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NAME

ipftest − test packet filter rules with arbitrary input.

SYNOPSIS

ipftest [ −vbdPRSTEHX ] [ −I interface ] −r <filename> [ −i <filename> ] [ −s <ipaddress> ]

DESCRIPTION

ipftest is provided for the purpose of being able to test a set of filter rules without having to put them in place, in operation and proceed to test their effectiveness. The hope is that this minimises disruptions in providing a secure IP environment.

ipftest will parse any standard ruleset for use with ipf and apply input, returning output as to the result. However, ipftest will return one of three values for packets passed through the filter: pass, block or nomatch. This is intended to give the operator a better idea of what is happening with packets passing through their filter ruleset.

When used without either of −S, −T or −E, ipftest uses its own text input format to generate "fake" IP packets. The format used is as follows:

"in"|"out" "on" if ["tcp"|"udp"|"icmp"]

srchost[,srcport] dsthost[,destport] [FSRPAU]

This allows for a packet going "in" or "out" of an interface (if) to be generated, being one of the three main protocols (optionally), and if either TCP or UDP, a port parameter is also expected. If TCP is selected, it is possible to (optionally) supply TCP flags at the end. Some examples are:

# a UDP packet coming in on le0

in on le0 udp 10.1.1.1,2210 10.2.1.5,23

# an IP packet coming in on le0 from localhost - hmm :)

in on le0 localhost 10.4.12.1

# a TCP packet going out of le0 with the SYN flag set.

out on le0 tcp 10.4.12.1,2245 10.1.1.1,23 S

OPTIONS

−v

Verbose mode. This provides more information about which parts of rule matching the input packet passes and fails.

−d

Turn on filter rule debugging. Currently, this only shows you what caused the rule to not match in the IP header checking (addresses/netmasks, etc).

−b

Cause the output to be a brief summary (one-word) of the result of passing the packet through the filter; either "pass", "block" or "nomatch". This is used in the regression testing.

−I <interface>

Set the interface name (used in rule matching) to be the name supplied. This is useful with the −P, −S, −T and −E options, where it is not otherwise possible to associate a packet with an interface. Normal "text packets" can override this setting.

−P

The input file specified by −i is a binary file produced using libpcap (i.e., tcpdump version 3). Packets are read from this file as being input (for rule purposes). An interface maybe specified using −I.

−R

Remove rules rather than load them. This is not a toggle option, so once set, it cannot be reset by further use of -R.

−S

The input file is to be in "snoop" format (see RFC 1761). Packets are read from this file and used as input from any interface. This is perhaps the most useful input type, currently.

−T

The input file is to be text output from tcpdump. The text formats which are currently supported are those which result from the following tcpdump option combinations:

tcpdump -n

tcpdump -nq

tcpdump -nqt

tcpdump -nqtt

tcpdump -nqte

−H

The input file is to be hex digits, representing the binary makeup of the packet. No length correction is made, if an incorrect length is put in the IP header. A packet may be broken up over several lines of hex digits, a blank line indicating the end of the packet. It is possible to specify both the interface name and direction of the packet (for filtering purposes) at the start of the line using this format: [direction,interface] To define a packet going in on le0, we would use [in,le0] - the []’s are required and part of the input syntax.

−X

The input file is composed of text descriptions of IP packets.

−E

The input file is to be text output from etherfind. The text formats which are currently supported are those which result from the following etherfind option combinations:

etherfind -n

etherfind -n -t

−i <filename>

Specify the filename from which to take input. Default is stdin.

−r <filename>

Specify the filename from which to read filter rules.

−s <ipaddress>

Where the input format is incapable of telling ipftest whther a packet is going in or out, setting this option to an IP address results in the direction being set to out if the source matches or in if the destination matches.

SEE ALSO

ipf(5), ipf(8), snoop(1m), tcpdump(8), etherfind(8c)

BUGS

Not all of the input formats are sufficiently capable of introducing a wide enough variety of packets for them to be all useful in testing.

COMMENTS