This rule applies only to packets of this protocol. Common proto‐
cols are ICMP, ICMP6, TCP, and UDP. For a list of all the protocol
name to number mappings used by pfctl(8), see protocols(5).
from <source> port <source> os <source> to <dest> port <dest>
This rule applies only to packets with the specified source and
destination addresses and ports.
Addresses can be specified in CIDR notation (matching netblocks) as
symbolic host names, interface names or as any of the following
keywords:
any Any address.
self Expands to all addresses assigned to all interfaces.
<table> Any address matching the given table.
Ranges of addresses are specified using the - operator. For in‐
stance: 10.1.1.10 - 10.1.1.12. This means all addresses from
10.1.1.10 to 10.1.1.12, hence addresses 10.1.1.10, 10.1.1.11, and
10.1.1.12.
Interface names including self can have modifiers appended:
:0 Do not include interface aliases.
:broadcast Translates to the interface's broadcast address(es).
:network Translates to the network(s) attached to the inter‐
face.
:peer Translates to the point-to-point interface's peer ad‐
dress(es).
Host names may also have the :0 option appended to restrict the
name resolution to the first of each v4 and v6 address found.
Host name resolution and interface to address translation are done
at ruleset load-time. When the address of an interface (or host
name) changes (under DHCP for instance), the ruleset must be re‐
loaded for the change to be reflected in the kernel.
Ports can be specified either by number or by name. For example,
port 80 can be specified as www. For a list of all port name to
number mappings used by pfctl(8), see services(5).
Ports and ranges of ports are specified using these operators:
= (equal)
!= (unequal)
< (less than)
<= (less than or equal)
> (greater than)
>= (greater than or equal)
: (range including boundaries)
>< (range excluding boundaries)
<> (except range)
><, <> and : are binary operators (they take two arguments). For
instance:
port 2000:2004 means all ports >= 2000 and <= 2004, hence
ports 2000, 2001, 2002, 2003, and 2004.
port 2000 >< 2004 means all ports > 2000 and < 2004, hence ports
2001, 2002, and 2003.
port 2000 <> 2004 means all ports < 2000 or > 2004, hence ports
1-1999 and 2005-65535.
The operating system of the source host can be specified in the
case of TCP rules with the os modifier. See the OPERATING SYSTEM
FINGERPRINTING section for more information.
The host, port, and OS specifications are optional, as in the fol‐
lowing examples:
pass in all
pass in from any to any
pass in proto tcp from any port < 1024 to any
pass in proto tcp from any to any port 25
pass in proto tcp from 10.0.0.0/8 port >= 1024\
to ! 10.1.2.3 port != ssh
pass in proto tcp from any os "OpenBSD"
pass in proto tcp from route "DTAG"
The following additional parameters can be used in the filter:
all
This is equivalent to from any to any.
allow-opts
By default, packets with IPv4 options or IPv6 hop-by-hop or desti‐
nation options header are blocked. When allow-opts is specified for
a pass rule, packets that pass the filter based on that rule (last
matching) do so even if they contain options. For packets that
match state, the rule that initially created the state is used. The
implicit pass rule that is used when a packet does not match any
rules, does not allow IP options or option headers. Note that IPv6
packets with type 0 routing headers are always dropped.
flags <a> /<b> | any
This rule only applies to TCP packets that have the flags <a> set
out of set <b>. Flags not specified in <b> are ignored. For state‐
ful connections, the default is flags S/SA. To indicate that flags
should not be checked at all, specify flags any. The flags are:
(F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
flags S/S Flag SYN is set. The other flags are ignored.
flags S/SA This is the default setting for stateful connec‐
tions. Out of SYN and ACK, exactly SYN may be set.
SYN, SYN+PSH, and SYN+RST match, but SYN+ACK, ACK,
and ACK+RST do not. This is more restrictive than
the previous example.
flags /SFRA If the first set is not specified, it defaults to
none. All of SYN, FIN, RST, and ACK must be unset.
As the flag S/SA is applied by default (unless no state is speci‐
fied), only the initial SYN packet of a TCP handshake will create a
state for a TCP connection. It is possible to be less restrictive,
and allow state creation from intermediate (non-SYN) packets, by
specifying flags any. This will cause PF to synchronize to existing
connections, for instance if one flushes the state table. However,
states created from such intermediate packets may be missing con‐
nection details such as the TCP window scaling factor. States which
modify the packet flow, such as those affected by modulate, nat-to,
rdr-to, or synproxy state options, or scrubbed with reassemble tcp,
will also not be recoverable from intermediate packets. Such con‐
nections will stall and time out.
group <group>
Similar to user, this rule only applies to packets of sockets owned
by the specified group.
icmp-type <type> code <code> and icmp6-type <type> code <code>
This rule only applies to ICMP or ICMP6 packets with the specified
type and code. Text names for ICMP types and codes are listed in
icmp() and icmp6(). The protocol and the ICMP type indicator (icmp-
type or icmp6-type) must match.
label <string>
Adds a label to the rule, which can be used to identify the rule.
For instance, pfctl -s labels shows per-rule statistics for rules
that have labels.
The following macros can be used in labels:
$dstaddr The destination IP address.
$dstport The destination port specification.
$if The interface.
$nr The rule number.
$proto The protocol name.
$srcaddr The source IP address.
$srcport The source port specification
For example:
ips = "{ 1.2.3.4, 1.2.3.5 }"
pass in proto tcp from any to $ips\
port > 1023 label "$dstaddr:$dstport"
Expands to:
pass in inet proto tcp from any to 1.2.3.4\
port > 1023 label "1.2.3.4:>1023"
pass in inet proto tcp from any to 1.2.3.5\
port > 1023 label "1.2.3.5:>1023"
The macro expansion for the label directive occurs only at configu‐
ration file parse time, not during runtime.
once
Creates a one shot rule that will remove itself from an active
ruleset after the first match. In case this is the only rule in the
anchor, the anchor will be destroyed automatically after the rule
is matched.
probability <number>
A probability attribute can be attached to a rule, with a value set
between 0 and 100%, in which case the rule is honoured using the
given probability value. For example, the following rule will drop
20% of incoming ICMP packets:
block in proto icmp probability 20%
received-on <interface>
Only match packets which were received on the specified interface.
set tos <string> | <number>
Enforces a TOS for matching packets. String may be one of critical,
inetcontrol, lowdelay, netcontrol, throughput, reliability, or one
of the DiffServ Code Points: ef, af11 ... af43, cs0 ... cs7; number
may be either a hex or decimal number.
tag <string>
Packets matching this rule will be tagged with the specified
string. The tag acts as an internal marker that can be used to
identify these packets later on. This can be used, for example, to
provide trust between interfaces and to determine if packets have
been processed by translation rules. Tags are sticky, meaning that
the packet will be tagged even if the rule is not the last matching
rule. Further matching rules can replace the tag with a new one but
will not remove a previously applied tag. A packet is only ever as‐
signed one tag at a time. Tags take the same macros as labels (see
above).
tagged <string>
Used with filter or translation rules to specify that packets must
already be tagged with the given tag in order to match the rule.
Inverse tag matching can also be done by specifying the ! operator
before the tagged keyword.
tos <string> | <number>
This rule applies to packets with the specified TOS bits set.
String may be one of critical, inetcontrol, lowdelay, netcontrol,
throughput, reliability, or one of the DiffServ Code Points: ef,
af11 ... af43, cs0 ... cs7; number may be either a hex or decimal
number.
For example, the following rules are identical:
pass all tos lowdelay
pass all tos 0x10
pass all tos 16
user <user>
This rule only applies to packets of sockets owned by the specified
user. For outgoing connections initiated from the firewall, this is
the user that opened the connection. For incoming connections to
the firewall itself, this is the user that listens on the destina‐
tion port. For forwarded connections, where the firewall is not a
connection endpoint, the user and group are unknown.
All packets, both outgoing and incoming, of one connection are as‐
sociated with the same user and group. Only TCP and UDP packets can
be associated with users.
User and group refer to the effective (as opposed to the real) IDs,
in case the socket is created by a setuid/setgid process. User and
group IDs are stored when a socket is created; when a process cre‐
ates a listening socket as root (for instance, by binding to a
privileged port) and subsequently changes to another user ID (to
drop privileges), the credentials will remain root.
User and group IDs can be specified as either numbers or names. The
syntax is similar to the one for ports. The value unknown matches
packets of forwarded connections. unknown can only be used with the
operators = and !=. Other constructs like user >= unknown are in‐
valid. Forwarded packets with unknown user and group ID match only
rules that explicitly compare unknown with the operators = or !=.
For instance user >= 0 does not match forwarded packets. The fol‐
lowing example allows only selected users to open outgoing connec‐
tions:
block out proto { tcp, udp } all
pass out proto { tcp, udp } all user { < 1000, dhartmei }
TRANSLATION
Translation options modify either the source or destination address and
port of the packets associated with a stateful connection. PF modifies
the specified address and/or port in the packet and recalculates IP,
TCP, and UDP checksums as necessary.
Subsequent rules will see packets as they look after any addresses and
ports have been translated. These rules will therefore have to filter
based on the translated address and port number.
The state entry created permits PF to keep track of the original ad‐
dress for traffic associated with that state and correctly direct re‐
turn traffic for that connection.
Different types of translation are possible with pf:
binat-to
A binat-to rule specifies a bidirectional mapping between an exter‐
nal IP netblock and an internal IP netblock. It expands to an out‐
bound nat-to rule and an inbound rdr-to rule.
nat-to
A nat-to option specifies that IP addresses are to be changed as
the packet traverses the given interface. This technique allows one
or more IP addresses on the translating host to support network
traffic for a larger range of machines on an "inside" network. Al‐
though in theory any IP address can be used on the inside, it is
strongly recommended that one of the address ranges defined by RFC
1918 be used. Those netblocks are:
10.0.0.0 - 10.255.255.255 (all of net 10, i.e. 10/8)
172.16.0.0 - 172.31.255.255 (i.e. 172.16/12)
192.168.0.0 - 192.168.255.255 (i.e. 192.168/16)
nat-to is usually applied outbound. If applied inbound, nat-to to a
local IP address is not supported.
rdr-to
The packet is redirected to another destination and possibly a dif‐
ferent port. rdr-to can optionally specify port ranges instead of
single ports. For instance:
match in ... port 2000:2999 rdr-to ... port 4000
redirects ports 2000 to 2999 (inclusive) to port 4000.
match in ... port 2000:2999 rdr-to ... port 4000:*
redirects port 2000 to 4000, port 2001 to 4001, ...,
port 2999 to 4999.
rdr-to is usually applied inbound. If applied outbound, rdr-to to a
local IP address is not supported.
In addition to modifying the address, some translation rules may modify
source or destination ports for TCP or UDP connections; implicitly in
the case of nat-to options and explicitly in the case of rdr-to ones.
Port numbers are never translated with a binat-to rule.
Translation options apply only to packets that pass through the speci‐
fied interface, and if no interface is specified, translation is ap‐
plied to packets on all interfaces. For instance, redirecting port 80
on an external interface to an internal web server will only work for
connections originating from the outside. Connections to the address of
the external interface from local hosts will not be redirected, since
such packets do not actually pass through the external interface. Redi‐
rections cannot reflect packets back through the interface they arrive
on, they can only be redirected to hosts connected to different inter‐
faces or to the firewall itself.
However packets may be redirected to hosts connected to the interface
the packet arrived on by using redirection with NAT. For example:
pass in on $int_if proto tcp from $int_net to $ext_if port 80\
rdr-to $server
pass out on $int_if proto tcp to $server port 80\
received-on $int_if nat-to $int_if
For nat-to and rdr-to options for which there is a single redirection
address which has a subnet mask smaller than 32 for IPv4 (more than one
IP address), a variety of different methods for assigning this address
can be used:
bitmask
The bitmask option applies the network portion of the redirection
address to the address to be modified (source with nat-to, destina‐
tion with rdr-to).
least-states [sticky-address]
The least-states option selects the address with the least active
states from a given address pool and considers given weights asso‐
ciated with address(es). Weights can be specified between 1 and
65535. Addresses with higher weights are selected more often.
The sticky-address can be specified to ensure that multiple connec‐
tions from the same source are mapped to the same redirection ad‐
dress. Associations are destroyed as soon as there are no longer
states which refer to them. In order to make the mappings last be‐
yond the lifetime of the states, increase the global options with
set timeout src.track.
random [sticky-address]
The random option selects an address at random within the defined
block of addresses. sticky-address is as described above.
round-robin [sticky-address]
The round-robin option loops through the redirection address(es)
and considers given weights associated with address(es). Weights
can be specified between 1 and 65535. Addresses with higher weights
are selected more often. sticky-address is as described above.
source-hash [key]
The source-hash option uses a hash of the source address to deter‐
mine the redirection address, ensuring that the redirection address
is always the same for a given source. An optional key can be spec‐
ified after this keyword either in hex or as a string; by default
pfctl(8) randomly generates a key for source-hash every time the
ruleset is reloaded.
static-port
With nat rules, the static-port option prevents PF from modifying
the source port on TCP and UDP packets.
When more than one redirection address or a table is specified, round-
robin and least-states are the only permitted pool types.
Routing
If a packet matches a rule with one of the following route options set,
the packet filter will route the packet according to the type of route
option. When such a rule creates state, the route option is also ap‐
plied to all packets matching the same connection.
dup-to
The dup-to option creates a duplicate of the packet and routes it
like route-to. The original packet gets routed as it normally
would.
reply-to
The reply-to option is similar to route-to, but routes packets that
pass in the opposite direction (replies) to the specified inter‐
face. Opposite direction is only defined in the context of a state
entry, and reply-to is useful only in rules that create state. It
can be used on systems with multiple external connections to route
all outgoing packets of a connection through the interface the in‐
coming connection arrives through (symmetric routing enforcement).
route-to
The route-to option routes the packet to the specified interface
with an optional address for the next hop. When a route-to rule
creates state, only packets that pass in the same direction as the
filter rule specifies will be routed in this way. Packets passing
in the opposite direction (replies) are not affected and are routed
normally.
For the dup-to, reply-to, and route-to route options for which there is
a single redirection address which has a subnet mask smaller than 32
for IPv4 or 128 for IPv6 (more than one IP address), the methods,
least-states, random, round-robin, and source-hash, as described above,
can be used.
OPTIONS
PF may be tuned for various situations using the set command.
set block-policy
The block-policy option sets the default behaviour for the packet
block action:
drop Packet is silently dropped.
return A TCP RST is returned for blocked TCP packets, an ICMP
UNREACHABLE is returned for blocked UDP packets, and all
other packets are silently dropped.
set debug
Set the debug level, which limits the severity of log messages
printed by 'PF'. This should be a keyword from the following or‐
dered list (highest to lowest): emerg, alert, crit, err, warning,
notice, info, and debug.
set fingerprints
Load fingerprints of known operating systems from the given file‐
name. By default, fingerprints of known operating systems are auto‐
matically loaded from pf.os(7), but can be overridden using this
option. Setting this option may leave a small period of time where
the fingerprints referenced by the currently active ruleset are in‐
consistent until the new ruleset finishes loading.
set limit
Sets hard limits on the memory pools used by the packet filter.
For example, to set the maximum number of entries in the memory
pool used by state table entries (generated by pass rules which do
not specify no state) to 20000:
set limit states 20000
To set the maximum number of entries in the memory pool used for
fragment reassembly to 2000:
set limit frags 2000
To set the maximum number of entries in the memory pool used for
tracking source IP addresses (generated by the sticky-address and
src.track options) to 2000:
set limit src-nodes 2000
To set limits on the memory pools used by tables:
set limit tables 1000
set limit table-entries 100000
The first limits the number of tables that can exist to 1000. The
second limits the overall number of addresses that can be stored in
tables to 100000.
Various limits can be combined on a single line:
set limit { states 20000, frags 2000, src-nodes 2000 }
set loginterface
Enable collection of packet and byte count statistics for the given
interface. These statistics can be viewed using:
# pfctl -s info
In this example PF collects statistics on the interface named net0:
set loginterface net0
One can disable the loginterface using:
set loginterface none
set optimization
Optimize state timeouts for one of the following network environ‐
ments:
aggressive
Aggressively expire connections. This can greatly reduce the
memory usage of the firewall at the cost of dropping idle con‐
nections early.
conservative
Extremely conservative settings. Avoid dropping legitimate con‐
nections at the expense of greater memory utilization (possibly
much greater on a busy network) and slightly increased proces‐
sor utilization.
high-latency
A high-latency environment (such as a satellite connection).
normal
A normal network environment. Suitable for almost all networks.
satellite
Alias for high-latency.
set reassemble
The reassemble option is used to enable or disable the reassembly
of fragmented packets, and can be set to yes (the default) or no.
If no-df is also specified, fragments with the dont-fragment bit
set are reassembled too, instead of being dropped. The reassembled
packet will have the dont-fragment bit cleared.
set ruleset-optimization
basic
Enable basic ruleset optimization. This is the default behav‐
iour. Basic ruleset optimization does four things to improve
the performance of ruleset evaluations:
1. remove duplicate rules
2. remove rules that are a subset of another rule
3. combine multiple rules into a table when advanta‐
geous
4. re-order the rules to improve evaluation performance
none
Disable the ruleset optimizer.
profile
Uses the currently loaded ruleset as a feedback profile to tai‐
lor the ordering of quick rules to actual network traffic.
It is important to note that the ruleset optimizer will modify the
ruleset to improve performance. A side effect of the ruleset modi‐
fication is that per-rule accounting statistics will have different
meanings than before. If per-rule accounting is important for
billing purposes, either the ruleset optimizer should not be used
or a label field should be added to all of the accounting rules to
act as optimization barriers.
Optimization can also be set as a command-line argument to
pfctl(8), overriding the settings in pf.conf.
set skip on <ifspec>
List interfaces for which packets should not be filtered. Packets
passing in or out on such interfaces are passed as if pf was dis‐
abled, which means, pf does not process them in any way. This can
be useful on loopback and other virtual interfaces, when packet
filtering is not desired and can have unexpected effects. ifspec is
only evaluated when the ruleset is loaded. Interfaces created later
will not get skipped.
set state-defaults
The state-defaults option sets the state options for states created
from rules without an explicit keep state. For example:
set state-defaults sloppy
set state-policy
The state-policy option sets the default behaviour for states:
if-bound States are bound to an interface.
floating States can match packets on any interfaces (the de‐
fault).
set timeout
frag Seconds before an unassembled fragment is expired.
interval Interval between purging expired states and fragments.
src.track Length of time to retain a source tracking entry after
the last state expires.
When a packet matches a stateful connection, the seconds to live
for the connection will be updated to that of the protocol and mod‐
ifier which corresponds to the connection state. Each packet which
matches this state will reset the TTL. Tuning these values may im‐
prove the performance of the firewall at the risk of dropping valid
idle connections.
tcp.closed The state after one endpoint sends an RST.
tcp.closing The state after the first FIN has been sent.
tcp.established The fully established state.
tcp.finwait The state after both FINs have been exchanged
and the connection is closed. Some hosts (no‐
tably web servers on Solaris) send TCP packets
even after closing the connection. Increasing
tcp.finwait (and possibly tcp.closing) can pre‐
vent blocking of such packets.
tcp.first The state after the first packet.
tcp.opening The state after the second packet but before
both endpoints have acknowledged the connection.
ICMP and UDP are handled in a similar process as TCP, but with a
much more limited set of states:
icmp.error The state after an ICMP error came back in response
to an ICMP packet.
icmp.first The state after the first packet.
udp.first The state after the first packet.
udp.multiple The state if both hosts have sent packets.
udp.single The state if the source host sends more than one
packet but the destination host has never sent one
back.
Other protocols are handled similarly to UDP:
other.first
other.multiple
other.single
Timeout values can be reduced adaptively as the number of state ta‐
ble entries grows.
adaptive.end
When reaching this number of state entries, all timeout values
become zero, effectively purging all state entries immediately.
This value is used to define the scale factor; it should not
actually be reached (set a lower state limit, see below).
adaptive.start
When the number of state entries exceeds this value, adaptive
scaling begins. All timeout values are scaled linearly with
factor (adaptive.end - number of states) / (adaptive.end -
adaptive.start).
Adaptive timeouts are enabled by default, with an adaptive.start
value equal to 60% of the state limit, and an adaptive.end value
equal to 120% of the state limit. They can be disabled by setting
both adaptive.start and adaptive.end to 0.
The adaptive timeout values can be defined both globally and for
each rule. When used on a per-rule basis, the values relate to the
number of states created by the rule, otherwise to the total number
of states. For example:
set timeout tcp.first 120
set timeout tcp.established 86400
set timeout { adaptive.start 6000, adaptive.end 12000 }
set limit states 10000
With 9000 state table entries, the timeout values are scaled to 50%
(tcp.first 60, tcp.established 43200).
TABLES
Tables are named structures which can hold a collection of addresses
and networks. Lookups against tables in PF are relatively fast, making
a single rule with tables much more efficient, in terms of processor
usage and memory consumption, than a large number of rules which differ
only in IP address (either created explicitly or automatically by rule
expansion).
Tables can be used as the source or destination of filter or transla‐
tion rules. They can also be used for the redirect address of nat-to
and rdr-to and in the routing options of filter rules, but only for
least-states and round-robin pools.
Tables can be defined with any of the following pfctl(8) mechanisms. As
with macros, reserved words may not be used as table names.
manually
Persistent tables can be manually created with the add or replace
option of pfctl(8), before or after the ruleset has been loaded.
pf.conf
Table definitions can be placed directly in this file and loaded at
the same time as other rules are loaded, atomically. Table defini‐
tions inside pf.conf use the table statement, and are especially
useful to define non-persistent tables. The contents of a pre-ex‐
isting table defined without a list of addresses to initialize it
is not altered when pf.conf is loaded. A table initialized with the
empty list, { }, will be cleared on load.
Tables may be defined with the following attributes:
const
The const flag prevents the user from altering the contents of the
table once it has been created. Without that flag, pfctl(8) can be
used to add or remove addresses from the table at any time.
counters
The counters flag enables per-address packet and byte counters,
which can be displayed with pfctl(8).
persist
The persist flag forces the kernel to keep the table even when no
rules refer to it. If the flag is not set, the kernel will automat‐
ically remove the table when the last rule referring to it is
flushed.
This example creates a table called private, to hold RFC 1918 private
network blocks, and a table called badhosts, which is initially empty.
A filter rule is set up to block all traffic coming from addresses
listed in either table:
table <private> const { 10/8, 172.16/12, 192.168/16 }
table <badhosts> persist
block on fxp0 from { <private>, <badhosts> } to any
The private table cannot have its contents changed and the badhosts ta‐
ble will exist even when no active filter rules reference it. Addresses
may later be added to the badhosts table, so that traffic from these
hosts can be blocked by using the following:
# pfctl -t badhosts -Tadd 204.92.77.111
A table can also be initialized with an address list specified in one
or more external files, using the following syntax:
table <spam> persist file "/etc/spammers" file "/etc/openrelays"
block on fxp0 from <spam> to any
The files /etc/spammers and /etc/openrelays list IP addresses, one per
line. Any lines beginning with a # are treated as comments and ignored.
In addition to being specified by IP address, hosts may also be speci‐
fied by their hostname. When the resolver is called to add a hostname
to a table, all resulting IPv4 and IPv6 addresses are placed into the
table. IP addresses can also be entered in a table by specifying a
valid interface name, a valid interface group, or the self keyword, in
which case all addresses assigned to the interface(s) will be added to
the table.
ANCHORS
Besides the main ruleset, pf.conf can specify anchor attachment points.
An anchor is a container that can hold rules, address tables, and other
anchors. When evaluation of the main ruleset reaches an anchor rule, PF
will proceed to evaluate all rules specified in that anchor.
The following example blocks all packets on the external interface by
default, then evaluates all rules in the anchor named spam, and finally
passes all outgoing connections and incoming connections to port 25:
ext_if = "kue0"
block on $ext_if all
anchor spam
pass out on $ext_if all
pass in on $ext_if proto tcp from any to $ext_if port smtp
Anchors can be manipulated through pfctl(8) without reloading the main
ruleset or other anchors. This loads a single rule into the anchor,
which blocks all packets from a specific address:
# echo "block in quick from 1.2.3.4 to any" | pfctl -a spam -f -
The anchor can also be populated by adding a load anchor rule after the
anchor rule. When pfctl(8) loads pf.conf, it will also load all the
rules from the file /etc/pf-spam.conf into the anchor.
anchor spam
load anchor spam from "/etc/pf-spam.conf"
Filter rule anchors can also be loaded inline in the ruleset within a
brace-delimited block. Brace delimited blocks may contain rules or
other brace-delimited blocks. When anchors are loaded this way the an‐
chor name becomes optional. Since the parser specification for anchor
names is a string, double quote characters ('"') should be placed
around the anchor name.
anchor "external" on egress {
block
anchor out {
pass proto tcp from any to port { 25, 80, 443 }
}
pass in proto tcp to any port 22
}
Anchor rules can also specify packet filtering parameters using the
same syntax as filter rules. When parameters are used, the anchor rule
is only evaluated for matching packets. This allows conditional evalua‐
tion of anchors, like:
block on $ext_if all
anchor spam proto tcp from any to any port smtp
pass out on $ext_if all
pass in on $ext_if proto tcp from any to $ext_if port smtp
The rules inside anchor spam are only evaluated for TCP packets with
destination port 25. Hence, the following will only block connections
from 1.2.3.4 to port 25:
# echo "block in quick from 1.2.3.4 to any" | pfctl -a spam -f -
Matching filter and translation rules marked with the quick option are
final and abort the evaluation of the rules in other anchors and the
main ruleset. If the anchor itself is marked with the quick option,
ruleset evaluation will terminate when the anchor is exited if the
packet is matched by any rule within the anchor.
An anchor references other anchor attachment points using the following
syntax:
anchor <name>
Evaluates the filter rules in the specified anchor.
An anchor has a name which specifies the path where pfctl(8) can be
used to access the anchor to perform operations on it, such as attach‐
ing child anchors to it or loading rules into it. Anchors may be
nested, with components separated by '/' characters, similar to how
file system hierarchies are laid out. The main ruleset is actually the
default anchor, so filter and translation rules, for example, may also
be contained in any anchor.
Anchor rules are evaluated relative to the anchor in which they are
contained. For example, all anchor rules specified in the main ruleset
will reference anchor attachment points underneath the main ruleset,
and anchor rules specified in a file loaded from a load anchor rule
will be attached under that anchor point.
Anchors may end with the asterisk ('*') character, which signifies that
all anchors attached at that point should be evaluated in the alphabet‐
ical ordering of their anchor name. For example, the following will
evaluate each rule in each anchor attached to the spam anchor:
anchor "spam/*"
Note that it will only evaluate anchors that are directly attached to
the spam anchor, and will not descend to evaluate anchors recursively.
Since anchors are evaluated relative to the anchor in which they are
contained, there is a mechanism for accessing the parent and ancestor
anchors of a given anchor. Similar to file system path name resolution,
if the sequence '..' appears as an anchor path component, the parent
anchor of the current anchor in the path evaluation at that point will
become the new current anchor. As an example, consider the following:
# printf 'anchor "spam/allowed"\n' | pfctl -f -
# printf 'anchor "../banned"\npass\n' | pfctl -a spam/allowed -f -
Evaluation of the main ruleset will lead into the spam/allowed anchor,
which will evaluate the rules in the spam/banned anchor, if any, before
finally evaluating the pass rule.
STATEFUL FILTERING
PF filters packets statefully, which has several advantages. For TCP
connections, comparing a packet to a state involves checking its se‐
quence numbers, as well as TCP timestamps if a rule using the reassem‐
ble tcp parameter applies to the connection. If these values are out‐
side the narrow windows of expected values, the packet is dropped. This
prevents spoofing attacks, such as when an attacker sends packets with
a fake source address/port but does not know the connection's sequence
numbers. Similarly, PF knows how to match ICMP replies to states. For
example, to allow echo requests (such as those created by ping(8)) out
statefully and match incoming echo replies correctly to states:
pass out inet proto icmp all icmp-type echoreq
Also, looking up states is usually faster than evaluating rules. If
there are 50 rules, all of them are evaluated sequentially in O(n).
Even with 50000 states, only 16 comparisons are needed to match a
state, since states are stored in a binary search tree that allows
searches in O(log2 n).
Furthermore, correct handling of ICMP error messages is critical to
many protocols, particularly TCP. PF matches ICMP error messages to the
correct connection, checks them against connection parameters, and
passes them if appropriate. For example if an ICMP source quench mes‐
sage referring to a stateful TCP connection arrives, it will be matched
to the state and get passed.
Finally, state tracking is required for nat-to and rdr-to options, in
order to track address and port translations and reverse the transla‐
tion on returning packets.
PF will also create state for other protocols which are effectively
stateless by nature. UDP packets are matched to states using only host
addresses and ports, and other protocols are matched to states using
only the host addresses.
If stateless filtering of individual packets is desired, the no state
keyword can be used to specify that state will not be created if this
is the last matching rule. Note that packets which match neither block
nor pass rules, and thus are passed by default, are effectively passed
as if no state had been specified.
A number of parameters can also be set to affect how PF handles state
tracking, as detailed below.
State Modulation
Much of the security derived from TCP is attributable to how well the
initial sequence numbers (ISNs) are chosen. Some popular stack imple‐
mentations choose very poor ISNs and thus are normally susceptible to
ISN prediction exploits. By applying a modulate state rule to a TCP
connection, PF will create a high quality random sequence number for
each connection endpoint.
The modulate state directive implicitly keeps state on the rule and is
only applicable to TCP connections. For instance:
block all
pass out proto tcp from any to any modulate state
pass in proto tcp from any to any port 25 flags S/SFRA\
modulate state
Note that modulated connections will not recover when the state table
is lost (firewall reboot, flushing the state table, etc.). PF will not
be able to infer a connection again after the state table flushes the
connection's modulator. When the state is lost, the connection may be
left dangling until the respective endpoints time out the connection.
It is possible on a fast local network for the endpoints to start an
ACK storm while trying to resynchronize after the loss of the modula‐
tor. The default flag settings (or a more strict equivalent) should be
used on modulate state rules to prevent ACK storms.
SYN Proxy
By default, PF passes packets that are part of a TCP handshake between
the endpoints. The synproxy state option can be used to cause PF itself
to complete the handshake with the active endpoint, perform a handshake
with the passive endpoint, and then forward packets between the end‐
points.
No packets are sent to the passive endpoint before the active endpoint
has completed the handshake, hence, the SYN floods with spoofed source
addresses will not reach the passive endpoint, as the sender will not
be able to complete the handshake.
The proxy is transparent to both endpoints; they each see a single con‐
nection from/to the other endpoint. PF chooses random initial sequence
numbers for both handshakes. Once the handshakes are completed, the se‐
quence number modulators (see previous section) are used to translate
further packets of the connection. Synproxy state includes modulate
state. Rules with synproxy will not work if PF operates on a bridge().
For example:
pass in proto tcp from any to any port www synproxy state
Stateful Tracking Options
A number of options related to stateful tracking can be applied on a
per-rule basis. One of keep state, modulate state, or synproxy state
must be specified explicitly to apply these options to a rule.
floating
States can match packets on any interfaces (the opposite of if-
bound). This is the default.
if-bound
States are bound to an interface (the opposite of floating).
max <number>
Limits the number of concurrent states the rule may create. When
this limit is reached, further packets that would create state are
dropped until existing states time out.
sloppy
Uses a sloppy TCP connection tracker that does not check sequence
numbers at all, which makes insertion and ICMP teardown attacks way
easier. This is intended to be used in situations where one does
not see all packets of a connection. Example, in asymmetric routing
situations. It cannot be used with modulate or synproxy state.
<timeout> <seconds>
Changes the timeout values used for states created by this rule.
For a list of all valid timeout names, see the OPTIONS section
above.
Multiple options can be specified, separated by commas:
pass in proto tcp from any to any\
port www keep state\
(max 100, source-track rule, max-src-nodes 75,\
max-src-states 3, tcp.established 60, tcp.closing 5)
When the source-track keyword is specified, the number of states per
source IP is tracked.
source-track global
The number of states created by all rules that use this option is
limited. Each rule can specify different max-src-nodes and max-src-
states options, however state entries created by any participating
rule count toward each individual rule's limits.
source-track rule
The maximum number of states created by this rule is limited by the
rule's max-src-nodes and max-src-states options. Only state entries
created by this particular rule count toward the rule's limits.
The following limits can be set:
max-src-nodes <number>
Limits the maximum number of source addresses which can simultane‐
ously have state table entries.
max-src-states <number>
Limits the maximum number of simultaneous state entries that a sin‐
gle source address can create with this rule.
For stateful TCP connections, limits on established connections (con‐
nections which have completed the TCP 3-way handshake) can also be en‐
forced per source IP.
max-src-conn <number>
Limits the maximum number of simultaneous TCP connections which
have completed the 3-way handshake that a single host can make.
max-src-conn-rate <number> / <seconds>
Limit the rate of new connections over a time interval. The connec‐
tion rate is an approximation calculated as a moving average.
When one of these limits is reached, further packets that would create
state are dropped until existing states time out. Since the 3-way hand‐
shake ensures that the source address is not being spoofed, more ag‐
gressive action can be taken based on these limits. With the overload
<table> state option, source IP addresses which hit either of the lim‐
its on established connections will be added to the named table. This
table can be used in the ruleset to block further activity from the of‐
fending host, redirect it to a tarpit process.
The optional flush keyword kills all states created by the matching
rule which originate from the host which exceeds these limits. The
global modifier to the flush command kills all states originating from
the offending host, regardless of which rule created the state.
For example, the following rules will protect the webserver against
hosts making more than 100 connections in 10 seconds. Any host which
connects faster than this rate will have its address added to the
<bad_hosts> table and have all states originating from it flushed. Any
new packets arriving from this host will be dropped unconditionally by
the block rule.
block quick from <bad_hosts>
pass in on $ext_if proto tcp to $webserver port www keep state\
(max-src-conn-rate 100/10, overload <bad_hosts> flush global)
Filtering on loopback
By default, PF filters the traffic on loopback. However, Oracle Solaris
provides optimizations for such traffic that makes transferred packets
invalid from the firewall point of view when stateful tracking is used.
Thus, such traffic may be severely impacted. For example, zone install
may fail as the process uses loopback. If you do not need to filter
traffic on loopback, supply the following rule to skip that filtering
completely:
o set skip on lo0
o Or else, use the sloppy option. For example, pass on lo0
keep state (sloppy)
For more information on how to use the sloppy option and its conse‐
quences, see the description of the sloppy option.
TRAFFIC NORMALISATION
Traffic normalisation is a term for aspects of the packet filter which
deal with verifying packets, packet fragments, spoof traffic, and other
irregularities.
Scrub
Scrub involves sanitising packet content in such a way that there are
no ambiguities in packet interpretation on the receiving side. It is
invoked with the scrub option, added to regular rules.
Parameters are specified enclosed in parentheses. At least one of the
following parameters must be specified:
max-mss <number>
Enforces a maximum segment size (MSS) for matching TCP packets.
min-ttl <number>
Enforces a minimum TTL for matching IP packets.
no-df
Clears the dont-fragment bit from a matching IPv4 packet. Some op‐
erating systems have NFS implementations which are known to gener‐
ate fragmented packets with the dont-fragment bit set. PF will drop
such fragmented dont-fragment packets unless no-df is specified.
Unfortunately some operating systems also generate their dont-frag‐
ment packets with a zero IP identification field. Clearing the
dont-fragment bit on packets with a zero IP ID may cause deleteri‐
ous results if an upstream router later fragments the packet. Using
random-id is recommended in combination with no-df to ensure unique
IP identifiers.
random-id
Replaces the IPv4 identification field with random values to com‐
pensate for predictable values generated by many hosts. This option
only applies to packets that are not fragmented after the optional
fragment reassembly.
reassemble tcp
Statefully normalises TCP connections. reassemble tcp performs the
following normalisations:
TTL
Neither side of the connection is allowed to reduce their IP
TTL. An attacker may send a packet such that it reaches the
firewall, affects the firewall state, and expires before reach‐
ing the destination host. reassemble tcp will raise the TTL of
all packets back up to the highest value seen on the connec‐
tion.
Timestamp Modulation
Modern TCP stacks will send a timestamp on every TCP packet and
echo the other endpoint's timestamp back to them. Many operat‐
ing systems will merely start the timestamp at zero when first
booted, and increment it several times a second. The uptime of
the host can be deduced by reading the timestamp and multiply‐
ing by a constant. Also observing several different timestamps
can be used to count hosts behind a NAT device. And spoofing
TCP packets into a connection requires knowing or guessing
valid timestamps. Timestamps merely need to be monotonically
increasing and not derived off a base time. reassemble tcp will
cause scrub to modulate the TCP timestamps with a random num‐
ber.
Extended PAWS Checks
There is a problem with TCP on long fat pipes, in that a packet
might get delayed for longer than it takes the connection to
wrap its 32-bit sequence space. In such an occurrence, the old
packet would be indistinguishable from a new packet and would
be accepted as such. The solution to this is called PAWS: Pro‐
tection Against Wrapped Sequence numbers. It protects against
it by making sure the timestamp on each packet does not go
backwards. reassemble tcp also makes sure the timestamp on the
packet does not go forward more than the RFC allows. By doing
this, PF artificially extends the security of TCP sequence num‐
bers by 10 to 18 bits when the host uses appropriately random‐
ized timestamps, since a blind attacker would have to guess the
timestamp as well. For example:
match in all scrub (no-df max-mss 1440)
Fragment Handling
The size of IP datagrams (packets) can be significantly larger than
the maximum transmission unit (MTU) of the network. In cases when
it is necessary or more efficient to send such large packets, the
large packet will be fragmented into many smaller packets that will
each fit onto the wire. Unfortunately for a firewalling device,
only the first logical fragment will contain the necessary header
information for the subprotocol that allows PF to filter on things
such as TCP ports or to perform NAT.
One alternative is to filter individual fragments with filter
rules. If packet reassembly is turned off, it is passed to the fil‐
ter. Filter rules with matching IP header parameters decide whether
the fragment is passed or blocked, in the same way as complete
packets are filtered. Without reassembly, fragments can only be
filtered based on IP header fields (source/destination address,
protocol), since subprotocol header fields are not available
(TCP/UDP port numbers, ICMP code/type). The fragment option can be
used to restrict filter rules to apply only to fragments, but not
complete packets. Filter rules without the fragment option still
apply to fragments, if they only specify IP header fields. For in‐
stance:
pass in proto tcp from any to any port 80
The rule above never applies to a fragment, even if the fragment is
part of a TCP packet with destination port 80, because without re‐
assembly this information is not available for each fragment. This
also means that fragments cannot create new or match existing state
table entries, which makes stateful filtering and address transla‐
tion (NAT, redirection) for fragments impossible.
In most cases, the benefits of reassembly outweigh the additional
memory cost, so reassembly is on by default.
The memory allocated for fragment caching can be limited using
pfctl(8). Once this limit is reached, fragments that would have to
be cached are dropped until other entries time out. The timeout
value can also be adjusted.
When forwarding reassembled IPv6 packets, pf refragments them with
the original maximum fragment size. This allows the sender to de‐
termine the optimal fragment size by path MTU discovery.
Blocking Spoofed Traffic
Spoofing is the faking of IP addresses, typically for malicious pur‐
poses. The antispoof directive expands to a set of filter rules which
will block all traffic with a source IP from the network(s) directly
connected to the specified interface(s) from entering the system
through any other interface. For example:
antispoof for lo0
Expands to:
block drop in on ! lo0 inet from 127.0.0.1/8 to any
block drop in on ! lo0 inet6 from ::1 to any
For non-loopback interfaces, there are additional rules to block incom‐
ing packets with a source IP address identical to the interface's
IP(s). For example, assuming the interface wi0 had an IP address of
10.0.0.1 and a netmask of 255.255.255.0:
antispoof for wi0 inet
Expands to:
block drop in on ! wi0 inet from 10.0.0.0/24 to any
block drop in inet from 10.0.0.1 to any
Note -
Rules created by the antispoof directive interfere with packets sent
over loopback interfaces to local addresses. One should pass these
explicitly.
OPERATING SYSTEM FINGERPRINTING
Passive OS fingerprinting is a mechanism to inspect nuances of a TCP
connection's initial SYN packet and guess at the host's operating sys‐
tem. Unfortunately these nuances are easily spoofed by an attacker so
the fingerprint is not useful in making security decisions. But the
fingerprint is typically accurate enough to make policy decisions upon.
The fingerprints may be specified by operating system class, by ver‐
sion, or by subtype/patchlevel. The class of an operating system is
typically the vendor or genre and would be OpenBSD for the PF firewall
itself. The version of the oldest available OpenBSD release on the main
FTP site would be 2.6 and the fingerprint would be written as: "OpenBSD
2.6".
The subtype of an operating system is typically used to describe the
patchlevel if that patch led to changes in the TCP stack behavior. In
the case of OpenBSD, the only subtype is for a fingerprint that was
normalised by the no-df scrub option and would be specified as:
"OpenBSD 3.3 no-df".
Fingerprints for most popular operating systems are provided by
pf.os(7). Once PF is running, a complete list of known operating system
fingerprints may be listed by running:
# pfctl -so
Filter rules can enforce policy at any level of operating system speci‐
fication assuming a fingerprint is present. Policy could limit traffic
to approved operating systems or even ban traffic from hosts that are
not at the latest service pack.
The unknown class can also be used as the fingerprint which will match
packets for which no operating system fingerprint is known. Examples:
pass out proto tcp from any os OpenBSD
block out proto tcp from any os Doors
block out proto tcp from any os "Doors PT"
block out proto tcp from any os "Doors PT SP3"
block out from any os "unknown"
pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
Operating system fingerprinting is limited only to the TCP SYN packet.
This means that it will not work on other protocols and will not match
a currently established connection.
Note -
Operating system fingerprints are occasionally wrong. There are three
problems: an attacker can trivially craft packets to appear as any
operating system; an operating system patch could change the stack
behavior and no fingerprints will match it until the database is up‐
dated; and multiple operating systems may have the same fingerprint.
EXAMPLES
In this example, the external interface is net0. We use a macro for the
interface name, so it can be changed easily. All incoming traffic is
"normalised", and everything is blocked and logged by default.
ext_if = "net0"
match in all scrub (no-df max-mss 1440)
block return log on $ext_if all
For ICMP, pass out/in ping queries. State matching is done on host ad‐
dresses and ICMP ID (not type/code), so replies (like 0/0 for 8/0) will
match queries. ICMP error messages (which always refer to a TCP/UDP
packet) are handled by the TCP/UDP states.
pass on $ext_if inet proto icmp all icmp-type 8 code 0
For UDP, pass out all UDP connections. DNS connections are passed in.
pass out on $ext_if proto udp all
pass in on $ext_if proto udp from any to any port domain
For TCP, pass out all TCP connections and modulate state. SSH, SMTP,
DNS, and IDENT connections are passed in. We do not allow Windows
9xSMTP connections since they are typically a viral worm.
pass out on $ext_if proto tcp all modulate state
pass in on $ext_if proto tcp from any to any\
port { ssh, smtp, domain, auth }
block in on $ext_if proto tcp from any\
os { "Windows 95", "Windows 98" } to any port smtp
Here we pass in/out all IPv6 traffic. Note that we have to enable this
in two different ways, on both physical interface and tunnel.
pass quick on net0 inet6
pass quick on $ext_if proto ipv6
This example illustrates packet tagging. There are three interfaces:
$int_if, $ext_if, and $wifi_if (wireless). NAT is being done on $ext_if
for all outgoing packets. Packets are passed in on $int_if, tagged, and
passed out on $ext_if. All other outgoing packets (i.e. packets from
the wireless network) are only permitted to access port 80.
pass in on $int_if from any to any tag INTNET
pass in on $wifi_if from any to any
block out on $ext_if from any to any
pass out quick on $ext_if tagged INTNET
pass out on $ext_if proto tcp from any to any port 80
In this example, we tag incoming packets. The tag is used to pass those
packets through the packet filter.
match in on $ext_if inet proto tcp from <spammers> to port smtp\
tag SPAMD rdr-to 192.168.1.1 port spamd
block in on $ext_if
pass in on $ext_if inet proto tcp tagged SPAMD
This example maps incoming requests on port 80 to port 8080, on which a
daemon is running (because, for example, it is not run as root, and
therefore lacks permission to bind to port 80).
match in on $ext_if proto tcp from any to any port 80\
rdr-to 192.168.1.2 port 8080
If a pass rule is used with the quick modifier, packets matching the
translation rule are passed without inspecting subsequent filter rules.
pass in quick on $ext_if proto tcp from any to any port 80\
rdr-to 192.168.1.2 port 8080
In the example below, vlan12 is configured as 192.168.168.1. The ma‐
chine translates all packets coming from 192.168.168.0/24 to
204.92.77.111 when they are going out any interface except vlan12. This
has the net effect of making traffic from the 192.168.168.0/24 network
appear as though it is the Internet routable address 204.92.77.111 to
nodes behind any interface on the router except for the nodes on
vlan12. Thus, 1463 192.168.168.1 can talk to the 192.168.168.0/24
nodes.
match out on ! vlan12 from 192.168.168.0/24 to any nat-to 204.92.77.111
In the example below, the machine sits between a fake internal 1468
144.19.74.* network, and a routable external IP of 204.92.77.100. The
1469 last rule excludes protocol AH from being translated.
pass out on $ext_if from 144.19.74.0/24 nat-to 204.92.77.100
pass out on $ext_if proto ah from 144.19.74.0/24
In the example below, packets bound for one specific server, as well as
those generated by the sysadmins are not proxied. All other connections
are.
pass in on $int_if proto { tcp, udp } from any to any port 80\
rdr-to 192.168.1.2 port 80
pass in on $int_if proto { tcp, udp } from any to $server port 80
pass in on $int_if proto { tcp, udp } from $sysadmins to any port 80
This example maps outgoing packets source port to an assigned proxy
port instead of an arbitrary port. In this case, proxy outgoing isakmp
with port 500 on the gateway.
match out on $ext_if inet proto udp from any port isakmp to any\
nat-to ($ext_if) port 500
One more example uses rdr-to to redirect a TCP and UDP port to an in‐
ternal machine.
match in on $ext_if inet proto tcp from any to ($ext_if) port 8080\
rdr-to 10.1.2.151 port 22
match in on $ext_if inet proto udp from any to ($ext_if) port 8080\
rdr-to 10.1.2.151 port 53
In this example, a NAT gateway is set up to translate internal ad‐
dresses using a pool of public addresses (192.0.2.16/28). A given
source address is always translated to the same pool address by using
the source-hash keyword. The gateway also translates incoming web
server connections to a group of web servers on the internal network.
match out on $ext_if inet from any to any nat-to 192.0.2.16/28\
source-hash
match in on $ext_if proto tcp from any to any port 80\
rdr-to { 10.1.2.155 weight 2, 10.1.2.160 weight 1,\
10.1.2.161 weight 8 } round-robin
The bidirectional address translation example uses a single binat-to
rule that expands to a nat-to and an rdr-to rule.
pass on $ext_if from 10.1.2.120 to any binat-to 192.0.2.17
The previous example is identical to the following set of rules:
pass out on $ext_if inet from 10.1.2.120 to any\
nat-to 192.0.2.17 static-port
pass in on $ext_if inet from any to 192.0.2.17 rdr-to 10.1.2.120
GRAMMAR
Syntax for pf.conf in BNF:
line = ( option | pf-rule |
antispoof-rule | altq-rule | queue-rule | anchor-rule |
anchor-close | load-anchor | table-rule | include )
option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
[ "ruleset-optimization" [ "none" | "basic" |
"profile" ] ] |
[ "optimization" [ "default" | "normal" | "high-latency" |
"satellite" | "aggressive" | "conservative" ] ]
[ "limit" ( limit-item | "{" limit-list "}" ) ] |
[ "loginterface" ( interface-name | "none" ) ] |
[ "block-policy" ( "drop" | "return" ) ] |
[ "state-policy" ( "if-bound" | "floating" ) ]
[ "state-defaults" state-opts ]
[ "fingerprints" filename ] |
[ "skip on" ifspec ] |
[ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] |
[ "reassemble" ( "yes" | "no" ) [ "no-df" ] ] )
pf-rule = action [ ( "in" | "out" ) ]
[ "log" [ "(" logopts ")"] ] [ "quick" ]
[ "on" ( ifspec | "rdomain" number ) ] [ af ]
[ protospec ] hosts [ filteropts ]
logopts = logopt [ [ "," ] logopts ]
logopt = "all" | "matches" | "user" | "to" interface-name
filteropts = filteropt [ [ "," ] filteropts ]
filteropt = user | group | flags | icmp-type | icmp6-type |
"tos" tos |
( "no" | "keep" | "modulate" | "synproxy" ) "state"
[ "(" state-opts ")" ] | "scrub" "(" scrubopts ")" |
"fragment" | "allow-opts" | "once" |
"divert-packet" "port" port | "divert-reply" |
"divert-to" host "port" port |
"label" string | "tag" string | [ ! ] "tagged" string |
"set prio" ( number | "(" number [ [ "," ] number ] ")" ) |
"set queue" ( string | "(" string [ [ "," ] string ] ")" ) |
"rtable" number | "probability" number"%" |
[ "to" ( redirhost | "{" redirhost-list "}" ) ] |
"binat-to" ( redirhost | "{" redirhost-list "}" )
[ portspec ] [ pooltype ] |
"rdr-to" ( redirhost | "{" redirhost-list "}" )
[ portspec ] [ pooltype ] |
"nat-to" ( redirhost | "{" redirhost-list "}" )
[ portspec ] [ pooltype ] [ "static-port" ] |
[ route ] | [ "set tos" tos ] |
[ "received-on" ( interface-name | interface-group ) ]
scrubopts = scrubopt [ [ "," ] scrubopts ]
scrubopt = "no-df" | "min-ttl" number | "max-mss" number |
"reassemble tcp" | "random-id"
antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
"for" ifspec [ af ] [ "label" string ]
table-rule = "table" "<" string ">" [ tableopts ]
tableopts = tableopt [ tableopts ]
tableopt = "persist" | "const" | "counters" |
"file" string | "{" [ tableaddrs ] "}"
tableaddrs = tableaddr-spec [ [ "," ] tableaddrs ]
tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
tableaddr = hostname | ifspec | "self" |
ipv4-dotted-quad | ipv6-coloned-hex
altq-rule = "altq on" interface-name queueopts-list
"queue" subqueue
queue-rule = "queue" string [ "on" interface-name ] queueopts-list
subqueue
anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ]
[ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ]
anchor-close = "}"
load-anchor = "load anchor" string "from" filename
action = "pass" | "match" | "block" [ return ]
return = "drop" | "return" |
"return-rst" [ "(" "ttl" number ")" ] |
"return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
"return-icmp6" [ "(" icmp6code ")" ]
icmpcode = ( icmp-code-name | icmp-code-number )
icmp6code = ( icmp6-code-name | icmp6-code-number )
ifspec = ( [ "!" ] ( interface-name | interface-group ) ) |
"{" interface-list "}"
interface-list = [ "!" ] ( interface-name | interface-group )
[ [ "," ] interface-list ]
route = ( "route-to" | "reply-to" | "dup-to" )
( routehost | "{" routehost-list "}" )
[ pooltype ]
af = "inet" | "inet6"
protospec = "proto" ( proto-name | proto-number |
"{" proto-list "}" )
proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
hosts = "all" |
"from" ( "any" | "self" | host | "{" host-list "}" | [ port ]
[ os ]
"to" ( "any" | "self" | host | "{" host-list "}" | [ port ]
ipspec = "any" | host | "{" host-list "}"
host = [ "!" ] ( address [ "weight" number ] |
address [ "/" mask-bits ] [ "weight" number ] |
"<" string ">" )
redirhost = address [ "/" mask-bits ]
routehost = host | host "@" interface-name |
"(" interface-name [ address [ "/" mask-bits ] ] ")"
address = ( interface-name | interface-group |
"(" ( interface-name | interface-group ) ")" |
hostname | ipv4-dotted-quad | ipv6-coloned-hex )
host-list = host [ [ "," ] host-list ]
redirhost-list = redirhost [ [ "," ] redirhost-list ]
routehost-list = routehost [ [ "," ] routehost-list ]
port = "port" ( unary-op | binary-op | "{" op-list "}" )
portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
os = "os" ( os-name | "{" os-list "}" )
user = "user" ( unary-op | binary-op | "{" op-list "}" )
group = "group" ( unary-op | binary-op | "{" op-list "}" )
unary-op = [ "=" | "!=" | "<" | "<=" | ">" | ">=" ]
( name | number )
binary-op = number ( "<>" | "><" | ":" ) number
op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
os-name = operating-system-name
os-list = os-name [ [ "," ] os-list ]
flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
[ "W" ]
icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
icmp-type-code = ( icmp-type-name | icmp-type-number )
[ "code" ( icmp-code-name | icmp-code-number ) ]
icmp-list = icmp-type-code [ [ "," ] icmp-list ]
tos = ( "lowdelay" | "throughput" | "reliability" |
[ "0x" ] number )
state-opts = state-opt [ [ "," ] state-opts ]
state-opt = ( "max" number | timeout | "sloppy" |
"source-track" [ ( "rule" | "global" ) ] |
"max-src-nodes" number | "max-src-states" number |
"max-src-conn" number |
"max-src-conn-rate" number "/" number |
"overload" "<" string ">" [ "flush" [ "global" ] ] |
"if-bound" | "floating" )
timeout-list = timeout [ [ "," ] timeout-list ]
timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
"tcp.closing" | "tcp.finwait" | "tcp.closed" |
"udp.first" | "udp.single" | "udp.multiple" |
"icmp.first" | "icmp.error" |
"other.first" | "other.single" | "other.multiple" |
"frag" | "interval" | "src.track" |
"adaptive.start" | "adaptive.end" ) number
limit-list = limit-item [ [ "," ] limit-list ]
limit-item = ( "states" | "frags" | "src-nodes" | "tables" |
"table-entries" ) number
pooltype = ( "bitmask" | "least-states" |
"random" | "round-robin" |
"source-hash" [ ( hex-key | string-key ) ] )
[ sticky-address ]
include = "include" filename
FILES
/etc/pf.conf Default location of the ruleset file.
/etc/pf.os Default location of OS fingerprints.
SEE ALSO
protocols(5), services(5), pf.os(7), pfctl(8)
HISTORY
The pf.conf file format first appeared in OpenBSD 3.0. It was added to
Oracle Solaris in Solaris 11.3.0.
SOLARIS
The pf.conf file has been introduced to Solaris as a part of firewall
modernization project. The project brings slightly modified version of
PF to Solaris. The manual page has been tailored to match a PF feature
set found on Solaris Operating System. The PF version is derived from
OpenBSD 5.5 release.
Oracle Solaris 11.4 4 Aug 2023 pf...f(7)