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Add weird for unhandled opcodes in DNS analyzer

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This commit is contained in:
Tim Wojtulewicz 2024-08-20 11:53:50 -07:00
parent cd10bd3747
commit 269ca3189c
5 changed files with 39 additions and 1 deletions
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16
src/analyzer/protocol/dns/DNS.cc
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@ -27,6 +27,7 @@ DNS_Interpreter::DNS_Interpreter(analyzer::Analyzer* arg_analyzer) {
}
void DNS_Interpreter::ParseMessage(const u_char* data, int len, int is_query) {
// Every packet for every opcode starts with same size header.
int hdr_len = sizeof(detail::DNS_RawMsgHdr);
if ( len < hdr_len ) {
@ -34,7 +35,20 @@ void DNS_Interpreter::ParseMessage(const u_char* data, int len, int is_query) {
return;
}
detail::DNS_MsgInfo msg((detail::DNS_RawMsgHdr*)data, is_query);
// The flags section may be different between the different opcodes, but the
// opcode is always in the same location. Parse out just that part of it here
// even though it will probably be reparsed later.
auto* hdr = (detail::DNS_RawMsgHdr*)data;
unsigned short flags = ntohs(hdr->flags);
int opcode = (flags & 0x7800) >> 11;
if ( opcode != DNS_OP_QUERY ) {
analyzer->Weird("DNS_unknown_opcode", util::fmt("%d", opcode));
analyzer->Conn()->CheckHistory(zeek::session::detail::HIST_UNKNOWN_PKT, 'X');
return;
}
detail::DNS_MsgInfo msg(hdr, is_query);
if ( first_message && msg.QR && is_query == 1 ) {
is_query = msg.is_query = 0;