Question

I want to record the handshake messages between server and client into the file and replay them later.

For example, when I run s_server command with -debug option, I get some output like follows:

read from 0x9482088 [0x948d518] (2064 bytes => 2064 (0x810))
0000 - 0b 00 08 0c 00 08 09 00-04 1a 30 82 04 16 30 82   ..........0...0.
0010 - 02 fe a0 03 02 01 02 02-01 02 30 0d 06 09 2a 86   ..........0...*.
0020 - 48 86 f7 0d 01 01 05 05-00 30 81 88 31 0b 30 09   H........0..1.0.
0030 - 06 03 55 04 06 13 02 4e-4c 31 0b 30 09 06 03 55   ..U....NL1.0...U
0040 - 04 08 0c 02 4e 42 31 12-30 10 06 03 55 04 07 0c   ....NB1.0...U...
0050 - 09 41 4d 53 54 45 52 44-41 4d 31 10 30 0e 06 03   .AMSTERDAM1.0...
0060 - 55 04 0a 0c 07 4d 41 49-4e 20 43 41 31 0c 30 0a   U....MAIN CA1.0.
0070 - 06 03 55 04 0b 0c 03 49-43 54 31 17 30 15 06 03   ..U....ICT1.0...
0080 - 55 04 03 0c 0e 77 77 77-2e 6d 61 69 6e 63 61 2e   U....www.mainca.

I can record this data into files. But How can I extract this data (bytes) into the buffer? Is there any utility in Openssl to do it? or anything can be done in C program?

Thank You!

Answer 1

Yes. Assuming you are saving your log as a pcap file, tcpreplay will do exactly what you want. If you’re not saving as a pcap, you can do so either with libpcap or by writing the file yourself (the format is not terribly complicated).