Rename intel to resolver

resolver/reverse.go

@@ -0,0 +1,82 @@
+package resolver
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/miekg/dns"
+	"github.com/safing/portbase/log"
+)
+
+// ResolveIPAndValidate finds (reverse DNS), validates (forward DNS) and returns the domain name assigned to the given IP.
+func ResolveIPAndValidate(ctx context.Context, ip string, securityLevel uint8) (domain string, err error) {
+	// get reversed DNS address
+	reverseIP, err := dns.ReverseAddr(ip)
+	if err != nil {
+		log.Tracef("intel: failed to get reverse address of %s: %s", ip, err)
+		return "", ErrInvalid
+	}
+
+	// get PTR record
+	q := &Query{
+		FQDN:          reverseIP,
+		QType:         dns.Type(dns.TypePTR),
+		SecurityLevel: securityLevel,
+	}
+	rrCache, err := Resolve(ctx, q)
+	if err != nil || rrCache == nil {
+		return "", fmt.Errorf("failed to resolve %s%s: %w", q.FQDN, q.QType, err)
+	}
+
+	// get result from record
+	var ptrName string
+	for _, rr := range rrCache.Answer {
+		ptrRec, ok := rr.(*dns.PTR)
+		if ok {
+			ptrName = ptrRec.Ptr
+			break
+		}
+	}
+
+	// check for nxDomain
+	if ptrName == "" {
+		return "", fmt.Errorf("%w: %s%s", ErrNotFound, q.FQDN, q.QType)
+	}
+
+	// get forward record
+	q = &Query{
+		FQDN:          ptrName,
+		SecurityLevel: securityLevel,
+	}
+	// IPv4/6 switch
+	if strings.Contains(ip, ":") {
+		q.QType = dns.Type(dns.TypeAAAA)
+	} else {
+		q.QType = dns.Type(dns.TypeA)
+	}
+	// resolve
+	rrCache, err = Resolve(ctx, q)
+	if err != nil || rrCache == nil {
+		return "", fmt.Errorf("failed to resolve %s%s: %w", q.FQDN, q.QType, err)
+	}
+
+	// check for matching A/AAAA record
+	for _, rr := range rrCache.Answer {
+		switch v := rr.(type) {
+		case *dns.A:
+			log.Infof("A: %s", v.A.String())
+			if ip == v.A.String() {
+				return ptrName, nil
+			}
+		case *dns.AAAA:
+			log.Infof("AAAA: %s", v.AAAA.String())
+			if ip == v.AAAA.String() {
+				return ptrName, nil
+			}
+		}
+	}
+
+	// no match
+	return "", ErrBlocked
+}