Doh: put in pkg/doh (#1946)

* DoH: put in pkg/doh

Factor out the DoH stuff into its own package, add function to request
a DoH response. This can be used by forward (and maybe proxy) to
implement DoH client support.
Signed-off-by: Miek Gieben <miek@miek.nl>

* lint
Signed-off-by: Miek Gieben <miek@miek.nl>

* ... and make it compile
Signed-off-by: Miek Gieben <miek@miek.nl>

core/dnsserver/https.go

 package dnsserver
 
 import (
-	"encoding/base64"
-	"fmt"
-	"io/ioutil"
 	"net"
-	"net/http"
 
 	"github.com/coredns/coredns/plugin/pkg/nonwriter"
-	"github.com/miekg/dns"
 )
 
-// mimeTypeDOH is the DoH mimetype that should be used.
-const mimeTypeDOH = "application/dns-message"
-
-// pathDOH is the URL path that should be used.
-const pathDOH = "/dns-query"
-
-// postRequestToMsg extracts the dns message from the request body.
-func postRequestToMsg(req *http.Request) (*dns.Msg, error) {
-	defer req.Body.Close()
-
-	buf, err := ioutil.ReadAll(req.Body)
-	if err != nil {
-		return nil, err
-	}
-	m := new(dns.Msg)
-	err = m.Unpack(buf)
-	return m, err
-}
-
-// getRequestToMsg extract the dns message from the GET request.
-func getRequestToMsg(req *http.Request) (*dns.Msg, error) {
-	values := req.URL.Query()
-	b64, ok := values["dns"]
-	if !ok {
-		return nil, fmt.Errorf("no 'dns' query parameter found")
-	}
-	if len(b64) != 1 {
-		return nil, fmt.Errorf("multiple 'dns' query values found")
-	}
-	return base64ToMsg(b64[0])
-}
-
-func base64ToMsg(b64 string) (*dns.Msg, error) {
-	buf, err := b64Enc.DecodeString(b64)
-	if err != nil {
-		return nil, err
-	}
-
-	m := new(dns.Msg)
-	err = m.Unpack(buf)
-
-	return m, err
-}
-
-var b64Enc = base64.RawURLEncoding
-
 // DoHWriter is a nonwriter.Writer that adds more specific LocalAddr and RemoteAddr methods.
 type DoHWriter struct {
 	nonwriter.Writer

core/dnsserver/server_https.go

@@ -10,9 +10,8 @@ import (
 	"time"
 
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/doh"
 	"github.com/coredns/coredns/plugin/pkg/response"
-
-	"github.com/miekg/dns"
 )
 
 // ServerHTTPS represents an instance of a DNS-over-HTTPS server.
@@ -99,24 +98,12 @@ func (s *ServerHTTPS) Stop() error {
 // chain, converts it back and write it to the client.
 func (s *ServerHTTPS) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
-	msg := new(dns.Msg)
-	var err error
-
-	if r.URL.Path != pathDOH {
+	if r.URL.Path != doh.Path {
 		http.Error(w, "", http.StatusNotFound)
 		return
 	}
 
-	switch r.Method {
-	case http.MethodPost:
-		msg, err = postRequestToMsg(r)
-	case http.MethodGet:
-		msg, err = getRequestToMsg(r)
-	default:
-		http.Error(w, "", http.StatusMethodNotAllowed)
-		return
-	}
-
+	msg, err := doh.RequestToMsg(r)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
@@ -136,7 +123,7 @@ func (s *ServerHTTPS) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	mt, _ := response.Typify(dw.Msg, time.Now().UTC())
 	age := dnsutil.MinimalTTL(dw.Msg, mt)
 
-	w.Header().Set("Content-Type", mimeTypeDOH)
+	w.Header().Set("Content-Type", doh.MimeType)
 	w.Header().Set("Cache-Control", fmt.Sprintf("max-age=%f", age.Seconds()))
 	w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
 	w.WriteHeader(http.StatusOK)

plugin/pkg/doh/doh.go

+package doh
+
+import (
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+
+	"github.com/miekg/dns"
+)
+
+// MimeType is the DoH mimetype that should be used.
+const MimeType = "application/dns-message"
+
+// Path is the URL path that should be used.
+const Path = "/dns-query"
+
+// NewRequest returns a new DoH request given a method, URL (without any paths, so exclude /dns-query) and dns.Msg.
+func NewRequest(method, url string, m *dns.Msg) (*http.Request, error) {
+	buf, err := m.Pack()
+	if err != nil {
+		return nil, err
+	}
+
+	switch method {
+	case http.MethodGet:
+		b64 := base64.RawURLEncoding.EncodeToString(buf)
+
+		req, err := http.NewRequest(http.MethodGet, "https://"+url+Path+"?dns="+b64, nil)
+		if err != nil {
+			return req, err
+		}
+
+		req.Header.Set("content-type", MimeType)
+		req.Header.Set("accept", MimeType)
+		return req, nil
+
+	case http.MethodPost:
+		req, err := http.NewRequest(http.MethodPost, "https://"+url+Path+"?bla=foo:443", bytes.NewReader(buf))
+		if err != nil {
+			return req, err
+		}
+
+		req.Header.Set("content-type", MimeType)
+		req.Header.Set("accept", MimeType)
+		return req, nil
+
+	default:
+		return nil, fmt.Errorf("method not allowed: %s", method)
+	}
+
+}
+
+// ResponseToMsg converts a http.Repsonse to a dns message.
+func ResponseToMsg(resp *http.Response) (*dns.Msg, error) {
+	defer resp.Body.Close()
+
+	return toMsg(resp.Body)
+}
+
+// RequestToMsg converts a http.Request to a dns message.
+func RequestToMsg(req *http.Request) (*dns.Msg, error) {
+	switch req.Method {
+	case http.MethodGet:
+		return requestToMsgGet(req)
+
+	case http.MethodPost:
+		return requestToMsgPost(req)
+
+	default:
+		return nil, fmt.Errorf("method not allowed: %s", req.Method)
+	}
+
+}
+
+// requestToMsgPost extracts the dns message from the request body.
+func requestToMsgPost(req *http.Request) (*dns.Msg, error) {
+	defer req.Body.Close()
+	return toMsg(req.Body)
+}
+
+// requestToMsgGet extract the dns message from the GET request.
+func requestToMsgGet(req *http.Request) (*dns.Msg, error) {
+	values := req.URL.Query()
+	b64, ok := values["dns"]
+	if !ok {
+		return nil, fmt.Errorf("no 'dns' query parameter found")
+	}
+	if len(b64) != 1 {
+		return nil, fmt.Errorf("multiple 'dns' query values found")
+	}
+	return base64ToMsg(b64[0])
+}
+
+func toMsg(r io.ReadCloser) (*dns.Msg, error) {
+	buf, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	m := new(dns.Msg)
+	err = m.Unpack(buf)
+	return m, err
+}
+
+func base64ToMsg(b64 string) (*dns.Msg, error) {
+	buf, err := b64Enc.DecodeString(b64)
+	if err != nil {
+		return nil, err
+	}
+
+	m := new(dns.Msg)
+	err = m.Unpack(buf)
+
+	return m, err
+}
+
+var b64Enc = base64.RawURLEncoding

core/dnsserver/https_test.go → plugin/pkg/doh/doh_test.go

-package dnsserver
+package doh
 
 import (
-	"bytes"
-	"encoding/base64"
 	"net/http"
 	"testing"
 
@@ -10,26 +8,21 @@ import (
 )
 
 func TestPostRequest(t *testing.T) {
-	const ex = "example.org."
-
 	m := new(dns.Msg)
-	m.SetQuestion(ex, dns.TypeDNSKEY)
+	m.SetQuestion("example.org.", dns.TypeDNSKEY)
 
-	out, _ := m.Pack()
-	req, err := http.NewRequest(http.MethodPost, "https://"+ex+pathDOH+"?bla=foo:443", bytes.NewReader(out))
+	req, err := NewRequest(http.MethodPost, "https://example.org:443", m)
 	if err != nil {
 		t.Errorf("Failure to make request: %s", err)
 	}
-	req.Header.Set("content-type", mimeTypeDOH)
-	req.Header.Set("accept", mimeTypeDOH)
 
-	m, err = postRequestToMsg(req)
+	m, err = RequestToMsg(req)
 	if err != nil {
 		t.Fatalf("Failure to get message from request: %s", err)
 	}
 
-	if x := m.Question[0].Name; x != ex {
-		t.Errorf("Qname expected %s, got %s", ex, x)
+	if x := m.Question[0].Name; x != "example.org." {
+		t.Errorf("Qname expected %s, got %s", "example.org.", x)
 	}
 	if x := m.Question[0].Qtype; x != dns.TypeDNSKEY {
 		t.Errorf("Qname expected %d, got %d", x, dns.TypeDNSKEY)
@@ -37,28 +30,21 @@ func TestPostRequest(t *testing.T) {
 }
 
 func TestGetRequest(t *testing.T) {
-	const ex = "example.org."
-
 	m := new(dns.Msg)
-	m.SetQuestion(ex, dns.TypeDNSKEY)
-
-	out, _ := m.Pack()
-	b64 := base64.RawURLEncoding.EncodeToString(out)
+	m.SetQuestion("example.org.", dns.TypeDNSKEY)
 
-	req, err := http.NewRequest(http.MethodGet, "https://"+ex+pathDOH+"?dns="+b64, nil)
+	req, err := NewRequest(http.MethodGet, "https://example.org:443", m)
 	if err != nil {
 		t.Errorf("Failure to make request: %s", err)
 	}
-	req.Header.Set("content-type", mimeTypeDOH)
-	req.Header.Set("accept", mimeTypeDOH)
 
-	m, err = getRequestToMsg(req)
+	m, err = RequestToMsg(req)
 	if err != nil {
 		t.Fatalf("Failure to get message from request: %s", err)
 	}
 
-	if x := m.Question[0].Name; x != ex {
-		t.Errorf("Qname expected %s, got %s", ex, x)
+	if x := m.Question[0].Name; x != "example.org." {
+		t.Errorf("Qname expected %s, got %s", "example.org.", x)
 	}
 	if x := m.Question[0].Qtype; x != dns.TypeDNSKEY {
 		t.Errorf("Qname expected %d, got %d", x, dns.TypeDNSKEY)