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image/png: have DecodeConfig read tRNS chunks

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Fixes #54325

Change-Id: Ie468180c4d6f21db7672dd71bd2a40f3a5881b7d
Reviewed-on: https://go-review.googlesource.com/c/go/+/424917
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Nigel Tao (INACTIVE; USE @golang.org INSTEAD) <nigeltao@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
This commit is contained in:
Nigel Tao 2022-08-19 16:39:38 +10:00
parent 1ab6b790be
commit b5a9459cd0
2 changed files with 70 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/image/png/reader.go
View File

@ -870,7 +870,7 @@ func (d *decoder) parseIEND(length uint32) error {
return d.verifyChecksum()
}
func (d *decoder) parseChunk() error {
func (d *decoder) parseChunk(configOnly bool) error {
// Read the length and chunk type.
if _, err := io.ReadFull(d.r, d.tmp[:8]); err != nil {
return err
@ -915,6 +915,9 @@ func (d *decoder) parseChunk() error {
break
}
d.stage = dsSeenIDAT
if configOnly {
return nil
}
return d.parseIDAT(length)
case "IEND":
if d.stage != dsSeenIDAT {
@ -974,7 +977,7 @@ func Decode(r io.Reader) (image.Image, error) {
return nil, err
}
for d.stage != dsSeenIEND {
if err := d.parseChunk(); err != nil {
if err := d.parseChunk(false); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
@ -997,21 +1000,26 @@ func DecodeConfig(r io.Reader) (image.Config, error) {
}
return image.Config{}, err
}
for {
if err := d.parseChunk(); err != nil {
if err := d.parseChunk(true); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return image.Config{}, err
}
paletted := cbPaletted(d.cb)
if d.stage == dsSeenIHDR && !paletted {
if cbPaletted(d.cb) {
if d.stage >= dsSeentRNS {
break
}
if d.stage == dsSeenPLTE && paletted {
} else {
if d.stage >= dsSeenIHDR {
break
}
}
}
var cm color.Model
switch d.cb {
case cbG1, cbG2, cbG4, cbG8:

53
src/image/png/reader_test.go
View File

@ -783,6 +783,59 @@ func TestDimensionOverflow(t *testing.T) {
}
}
func TestDecodePalettedWithTransparency(t *testing.T) {
// These bytes come from https://go.dev/issue/54325
//
// Per the PNG spec, a PLTE chunk contains 3 (not 4) bytes per palette
// entry: RGB (not RGBA). The alpha value comes from the optional tRNS
// chunk. Here, the PLTE chunk (0x50, 0x4c, 0x54, 0x45, etc) has 16 entries
// (0x30 = 48 bytes) and the tRNS chunk (0x74, 0x52, 0x4e, 0x53, etc) has 1
// entry (0x01 = 1 byte) that sets the first palette entry's alpha to zero.
//
// Both Decode and DecodeConfig should pick up that the first palette
// entry's alpha is zero.
src := []byte{
0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x20, 0x04, 0x03, 0x00, 0x00, 0x00, 0x81, 0x54, 0x67,
0xc7, 0x00, 0x00, 0x00, 0x30, 0x50, 0x4c, 0x54, 0x45, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x0e,
0x00, 0x23, 0x27, 0x7b, 0xb1, 0x2d, 0x0a, 0x49, 0x3f, 0x19, 0x78, 0x5f, 0xcd, 0xe4, 0x69, 0x69,
0xe4, 0x71, 0x59, 0x53, 0x80, 0x11, 0x14, 0x8b, 0x00, 0xa9, 0x8d, 0x95, 0xcb, 0x99, 0x2f, 0x6b,
0xd7, 0x29, 0x91, 0xd7, 0x7b, 0xba, 0xff, 0xe3, 0xd7, 0x13, 0xc6, 0xd3, 0x58, 0x00, 0x00, 0x00,
0x01, 0x74, 0x52, 0x4e, 0x53, 0x00, 0x40, 0xe6, 0xd8, 0x66, 0x00, 0x00, 0x00, 0xfd, 0x49, 0x44,
0x41, 0x54, 0x28, 0xcf, 0x63, 0x60, 0x00, 0x83, 0x55, 0x0c, 0x68, 0x60, 0x9d, 0x02, 0x9a, 0x80,
0xde, 0x23, 0x74, 0x15, 0xef, 0x50, 0x94, 0x70, 0x2d, 0xd2, 0x7b, 0x87, 0xa2, 0x84, 0xeb, 0xee,
0xbb, 0x77, 0x6f, 0x51, 0x94, 0xe8, 0xbd, 0x7d, 0xf7, 0xee, 0x12, 0xb2, 0x80, 0xd2, 0x3d, 0x54,
0x01, 0x26, 0x10, 0x1f, 0x59, 0x40, 0x0f, 0xc8, 0xd7, 0x7e, 0x84, 0x70, 0x1c, 0xd7, 0xba, 0xb7,
0x4a, 0xda, 0xda, 0x77, 0x11, 0xf6, 0xac, 0x5a, 0xa5, 0xf4, 0xf9, 0xbf, 0xfd, 0x3d, 0x24, 0x6b,
0x98, 0x94, 0xf4, 0xff, 0x7f, 0x52, 0x42, 0x16, 0x30, 0x0e, 0xd9, 0xed, 0x6a, 0x8c, 0xec, 0x10,
0x65, 0x53, 0x97, 0x60, 0x23, 0x64, 0x1d, 0x8a, 0x2e, 0xc6, 0x2e, 0x42, 0x08, 0x3d, 0x4c, 0xca,
0x81, 0xc1, 0x82, 0xa6, 0xa2, 0x46, 0x08, 0x3d, 0x4a, 0xa1, 0x82, 0xc6, 0x82, 0xa1, 0x4a, 0x08,
0x3d, 0xfa, 0xa6, 0x81, 0xa1, 0xa2, 0xc1, 0x9f, 0x10, 0x66, 0xd4, 0x2b, 0x87, 0x0a, 0x86, 0x1a,
0x7d, 0x57, 0x80, 0x9b, 0x99, 0xaf, 0x62, 0x1a, 0x1a, 0xec, 0xf0, 0x0d, 0x66, 0x2a, 0x7b, 0x5a,
0xba, 0xd2, 0x64, 0x63, 0x4b, 0xa6, 0xb2, 0xb4, 0x02, 0xa8, 0x12, 0xb5, 0x24, 0xa5, 0x99, 0x2e,
0x33, 0x95, 0xd4, 0x92, 0x10, 0xee, 0xd0, 0x59, 0xb9, 0x6a, 0xd6, 0x21, 0x24, 0xb7, 0x33, 0x9d,
0x01, 0x01, 0x64, 0xbf, 0xac, 0x59, 0xb2, 0xca, 0xeb, 0x14, 0x92, 0x80, 0xd6, 0x9a, 0x53, 0x4a,
0x6b, 0x4e, 0x2d, 0x42, 0x52, 0xa1, 0x73, 0x28, 0x54, 0xe7, 0x90, 0x6a, 0x00, 0x92, 0x92, 0x45,
0xa1, 0x40, 0x84, 0x2c, 0xe0, 0xc4, 0xa0, 0xb2, 0x28, 0x14, 0xc1, 0x67, 0xe9, 0x50, 0x60, 0x60,
0xea, 0x70, 0x40, 0x12, 0x00, 0x79, 0x54, 0x09, 0x22, 0x00, 0x00, 0x30, 0xf3, 0x52, 0x87, 0xc6,
0xe4, 0xbd, 0x70, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82,
}
cfg, err := DecodeConfig(bytes.NewReader(src))
if err != nil {
t.Fatalf("DecodeConfig: %v", err)
} else if _, _, _, alpha := cfg.ColorModel.(color.Palette)[0].RGBA(); alpha != 0 {
t.Errorf("DecodeConfig: got %d, want 0", alpha)
}
img, err := Decode(bytes.NewReader(src))
if err != nil {
t.Fatalf("Decode: %v", err)
} else if _, _, _, alpha := img.ColorModel().(color.Palette)[0].RGBA(); alpha != 0 {
t.Errorf("Decode: got %d, want 0", alpha)
}
}
func benchmarkDecode(b *testing.B, filename string, bytesPerPixel int) {
data, err := os.ReadFile(filename)
if err != nil {