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Ensure that only one eXIf chunk is written in the entire datastream

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EXIF data can be stored in an eXIf chunk before IDAT, or after IDAT,
but the entire PNG datastream may contain one eXIf chunk at most.

Introduce the private mode flag PNG_WROTE_eXIf, which is meant to be
used like the PNG_WROTE_tIME flag. The eXIf chunk and the tIME chunk
have the same ordering rules (i.e. no constraints are imposed), and
the same multiplicity rules (i.e. no multiples are allowed), and they
should be initialized and checked using the same algorithm.

This fixes commit cd03aaf7bf,
previously reverted in 3d57708c91.

Reported-by: Ben Bullock <benkasminbullock@gmail.com>
This commit is contained in:
Cosmin Truta
2023-06-21 16:16:07 +03:00
parent 8be5c147d5
commit e6c5bf46c4
3 changed files with 22 additions and 23 deletions
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4
pngpriv.h
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@@ -1,7 +1,7 @@
/* pngpriv.h - private declarations for use inside libpng
*
* Copyright (c) 2018-2022 Cosmin Truta
* Copyright (c) 2018-2023 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -626,7 +626,7 @@
#define PNG_BACKGROUND_IS_GRAY 0x800U
#define PNG_HAVE_PNG_SIGNATURE 0x1000U
#define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000U /* Have another chunk after IDAT */
/* 0x4000U (unused) */
#define PNG_WROTE_eXIf 0x4000U
#define PNG_IS_READ_STRUCT 0x8000U /* Else is a write struct */
/* Flags for the transformations the PNG library does on the image data */