implemented blacklist

blacklist.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"io/ioutil"
+	"log"
+	"net/http"
+	"regexp"
+
+	"github.com/miekg/dns"
+)
+
+func loadBlacklist(config []configBlacklist) map[string]bool {
+	list := make([]string, 0)
+	for _, element := range config {
+		raw, err := requestBacklist(element)
+
+		if err != nil {
+			log.Printf("Failed to load blacklist %s reason: %s", element.URL, err.Error())
+			continue
+		}
+
+		domains := parseRawBlacklist(element, *raw)
+		list = append(list, domains...)
+	}
+
+	// list = removeDuplicates(list)
+	// sort.Strings(list)
+
+	domainMap := make(map[string]bool)
+	for _, e := range list {
+		domainMap[e] = true
+	}
+
+	return domainMap
+}
+
+func removeDuplicates(elements []string) []string {
+	encountered := map[string]bool{}
+	result := []string{}
+
+	for v := range elements {
+		if !encountered[elements[v]] {
+			encountered[elements[v]] = true
+
+			result = append(result, elements[v])
+		}
+	}
+
+	return result
+}
+
+func requestBacklist(blacklist configBlacklist) (*string, error) {
+	// Request list
+	resp, err := http.Get(blacklist.URL)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	bodyString := string(body)
+
+	log.Printf("Downloaded blacklist %s", blacklist.URL)
+
+	return &bodyString, err
+}
+
+func parseRawBlacklist(blacklist configBlacklist, raw string) []string {
+	finalList := make([]string, 0)
+	reg := regexp.MustCompile(`(?mi)^\s*(#*)\s*(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+([a-zA-Z0-9\.\- ]+)$`)
+	matches := reg.FindAllStringSubmatch(raw, -1)
+	for _, match := range matches {
+		if match[1] != "#" {
+			finalList = append(finalList, dns.Fqdn(match[3]))
+		}
+	}
+
+	return finalList
+}

config.yml

@@ -17,7 +17,11 @@ acl:
 
 forward:
   acl:
-    - vpn
+    - local
   server: "8.8.8.8:53"
 
-address: 0.0.0.0:8053
+address: 0.0.0.0:8053
+
+blacklist:
+  - url: https://raw.githubusercontent.com/anudeepND/blacklist/master/adservers.txt
+    format: host

coolDns.go

@@ -24,10 +24,11 @@ type zoneMap map[string][]zoneView
 type rrMap map[uint16]map[string][]dns.RR
 
 type config struct {
-	Zones   []configZone  `yaml:"zones"`
-	ACL     []configACL   `yaml:"acl"`
-	Forward configForward `yaml:"forward"`
-	Address string        `yaml:"address"`
+	Zones     []configZone      `yaml:"zones"`
+	ACL       []configACL       `yaml:"acl"`
+	Forward   configForward     `yaml:"forward"`
+	Address   string            `yaml:"address"`
+	Blacklist []configBlacklist `yaml:"blacklist"`
 }
 
 type configForward struct {
@@ -46,6 +47,11 @@ type configZone struct {
 	ACL  []string `yaml:"acl"`
 }
 
+type configBlacklist struct {
+	URL    string `yaml:"url"`
+	Format string `yaml:"format"`
+}
+
 var anyRecordTypes = []uint16{
 	dns.TypeSOA,
 	dns.TypeA,
@@ -149,7 +155,7 @@ func createACLList(config []configACL) (map[string]*net.IPNet, error) {
 	return acls, nil
 }
 
-func createServer(zones zoneMap, config config, aclList map[string]*net.IPNet) *dns.ServeMux {
+func createServer(zones zoneMap, config config, aclList map[string]*net.IPNet, blacklist map[string]bool) *dns.ServeMux {
 	srv := dns.NewServeMux()
 	c := new(dns.Client)
 
@@ -198,15 +204,45 @@ func createServer(zones zoneMap, config config, aclList map[string]*net.IPNet) *
 			return
 		}
 
-		// Forward request
-		in, _, err := c.Exchange(r, config.Forward.Server)
+		if _, ok := blacklist[r.Question[0].Name]; ok {
+			// Domain is blocked
+			m := new(dns.Msg)
+			m.SetReply(r)
+			if r.Question[0].Qtype == dns.TypeA {
+				m.Answer = append(m.Answer, &dns.A{
+					Hdr: dns.RR_Header{
+						Name:   r.Question[0].Name,
+						Rrtype: dns.TypeA,
+						Class:  dns.ClassINET,
+						Ttl:    1000,
+					},
+					A: net.IPv4(0, 0, 0, 0),
+				})
+			} else if r.Question[0].Qtype == dns.TypeAAAA {
+				m.Answer = append(m.Answer, &dns.AAAA{
+					Hdr: dns.RR_Header{
+						Name:   r.Question[0].Name,
+						Rrtype: dns.TypeA,
+						Class:  dns.ClassINET,
+						Ttl:    1000,
+					},
+					AAAA: net.ParseIP("::/0"),
+				})
+			}
 
-		if err != nil {
-			rcodeRequest(w, r, dns.RcodeServerFailure)
-			return
+			w.WriteMsg(m)
+
+		} else {
+			// Forward request
+			in, _, err := c.Exchange(r, config.Forward.Server)
+
+			if err != nil {
+				rcodeRequest(w, r, dns.RcodeServerFailure)
+				return
+			}
+			w.WriteMsg(in)
 		}
 
-		w.WriteMsg(in)
 	})
 
 	return srv
@@ -338,7 +374,9 @@ func main() {
 		log.Fatalf("Failed to parse ACL rules: %s\n", err.Error())
 	}
 
-	server := createServer(zones, *config, aclList)
+	blacklist := loadBlacklist(config.Blacklist)
+
+	server := createServer(zones, *config, aclList, blacklist)
 
 	listenAndServer(server, config.Address)