AdGuardHome/internal/dnsforward/dnsrewrite.go

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package dnsforward
import (
"fmt"
"net"
"github.com/AdguardTeam/AdGuardHome/internal/filtering"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/log"
"github.com/AdguardTeam/urlfilter/rules"
"github.com/miekg/dns"
)
// filterDNSRewriteResponse handles a single DNS rewrite response entry. It
// returns the properly constructed answer resource record.
func (s *Server) filterDNSRewriteResponse(
req *dns.Msg,
rr rules.RRType,
v rules.RRValue,
) (ans dns.RR, err error) {
switch rr {
case
dns.TypeA,
dns.TypeAAAA:
return s.ansFromDNSRewriteIP(v, rr, req)
case
dns.TypePTR,
dns.TypeTXT:
return s.ansFromDNSRewriteText(v, rr, req)
case dns.TypeMX:
return s.ansFromDNSRewriteMX(v, rr, req)
case
dns.TypeHTTPS,
dns.TypeSVCB:
return s.ansFromDNSRewriteSVCB(v, rr, req)
case dns.TypeSRV:
return s.ansFromDNSRewriteSRV(v, rr, req)
default:
log.Debug("don't know how to handle dns rr type %d, skipping", rr)
return nil, nil
}
}
// ansFromDNSRewriteIP creates a new answer resource record from the A/AAAA
// dnsrewrite rule data.
func (s *Server) ansFromDNSRewriteIP(
v rules.RRValue,
rr rules.RRType,
req *dns.Msg,
) (ans dns.RR, err error) {
ip, ok := v.(net.IP)
if !ok {
return nil, fmt.Errorf("value for rr type %s has type %T, not net.IP", dns.Type(rr), v)
}
if rr == dns.TypeA {
return s.genAnswerA(req, ip.To4()), nil
}
return s.genAnswerAAAA(req, ip), nil
}
// ansFromDNSRewriteText creates a new answer resource record from the TXT/PTR
// dnsrewrite rule data.
func (s *Server) ansFromDNSRewriteText(
v rules.RRValue,
rr rules.RRType,
req *dns.Msg,
) (ans dns.RR, err error) {
str, ok := v.(string)
if !ok {
return nil, fmt.Errorf("value for rr type %s has type %T, not string", dns.Type(rr), v)
}
if rr == dns.TypeTXT {
return s.genAnswerTXT(req, []string{str}), nil
}
return s.genAnswerPTR(req, str), nil
}
// ansFromDNSRewriteMX creates a new answer resource record from the MX
// dnsrewrite rule data.
func (s *Server) ansFromDNSRewriteMX(
v rules.RRValue,
rr rules.RRType,
req *dns.Msg,
) (ans dns.RR, err error) {
mx, ok := v.(*rules.DNSMX)
if !ok {
return nil, fmt.Errorf(
"value for rr type %s has type %T, not *rules.DNSMX",
dns.Type(rr),
v,
)
}
return s.genAnswerMX(req, mx), nil
}
// ansFromDNSRewriteSVCB creates a new answer resource record from the
// SVCB/HTTPS dnsrewrite rule data.
func (s *Server) ansFromDNSRewriteSVCB(
v rules.RRValue,
rr rules.RRType,
req *dns.Msg,
) (ans dns.RR, err error) {
svcb, ok := v.(*rules.DNSSVCB)
if !ok {
return nil, fmt.Errorf(
"value for rr type %s has type %T, not *rules.DNSSVCB",
dns.Type(rr),
v,
)
}
if rr == dns.TypeHTTPS {
return s.genAnswerHTTPS(req, svcb), nil
}
return s.genAnswerSVCB(req, svcb), nil
}
// ansFromDNSRewriteSRV creates a new answer resource record from the SRV
// dnsrewrite rule data.
func (s *Server) ansFromDNSRewriteSRV(
v rules.RRValue,
rr rules.RRType,
req *dns.Msg,
) (dns.RR, error) {
srv, ok := v.(*rules.DNSSRV)
if !ok {
return nil, fmt.Errorf(
"value for rr type %s has type %T, not *rules.DNSSRV",
dns.Type(rr),
v,
)
}
return s.genAnswerSRV(req, srv), nil
}
// filterDNSRewrite handles dnsrewrite filters. It constructs a DNS response
// and sets it into pctx.Res. All parameters must not be nil.
func (s *Server) filterDNSRewrite(
req *dns.Msg,
res *filtering.Result,
pctx *proxy.DNSContext,
) (err error) {
resp := s.makeResponse(req)
dnsrr := res.DNSRewriteResult
if dnsrr == nil {
return errors.Error("no dns rewrite rule content")
}
resp.Rcode = dnsrr.RCode
if resp.Rcode != dns.RcodeSuccess {
pctx.Res = resp
return nil
}
if dnsrr.Response == nil {
return errors.Error("no dns rewrite rule responses")
}
rr := req.Question[0].Qtype
values := dnsrr.Response[rr]
for i, v := range values {
var ans dns.RR
ans, err = s.filterDNSRewriteResponse(req, rr, v)
if err != nil {
return fmt.Errorf("dns rewrite response for %d[%d]: %w", rr, i, err)
}
resp.Answer = append(resp.Answer, ans)
}
pctx.Res = resp
return nil
}