Fuzzer 01 - Dispatcher, Packet: always check if we have enough 'len' before pulling bytes out of the raw frame - #3267
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Every received frame is first turned into a 'Packet' struct by Dispatcher::tryParsePacket(). The frame is a length-prefixed byte string: [header][transport_codes(optional)][path_length][path][payload] The parser has to read the 'header' *first*, and only then does it know how many more bytes it is required to read. The bug is that it never checks that those bytes actually arrived.
Packet::readFrom() is a second, independent parser for the same wire format: [header][transport_codes(optional)][path_length][path][payload] It is used by the ESP-NOW bridge (src/helpers/bridges/ESPNowBridge.cpp) to turn a received blob back into a 'Packet'. It duplicates the parsing logic of Dispatcher::tryParsePacket() and has the same length-check problems, plus one more: the `path` read is not bounds-checked either.
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I started playing around with a fuzzer. This is the first result.