Missing I/Q data for FSK_Messaging_Service example

[Brad Dixon]

I'm working on duplicating the examples from Fuzzing the Unfuzzable and ran into some missing parts:

• FSK_Messaging_Service binary: I built this from the cb-multios repo
• Valid input data for the test binary. I thought this would be in the cb-multios repo but if it is I've not found it.

My planned contribution is to create a simple test suite (pytest) that mirrors the two blog posts. These are great examples and It would be good to make sure they keep working as the project evolves.

[Nathan Voss]

I really like the idea of creating a pytest suite!

You've found my dirty little secret...I had to hack up the 'pov.c' file in the FSK_Messaging_Service binary in order to get a valid IQ input that I could use. I've attached the modified version of pov.c that I used to generate the sample input (no promises on cleanliness, it was a quick hack). You can build this by just dropping it in temporarily over the pov.c that is in the cb-multios repo.

pov_modified.zip

One other potential pitfall is making sure that any addresses used in the PoC unicorn test harness are valid, as I think those could change if the binary is compiled on different systems. This could be mitigated by shipping the binary itself pre-built with the correct addresses.

[Brad Dixon]

Thank you. I've got some time next week to put this together.

[LagrangedWho]

Thank you. I build you pov_modified.c and get the new binary. And I also want to know how can I use the binary pov_1.pov to generate the sample input. Should I run ./pov_1.pov > output? but the context in this output file likes a binary file.
I also try the follow command:

~$ ./FSK_Messaging_Service < ./pov_1.pov # 1st
[[RECEIVER STARTED -- TIMESTAMP: 1453110580]]
[[RECEIVE ERROR]]
~$ ./pov_1.pov | ./FSK_Messaging_Service # 2nd
[[RECEIVER STARTED -- TIMESTAMP: 1453110580]]
Total 12 bytes received and 0 invalid packets.
Displaying 2 received packets:
Displaying packet 0 type 3:
[CONNECT MESSAGE]ASDF connected
Displaying packet 1 type 3:
[CONNECT MESSAGE]ASDF connected
^C # Ctrl+C
~$ ./FSK_Messaging_Service < output # 3rd
[[RECEIVER STARTED -- TIMESTAMP: 1453110580]]
Total 12 bytes received and 0 invalid packets.
Displaying 2 received packets:
Displaying packet 0 type 3:
[CONNECT MESSAGE]ASDF connected
Displaying packet 1 type 3:
[CONNECT MESSAGE]ASDF connected
~$

I think the 2nd and 3rd example are right, but it is just only one valid IQ input, isn't it?

[Nathan Voss]

It's been a while since I actually ran this so my memory is a bit fuzzy on this, but I believe that you are correct. Generate sample inputs using ./pov_1.pov > output, since the pov binary 'transmits' by writing to stdout. Within the pov.c file, you'll see multiple calls to cgc_transmit_all. I beiieve that the receiver code parses the output as multiple packets, causing the output that you see above (2 packets on each run).