[fprint] Update to what we found out so far

[Vasily Khoruzhick]

On Wed, Nov 14, 2012 at 12:33 PM, Andreas Loos <a.loos at andreas-loos.com> wrote:
> Hi Vasily,
>
>
>> please also forward your post into fprint maillist. It's not a good
>> idea to keep this discussion private,
>> maybe someone wants to join it and needs some starting point.
>
>
> I will, sorry. Before I do, one question:

Don't drop maillist from CC please :)

>> Looks like they're encrypted and wrapped into some kind of envelope,
>> so it looks like this:
>>
>> 0xZZ - envelope cmd type (not sure what's its code yet)
>> 0xLL - size of message without 3-byte header, LSB
>> 0xMM - size of message without 3-byte hedaer, MSB
>> rest of message is encrypted command
>
>
> Don't understand what you mean. Take for instance command:
>
> -> 0x44, 0x02, 0x00, 0x08, 0x00
> -> 0x07
> <- 0x07, 0x05, 0x00, 0x8f, 0x16, 0x25, 0x01, 0x00
>
> a.k.a. COMMAND(08/00) + 0x07 + LONGANSWER(23)
>
> What are bytes 0xZZ, 0xLL and 0xMM?

It's some short non-encrypted command, but there are long (multibyte)
commands for sure,
see wireshark log you've sent to me, there're long transfers from host to device
first is 271-byte long and others are 269 bytes:

1st:
0x0d - some 1-byte (short) command
0x23 - some 1-byte (short) command
0x42 - envelope cmd? (multibyte)
0xca - size, LSB
0x00 - size, MSB
... - rest

2nd (and rest)
0x42 - envelope cmd? (multibyte)
0xca - size, LSB
0x00 - size, MSB