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[libpng16] Silently truncate over-length PLTE chunk while reading.

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Glenn Randers-Pehrson
2015-10-30 11:34:37 -05:00
parent a901eb3ce6
commit 1bef8e9799
4 changed files with 16 additions and 7 deletions
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15
pngrutil.c
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@@ -872,7 +872,7 @@ void /* PRIVATE */
png_handle_PLTE(png_structrp png_ptr, png_inforp 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
@@ -930,9 +930,19 @@ png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
return;
}
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++)
{
@@ -1002,9 +1012,6 @@ png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
* confusing.
*
* Fix this by not sharing the palette in this way.
*
* Starting with libpng-1.6.19, png_set_PLTE() also issues a png_error() when
* it attempts to set a palette length that is too large for the bit depth.
*/
png_set_PLTE(png_ptr, info_ptr, palette, num);