Add googlefront provider.

This provider fronts dns.google.com with www.google.com.

cmd/root.go

@@ -54,7 +54,8 @@ func init() {
 	}
 
 	rootCmd.PersistentFlags().StringVarP(&dnsProviderName,
-		"provider", "p", "google", "Preferred DNS provider to use. [possible: google, cloudflare, quad9, raw]")
+		"provider", "p", "googlefront",
+		"Preferred DNS provider to use. [possible: googlefront, google, cloudflare, quad9, raw]")
 	rootCmd.PersistentFlags().BoolVarP(&validateSSL,
 		"validate-certificate", "K", false, "Validate DoH provider SSL certificates")
 }
@@ -77,6 +78,9 @@ func validateDNSDomain() {
 
 func validateDNSProvider() {
 	switch dnsProviderName {
+	case "googlefront":
+		dnsProvider = dnsclient.NewGoogleFrontDNS()
+		break
 	case "google":
 		dnsProvider = dnsclient.NewGoogleDNS()
 		break

dnsclient/client.go

@@ -10,6 +10,12 @@ func NewGoogleDNS() *GoogleDNS {
 	return &GoogleDNS{BaseURL: "https://dns.google.com/resolve"}
 }
 
+// NewGoogleFrontDNS starts a new Google DNS-over-HTTPS resolver Client
+// The Host header for this request is updated in the client itself
+func NewGoogleFrontDNS() *GoogleFrontDNS {
+	return &GoogleFrontDNS{BaseURL: "https://www.google.com/resolve"}
+}
+
 // NewCloudFlareDNS starts a new Cloudflare DNS-over-HTTPS resolver Client
 func NewCloudFlareDNS() *CloudflareDNS {
 	return &CloudflareDNS{BaseURL: "https://cloudflare-dns.com/dns-query"}

dnsclient/google_front.go

@@ -0,0 +1,70 @@
+package dnsclient
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+// GoogleFrontDNS is a Client instance resolving using Googles DNS-over-HTTPS service,
+// fronted using www.google.com
+type GoogleFrontDNS struct {
+	BaseURL string
+}
+
+// Lookup performs a DNS lookup using Google
+func (c *GoogleFrontDNS) Lookup(name string, rType uint16) Response {
+
+	client := http.Client{
+		Timeout: time.Second * 20,
+	}
+
+	req, err := http.NewRequest("GET", c.BaseURL, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Update the Host client header to dns.google.com
+	// Ref: https://twitter.com/vysecurity/status/1058947074392125440
+	req.Host = "dns.google.com"
+
+	q := req.URL.Query()
+	q.Add("name", name)
+	q.Add("type", strconv.Itoa(int(rType)))
+	q.Add("cd", "false") // ignore DNSSEC
+	// TODO: add random_padding
+	req.URL.RawQuery = q.Encode()
+
+	res, err := client.Do(req)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	dnsRequestResponse := requestResponse{}
+	err = json.Unmarshal(body, &dnsRequestResponse)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fout := Response{}
+
+	if len(dnsRequestResponse.Answer) <= 0 {
+		return fout
+	}
+
+	fout.TTL = dnsRequestResponse.Answer[0].TTL
+	fout.Data = dnsRequestResponse.Answer[0].Data
+	fout.Status = dns.RcodeToString[dnsRequestResponse.Status]
+
+	return fout
+}