net/http: make Transport support international domain names

This CL makes code like this work:

     res, err := http.Get("https://фу.бар/баз")

So far, IDNA support is limited to the http1 and http2 Transports.
The http package is currently responsible for converting domain names
into Punycode before calling the net layer. The http package also has
to Punycode-ify the hostname for the Host & :authority headers for
HTTP/1 and HTTP/2, respectively.

No automatic translation from Punycode back to Unicode is performed,
per Go's historical behavior. Docs are updated where relevant.  No
changes needed to the Server package. Things are already in ASCII
at that point.

No changes to the net package, at least yet.

Updates x/net/http2 to git rev 57c7820 for https://golang.org/cl/29071

Updates #13835

Change-Id: I1e9a74c60d00a197ea951a9505da5c3c3187099b
Reviewed-on: https://go-review.googlesource.com/29072
Reviewed-by: Chris Broadfoot <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: bradfitz

src/net/http/http_test.go

@@ -51,6 +51,10 @@ func TestCleanHost(t *testing.T) {
 		{"www.google.com foo", "www.google.com"},
 		{"www.google.com/foo", "www.google.com"},
 		{" first character is a space", ""},
+		{"гофер.рф/foo", "xn--c1ae0ajs.xn--p1ai"},
+		{"bücher.de", "xn--bcher-kva.de"},
+		{"bücher.de:8080", "xn--bcher-kva.de:8080"},
+		{"[1::6]:8080", "[1::6]:8080"},
 	}
 	for _, tt := range tests {
 		got := cleanHost(tt.in)

src/net/http/request.go

@@ -18,12 +18,15 @@ import (
 	"io/ioutil"
 	"mime"
 	"mime/multipart"
+	"net"
 	"net/http/httptrace"
 	"net/textproto"
 	"net/url"
 	"strconv"
 	"strings"
 	"sync"
+
+	"golang_org/x/net/idna"
 )
 
 const (
@@ -175,11 +178,15 @@ type Request struct {
 	// For server requests Host specifies the host on which the
 	// URL is sought. Per RFC 2616, this is either the value of
 	// the "Host" header or the host name given in the URL itself.
-	// It may be of the form "host:port".
+	// It may be of the form "host:port". For international domain
+	// names, Host may be in Punycode or Unicode form. Use
+	// golang.org/x/net/idna to convert it to either format if
+	// needed.
 	//
 	// For client requests Host optionally overrides the Host
 	// header to send. If empty, the Request.Write method uses
-	// the value of URL.Host.
+	// the value of URL.Host. Host may contain an international
+	// domain name.
 	Host string
 
 	// Form contains the parsed form data, including both the URL
@@ -573,7 +580,11 @@ func (req *Request) write(w io.Writer, usingProxy bool, extraHeaders Header, wai
 	return nil
 }
 
-// cleanHost strips anything after '/' or ' '.
+// cleanHost cleans up the host sent in request's Host header.
+//
+// It both strips anything after '/' or ' ', and puts the value
+// into Punycode form, if necessary.
+//
 // Ideally we'd clean the Host header according to the spec:
 //   https://tools.ietf.org/html/rfc7230#section-5.4 (Host = uri-host [ ":" port ]")
 //   https://tools.ietf.org/html/rfc7230#section-2.7 (uri-host -> rfc3986's host)
@@ -584,9 +595,21 @@ func (req *Request) write(w io.Writer, usingProxy bool, extraHeaders Header, wai
 // first offending character.
 func cleanHost(in string) string {
 	if i := strings.IndexAny(in, " /"); i != -1 {
-		return in[:i]
+		in = in[:i]
+	}
+	host, port, err := net.SplitHostPort(in)
+	if err != nil { // input was just a host
+		a, err := idna.ToASCII(in)
+		if err != nil {
+			return in // garbage in, garbage out
+		}
+		return a
+	}
+	a, err := idna.ToASCII(host)
+	if err != nil {
+		return in // garbage in, garbage out
 	}
-	return in
+	return net.JoinHostPort(a, port)
 }
 
 // removeZone removes IPv6 zone identifier from host.

src/net/http/transport.go

@@ -27,6 +27,7 @@ import (
 	"sync"
 	"time"
 
+	"golang_org/x/net/idna"
 	"golang_org/x/net/lex/httplex"
 )
 
@@ -1943,11 +1944,15 @@ var portMap = map[string]string{
 
 // canonicalAddr returns url.Host but always with a ":port" suffix
 func canonicalAddr(url *url.URL) string {
-	addr := url.Host
-	if !hasPort(addr) {
-		return addr + ":" + portMap[url.Scheme]
+	addr := url.Hostname()
+	if v, err := idna.ToASCII(addr); err == nil {
+		addr = v
 	}
-	return addr
+	port := url.Port()
+	if port == "" {
+		port = portMap[url.Scheme]
+	}
+	return net.JoinHostPort(addr, port)
 }
 
 // bodyEOFSignal is used by the HTTP/1 transport when reading response

src/net/http/transport_test.go

@@ -3629,6 +3629,76 @@ func TestTransportReturnsPeekError(t *testing.T) {
 	}
 }
 
+// Issue 13835: international domain names should work
+func TestTransportIDNA_h1(t *testing.T) { testTransportIDNA(t, h1Mode) }
+func TestTransportIDNA_h2(t *testing.T) { testTransportIDNA(t, h2Mode) }
+func testTransportIDNA(t *testing.T, h2 bool) {
+	defer afterTest(t)
+
+	const uniDomain = "гофер.го"
+	const punyDomain = "xn--c1ae0ajs.xn--c1aw"
+
+	var port string
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		want := punyDomain + ":" + port
+		if r.Host != want {
+			t.Errorf("Host header = %q; want %q", r.Host, want)
+		}
+		if h2 {
+			if r.TLS == nil {
+				t.Errorf("r.TLS == nil")
+			} else if r.TLS.ServerName != punyDomain {
+				t.Errorf("TLS.ServerName = %q; want %q", r.TLS.ServerName, punyDomain)
+			}
+		}
+		w.Header().Set("Hit-Handler", "1")
+	}))
+	defer cst.close()
+
+	ip, port, err := net.SplitHostPort(cst.ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Install a fake DNS server.
+	ctx := context.WithValue(context.Background(), nettrace.LookupIPAltResolverKey{}, func(ctx context.Context, host string) ([]net.IPAddr, error) {
+		if host != punyDomain {
+			t.Errorf("got DNS host lookup for %q; want %q", host, punyDomain)
+			return nil, nil
+		}
+		return []net.IPAddr{{IP: net.ParseIP(ip)}}, nil
+	})
+
+	req, _ := NewRequest("GET", cst.scheme()+"://"+uniDomain+":"+port, nil)
+	trace := &httptrace.ClientTrace{
+		GetConn: func(hostPort string) {
+			want := net.JoinHostPort(punyDomain, port)
+			if hostPort != want {
+				t.Errorf("getting conn for %q; want %q", hostPort, want)
+			}
+		},
+		DNSStart: func(e httptrace.DNSStartInfo) {
+			if e.Host != punyDomain {
+				t.Errorf("DNSStart Host = %q; want %q", e.Host, punyDomain)
+			}
+		},
+	}
+	req = req.WithContext(httptrace.WithClientTrace(ctx, trace))
+
+	res, err := cst.tr.RoundTrip(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if res.Header.Get("Hit-Handler") != "1" {
+		out, err := httputil.DumpResponse(res, true)
+		if err != nil {
+			t.Fatal(err)
+		}
+		t.Errorf("Response body wasn't from Handler. Got:\n%s\n", out)
+	}
+}
+
 var errFakeRoundTrip = errors.New("fake roundtrip")
 
 type funcRoundTripper func()