Unit test 1655

Hi.

[I’ve had a lot of trouble sending this. Apologies in case
 multiple copies arrive on the list.]

I’m looking to extend `dohprobe()` to allow retrieval of other
host attributes than addresses, some of which are published
at prefixed DNS names relative to the host name. I have had to
take account of unit test 1655, which puzzles me. I’m wondering
whether it may be appropriate to open an issue.

The very long name (`const char *bad = "this.is.` _et seq_.) is
invalid according to RFCs 1034 and 1035 both because it is too
long and because it contains embedded zero-length labels (which
are represented by consecutive dots). A strict encoder should
reject it early, and so frustrate the attempt to force a buffer
overflow.

A validly encoded pure (without EDNS) single query must fit
in 272 (12 + 256 + 4) octets, which is well below the buffer
size of 512 provided in `struct dnsprobe`.

Thanks in anticipation for advice on how best to proceed.

Niall O’Reilly

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Received on 2019-11-12