NAME

acap2pcap - convert Cisco ASA capture text to PCAP file

SYNOPSIS

  acap2pcap [options] [filename]

OPTIONS

--help | -?

Show a short help text and exit.

--man

Show the full manual page and exit.

--dlt $data_link_type

Specify the data link type for the PCAP file.

--output

Specify the name of the PCAP file (default: asa.pcap)

DESCRIPTION

This program reads a packet capture from the Cisco ASA and writes it to a file in PCAP format. To use it, you can start the show capture command on the command line interface and send the output to this program.

  ssh asa show capture $name dump | acap2pcap

If you saved the output of the show capture command to a file, you may instead give the name of the file as an argument to the program.

  acap2pcap $filename

ASA output

A typical packet capture on a Cisco ASA looks like the following:

  pix515# show capture test dump
  522 packets captured
   1: 21:24:38.629087 192.168.1.2 > 192.168.1.1: icmp: echo request
  0x0000   4500 003c 12a7 0000 7e01 9781 ac11 2324       E..<....~.....#$
  0x0010   c0a8 02bb 0800 35cb 0001 1790 6162 6364       ......5.....abcd
  0x0020   6566 6768 696a 6b6c 6d6e 6f70 7172 7374       efghijklmnopqrst
  0x0030   7576 7761 6263 6465 6667 6869                 uvwabcdefghi
   2: 21:24:38.630765 192.168.1.1 > 192.168.1.2: icmp: echo reply
  0x0000   4500 003c 4656 0000 ff01 e2d1 c0a8 02bb       E..<FV..........
  0x0010   ac11 2324 0000 3dcb 0001 1790 6162 6364       ..#$..=.....abcd
  0x0020   6566 6768 696a 6b6c 6d6e 6f70 7172 7374       efghijklmnopqrst
  0x0030   7576 7761 6263 6465 6667 6869                 uvwabcdefghi

This output shows raw IP traffic without layer 2 headers. To convert this to a readable PCAP file, you would choose the data link type 101 (see next section).

The program takes the timestamp from the first line of each packet and the hex values from the following lines to create the packet header and buffer for the PCAP file.

Data link type

The data link type defaults to 1, also named DLT_EN10MB. You use this if the output from the ASA shows the Ethernet header, that means the MAC addresses of the sender and receiver.

For ASA captures that only contain the raw IP traffic without link level header please use data link type 101 (DLT_RAW).

Use the option --dlt to change the data link type.

If you try to open the PCAP file with wireshark or tcpdump and it complains about corrupt packets, try the other data link type.

DIAGNOSTICS

Can't open file $filename to read ASA capture output

You can either feed the ASA output via standard input or a file. If you specify a filename, make sure that the file exists, and that it is readable.

SEE ALSO

Libpcap File Format https://wiki.wireshark.org/Development/LibpcapFileFormat

Link-Layer Header Types http://www.tcpdump.org/linktypes.html

AUTHOR

Mathias Weidner <mamawe@cpan.org>

LICENSE AND COPYRIGHT

Copyright 2017 Mathias Weidner.

This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:

http://www.perlfoundation.org/artistic_license_2_0

Any use, modification, and distribution of the Standard or Modified Versions is governed by this Artistic License. By using, modifying or distributing the Package, you accept this license. Do not use, modify, or distribute the Package, if you do not accept this license.

If your Modified Version has been derived from a Modified Version made by someone other than you, you are nevertheless required to ensure that your Modified Version complies with the requirements of this license.

This license does not grant you the right to use any trademark, service mark, tradename, or logo of the Copyright Holder.

This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.

Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES. THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER OR CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

cpanm File::PCAP

perl -MCPAN -e shell
install File::PCAP