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reverse.go
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reverse.go
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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("resolver: 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.Debugf("A: %s", v.A.String())
if ip == v.A.String() {
return ptrName, nil
}
case *dns.AAAA:
// log.Debugf("AAAA: %s", v.AAAA.String())
if ip == v.AAAA.String() {
return ptrName, nil
}
}
}
// no match
return "", ErrBlocked
}