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Diffstat (limited to 'sbin/ipf/ipf.5')
| -rw-r--r-- | sbin/ipf/ipf.5 | 790 |
1 files changed, 326 insertions, 464 deletions
diff --git a/sbin/ipf/ipf.5 b/sbin/ipf/ipf.5 index 45f81398d1c..8692ea3794e 100644 --- a/sbin/ipf/ipf.5 +++ b/sbin/ipf/ipf.5 @@ -1,33 +1,25 @@ -.\" $OpenBSD: ipf.5,v 1.23 2000/04/12 21:47:58 aaron Exp $ -.Dd July 9, 1999 -.Dt IPF 5 -.Os -.Sh NAME -.Nm ipf -.Nd "IP packet filter rule syntax" -.Sh DESCRIPTION -A rule file for -.Nm -may have any name or even be stdin. -As -.Xr ipfstat 8 -produces parseable rules as output when displaying the internal +.\" $OpenBSD: ipf.5,v 1.24 2000/04/13 19:59:39 kjell Exp $ +.\" +.TH IPF 5 +.SH NAME +ipf, ipf.conf \- IP packet filter rule syntax +.SH DESCRIPTION +.PP +A rule file for \fBipf\fP may have any name or even be stdin. As +\fBipfstat\fP produces parseable rules as output when displaying the internal kernel filter lists, it is quite plausible to use its output to feed back -into -.Nm ipf . -Thus, to remove all filters on input packets, the following +into \fBipf\fP. Thus, to remove all filters on input packets, the following could be done: .nf -.Dl # ipfstat -i | ipf -rf - -.Pp -.Sh GRAMMAR -.Pp -The format used by -.Nm -for construction of filtering rules can be +\fC# ipfstat \-i | ipf \-rf \-\fP +.fi +.SH GRAMMAR +.PP +The format used by \fBipf\fP for construction of filtering rules can be described using the following grammar in BNF: -.Bd -literal +\fC +.nf filter-rule = [ insert ] action in-out [ options ] [ tos ] [ ttl ] [ proto ] [ ip ] [ group ]. @@ -82,7 +74,8 @@ icmp-type = "unreach" | "echo" | "echorep" | "squench" | "redir" | "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" . + "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" . @@ -91,7 +84,7 @@ facility = "kern" | "user" | "mail" | "daemon" | "auth" | "syslog" | "audit" | "logalert" | "local0" | "local1" | "local2" | "local3" | "local4" | "local5" | "local6" | "local7" . priority = "emerg" | "alert" | "crit" | "err" | "warn" | "notice" | - "info" | "debug" . + "info" | "debug" . hexnumber = "0" "x" hexstring . hexstring = hexdigit [ hexstring ] . @@ -103,578 +96,447 @@ 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" . -.Ed -.Pp +.fi +.PP This syntax is somewhat simplified for readability, some combinations that match this grammar are disallowed by the software because they do -not make sense (such as tcp -.Cm flags -for non-TCP packets). -.Sh FILTER RULES +not make sense (such as tcp \fBflags\fP for non-TCP packets). +.SH FILTER RULES +.PP The "briefest" valid rules are (currently) no-ops and are of the form: -.Bd -literal -offset indent -block in all -pass in all -log out all -count in all -.Ed -.Pp +.nf + block in all + pass in all + log out all + count in all +.fi +.PP Filter rules are checked in order, with the last matching rule -determining the fate of the packet (but see the -.Cm quick -option, below). -.Pp +determining the fate of the packet (but see the \fBquick\fP option, +below). +.PP Filters are installed by default at the end of the kernel's filter -lists, prepending the rule with -.Cm @n -will cause it to be inserted -as the n'th entry in the current list. -This is especially useful when -modifying and testing active filter rulesets. -.Sh ACTIONS +lists, prepending the rule with \fB@n\fP will cause it to be inserted +as the n'th entry in the current list. This is especially useful when +modifying and testing active filter rulesets. See ipf(1) for more +information. +.SH ACTIONS +.PP The action indicates what to do with the packet if it matches the rest -of the filter rule. -Each rule -.Em must -have an action. -The following actions are recognized: -.Pp -.Bl -tag -width XXXXXXXX -offset indent -.It block -indicates that the packet should be flagged to be dropped. -In response +of the filter rule. Each rule MUST have an action. The following +actions are recognised: +.TP +.B block +indicates that the packet should be flagged to be dropped. In response to blocking a packet, the filter may be instructed to send a reply -packet, either an ICMP packet -.Pq Cm return-icmp , -an ICMP packet masquerading as being from the original packet's destination ( -.Pq Cm return-icmp-as-dest , -or a TCP reset -.Pq Cm return-rst . -An ICMP packet may be generated in response to -any IP packet, and its type may optionally be specified, but a TCP -reset may only be used with a rule which is being applied to TCP -packets. -When using -.Cm return-icmp -or -.Cm return-icmp-as-dest , -it is possible to specify the actual unreachable `type'. -That is, whether -it is a network unreachable, port unreachable or even administratively -prohibited. -This is done by enclosing the ICMP code associated with it -in parenthesis directly following -.Cm return-icmp -or -.Cm return-icmp-as-dest -as follows: -.Bd -literal -offset indent -block return-icmp(11) ... -.Ed -.Pp -would return a Type-Of-Service (TOS) ICMP unreachable error. -.It pass -will flag the packet to be let through the filter. -.It log +packet, either an ICMP packet (\fBreturn-icmp\fP), an ICMP packet +masquerading as being from the original packet's destination +(\fBreturn-icmp-as-dest\fP), or a TCP "reset" (\fBreturn-rst\fP). An +ICMP packet may be generated in response to any IP packet, and its +type may optionally be specified, but a TCP reset may only be used +with a rule which is being applied to TCP packets. When using +\fBreturn-icmp\fP or \fBreturn-icmp-as-dest\fP, it is possible to specify +the actual unreachable `type'. That is, whether it is a network +unreachable, port unreachable or even administratively +prohibitied. This is done by enclosing the ICMP code associated with +it in parenthesis directly following \fBreturn-icmp\fP or +\fBreturn-icmp-as-dest\fP as follows: +.nf + block return-icmp(11) ... +.fi +.PP +Would return a Type-Of-Service (TOS) ICMP unreachable error. +.TP +.B pass +will flag the packet to be let through the filter. +.TP +.B log causes the packet to be logged (as described in the LOGGING section below) and has no effect on whether the packet will be allowed through the filter. -.It count +.TP +.B count causes the packet to be included in the accounting statistics kept by the filter, and has no effect on whether the packet will be allowed through -the filter. -These statistics are viewable with -.Xr ipfstat 8 . -.It call +the filter. These statistics are viewable with ipfstat(8). +.TP +.B call this action is used to invoke the named function in the kernel, which -must conform to a specific calling interface. -Customized actions and -semantics can thus be implemented to supplement those available. -This feature is for use by knowledgeable hackers, and is not currently +must conform to a specific calling interface. Customised actions and +semantics can thus be implemented to supplement those available. This +feature is for use by knowledgeable hackers, and is not currently documented. -.It "skip <n>" -causes the filter to skip over the next -.Cm n -filter rules. -If a rule is inserted or deleted inside the region being -skipped over, then the value of -.Cm n -is adjusted appropriately. -.It auth +.TP +.B "skip <n>" +causes the filter to skip over the next \fIn\fP filter rules. If a rule is +inserted or deleted inside the region being skipped over, then the value of +\fIn\fP is adjusted appropriately. +.TP +.B auth this allows authentication to be performed by a user-space program running -and waiting for packet information to validate. -The packet is held for a +and waiting for packet information to validate. The packet is held for a period of time in an internal buffer whilst it waits for the program to return -to the kernel the -.Em real -flags for whether it should be allowed through -or not. -Such a program might look at the source address and request some sort +to the kernel the \fIreal\fP flags for whether it should be allowed through +or not. Such a program might look at the source address and request some sort of authentication from the user (such as a password) before allowing the packet through or telling the kernel to drop it if from an unrecognised source. -.It preauth +.TP +.B preauth tells the filter that for packets of this class, it should look in the -pre-authenticated list for further clarification. -If no further matching +pre-authenticated list for further clarification. If no further matching rule is found, the packet will be dropped (the FR_PREAUTH is not the same -as FR_PASS). -If a further matching rule is found, the result from that is -used in its instead. -This might be used in a situation where a person -.Em logs in -to the firewall and it sets up some temporary rules defining +as FR_PASS). If a further matching rule is found, the result from that is +used in its instead. This might be used in a situation where a person +\fIlogs in\fP to the firewall and it sets up some temporary rules defining the access for that person. -.El -.Pp -The next word must be either -.Cm in -or -.Cm out . -Each packet moving through the kernel is either inbound (just been received -on an interface, and moving towards the kernel's protocol processing) or +.PP +The next word must be either \fBin\fP or \fBout\fP. Each packet +moving through the kernel is either inbound (just been received on an +interface, and moving towards the kernel's protocol processing) or outbound (transmitted or forwarded by the stack, and on its way to an -interface). -There is a requirement that each filter rule explicitly +interface). There is a requirement that each filter rule explicitly state which side of the I/O it is to be used on. -.Sh OPTIONS -The list of options is brief, and all are indeed optional. -Where options are used, they must be present in the order shown here. -These are the currently supported options: -.Pp -.Bl -tag -width dup-to -offset indent -.It log +.SH OPTIONS +.PP +The list of options is brief, and all are indeed optional. Where +options are used, they must be present in the order shown here. These +are the currently supported options: +.TP +.B log indicates that, should this be the last matching rule, the packet -header will be written to the -.Pa ipl -log (as described in the LOGGING section below). -.It quick +header will be written to the \fBipl\fP log (as described in the +LOGGING section below). +.TP +.B quick allows "short-cut" rules in order to speed up the filter or override -later rules. -If a packet matches a filter rule which is marked as -.Cm quick , -this rule will be the last rule checked, allowing a +later rules. If a packet matches a filter rule which is marked as +\fBquick\fP, this rule will be the last rule checked, allowing a "short-circuit" path to avoid processing later rules for this -packet. -The current status of the packet (after any effects of the +packet. The current status of the packet (after any effects of the current rule) will determine whether it is passed or blocked. -.Pp +.IP If this option is missing, the rule is taken to be a "fall-through" rule, meaning that the result of the match (block/pass) is saved and that processing will continue to see if there are any more matches. -.It on +.TP +.B on allows an interface name to be incorporated into the matching -procedure. -Interface names are as printed by -.Ic "netstat -i" . -If this option is used, the rule will only match if the packet is going -through that interface in the specified direction (in/out). -If this option is absent, the rule is taken to be applied to a packet -regardless of the interface it is present on (i.e., on all interfaces). +procedure. Interface names are as printed by "netstat \-i". If this +option is used, the rule will only match if the packet is going +through that interface in the specified direction (in/out). If this +option is absent, the rule is taken to be applied to a packet +regardless of the interface it is present on (i.e. on all interfaces). Filter rulesets are common to all interfaces, rather than having a filter list for each interface. -.Pp +.IP This option is especially useful for simple IP-spoofing protection: packets should only be allowed to pass inbound on the interface from which the specified source address would be expected, others may be logged and/or dropped. -.It dup-to +.TP +.B dup-to causes the packet to be copied, and the duplicate packet to be sent outbound on the specified interface, optionally with the destination -IP address changed to that specified. -This is useful for off-host logging, using a network sniffer. -.It to +IP address changed to that specified. This is useful for off-host +logging, using a network sniffer. +.TP +.B to causes the packet to be moved to the outbound queue on the -specified interface. -This can be used to circumvent kernel routing +specified interface. This can be used to circumvent kernel routing decisions, and even to bypass the rest of the kernel processing of the -packet (if applied to an inbound rule). -It is thus possible to +packet (if applied to an inbound rule). It is thus possible to construct a firewall that behaves transparently, like a filtering hub -or switch, rather than a router. -The -.Cm fastroute -keyword is a synonym for this option. -.Sh MATCHING PARAMETERS +or switch, rather than a router. The \fBfastroute\fP keyword is a +synonym for this option. +.SH MATCHING PARAMETERS +.PP The keywords described in this section are used to describe attributes of the packet to be used when determining whether rules match or don't -match. -The following general-purpose attributes are provided for +match. The following general-purpose attributes are provided for matching, and must be used in this order: -.Pp -.Bl -tag -width XXXXXXX -offset indent -.It tos +.TP +.B tos packets with different Type-Of-Service values can be filtered. -Individual service levels or combinations can be filtered upon. -The value for the TOS mask can either be represented as a hex number or a +Individual service levels or combinations can be filtered upon. The +value for the TOS mask can either be represented as a hex number or a decimal integer value. -.It ttl -packets may also be selected by their Time-To-Live value. -The value given in +.TP +.B ttl +packets may also be selected by their Time-To-Live value. The value given in the filter rule must exactly match that in the packet for a match to occur. This value can only be given as a decimal integer value. -.It proto -allows a specific protocol to be matched against. -All protocol names found in -.Pn /etc/protocols -are recognized and may be used. +.TP +.B proto +allows a specific protocol to be matched against. All protocol names +found in \fB/etc/protocols\fP are recognised and may be used. However, the protocol may also be given as a DECIMAL number, allowing for rules to match your own protocols, or new ones which would out-date any attempted listing. -.Pp -The special protocol keyword -.Cm tcp/udp -may be used to match either +.IP +The special protocol keyword \fBtcp/udp\fP may 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. .\" XXX grammar should reflect this (/etc/protocols) -.El -.Pp -The -.Cm from -and -.Cm to -keywords are used to match against IP -addresses (and optionally port numbers). -Rules must specify -.Em both +.PP +The \fBfrom\fP and \fBto\fP keywords are used to match against IP +addresses (and optionally port numbers). Rules must specify BOTH source and destination parameters. -.Pp +.PP IP addresses may be specified in one of two ways: as a numerical -address/mask, or as a hostname -.Cm mask -netmask. -The hostname +address\fB/\fPmask, or as a hostname \fBmask\fP netmask. The hostname may either be a valid hostname, from either the hosts file or DNS -(depending on your configuration and library), an interface name -(in the case of IP address aliases, only the first IP address is used) -or of the dotted numeric -form. -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 -.Em highly -discouraged. -.Pp -There is a special case for the hostname -.Cm any -which is taken to +(depending on your configuration and library) or of the dotted numeric +form. There is no special designation for networks but network names +are recognised. Note that having your filter rules depend on DNS +results can introduce an avenue of attack, and is discouraged. +.PP +There is a special case for the hostname \fBany\fP which is taken to be 0.0.0.0/0 (see below for mask syntax) 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 +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 is non-sensical. -.Pp -The numerical format "x/y" indicates that a mask of y +.PP +The numerical format "x\fB/\fPy" indicates that a mask of y consecutive 1 bits set is generated, starting with the MSB, so a y value -of 16 would give 0xffff0000. -The symbolic "x mask y" indicates +of 16 would give 0xffff0000. The symbolic "x \fBmask\fP 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 +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 isn't currently a way to invert the sense of the match, or to match ranges of IP addresses which do not express themselves easily as bitmasks (anthropomorphization; it's not just for breakfast anymore). -.Pp -If a -.Cm port -match is included, for either or both of source and +.PP +If a \fBport\fP match is included, for either or both of source and destination, then it is only applied to .\" XXX - "may only be" ? how does this apply to other protocols? will it not match, or will it be ignored? -TCP and UDP packets. -If there is no -.Cm proto -match parameter, -packets from both protocols are compared. -This is equivalent to "proto tcp/udp". -When composing -.Cm port -comparisons, either the service -name or an integer port number may be used. -Port comparisons may be +TCP and UDP packets. If there is no \fBproto\fP match parameter, +packets from both protocols are compared. This is equivalent to "proto +tcp/udp". When composing \fBport\fP comparisons, either the service +name or an integer port number may be used. Port comparisons may be done in a number of forms, with a number of comparison operators, or -port ranges may be specified. -When the port appears as part of the -.Cm from -object, it matches the source port number, when it appears -as part of the -.Cm to -object, it matches the destination port number. +port ranges may be specified. When the port appears as part of the +\fBfrom\fP object, it matches the source port number, when it appears +as part of the \fBto\fP object, it matches the destination port number. See the examples for more information. -.Pp -The -.Cm all -keyword is essentially a synonym for "from any to any" +.PP +The \fBall\fP keyword is essentially a synonym for "from any to any" with no other match parameters. -.Pp +.PP Following the source and destination matching parameters, the following additional parameters may be used: -.Bl -tag -width XXXXXXX -offset indent -.It with +.TP +.B with is used to match irregular attributes that some packets may have -associated with them. -To match the presence of IP options in general, use -.Cm "with ipopts" . -To match packets that are too short to contain -a complete header, use -.Cm "with short" . -To match fragmented packets, -.Cm "with frag" . -For more specific filtering on IP options, +associated with them. To match the presence of IP options in general, +use \fBwith ipopts\fP. To match packets that are too short to contain +a complete header, use \fBwith short\fP. To match fragmented packets, +use \fBwith frag\fP. For more specific filtering on IP options, individual options can be listed. -.Pp -Before any parameter used after the -.Cm with -keyword, the word -.Cm not -or -.Cm no -may be inserted to cause the filter rule to only +.IP +Before any parameter used after the \fBwith\fP keyword, the word +\fBnot\fP or \fBno\fP may be inserted to cause the filter rule to only match if the option(s) is not present. -.Pp -Multiple consecutive -.Cm with -clauses are allowed. -Alternatively, the keyword -.Cm and -may be used in place of -.Cm with , -this is +.IP +Multiple consecutive \fBwith\fP clauses are allowed. Alternatively, +the keyword \fBand\fP may be used in place of \fBwith\fP, this is provided purely to make the rules more readable ("with ... and ..."). When multiple clauses are listed, all those must match to cause a match of the rule. .\" XXX describe the options more specifically in a separate section -.It flags -is only effective for TCP filtering. -Each of the letters possible +.TP +.B flags +is only effective for TCP filtering. Each of the letters possible represents one of the possible flags that can be set in the TCP -header. -The association is as follows: -.Bd -literal +header. The association is as follows: +.LP +.nf F - FIN S - SYN R - RST P - PUSH A - ACK U - URG -.Ed -.Pp +.fi +.IP The various flag symbols may be used in combination, so that "SA" -would represent a SYN-ACK combination present in a packet. -There is +would represent a SYN-ACK combination present in a packet. There is nothing preventing the specification of combinations, such as "SFR", that would not normally be generated by law-abiding TCP -implementations. -However, to guard against weird aberrations, it is -necessary to state which flags you are filtering against. -To allow +implementations. However, to guard against weird aberrations, it is +necessary to state which flags you are filtering against. To allow this, it is possible to set a mask indicating which TCP flags you wish -to compare (i.e., those you deem significant). -This is done by +to compare (i.e., those you deem significant). This is done by appending "/<flags>" to the set of TCP flags you wish to match against, e.g.: -.Bd -literal - ... flags S - # becomes "flags S/AUPRFS" and - # will match packets with ONLY - # the SYN flag set. +.LP +.nf + ... flags S + # becomes "flags S/AUPRFS" and will match + # packets with ONLY the SYN flag set. - ... flags SA - # becomes "flags SA/AUPRFS" and will match - # any packet with only the SYN and ACK - # flags set. + ... flags SA + # becomes "flags SA/AUPRFS" and will match any + # packet with only the SYN and ACK flags set. - ... flags S/SA - # will match any packet with just the SYN - # flag set out of the SYN-ACK pair; the - # common "establish" keyword action. - # "S/SA" will NOT match a packet with BOTH - # SYN and ACK set, but WILL match "SFP". -.Ed -.It icmp-type + ... flags S/SA + # will match any packet with just the SYN flag set + # out of the SYN-ACK pair; the common "establish" + # keyword action. "S/SA" will NOT match a packet + # with BOTH SYN and ACK set, but WILL match "SFP". +.fi +.TP +.B icmp-type is only effective when used with \fBproto icmp\fP and must NOT be used -in conjunction with \fBflags\fP. -There are a number of types, which can be -referred to by an abbreviation recognized by this language, or the numbers -with which they are associated can be used. -The most important from a security point of view is the ICMP redirect. -.El -.Sh KEEP HISTORY -The second last parameter that can be set for a filter rule is whether or not -to record historical information for that packet, and what sort to keep. -The following information can be kept: -.Pp -.Bl -tag -width XXXXXXX -offset indent -.It state -keeps information about the flow of a communication session. -State can be kept for TCP, UDP, and ICMP packets. -.It frags +in conjuction with \fBflags\fP. There are a number of types, which can be +referred to by an abbreviation recognised by this language, or the numbers +with which they are associated can be used. The most important from +a security point of view is the ICMP redirect. +.SH KEEP HISTORY +.PP +The second last parameter which can be set for a filter rule is whether or not +to record historical information for that packet, and what sort to keep. The +following information can be kept: +.TP +.B state +keeps information about the flow of a communication session. State can +be kept for TCP, UDP, and ICMP packets. +.TP +.B frags keeps information on fragmented packets, to be applied to later fragments. -.El -.Pp +.PP allowing packets which match these to flow straight through, rather than going through the access control list. -.Sh GROUPS -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 +.SH GROUPS +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 -.Cm head . -If a packet matches a rule which is the -.Cm head -of a group, the filter processing then switches to the group, using -that rule as the default for the group. -If -.Cm quick -is used with a -.Cm head -rule, rule processing isn't stopped until it has returned from processing -the group. -.Pp +group \fIhead\fP. If a packet matches a rule which is the \fIhead\fP of a +group, the filter processing then switches to the group, using that rule as +the default for the group. If \fBquick\fP is used with a \fBhead\fP rule, rule +processing isn't stopped until it has returned from processing the group. +.PP A rule may be both the head for a new group and a member of a non-default -group -.Pf ( Cm head -and -.Cm group -may be used together in a rule). -.Pp -There may be only one -.Cm head -rule per -.Cm group. -.Bl -tag -width XXXXXXXXX -offset indent -.It "head <n>" +group (\fBhead\fP and \fBgroup\fP may be used together in a rule). +.TP +.B "head <n>" indicates that a new group (number n) should be created. -.It "group <n>" +.TP +.B "group <n>" indicates that the rule should be put in group (number n) rather than group 0. -.El -.Sh LOGGING +.SH LOGGING +.PP When a packet is logged, with either the \fBlog\fP action or option, the headers of the packet are written to the \fBipl\fP packet logging -pseudo-device. -Immediately following the \fBlog\fP keyword, the +psuedo-device. Immediately following the \fBlog\fP keyword, the following qualifiers may be used (in order): -.Bl -tag -width XXXXXXXX -offset indent -.It body +.TP +.B body indicates that the first 128 bytes of the packet contents will be -logged after the headers. -.It first -If log is being used in conjunction with a -.Cm keep -option, it is recommended that this option is also applied so that only -the triggering packet is logged and not every packet which thereafter -matches state information. -.It or-block +logged after the headers. +.TP +.B first +If log is being used in conjunction with a "keep" option, it is recommended +that this option is also applied so that only the triggering packet is logged +and not every packet which thereafter matches state information. +.TP +.B or-block indicates that, if for some reason the filter is unable to log the packet (such as the log reader being too slow) then the rule should be -interpreted as if the action was -.Cm block -for this packet. -.It "level <loglevel>" -indicates the logging facility and priority that will be used to log -information about this packet using -.Xr ipmon 8 's -.Fl s -option. -If no facility is specified, the default facility is assumed. -.El -.Pp -See -.Xr ipl 4 -for the format of records written -to this device. -The -.Xr ipmon 8 -program can be used to read and format this log. -.Sh EXAMPLES +interpreted as if the action was \fBblock\fP for this packet. +.TP +.B "level <loglevel>" +indicates what logging facility and priority, or just priority with +the default facility being used, will be used to log information about +this packet using ipmon's -s option. +.PP +See ipl(4) for the format of records written +to this device. The ipmon(8) program can be used to read and format +this log. +.SH EXAMPLES +.PP The \fBquick\fP option is good for rules such as: -.Pp -.Dl block in quick from any to any with ipopts -.Pp +\fC +.nf +block in quick from any to any with ipopts +.fi +.PP which will match any packet with a non-standard header length (IP options present) and abort further processing of later rules, recording a match and also that the packet should be blocked. -.Pp +.PP The "fall-through" rule parsing allows for effects such as this: -.Bd -literal +.LP +.nf block in from any to any port < 6000 pass in from any to any port >= 6000 block in from any to any port > 6003 -.Ed -.Pp +.fi +.PP which sets 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: -.Bd -literal +denied. Note that the effect of the first rule is overridden by subsequent +rules. Another (easier) way to do the same is: +.LP +.nf block in from any to any port 6000 <> 6003 pass in from any to any port 5999 >< 6004 -.Ed -.Pp +.fi +.PP Note that both the "block" and "pass" are needed here to effect a result as a failed match on the "block" action does not imply a pass, -only that the rule hasn't taken effect. -To then allow ports < 1024, a rule such as: -.Pp -.Dl pass in quick from any to any port < 1024 -.Pp -would be needed before the first block. -To create a new group for +only that the rule hasn't taken effect. To then allow ports < 1024, a +rule such as: +.LP +.nf + pass in quick from any to any port < 1024 +.fi +.PP +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, we would do something like: -.Bd -literal +.LP +.nf 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 -.Ed -.Pp +.fi +.PP + and to then allow ICMP packets in on le0, only, we would do: -.Pp -.Dl pass in proto icmp all group 100 -.Pp +.LP +.nf + pass in proto icmp all group 100 +.fi +.PP Note that because only inbound packets on le0 are used processed by group 100, -there is no need to respecify the interface name. -Likewise, we could further breakup processing of TCP, etc, as follows: -.Bd -literal +there is no need to respecify the interface name. Likewise, we could further +breakup processing of TCP, etc, as follows: +.LP +.nf block in proto tcp all head 110 group 100 pass in from any to any port = 23 group 110 -.Ed -.Pp -and so on. -The last line, if written without the groups would be: -.Pp -.Dl pass in on le0 proto tcp from any to any port = telnet -.Pp +.fi +.PP +and so on. The last line, if written without the groups would be: +.LP +.nf + pass in on le0 proto tcp from any to any port = telnet +.fi +.PP Note, that if we wanted to say "port = telnet", "proto tcp" would need to be specified as the parser interprets each rule on its own and qualifies all service/port names with the protocol specified. -.Sh FILES -.Bl -tag -width /usr/share/ipf -compact -.It /etc/services -port names -.It /etc/hosts -host names -.It /usr/share/ipf -sample configuration files -.It /dev/ipauth -.It /dev/ipl -.It /dev/ipstate -.El -.Sh SEE ALSO -.Xr ipftest 1 , -.Xr ipf 4 , -.Xr ipl 4 , -.Xr ipnat 4 , -.Xr hosts 5 , -.Xr ipnat 5 , -.Xr services 5 , -.Xr ipf 8 , -.Xr ipfstat 8 , -.Xr ipmon 8 , -.Xr ipnat 8 +.SH FILES +/dev/ipauth +.br +/dev/ipl +.br +/dev/ipstate +.br +/etc/hosts +.br +/etc/services +.SH SEE ALSO +ipftest(1), iptest(1), mkfilters(1), ipf(4), ipnat(5), ipf(8), ipfstat(8) |