http: support Trailers in ReadRequest

Available after closing Request.Body.

R=adg, rsc
CC=golang-dev
https://golang.org/cl/5348041

src/pkg/net/http/readrequest_test.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"reflect"
 	"testing"
 	"url"
 )
@@ -17,11 +18,13 @@ type reqTest struct {
 	Raw     string
 	Req     *Request
 	Body    string
+	Trailer Header
 	Error   string
 }
 
 var noError = ""
 var noBody = ""
+var noTrailer Header = nil
 
 var reqTests = []reqTest{
 	// Baseline test; All Request fields included for template use
@@ -72,6 +75,7 @@ var reqTests = []reqTest{
 
 		"abcdef\n",
 
+		noTrailer,
 		noError,
 	},
 
@@ -97,6 +101,7 @@ var reqTests = []reqTest{
 		},
 
 		noBody,
+		noTrailer,
 		noError,
 	},
 
@@ -130,6 +135,7 @@ var reqTests = []reqTest{
 		},
 
 		noBody,
+		noTrailer,
 		noError,
 	},
 
@@ -139,6 +145,7 @@ var reqTests = []reqTest{
 			"Host: test\r\n\r\n",
 		nil,
 		noBody,
+		noTrailer,
 		"parse ../../../../etc/passwd: invalid URI for request",
 	},
 
@@ -148,8 +155,42 @@ var reqTests = []reqTest{
 			"Host: test\r\n\r\n",
 		nil,
 		noBody,
+		noTrailer,
 		"parse : empty url",
 	},
+
+	// Tests chunked body with trailer:
+	{
+		"POST / HTTP/1.1\r\n" +
+			"Host: foo.com\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			"3\r\nfoo\r\n" +
+			"3\r\nbar\r\n" +
+			"0\r\n" +
+			"Trailer-Key: Trailer-Value\r\n" +
+			"\r\n",
+		&Request{
+			Method: "POST",
+			URL: &url.URL{
+				Raw:     "/",
+				Path:    "/",
+				RawPath: "/",
+			},
+			TransferEncoding: []string{"chunked"},
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			ContentLength:    -1,
+			Host:             "foo.com",
+			Form:             url.Values{},
+		},
+
+		"foobar",
+		Header{
+			"Trailer-Key": {"Trailer-Value"},
+		},
+		noError,
+	},
 }
 
 func TestReadRequest(t *testing.T) {
@@ -169,12 +210,18 @@ func TestReadRequest(t *testing.T) {
 		diff(t, fmt.Sprintf("#%d Request", i), req, tt.Req)
 		var bout bytes.Buffer
 		if rbody != nil {
-			io.Copy(&bout, rbody)
+			_, err := io.Copy(&bout, rbody)
+			if err != nil {
+				t.Fatalf("#%d. copying body: %v", i, err)
+			}
 			rbody.Close()
 		}
 		body := bout.String()
 		if body != tt.Body {
 			t.Errorf("#%d: Body = %q want %q", i, body, tt.Body)
 		}
+		if !reflect.DeepEqual(tt.Trailer, req.Trailer) {
+			t.Errorf("%#d. Trailers differ.\n got: %v\nwant: %v", i, req.Trailer, tt.Trailer)
+		}
 	}
 }

src/pkg/net/http/request.go

@@ -142,6 +142,8 @@ type Request struct {
 	// Trailer maps trailer keys to values.  Like for Header, if the
 	// response has multiple trailer lines with the same key, they will be
 	// concatenated, delimited by commas.
+	// For server requests, Trailer is only populated after Body has been
+	// closed or fully consumed.
 	// Trailer support is only partially complete.
 	Trailer Header
 
@@ -464,16 +466,6 @@ func (cr *chunkedReader) beginChunk() {
 		return
 	}
 	if cr.n == 0 {
-		// trailer CRLF
-		for {
-			line, cr.err = readLine(cr.r)
-			if cr.err != nil {
-				return
-			}
-			if line == "" {
-				break
-			}
-		}
 		cr.err = io.EOF
 	}
 }

src/pkg/net/http/transfer.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/textproto"
 	"strconv"
 	"strings"
 )
@@ -532,7 +533,68 @@ func (b *body) Read(p []byte) (n int, err error) {
 	if b.closed {
 		return 0, ErrBodyReadAfterClose
 	}
-	return b.Reader.Read(p)
+	n, err = b.Reader.Read(p)
+
+	// Read the final trailer once we hit EOF.
+	if err == io.EOF && b.hdr != nil {
+		err = b.readTrailer()
+		b.hdr = nil
+	}
+	return n, err
+}
+
+var (
+	singleCRLF = []byte("\r\n")
+	doubleCRLF = []byte("\r\n\r\n")
+)
+
+func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
+	for peekSize := 4; ; peekSize++ {
+		// This loop stops when Peek returns an error,
+		// which it does when r's buffer has been filled.
+		buf, err := r.Peek(peekSize)
+		if bytes.HasSuffix(buf, doubleCRLF) {
+			return true
+		}
+		if err != nil {
+			break
+		}
+	}
+	return false
+}
+
+func (b *body) readTrailer() error {
+	// The common case, since nobody uses trailers.
+	buf, _ := b.r.Peek(2)
+	if bytes.Equal(buf, singleCRLF) {
+		b.r.ReadByte()
+		b.r.ReadByte()
+		return nil
+	}
+
+	// Make sure there's a header terminator coming up, to prevent
+	// a DoS with an unbounded size Trailer.  It's not easy to
+	// slip in a LimitReader here, as textproto.NewReader requires
+	// a concrete *bufio.Reader.  Also, we can't get all the way
+	// back up to our conn's LimitedReader that *might* be backing
+	// this bufio.Reader.  Instead, a hack: we iteratively Peek up
+	// to the bufio.Reader's max size, looking for a double CRLF.
+	// This limits the trailer to the underlying buffer size, typically 4kB.
+	if !seeUpcomingDoubleCRLF(b.r) {
+		return errors.New("http: suspiciously long trailer after chunked body")
+	}
+
+	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
+	if err != nil {
+		return err
+	}
+	switch rr := b.hdr.(type) {
+	case *Request:
+		rr.Trailer = Header(hdr)
+	case *Response:
+		rr.Trailer = Header(hdr)
+	}
+	return nil
 }
 
 func (b *body) Close() error {
@@ -557,15 +619,10 @@ func (b *body) Close() error {
 		return nil
 	}
 
+	// Fully consume the body, which will also lead to us reading
+	// the trailer headers after the body, if present.
 	if _, err := io.Copy(ioutil.Discard, b); err != nil {
 		return err
 	}
-
-	if b.hdr == nil { // not reading trailer
-		return nil
-	}
-
-	// TODO(petar): Put trailer reader code here
-
 	return nil
 }