AdGuardHome/coredns_plugin/coredns_plugin.go

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package dnsfilter
import (
"bufio"
"errors"
"fmt"
"log"
"net"
"os"
"strconv"
"strings"
"sync"
"time"
"github.com/coredns/coredns/core/dnsserver"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metrics"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/pkg/upstream"
"github.com/coredns/coredns/request"
"github.com/mholt/caddy"
"github.com/miekg/dns"
"github.com/prometheus/client_golang/prometheus"
"github.com/AdguardTeam/AdguardDNS/dnsfilter"
"golang.org/x/net/context"
)
var defaultSOA = &dns.SOA{
// values copied from verisign's nonexistent .com domain
// their exact values are not important in our use case because they are used for domain transfers between primary/secondary DNS servers
Refresh: 1800,
Retry: 900,
Expire: 604800,
Minttl: 86400,
}
func init() {
caddy.RegisterPlugin("dnsfilter", caddy.Plugin{
ServerType: "dns",
Action: setup,
})
}
type plug struct {
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d *dnsfilter.Dnsfilter
Next plugin.Handler
upstream upstream.Upstream
hosts map[string]net.IP
SafeBrowsingBlockHost string
ParentalBlockHost string
QueryLogEnabled bool
BlockedTTL uint32 // in seconds, default 3600
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}
var defaultPlugin = plug{
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SafeBrowsingBlockHost: "safebrowsing.block.dns.adguard.com",
ParentalBlockHost: "family.block.dns.adguard.com",
BlockedTTL: 3600, // in seconds
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}
func newDNSCounter(name string, help string) prometheus.Counter {
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return prometheus.NewCounter(prometheus.CounterOpts{
Namespace: plugin.Namespace,
Subsystem: "dnsfilter",
Name: name,
Help: help,
})
}
var (
requests = newDNSCounter("requests_total", "Count of requests seen by dnsfilter.")
filtered = newDNSCounter("filtered_total", "Count of requests filtered by dnsfilter.")
filteredLists = newDNSCounter("filtered_lists_total", "Count of requests filtered by dnsfilter using lists.")
filteredSafebrowsing = newDNSCounter("filtered_safebrowsing_total", "Count of requests filtered by dnsfilter using safebrowsing.")
filteredParental = newDNSCounter("filtered_parental_total", "Count of requests filtered by dnsfilter using parental.")
filteredInvalid = newDNSCounter("filtered_invalid_total", "Count of requests filtered by dnsfilter because they were invalid.")
whitelisted = newDNSCounter("whitelisted_total", "Count of requests not filtered by dnsfilter because they are whitelisted.")
safesearch = newDNSCounter("safesearch_total", "Count of requests replaced by dnsfilter safesearch.")
errorsTotal = newDNSCounter("errors_total", "Count of requests that dnsfilter couldn't process because of transitive errors.")
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)
//
// coredns handling functions
//
func setupPlugin(c *caddy.Controller) (*plug, error) {
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// create new Plugin and copy default values
var p = new(plug)
*p = defaultPlugin
p.d = dnsfilter.New()
p.hosts = make(map[string]net.IP)
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filterFileNames := []string{}
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for c.Next() {
args := c.RemainingArgs()
if len(args) > 0 {
filterFileNames = append(filterFileNames, args...)
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}
for c.NextBlock() {
switch c.Val() {
case "safebrowsing":
p.d.EnableSafeBrowsing()
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if c.NextArg() {
if len(c.Val()) == 0 {
return nil, c.ArgErr()
}
p.d.SetSafeBrowsingServer(c.Val())
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}
case "safesearch":
p.d.EnableSafeSearch()
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case "parental":
if !c.NextArg() {
return nil, c.ArgErr()
}
sensitivity, err := strconv.Atoi(c.Val())
if err != nil {
return nil, c.ArgErr()
}
err = p.d.EnableParental(sensitivity)
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if err != nil {
return nil, c.ArgErr()
}
if c.NextArg() {
if len(c.Val()) == 0 {
return nil, c.ArgErr()
}
p.ParentalBlockHost = c.Val()
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}
case "blocked_ttl":
if !c.NextArg() {
return nil, c.ArgErr()
}
blockttl, err := strconv.ParseUint(c.Val(), 10, 32)
if err != nil {
return nil, c.ArgErr()
}
p.BlockedTTL = uint32(blockttl)
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case "querylog":
p.QueryLogEnabled = true
onceQueryLog.Do(func() {
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go startQueryLogServer() // TODO: how to handle errors?
})
}
}
}
log.Printf("filterFileNames = %+v", filterFileNames)
for i, filterFileName := range filterFileNames {
file, err := os.Open(filterFileName)
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if err != nil {
return nil, err
}
defer file.Close()
count := 0
scanner := bufio.NewScanner(file)
for scanner.Scan() {
text := scanner.Text()
if p.parseEtcHosts(text) {
continue
}
err = p.d.AddRule(text, uint32(i))
if err == dnsfilter.ErrInvalidSyntax {
continue
}
if err != nil {
return nil, err
}
count++
}
log.Printf("Added %d rules from %s", count, filterFileName)
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if err = scanner.Err(); err != nil {
return nil, err
}
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}
var err error
p.upstream, err = upstream.New(nil)
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if err != nil {
return nil, err
}
return p, nil
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}
func setup(c *caddy.Controller) error {
p, err := setupPlugin(c)
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if err != nil {
return err
}
config := dnsserver.GetConfig(c)
config.AddPlugin(func(next plugin.Handler) plugin.Handler {
p.Next = next
return p
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})
c.OnStartup(func() error {
m := dnsserver.GetConfig(c).Handler("prometheus")
if m == nil {
return nil
}
if x, ok := m.(*metrics.Metrics); ok {
x.MustRegister(requests)
x.MustRegister(filtered)
x.MustRegister(filteredLists)
x.MustRegister(filteredSafebrowsing)
x.MustRegister(filteredParental)
x.MustRegister(whitelisted)
x.MustRegister(safesearch)
x.MustRegister(errorsTotal)
x.MustRegister(p)
}
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return nil
})
c.OnShutdown(p.onShutdown)
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return nil
}
func (p *plug) parseEtcHosts(text string) bool {
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if pos := strings.IndexByte(text, '#'); pos != -1 {
text = text[0:pos]
}
fields := strings.Fields(text)
if len(fields) < 2 {
return false
}
addr := net.ParseIP(fields[0])
if addr == nil {
return false
}
for _, host := range fields[1:] {
if val, ok := p.hosts[host]; ok {
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log.Printf("warning: host %s already has value %s, will overwrite it with %s", host, val, addr)
}
p.hosts[host] = addr
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}
return true
}
func (p *plug) onShutdown() error {
p.d.Destroy()
p.d = nil
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return nil
}
type statsFunc func(ch interface{}, name string, text string, value float64, valueType prometheus.ValueType)
func doDesc(ch interface{}, name string, text string, value float64, valueType prometheus.ValueType) {
realch, ok := ch.(chan<- *prometheus.Desc)
if !ok {
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log.Printf("Couldn't convert ch to chan<- *prometheus.Desc\n")
return
}
realch <- prometheus.NewDesc(name, text, nil, nil)
}
func doMetric(ch interface{}, name string, text string, value float64, valueType prometheus.ValueType) {
realch, ok := ch.(chan<- prometheus.Metric)
if !ok {
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log.Printf("Couldn't convert ch to chan<- prometheus.Metric\n")
return
}
desc := prometheus.NewDesc(name, text, nil, nil)
realch <- prometheus.MustNewConstMetric(desc, valueType, value)
}
func gen(ch interface{}, doFunc statsFunc, name string, text string, value float64, valueType prometheus.ValueType) {
doFunc(ch, name, text, value, valueType)
}
func doStatsLookup(ch interface{}, doFunc statsFunc, name string, lookupstats *dnsfilter.LookupStats) {
gen(ch, doFunc, fmt.Sprintf("coredns_dnsfilter_%s_requests", name), fmt.Sprintf("Number of %s HTTP requests that were sent", name), float64(lookupstats.Requests), prometheus.CounterValue)
gen(ch, doFunc, fmt.Sprintf("coredns_dnsfilter_%s_cachehits", name), fmt.Sprintf("Number of %s lookups that didn't need HTTP requests", name), float64(lookupstats.CacheHits), prometheus.CounterValue)
gen(ch, doFunc, fmt.Sprintf("coredns_dnsfilter_%s_pending", name), fmt.Sprintf("Number of currently pending %s HTTP requests", name), float64(lookupstats.Pending), prometheus.GaugeValue)
gen(ch, doFunc, fmt.Sprintf("coredns_dnsfilter_%s_pending_max", name), fmt.Sprintf("Maximum number of pending %s HTTP requests", name), float64(lookupstats.PendingMax), prometheus.GaugeValue)
}
func (p *plug) doStats(ch interface{}, doFunc statsFunc) {
stats := p.d.GetStats()
doStatsLookup(ch, doFunc, "safebrowsing", &stats.Safebrowsing)
doStatsLookup(ch, doFunc, "parental", &stats.Parental)
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}
// Describe is called by prometheus handler to know stat types
func (p *plug) Describe(ch chan<- *prometheus.Desc) {
p.doStats(ch, doDesc)
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}
// Collect is called by prometheus handler to collect stats
func (p *plug) Collect(ch chan<- prometheus.Metric) {
p.doStats(ch, doMetric)
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}
func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWriter, r *dns.Msg, host string, val string, question dns.Question) (int, error) {
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// check if it's a domain name or IP address
addr := net.ParseIP(val)
var records []dns.RR
log.Println("Will give", val, "instead of", host)
if addr != nil {
// this is an IP address, return it
result, err := dns.NewRR(fmt.Sprintf("%s %d A %s", host, p.BlockedTTL, val))
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if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, fmt.Errorf("plugin/dnsfilter: %s", err)
}
records = append(records, result)
} else {
// this is a domain name, need to look it up
req := new(dns.Msg)
req.SetQuestion(dns.Fqdn(val), question.Qtype)
req.RecursionDesired = true
reqstate := request.Request{W: w, Req: req, Context: ctx}
result, err := p.upstream.Lookup(reqstate, dns.Fqdn(val), reqstate.QType())
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if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, fmt.Errorf("plugin/dnsfilter: %s", err)
}
if result != nil {
for _, answer := range result.Answer {
answer.Header().Name = question.Name
}
records = result.Answer
}
}
m := new(dns.Msg)
m.SetReply(r)
m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
m.Answer = append(m.Answer, records...)
state := request.Request{W: w, Req: r, Context: ctx}
state.SizeAndDo(m)
err := state.W.WriteMsg(m)
if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, fmt.Errorf("plugin/dnsfilter: %s", err)
}
return dns.RcodeSuccess, nil
}
// generate SOA record that makes DNS clients cache NXdomain results
// the only value that is important is TTL in header, other values like refresh, retry, expire and minttl are irrelevant
func (p *plug) genSOA(r *dns.Msg) []dns.RR {
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zone := r.Question[0].Name
header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: p.BlockedTTL, Class: dns.ClassINET}
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Mbox := "hostmaster."
if zone[0] != '.' {
Mbox += zone
}
Ns := "fake-for-negative-caching.adguard.com."
soa := defaultSOA
soa.Hdr = header
soa.Mbox = Mbox
soa.Ns = Ns
soa.Serial = uint32(time.Now().Unix())
return []dns.RR{soa}
}
func (p *plug) writeNXdomain(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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state := request.Request{W: w, Req: r, Context: ctx}
m := new(dns.Msg)
m.SetRcode(state.Req, dns.RcodeNameError)
m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
m.Ns = p.genSOA(r)
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state.SizeAndDo(m)
err := state.W.WriteMsg(m)
if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, err
}
return dns.RcodeNameError, nil
}
func (p *plug) serveDNSInternal(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, dnsfilter.Result, error) {
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if len(r.Question) != 1 {
// google DNS, bind and others do the same
return dns.RcodeFormatError, dnsfilter.Result{}, fmt.Errorf("Got DNS request with != 1 questions")
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}
for _, question := range r.Question {
host := strings.ToLower(strings.TrimSuffix(question.Name, "."))
// is it a safesearch domain?
if val, ok := p.d.SafeSearchDomain(host); ok {
rcode, err := p.replaceHostWithValAndReply(ctx, w, r, host, val, question)
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if err != nil {
return rcode, dnsfilter.Result{}, err
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}
return rcode, dnsfilter.Result{Reason: dnsfilter.FilteredSafeSearch}, err
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}
// is it in hosts?
if val, ok := p.hosts[host]; ok {
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// it is, if it's a loopback host, reply with NXDOMAIN
// TODO: research if it's better than 127.0.0.1
if false && val.IsLoopback() {
rcode, err := p.writeNXdomain(ctx, w, r)
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if err != nil {
return rcode, dnsfilter.Result{}, err
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}
return rcode, dnsfilter.Result{Reason: dnsfilter.FilteredInvalid}, err
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}
// it's not a loopback host, replace it with value specified
rcode, err := p.replaceHostWithValAndReply(ctx, w, r, host, val.String(), question)
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if err != nil {
return rcode, dnsfilter.Result{}, err
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}
return rcode, dnsfilter.Result{Reason: dnsfilter.FilteredSafeSearch}, err
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}
// needs to be filtered instead
result, err := p.d.CheckHost(host)
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if err != nil {
log.Printf("plugin/dnsfilter: %s\n", err)
return dns.RcodeServerFailure, dnsfilter.Result{}, fmt.Errorf("plugin/dnsfilter: %s", err)
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}
if result.IsFiltered {
switch result.Reason {
case dnsfilter.FilteredSafeBrowsing:
// return cname safebrowsing.block.dns.adguard.com
val := p.SafeBrowsingBlockHost
rcode, err := p.replaceHostWithValAndReply(ctx, w, r, host, val, question)
if err != nil {
return rcode, dnsfilter.Result{}, err
}
return rcode, result, err
case dnsfilter.FilteredParental:
// return cname family.block.dns.adguard.com
val := p.ParentalBlockHost
rcode, err := p.replaceHostWithValAndReply(ctx, w, r, host, val, question)
if err != nil {
return rcode, dnsfilter.Result{}, err
}
return rcode, result, err
case dnsfilter.FilteredBlackList:
// return NXdomain
rcode, err := p.writeNXdomain(ctx, w, r)
if err != nil {
return rcode, dnsfilter.Result{}, err
}
return rcode, result, err
case dnsfilter.FilteredInvalid:
// return NXdomain
rcode, err := p.writeNXdomain(ctx, w, r)
if err != nil {
return rcode, dnsfilter.Result{}, err
}
return rcode, result, err
default:
log.Printf("SHOULD NOT HAPPEN -- got unknown reason for filtering host \"%s\": %v, %+v", host, result.Reason, result)
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}
} else {
switch result.Reason {
case dnsfilter.NotFilteredWhiteList:
rcode, err := plugin.NextOrFailure(p.Name(), p.Next, ctx, w, r)
return rcode, result, err
case dnsfilter.NotFilteredNotFound:
// do nothing, pass through to lower code
default:
log.Printf("SHOULD NOT HAPPEN -- got unknown reason for not filtering host \"%s\": %v, %+v", host, result.Reason, result)
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}
}
}
rcode, err := plugin.NextOrFailure(p.Name(), p.Next, ctx, w, r)
return rcode, dnsfilter.Result{}, err
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}
// ServeDNS handles the DNS request and refuses if it's in filterlists
func (p *plug) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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start := time.Now()
requests.Inc()
state := request.Request{W: w, Req: r}
ip := state.IP()
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// capture the written answer
rrw := dnstest.NewRecorder(w)
rcode, result, err := p.serveDNSInternal(ctx, rrw, r)
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if rcode > 0 {
// actually send the answer if we have one
answer := new(dns.Msg)
answer.SetRcode(r, rcode)
state.SizeAndDo(answer)
err = w.WriteMsg(answer)
if err != nil {
return dns.RcodeServerFailure, err
}
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}
// increment counters
switch {
case err != nil:
errorsTotal.Inc()
case result.Reason == dnsfilter.FilteredBlackList:
filtered.Inc()
filteredLists.Inc()
case result.Reason == dnsfilter.FilteredSafeBrowsing:
filtered.Inc()
filteredSafebrowsing.Inc()
case result.Reason == dnsfilter.FilteredParental:
filtered.Inc()
filteredParental.Inc()
case result.Reason == dnsfilter.FilteredInvalid:
filtered.Inc()
filteredInvalid.Inc()
case result.Reason == dnsfilter.FilteredSafeSearch:
// the request was passsed through but not filtered, don't increment filtered
safesearch.Inc()
case result.Reason == dnsfilter.NotFilteredWhiteList:
whitelisted.Inc()
case result.Reason == dnsfilter.NotFilteredNotFound:
// do nothing
case result.Reason == dnsfilter.NotFilteredError:
text := "SHOULD NOT HAPPEN: got DNSFILTER_NOTFILTERED_ERROR without err != nil!"
log.Println(text)
err = errors.New(text)
rcode = dns.RcodeServerFailure
}
// log
if p.QueryLogEnabled {
logRequest(r, rrw.Msg, result, time.Since(start), ip)
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}
return rcode, err
}
// Name returns name of the plugin as seen in Corefile and plugin.cfg
func (p *plug) Name() string { return "dnsfilter" }
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var onceQueryLog sync.Once