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Fix bug: internet intents discovered with CNAME instead of the actual domain name #223

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merged 2 commits into from
Jun 20, 2024
Merged

Fix bug: internet intents discovered with CNAME instead of the actual domain name #223

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08afcb5
Fix bug: internet intents discovered with CNAME instead of the actual…
NetanelBollag Jun 18, 2024
6622ca9
Add test
NetanelBollag Jun 20, 2024
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32 changes: 30 additions & 2 deletions src/sniffer/pkg/collectors/dnssniffer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import (
"github.com/otterize/network-mapper/src/sniffer/pkg/config"
"github.com/otterize/network-mapper/src/sniffer/pkg/ipresolver"
"github.com/otterize/nilable"
"github.com/samber/lo"
"github.com/sirupsen/logrus"
"github.com/spf13/viper"
"net"
Expand Down Expand Up @@ -136,13 +137,21 @@ func (s *DNSSniffer) HandlePacket(packet gopacket.Packet) {
ip, _ := ipLayer.(*layers.IPv4)
dns, _ := dnsLayer.(*layers.DNS)
if dns.OpCode == layers.DNSOpCodeQuery && dns.ResponseCode == layers.DNSResponseCodeNoErr {
cnameToA := getCNameTranslation(dns)

for _, answer := range dns.Answers {
// This is the DNS Answer, so the Dst IP is the pod IP
if answer.Type != layers.DNSTypeA && answer.Type != layers.DNSTypeAAAA {
continue
}
hostName := string(answer.Name)
if nameFromCNAME, ok := cnameToA[hostName]; ok {
logrus.Debugf("Found CNAME record for %s: %s", hostName, nameFromCNAME)
hostName = nameFromCNAME
}

if !s.isRunningOnAWS {
s.addCapturedRequest(ip.DstIP.String(), "", string(answer.Name), answer.IP.String(), captureTime, nilable.From(int(answer.TTL)), nil)
s.addCapturedRequest(ip.DstIP.String(), "", hostName, answer.IP.String(), captureTime, nilable.From(int(answer.TTL)), nil)
continue
}
hostname, err := s.resolver.ResolveIP(ip.DstIP.String())
Expand All @@ -153,7 +162,7 @@ func (s *DNSSniffer) HandlePacket(packet gopacket.Packet) {
s.pending = append(s.pending, pendingCapture{
srcIp: ip.DstIP.String(),
srcHostname: hostname,
destHostnameOrIP: string(answer.Name),
destHostnameOrIP: hostName,
destIPFromDNS: answer.IP.String(),
time: captureTime,
ttl: nilable.From(int(answer.TTL)),
Expand All @@ -164,6 +173,25 @@ func (s *DNSSniffer) HandlePacket(packet gopacket.Packet) {
}
}

func getCNameTranslation(dns *layers.DNS) map[string]string {
// Probably there is one CNAME record per DNS packet, so we could just use the first one we find
// But, since the implementation uses a list of answers, we will support multiple CNAME records with one
// caveat: it won't work with multiple domains for the same CNAME which is really unlikely in the same packet
cnameAnswer := lo.Filter(dns.Answers, func(answer layers.DNSResourceRecord, _ int) bool {
return answer.Type == layers.DNSTypeCNAME && len(answer.CNAME) > 0 && len(answer.Name) > 0
})

cnameToA := make(map[string]string)
for _, answer := range cnameAnswer {
existing, found := cnameToA[string(answer.CNAME)]
if found && existing != string(answer.Name) {
logrus.Debugf("Multiple CNAME records for the same CNAME, overwriting %s with %s", existing, string(answer.Name))
}
cnameToA[string(answer.CNAME)] = string(answer.Name)
}
return cnameToA
}

func (s *DNSSniffer) RefreshHostsMapping() error {
if !s.isRunningOnAWS {
return nil
Expand Down
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