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More heuristics to detect valid plain DNS responses

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This commit is contained in:
Frank Denis 2025-01-11 15:29:49 +01:00
parent f332394c4b
commit 6dd22becac
1 changed files with 21 additions and 17 deletions
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38
dnscrypt-proxy/serversInfo.go
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@ -620,25 +620,29 @@ func fetchDNSCryptServerInfo(proxy *Proxy, name string, stamp stamps.ServerStamp
&name, &name,
false, false,
) )
if err == nil { if err == nil && len(msg.Question) > 0 {
if msg.Id != 0xcafe { question := msg.Question[0]
dlog.Infof("[%s] handling of DNS message identifiers is broken", name) if question.Qtype == query.Question[0].Qtype && strings.EqualFold(question.Name, query.Question[0].Name) {
} dlog.Debugf("[%s] also serves plaintext DNS", name)
for _, rr := range msg.Answer { if msg.Id != 0xcafe {
if rr.Header().Rrtype == dns.TypeA || rr.Header().Rrtype == dns.TypeAAAA { dlog.Infof("[%s] handling of DNS message identifiers is broken", name)
dlog.Warnf("[%s] may be a lying resolver -- skipping", name)
return ServerInfo{}, fmt.Errorf("[%s] unexpected record: [%s]", name, rr.String())
} }
} for _, rr := range msg.Answer {
for _, rr := range msg.Extra { if rr.Header().Rrtype == dns.TypeA || rr.Header().Rrtype == dns.TypeAAAA {
if rr.Header().Rrtype == dns.TypeTXT { dlog.Warnf("[%s] may be a lying resolver -- skipping", name)
dlog.Warnf("[%s] may be a dummy resolver -- skipping", name) return ServerInfo{}, fmt.Errorf("[%s] unexpected record: [%s]", name, rr.String())
txts := rr.(*dns.TXT).Txt }
cause := "" }
if len(txts) > 0 { for _, rr := range msg.Extra {
cause = txts[0] if rr.Header().Rrtype == dns.TypeTXT {
dlog.Warnf("[%s] may be a dummy resolver -- skipping", name)
txts := rr.(*dns.TXT).Txt
cause := ""
if len(txts) > 0 {
cause = txts[0]
}
return ServerInfo{}, fmt.Errorf("[%s] unexpected record: [%s]", name, cause)
} }
return ServerInfo{}, fmt.Errorf("[%s] unexpected record: [%s]", name, cause)
} }
} }
} }