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[libpng12] Prevent writing over-length PLTE chunk (Cosmin Truta) and

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silently truncate over-length PLTE chunk while reading.
This commit is contained in:
Glenn Randers-Pehrson
2015-10-31 08:39:01 -05:00
parent 856a76b285
commit 475bab6170
4 changed files with 29 additions and 10 deletions
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15
pngrutil.c
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@@ -1,7 +1,7 @@
/* pngrutil.c - utilities to read a PNG file
*
* Last changed in libpng 1.2.53 [February 26, 2015]
* Last changed in libpng 1.2.54 [October 31, 2015]
* Copyright (c) 1998-2015 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -506,7 +506,7 @@ void /* PRIVATE */
png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
png_color palette[PNG_MAX_PALETTE_LENGTH];
int num, i;
int max_palette_length, num, i;
#ifdef PNG_POINTER_INDEXING_SUPPORTED
png_colorp pal_ptr;
#endif
@@ -558,8 +558,19 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
}
}
max_palette_length = (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
(1 << png_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
/* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
num = (int)length / 3;
/* If the palette has 256 or fewer entries but is too large for the bit depth,
* we don't issue an error, to preserve the behavior of previous libpng versions.
* We silently truncate the unused extra palette entries here.
*/
if (num > max_palette_length)
num = max_palette_length;
#ifdef PNG_POINTER_INDEXING_SUPPORTED
for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
{