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