TryReadNdefMessage can trim off terminator TLV (0xFE) causing validation to throw exception

Describe the bug

Reading NDEF message who's length is in a 16 byte boundary crashes in NdefMessage.ExtractMessage with IndexOutOfRangeException

This piece of code in UltralightCard.TryReadNdefMessage(...) will trim off the terminator TLV (0xFE) for a payload who's size is a factor of BlockSize

int blocksToRead = (size + start) / BlockSize + ((size + start) % BlockSize != 0 ? 1 : 0);

MifareCard.TryReadNdefMessage(...) appears to do something similar but slightly differently, but I haven't tried it.

Then this code (in NdefMessage.ExtractMessage) throws the exception:

bool isRealEnd = toExtract[idx + size] == 0xFE;

I find it hard to believe I'm the only one to have seen this, so perhaps the issue lies somewhere else?

If this is a real bug, I'm not sure on the best approach to fix it.

Option 1: ExtractMessage could loosen its constraints (the specs seem to indicate that the terminator is optional anyway?), e.g.

// Finally check that the optional end terminator TLV is 0xFE
bool isRealEnd = (toExtract.Length == idx + size) || (toExtract[idx + size] == 0xFE);

Option 2: Include the terminator by reading an extra block:

int blocksToRead = (size + start) / BlockSize + 1;

Option 3: Both option 1 and 2

dotnet / iot

TryReadNdefMessage can trim off terminator TLV (0xFE) causing validation to throw exception #2286