net/http: add missing error checking reading trailers

This is a simplified version of earlier versions of this CL
and now only fixes obviously incorrect things, without
changing the locking on bodyEOFReader.

I'd like to see if this is sufficient before changing the
locking.

Update #4191

R=golang-dev, rsc, dave
CC=golang-dev
https://golang.org/cl/6739055

src/pkg/net/http/client_test.go

@@ -219,6 +219,9 @@ func TestRedirects(t *testing.T) {
 		return checkErr
 	}}
 	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get error: %v", err)
+	}
 	finalUrl := res.Request.URL.String()
 	if e, g := "<nil>", fmt.Sprintf("%v", err); e != g {
 		t.Errorf("with custom client, expected error %q, got %q", e, g)
@@ -335,7 +338,10 @@ func TestRedirectCookiesJar(t *testing.T) {
 	c.Jar = &TestJar{perURL: make(map[string][]*Cookie)}
 	u, _ := url.Parse(ts.URL)
 	c.Jar.SetCookies(u, []*Cookie{expectedCookies[0]})
-	resp, _ := c.Get(ts.URL)
+	resp, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
 	matchReturnedCookies(t, expectedCookies, resp.Cookies())
 }
 

src/pkg/net/http/transfer.go

@@ -567,14 +567,22 @@ func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
 	return false
 }
 
+var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
+
 func (b *body) readTrailer() error {
 	// The common case, since nobody uses trailers.
-	buf, _ := b.r.Peek(2)
+	buf, err := b.r.Peek(2)
 	if bytes.Equal(buf, singleCRLF) {
 		b.r.ReadByte()
 		b.r.ReadByte()
 		return nil
 	}
+	if len(buf) < 2 {
+		return errTrailerEOF
+	}
+	if err != nil {
+		return err
+	}
 
 	// Make sure there's a header terminator coming up, to prevent
 	// a DoS with an unbounded size Trailer.  It's not easy to
@@ -590,6 +598,9 @@ func (b *body) readTrailer() error {
 
 	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
 	if err != nil {
+		if err == io.EOF {
+			return errTrailerEOF
+		}
 		return err
 	}
 	switch rr := b.hdr.(type) {

src/pkg/net/http/transfer_test.go

@@ -0,0 +1,37 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bufio"
+	"strings"
+	"testing"
+)
+
+func TestBodyReadBadTrailer(t *testing.T) {
+	b := &body{
+		Reader: strings.NewReader("foobar"),
+		hdr:    true, // force reading the trailer
+		r:      bufio.NewReader(strings.NewReader("")),
+	}
+	buf := make([]byte, 7)
+	n, err := b.Read(buf[:3])
+	got := string(buf[:n])
+	if got != "foo" || err != nil {
+		t.Fatalf(`first Read = %n (%q), %v; want 3 ("foo")`, n, got, err)
+	}
+
+	n, err = b.Read(buf[:])
+	got = string(buf[:n])
+	if got != "bar" || err != nil {
+		t.Fatalf(`second Read = %n (%q), %v; want 3 ("bar")`, n, got, err)
+	}
+
+	n, err = b.Read(buf[:])
+	got = string(buf[:n])
+	if err == nil {
+		t.Errorf("final Read was successful (%q), expected error from trailer read", got)
+	}
+}

src/pkg/net/http/transport.go

@@ -605,6 +605,9 @@ func (pc *persistConn) readLoop() {
 			alive = false
 		}
 
+		// TODO(bradfitz): this hasBody conflicts with the defition
+		// above which excludes HEAD requests.  Is this one
+		// incomplete?
 		hasBody := resp != nil && resp.ContentLength != 0
 		var waitForBodyRead chan bool
 		if hasBody {
@@ -806,11 +809,6 @@ func canonicalAddr(url *url.URL) string {
 	return addr
 }
 
-func responseIsKeepAlive(res *Response) bool {
-	// TODO: implement.  for now just always shutting down the connection.
-	return false
-}
-
 // bodyEOFSignal wraps a ReadCloser but runs fn (if non-nil) at most
 // once, right before the final Read() or Close() call returns, but after
 // EOF has been seen.