compress/flate: detect truncated streams

Reader failed to detect truncated streams since calls to
io.ReadFull did not check if the error is io.EOF.

Change-Id: I0634e0d8de1ab04e8f93242c27a9f89e57743e87
Reviewed-on: https://go-review.googlesource.com/14833
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/compress/flate/flate_test.go

@@ -11,7 +11,9 @@ package flate
 import (
 	"bytes"
 	"encoding/hex"
+	"io"
 	"io/ioutil"
+	"strings"
 	"testing"
 )
 
@@ -258,3 +260,18 @@ func TestStreams(t *testing.T) {
 		}
 	}
 }
+
+func TestTruncatedStreams(t *testing.T) {
+	const data = "\x00\f\x00\xf3\xffhello, world\x01\x00\x00\xff\xff"
+
+	for i := 0; i < len(data)-1; i++ {
+		r := NewReader(strings.NewReader(data[:i]))
+		_, err := io.Copy(ioutil.Discard, r)
+		if ferr, ok := err.(*ReadError); ok {
+			err = ferr.Err
+		}
+		if err != io.ErrUnexpectedEOF {
+			t.Errorf("io.Copy(%d) on truncated stream: got %v, want %v", i, err, io.ErrUnexpectedEOF)
+		}
+	}
+}

src/compress/flate/inflate.go

@@ -637,6 +637,9 @@ func (f *decompressor) dataBlock() {
 	nr, err := io.ReadFull(f.r, f.buf[0:4])
 	f.roffset += int64(nr)
 	if err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
 		f.err = &ReadError{f.roffset, err}
 		return
 	}
@@ -669,6 +672,9 @@ func (f *decompressor) copyData() {
 		m, err := io.ReadFull(f.r, f.hist[f.hp:f.hp+m])
 		f.roffset += int64(m)
 		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
 			f.err = &ReadError{f.roffset, err}
 			return
 		}