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When decoding a paletted PNG, require that a PLTE chunk is seen before

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the first IDAT chunk.

R=rsc
APPROVED=rsc
DELTA=7  (2 added, 0 deleted, 5 changed)
OCL=34583
CL=34585
This commit is contained in:
Nigel Tao 2009-09-13 21:47:54 -07:00
parent d3013d8aa1
commit 8a0cb9302f
1 changed files with 7 additions and 5 deletions
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12
src/pkg/image/png/reader.go
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@ -65,6 +65,8 @@ func (e FormatError) String() string {
return "invalid PNG format: " + e;
}
var chunkOrderError = FormatError("chunk out of order")
// An IDATDecodingError wraps an inner error (such as a ZLIB decoding error) encountered while processing an IDAT chunk.
type IDATDecodingError struct {
Err os.Error;
@ -347,25 +349,25 @@ func (d *decoder) parseChunk(r io.Reader) os.Error {
switch string(d.scratch[0:4]) {
case "IHDR":
if d.stage != dsStart {
return FormatError("chunk out of order");
return chunkOrderError;
}
d.stage = dsSeenIHDR;
err = d.parseIHDR(r, crc, length);
case "PLTE":
if d.stage != dsSeenIHDR {
return FormatError("chunk out of order");
return chunkOrderError;
}
d.stage = dsSeenPLTE;
err = d.parsePLTE(r, crc, length);
case "IDAT":
if d.stage < dsSeenIHDR || d.stage > dsSeenIDAT {
return FormatError("chunk out of order");
if d.stage < dsSeenIHDR || d.stage > dsSeenIDAT || (d.colorType == ctPaletted && d.stage == dsSeenIHDR) {
return chunkOrderError;
}
d.stage = dsSeenIDAT;
err = d.parseIDAT(r, crc, length);
case "IEND":
if d.stage != dsSeenIDAT {
return FormatError("chunk out of order");
return chunkOrderError;
}
d.stage = dsSeenIEND;
err = d.parseIEND(r, crc, length);