[release-branch.go1.8] image/png: restore Go 1.7 rejection of transparent gray8 images

Go 1.7 and earlier rejected these images with chunkOrderError.
Go 1.8 panicked during decoding.
Go 1.9 will handle them successfully.

Make Go 1.8.1 match Go 1.7 and earlier, to remove the panic
without introducing new functionality in a minor release.

Fixes #19553.

Change-Id: I3c73a27aa3932300326273b6b563cdf606f3ab64
Reviewed-on: https://go-review.googlesource.com/39593
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/image/png/reader.go b/src/image/png/reader.go
index 32f78f0ffe84c0ccef600bad00c556264f35f7be..8299df56735df09e27669143245bd9a365c3e67a 100644 (file)
--- a/src/image/png/reader.go
+++ b/src/image/png/reader.go
@@ -612,6 +612,11 @@ func (d *decoder) readImagePass(r io.Reader, pass int, allocateOnly bool) (image
                                }
                        }
                case cbG8:
+                       if d.useTransparent {
+                               // Match error from Go 1.7 and earlier.
+                               // Go 1.9 will decode this properly.
+                               return nil, chunkOrderError
+                       }
                        copy(gray.Pix[pixOffset:], cdat)
                        pixOffset += gray.Stride
                case cbGA8:

diff --git a/src/image/png/reader_test.go b/src/image/png/reader_test.go
index b9e9f4d02c671e652dff9f2345fdd8d3c8d8e26f..503b5dc567b27df9d58385464feb726bd2d2bb35 100644 (file)
--- a/src/image/png/reader_test.go
+++ b/src/image/png/reader_test.go
@@ -629,3 +629,13 @@ func BenchmarkDecodeRGB(b *testing.B) {
 func BenchmarkDecodeInterlacing(b *testing.B) {
        benchmarkDecode(b, "testdata/benchRGB-interlace.png", 4)
 }
+
+func TestIssue19553(t *testing.T) {
+       var buf = []byte{
+               0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x0b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x85, 0x2c, 0x88, 0x80, 0x00, 0x00, 0x00, 0x02, 0x74, 0x52, 0x4e, 0x53, 0x00, 0xff, 0x5b, 0x91, 0x22, 0xb5, 0x00, 0x00, 0x00, 0x02, 0x62, 0x4b, 0x47, 0x44, 0x00, 0xff, 0x87, 0x8f, 0xcc, 0xbf, 0x00, 0x00, 0x00, 0x09, 0x70, 0x48, 0x59, 0x73, 0x00, 0x00, 0x0a, 0xf0, 0x00, 0x00, 0x0a, 0xf0, 0x01, 0x42, 0xac, 0x34, 0x98, 0x00, 0x00, 0x00, 0x07, 0x74, 0x49, 0x4d, 0x45, 0x07, 0xd5, 0x04, 0x02, 0x12, 0x11, 0x11, 0xf7, 0x65, 0x3d, 0x8b, 0x00, 0x00, 0x00, 0x4f, 0x49, 0x44, 0x41, 0x54, 0x08, 0xd7, 0x63, 0xf8, 0xff, 0xff, 0xff, 0xb9, 0xbd, 0x70, 0xf0, 0x8c, 0x01, 0xc8, 0xaf, 0x6e, 0x99, 0x02, 0x05, 0xd9, 0x7b, 0xc1, 0xfc, 0x6b, 0xff, 0xa1, 0xa0, 0x87, 0x30, 0xff, 0xd9, 0xde, 0xbd, 0xd5, 0x4b, 0xf7, 0xee, 0xfd, 0x0e, 0xe3, 0xef, 0xcd, 0x06, 0x19, 0x14, 0xf5, 0x1e, 0xce, 0xef, 0x01, 0x31, 0x92, 0xd7, 0x82, 0x41, 0x31, 0x9c, 0x3f, 0x07, 0x02, 0xee, 0xa1, 0xaa, 0xff, 0xff, 0x9f, 0xe1, 0xd9, 0x56, 0x30, 0xf8, 0x0e, 0xe5, 0x03, 0x00, 0xa9, 0x42, 0x84, 0x3d, 0xdf, 0x8f, 0xa6, 0x8f, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82,
+       }
+       _, err := Decode(bytes.NewReader(buf))
+       if err != chunkOrderError {
+               t.Errorf("Decode: expected chunkOrderError for transparent gray8, got %v", err)
+       }
+}