fuzz: some improvements and add two new fuzzers (#1881)

Remove `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` define from
`fuzz/Makefile.am`; it is already included by the main configure script
(when fuzzing).

Add a knob to force disabling of AESNI optimizations: this way we can
fuzz also no-aesni crypto code.

Move CRC32 algorithm into the library.

Add some fake traces to extend fuzzing coverage. Note that these traces
are hand-made (via scapy/curl) and must not be used as "proof" that the
dissectors are really able to identify this kind of traffic.

Some small updates to some dissectors:

CSGO: remove a wrong rule (never triggered, BTW). Any UDP packet starting
with "VS01" will be classified as STEAM (see steam.c around line 111).
Googling it, it seems right so.

XBOX: XBOX only analyses UDP flows while HTTP only TCP ones; therefore
that condition is false.

RTP, STUN: removed useless "break"s

Zattoo: `flow->zattoo_stage` is never set to any values greater or equal
to 5, so these checks are never true.

PPStream: `flow->l4.udp.ppstream_stage` is never read. Delete it.

TeamSpeak: we check for `flow->packet_counter == 3` just above, so the
following check `flow->packet_counter >= 3` is always false.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/protocols/tcp_udp.c b/src/lib/protocols/tcp_udp.c
index 9aa0349f0..ec49e63ba 100644
--- a/src/lib/protocols/tcp_udp.c
+++ b/src/lib/protocols/tcp_udp.c
@@ -53,11 +53,13 @@ void ndpi_search_tcp_or_udp(struct ndpi_detection_module_struct *ndpi_struct, st
 {
   u_int16_t sport, dport;
   u_int proto;
-  struct ndpi_packet_struct *packet = &ndpi_struct->packet;
+  struct ndpi_packet_struct *packet;
 
-  if(flow->host_server_name[0] != '\0')
+  if(!ndpi_struct || !flow || flow->host_server_name[0] != '\0')
     return;
 
+  packet = &ndpi_struct->packet;
+
   if(packet->udp) sport = ntohs(packet->udp->source), dport = ntohs(packet->udp->dest);
   else if(packet->tcp) sport = ntohs(packet->tcp->source), dport = ntohs(packet->tcp->dest);
   else sport = dport = 0;