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 | acap2pcapIf 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 $filenameASA output
A typical packet capture on a Cisco ASA looks like the following:
pix515# show capture test dump
522 packets captured
1: 21:24:38.629087 192.168.1.2 > 192.168.1.1: icmp: echo request
0x0000 4500 003c 12a7 0000 7e01 9781 ac11 2324 E..<....~.....#$
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 uvwabcdefghiThis 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
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