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image/gif: check handling of truncated GIF files

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All the prefixes of the testGIF produce errors today,
but they differ wildly in which errors: some are io.EOF,
others are io.ErrUnexpectedEOF, and others are gif-specific.
Make them all gif-specific to explain context, and make
any complaining about EOF be sure to mention the EOF
is unexpected.

Fixes #11390.

Change-Id: I742c39c88591649276268327ea314e68d1de1845
Reviewed-on: https://go-review.googlesource.com/17493
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Jeff R. Allen 2015-12-05 21:06:05 +06:00 committed by Brad Fitzpatrick
parent a39920fdbb
commit d1d798dd15
2 changed files with 71 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
src/image/gif/reader.go
View File

@ -63,6 +63,22 @@ const (
eApplication = 0xFF // Application
)
func readFull(r io.Reader, b []byte) error {
_, err := io.ReadFull(r, b)
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
func readByte(r io.ByteReader) (byte, error) {
b, err := r.ReadByte()
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return b, err
}
// decoder is the type used to decode a GIF file.
type decoder struct {
r reader
@ -124,7 +140,7 @@ func (b *blockReader) Read(p []byte) (int, error) {
return 0, b.err
}
b.slice = b.tmp[:blockLen]
if _, b.err = io.ReadFull(b.r, b.slice); b.err != nil {
if b.err = readFull(b.r, b.slice); b.err != nil {
return 0, b.err
}
}
@ -151,9 +167,9 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
}
for {
c, err := d.r.ReadByte()
c, err := readByte(d.r)
if err != nil {
return err
return fmt.Errorf("gif: reading frames: %v", err)
}
switch c {
case sExtension:
@ -198,9 +214,9 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
m.Palette = p
}
}
litWidth, err := d.r.ReadByte()
litWidth, err := readByte(d.r)
if err != nil {
return err
return fmt.Errorf("gif: reading image data: %v", err)
}
if litWidth < 2 || litWidth > 8 {
return fmt.Errorf("gif: pixel size in decode out of range: %d", litWidth)
@ -209,9 +225,9 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
br := &blockReader{r: d.r}
lzwr := lzw.NewReader(br, lzw.LSB, int(litWidth))
defer lzwr.Close()
if _, err = io.ReadFull(lzwr, m.Pix); err != nil {
if err = readFull(lzwr, m.Pix); err != nil {
if err != io.ErrUnexpectedEOF {
return err
return fmt.Errorf("gif: reading image data: %v", err)
}
return errNotEnough
}
@ -228,13 +244,13 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
// See https://golang.org/issue/9856 for an example GIF.
if n, err := lzwr.Read(d.tmp[:1]); n != 0 || (err != io.EOF && err != io.ErrUnexpectedEOF) {
if err != nil {
return err
return fmt.Errorf("gif: reading image data: %v", err)
}
return errTooMuch
}
if n, err := br.Read(d.tmp[:1]); n != 0 || err != io.EOF {
if err != nil {
return err
return fmt.Errorf("gif: reading image data: %v", err)
}
return errTooMuch
}
@ -264,7 +280,7 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
case sTrailer:
if len(d.image) == 0 {
return io.ErrUnexpectedEOF
return fmt.Errorf("gif: missing image data")
}
return nil
@ -275,13 +291,13 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
}
func (d *decoder) readHeaderAndScreenDescriptor() error {
_, err := io.ReadFull(d.r, d.tmp[:13])
err := readFull(d.r, d.tmp[:13])
if err != nil {
return err
return fmt.Errorf("gif: reading header: %v", err)
}
d.vers = string(d.tmp[:6])
if d.vers != "GIF87a" && d.vers != "GIF89a" {
return fmt.Errorf("gif: can't recognize format %s", d.vers)
return fmt.Errorf("gif: can't recognize format %q", d.vers)
}
d.width = int(d.tmp[6]) + int(d.tmp[7])<<8
d.height = int(d.tmp[8]) + int(d.tmp[9])<<8
@ -298,9 +314,9 @@ func (d *decoder) readHeaderAndScreenDescriptor() error {
func (d *decoder) readColorTable(fields byte) (color.Palette, error) {
n := 1 << (1 + uint(fields&fColorTableBitsMask))
_, err := io.ReadFull(d.r, d.tmp[:3*n])
err := readFull(d.r, d.tmp[:3*n])
if err != nil {
return nil, fmt.Errorf("gif: short read on color table: %s", err)
return nil, fmt.Errorf("gif: reading color table: %s", err)
}
j, p := 0, make(color.Palette, n)
for i := range p {
@ -311,9 +327,9 @@ func (d *decoder) readColorTable(fields byte) (color.Palette, error) {
}
func (d *decoder) readExtension() error {
extension, err := d.r.ReadByte()
extension, err := readByte(d.r)
if err != nil {
return err
return fmt.Errorf("gif: reading extension: %v", err)
}
size := 0
switch extension {
@ -324,9 +340,9 @@ func (d *decoder) readExtension() error {
case eComment:
// nothing to do but read the data.
case eApplication:
b, err := d.r.ReadByte()
b, err := readByte(d.r)
if err != nil {
return err
return fmt.Errorf("gif: reading extension: %v", err)
}
// The spec requires size be 11, but Adobe sometimes uses 10.
size = int(b)
@ -334,8 +350,8 @@ func (d *decoder) readExtension() error {
return fmt.Errorf("gif: unknown extension 0x%.2x", extension)
}
if size > 0 {
if _, err := io.ReadFull(d.r, d.tmp[:size]); err != nil {
return err
if err := readFull(d.r, d.tmp[:size]); err != nil {
return fmt.Errorf("gif: reading extension: %v", err)
}
}
@ -343,8 +359,11 @@ func (d *decoder) readExtension() error {
// this extension defines a loop count.
if extension == eApplication && string(d.tmp[:size]) == "NETSCAPE2.0" {
n, err := d.readBlock()
if n == 0 || err != nil {
return err
if err != nil {
return fmt.Errorf("gif: reading extension: %v", err)
}
if n == 0 {
return nil
}
if n == 3 && d.tmp[0] == 1 {
d.loopCount = int(d.tmp[1]) | int(d.tmp[2])<<8
@ -352,14 +371,17 @@ func (d *decoder) readExtension() error {
}
for {
n, err := d.readBlock()
if n == 0 || err != nil {
return err
if err != nil {
return fmt.Errorf("gif: reading extension: %v", err)
}
if n == 0 {
return nil
}
}
}
func (d *decoder) readGraphicControl() error {
if _, err := io.ReadFull(d.r, d.tmp[:6]); err != nil {
if err := readFull(d.r, d.tmp[:6]); err != nil {
return fmt.Errorf("gif: can't read graphic control: %s", err)
}
if d.tmp[0] != 4 {
@ -379,7 +401,7 @@ func (d *decoder) readGraphicControl() error {
}
func (d *decoder) newImageFromDescriptor() (*image.Paletted, error) {
if _, err := io.ReadFull(d.r, d.tmp[:9]); err != nil {
if err := readFull(d.r, d.tmp[:9]); err != nil {
return nil, fmt.Errorf("gif: can't read image descriptor: %s", err)
}
left := int(d.tmp[0]) + int(d.tmp[1])<<8
@ -399,11 +421,14 @@ func (d *decoder) newImageFromDescriptor() (*image.Paletted, error) {
}
func (d *decoder) readBlock() (int, error) {
n, err := d.r.ReadByte()
n, err := readByte(d.r)
if n == 0 || err != nil {
return 0, err
}
return io.ReadFull(d.r, d.tmp[:n])
if err := readFull(d.r, d.tmp[:n]); err != nil {
return 0, err
}
return int(n), nil
}
// interlaceScan defines the ordering for a pass of the interlace algorithm.

17
src/image/gif/reader_test.go
View File

@ -10,6 +10,7 @@ import (
"image"
"image/color"
"reflect"
"strings"
"testing"
)
@ -292,3 +293,19 @@ func TestLoopCount(t *testing.T) {
t.Errorf("loop count mismatch: %d vs %d", img.LoopCount, img1.LoopCount)
}
}
func TestUnexpectedEOF(t *testing.T) {
for i := len(testGIF) - 1; i >= 0; i-- {
_, err := Decode(bytes.NewReader(testGIF[:i]))
if err == errNotEnough {
continue
}
text := ""
if err != nil {
text = err.Error()
}
if !strings.HasPrefix(text, "gif:") || !strings.HasSuffix(text, ": unexpected EOF") {
t.Errorf("Decode(testGIF[:%d]) = %v, want gif: ...: unexpected EOF", i, err)
}
}
}