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Fix dnssnooper probe for multiple CNAMEs.

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This commit is contained in:
tiriplicamihai
2019-01-28 13:49:16 +02:00
parent fb32d6e9bb
commit 1aadf5c606
1 changed files with 13 additions and 7 deletions
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20
probe/endpoint/dns_snooper.go
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@@ -250,15 +250,14 @@ func (s *DNSSnooper) processDNSMessage(dns *layers.DNS) {
domainQueried = question.Name
records = append(dns.Answers, dns.Additionals...)
ips = map[string]struct{}{}
alias []byte
aliases = [][]byte{}
)
// Traverse records for a CNAME first since the DNS RFCs don't seem to guarantee it
// appearing before its A-records
// Traverse all the CNAME records and the get the aliases. There are cases when the A record is for only one of the
// aliases. We traverse CNAME records first because there is no guarantee that the A records will be the first ones
for _, record := range records {
if record.Type == layers.DNSTypeCNAME && record.Class == layers.DNSClassIN && bytes.Equal(domainQueried, record.Name) {
alias = record.CNAME
break
if record.Type == layers.DNSTypeCNAME && record.Class == layers.DNSClassIN {
aliases = append(aliases, record.CNAME)
}
}
@@ -267,8 +266,15 @@ func (s *DNSSnooper) processDNSMessage(dns *layers.DNS) {
if record.Type != layers.DNSTypeA || record.Class != layers.DNSClassIN {
continue
}
if bytes.Equal(domainQueried, record.Name) || (alias != nil && bytes.Equal(alias, record.Name)) {
if bytes.Equal(domainQueried, record.Name) {
ips[record.IP.String()] = struct{}{}
continue
}
for _, alias := range aliases {
if bytes.Equal(alias, record.Name) {
ips[record.IP.String()] = struct{}{}
continue
}
}
}