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image/gif: don't panic on large or nil-containing color.Palettes.

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Fixes #20249

Change-Id: I5dceaef31de96345f8e6c155e12775dc4cc31bfb
Reviewed-on: https://go-review.googlesource.com/42790
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Nigel Tao 2017-05-05 16:44:42 +10:00
parent 2eeaba4172
commit 6d9b900a6f
2 changed files with 62 additions and 8 deletions
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37
src/image/gif/writer.go
View File

@ -132,7 +132,12 @@ func (e *encoder) writeHeader() {
e.buf[1] = e.g.BackgroundIndex
e.buf[2] = 0x00 // Pixel Aspect Ratio.
e.write(e.buf[:3])
e.globalCT = encodeColorTable(e.globalColorTable[:], p, paddedSize)
var err error
e.globalCT, err = encodeColorTable(e.globalColorTable[:], p, paddedSize)
if err != nil && e.err == nil {
e.err = err
return
}
e.write(e.globalColorTable[:e.globalCT])
} else {
// All frames have a local color table, so a global color table
@ -149,8 +154,9 @@ func (e *encoder) writeHeader() {
e.buf[1] = 0xff // Application Label.
e.buf[2] = 0x0b // Block Size.
e.write(e.buf[:3])
_, e.err = io.WriteString(e.w, "NETSCAPE2.0") // Application Identifier.
if e.err != nil {
_, err := io.WriteString(e.w, "NETSCAPE2.0") // Application Identifier.
if err != nil && e.err == nil {
e.err = err
return
}
e.buf[0] = 0x03 // Block Size.
@ -161,11 +167,18 @@ func (e *encoder) writeHeader() {
}
}
func encodeColorTable(dst []byte, p color.Palette, size int) int {
func encodeColorTable(dst []byte, p color.Palette, size int) (int, error) {
if uint(size) >= uint(len(log2Lookup)) {
return 0, errors.New("gif: cannot encode color table with more than 256 entries")
}
n := log2Lookup[size]
for i := 0; i < n; i++ {
if i < len(p) {
r, g, b, _ := p[i].RGBA()
c := p[i]
if c == nil {
return 0, errors.New("gif: cannot encode color table with nil entries")
}
r, g, b, _ := c.RGBA()
dst[3*i+0] = uint8(r >> 8)
dst[3*i+1] = uint8(g >> 8)
dst[3*i+2] = uint8(b >> 8)
@ -176,7 +189,7 @@ func encodeColorTable(dst []byte, p color.Palette, size int) int {
dst[3*i+2] = 0x00
}
}
return 3 * n
return 3 * n, nil
}
func (e *encoder) writeImageBlock(pm *image.Paletted, delay int, disposal byte) {
@ -201,6 +214,10 @@ func (e *encoder) writeImageBlock(pm *image.Paletted, delay int, disposal byte)
transparentIndex := -1
for i, c := range pm.Palette {
if c == nil {
e.err = errors.New("gif: cannot encode color table with nil entries")
return
}
if _, _, _, a := c.RGBA(); a == 0 {
transparentIndex = i
break
@ -235,8 +252,12 @@ func (e *encoder) writeImageBlock(pm *image.Paletted, delay int, disposal byte)
e.write(e.buf[:9])
paddedSize := log2(len(pm.Palette)) // Size of Local Color Table: 2^(1+n).
ct := encodeColorTable(e.localColorTable[:], pm.Palette, paddedSize)
if ct != e.globalCT || !bytes.Equal(e.globalColorTable[:ct], e.localColorTable[:ct]) {
if ct, err := encodeColorTable(e.localColorTable[:], pm.Palette, paddedSize); err != nil {
if e.err == nil {
e.err = err
}
return
} else if ct != e.globalCT || !bytes.Equal(e.globalColorTable[:ct], e.localColorTable[:ct]) {
// Use a local color table.
e.writeByte(fColorTable | uint8(paddedSize))
e.write(e.localColorTable[:ct])

33
src/image/gif/writer_test.go
View File

@ -438,6 +438,39 @@ func TestEncodePalettes(t *testing.T) {
}
}
func TestEncodeBadPalettes(t *testing.T) {
const w, h = 5, 5
for _, n := range []int{256, 257} {
for _, nilColors := range []bool{false, true} {
pal := make(color.Palette, n)
if !nilColors {
for i := range pal {
pal[i] = color.Black
}
}
err := EncodeAll(ioutil.Discard, &GIF{
Image: []*image.Paletted{
image.NewPaletted(image.Rect(0, 0, w, h), pal),
},
Delay: make([]int, 1),
Disposal: make([]byte, 1),
Config: image.Config{
ColorModel: pal,
Width: w,
Height: h,
},
})
got := err != nil
want := n > 256 || nilColors
if got != want {
t.Errorf("n=%d, nilColors=%t: err != nil: got %t, want %t", n, nilColors, got, want)
}
}
}
}
func BenchmarkEncode(b *testing.B) {
b.StopTimer()