DNS: fix parsing of hostname for empty response messages (#2731)

3 files changed, 11 insertions, 6 deletions

diff --git a/src/lib/protocols/dns.c b/src/lib/protocols/dns.c
index 36b928980..7199d51f6 100644
--- a/src/lib/protocols/dns.c
+++ b/src/lib/protocols/dns.c
@@ -706,6 +706,7 @@ static int search_dns_again(struct ndpi_detection_module_struct *ndpi_struct, st
 
 static int process_hostname(struct ndpi_detection_module_struct *ndpi_struct,
                             struct ndpi_flow_struct *flow,
+                            struct ndpi_dns_packet_header *dns_header,
                             ndpi_master_app_protocol *proto) {
   struct ndpi_packet_struct *packet = &ndpi_struct->packet;
   char *dot;
@@ -716,6 +717,10 @@ static int process_hostname(struct ndpi_detection_module_struct *ndpi_struct,
   proto->master_protocol = checkDNSSubprotocol(ntohs(flow->c_port), ntohs(flow->s_port));
   proto->app_protocol = NDPI_PROTOCOL_UNKNOWN;
 
+  /* We try to get hostname only from "standard" query/answer */
+  if(dns_header->num_queries == 0 && dns_header->num_answers == 0)
+    return -1;
+
   is_mdns = (proto->master_protocol == NDPI_PROTOCOL_MDNS);
 
   /* TODO: should we overwrite existing hostname?
@@ -803,7 +808,7 @@ static void search_dns(struct ndpi_detection_module_struct *ndpi_struct, struct
     return;
   }
 
-  process_hostname(ndpi_struct, flow, &proto);
+  process_hostname(ndpi_struct, flow, &dns_header, &proto);
 
   off = sizeof(struct ndpi_dns_packet_header) + payload_offset;
 
diff --git a/tests/cfgs/default/result/dns_invert_query.pcapng.out b/tests/cfgs/default/result/dns_invert_query.pcapng.out
index f7291ba64..014c71f58 100644
--- a/tests/cfgs/default/result/dns_invert_query.pcapng.out
+++ b/tests/cfgs/default/result/dns_invert_query.pcapng.out
@@ -24,4 +24,4 @@ DNS	2	134	1
 
 Acceptable                       2 134           1            
 
-	1	UDP 173.147.108.174:18427 <-> 244.187.95.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/78 bytes <-> 1 pkts/56 bytes][Goodput ratio: 46/21][0.00 sec][0.0.0.0][DNS Id: 0x77fc][Risk: ** Error Code **][Risk Score: 10][Risk Info: DNS Error Code NOTIMP][Plen Bins: 50,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	1	UDP 173.147.108.174:18427 <-> 244.187.95.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 2][cat: Network/14][1 pkts/78 bytes <-> 1 pkts/56 bytes][Goodput ratio: 46/21][0.00 sec][Hostname/SNI: 216.58.202.4][0.0.0.0][DNS Id: 0x77fc][Risk: ** Error Code **][Risk Score: 10][Risk Info: DNS Error Code NOTIMP][Plen Bins: 50,50,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
diff --git a/tests/cfgs/default/result/fuzz-2006-06-26-2594.pcap.out b/tests/cfgs/default/result/fuzz-2006-06-26-2594.pcap.out
index 3871a8f07..0c459e29e 100644
--- a/tests/cfgs/default/result/fuzz-2006-06-26-2594.pcap.out
+++ b/tests/cfgs/default/result/fuzz-2006-06-26-2594.pcap.out
@@ -14,10 +14,10 @@ LRU cache tls_cert:   0/0/0 (insert/search/found)
 LRU cache mining:     0/66/0 (insert/search/found)
 LRU cache msteams:    0/0/0 (insert/search/found)
 LRU cache fpc_dns:    0/66/0 (insert/search/found)
-Automa host:          238/0 (search/found)
-Automa domain:        231/0 (search/found)
+Automa host:          237/0 (search/found)
+Automa domain:        230/0 (search/found)
 Automa tls cert:      0/0 (search/found)
-Automa risk mask:     125/0 (search/found)
+Automa risk mask:     124/0 (search/found)
 Automa common alpns:  0/0 (search/found)
 Patricia risk mask:   372/0 (search/found)
 Patricia risk mask IPv6: 0/0 (search/found)
@@ -211,7 +211,7 @@ Unrated                         33 4066          33
 	168	UDP 192.168.1.53:2791 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][Hostname/SNI: _sip._udp.sip.cybercity.dk][0.0.0.0][DNS Id: 0x82eb][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 	169	UDP 192.168.1.110:2713 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][0.0.0.0][DNS Id: 0x4cd2][Risk: ** Malformed Packet **** Unidirectional Traffic **][Risk Score: 20][Risk Info: No server to client traffic / Invalid DNS Query Lenght][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 	170	UDP 192.168.1.172:2766 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][Hostname/SNI: _sip._udp.sip.cybercity.dk][0.0.0.0][DNS Id: 0x7bfd][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
-	171	UDP 192.168.9.2:2774 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][Hostname/SNI: _sip._udp.sip.cybercity.dk][0.0.0.0][DNS Id: 0xdae2][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+	171	UDP 192.168.9.2:2774 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][0.0.0.0][DNS Id: 0xdae2][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 	172	UDP 192.168.37.115:2758 -> 128.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: Match by port][FPC: 0/Unknown, Confidence: Unknown][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][0.0.0.0][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 	173	UDP 192.168.54.2:2829 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][0.0.0.0][DNS Id: 0xd033][Risk: ** Malformed Packet **** Unidirectional Traffic **][Risk Score: 20][Risk Info: No server to client traffic / Invalid DNS Query Lenght][PLAIN TEXT (cibercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 	174	UDP 192.168.79.2:2791 -> 192.168.1.1:53 [proto: 5/DNS][IP: 0/Unknown][ClearText][Confidence: DPI][FPC: 5/DNS, Confidence: DPI][DPI packets: 1][cat: Network/14][1 pkts/86 bytes -> 0 pkts/0 bytes][Goodput ratio: 51/0][< 1 sec][Hostname/SNI: _sip._udp.sip.cybercity.dk][0.0.0.0][DNS Id: 0x82eb][Risk: ** Unidirectional Traffic **][Risk Score: 10][Risk Info: No server to client traffic][PLAIN TEXT (cybercity)][Plen Bins: 0,100,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]