Hello,
I've written a filter to parse out punicode from DNS payloads and rewrite the packet in case it contains any IDN (xn--) marker unless the IDN is on a whitelist. Valgrind reports that nfq_create_queue() returns uninitialized
bytes resulting in thiserror:
sudo valgrind --tool=memcheck --leak-check=yes --show-reachable=yes \
--num-callers=20 --track-fds=yes --track-origins=yes -s \
./nfq --syslog --facility LOG_LOCAL0 --log-level info \
--port 53 --renice -20 --rewrite-answer
==714384==
==714384== Syscall param socketcall.sendto(msg) points to uninitialised byte(s)
==714384== at 0x4B977C7: sendto (sendto.c:27)
==714384== by 0x486BE02: nfnl_send (in /usr/lib/x86_64-linux-gnu/libnfnetlink.so.0.2.0)
==714384== by 0x486DBD2: nfnl_query (in /usr/lib/x86_64-linux-gnu/libnfnetlink.so.0.2.0)
==714384== by 0x4A73995: nfq_set_mode (libnetfilter_queue.c:639)
==714384== by 0x10B247: start_nfqueue_processing (nfq.c:532)
==714384== by 0x10C289: main (nfq.c:987)
==714384== Address 0x1ffefefbfd is on thread 1's stack
==714384== in frame #3, created by nfq_set_mode (libnetfilter_queue.c:623)
==714384== Uninitialised value was created by a stack allocation
==714384== at 0x10A1B0: ??? (in /src/nfq/src/nfq)
After searching on this list archive, I found 1 question but without a follow-up answer:
https://marc.info/?l=netfilter-devel&m=137132916826745&w=4
Having already spent over a day chasing this. Not having come across other cases on github except this person self reporting[1] made me think it must be indeed something in my code that I'm missing and that could have triggered this. Or is it really rare (harmless) bug in libnetfilter?
[1] https://github.com/misje/dhcpoptinj/issues/5
thanks for any help,
~DA
