Message signature verification in the python library does not properly check the timstamp.

[pv42]

The function check_signature(..) -> bool in mavutil.py generated from mavgen_python.py

pymavlink/generator/mavgen_python.py

Line 963 in e192ad8

def check_signature(self, msgbuf${type_bytearray}, srcSystem${type_int}, srcComponent${type_int})${type_bool_ret}:

does not increase the value of self.signing.stream_timestamps[stream_key] after initially setting it on the first message received per logical stream.
The documentation says that a packet should be rejected if

Timestamp is older than the previous packet from the same logical stream - where a logical stream is defined as the sequence of MAVLink packets with the same (SystemID, ComponentID, LinkID) tuple.

but since the value is never updated this comparison is only done against the first packet of the stream.

[tridge]

@pv42 I think you are right and this needs to be fixed. Would you like to do a PR yourself? or shall I do it?

[pv42]

Hello @tridge, thanks for the response.
I just noticed the issue when comparing the c implementation, this python implementation and the documentation. While I was reasonably confident that there is something wrong with this implementation I am not sufficiently confident to write the security critical code of a codebase I am not familiar with.