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[libpng16] Check length of IDAT against maximum possible IDAT size, accounting

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for height, rowbytes, interlacing and zlib/deflate overhead.
This commit is contained in:
Glenn Randers-Pehrson
2017-08-03 10:01:35 -05:00
parent 6b53a5ed7b
commit a1fe2c9848
4 changed files with 36 additions and 7 deletions
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17
pngpread.c
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@@ -170,6 +170,7 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
int keep; /* unknown handling method */
#endif
png_alloc_size_t limit = PNG_UINT_31_MAX;
/* First we make sure we have enough data for the 4-byte chunk name
* and the 4-byte chunk length before proceeding with decoding the
@@ -223,9 +224,19 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
png_benign_error(png_ptr, "Too many IDATs found");
}
if (chunk_name == png_IDAT)
{
size_t row_factor =
(png_ptr->rowbytes + 1 + (png_ptr->interlaced? 6: 0));
if (png_ptr->height > PNG_UINT_32_MAX/row_factor)
limit=PNG_UINT_31_MAX;
else
limit = png_ptr->height * row_factor;
limit += 6 + 5*limit/32566; /* zlib+deflate overhead */
limit=limit < PNG_UINT_31_MAX? limit : PNG_UINT_31_MAX;
}
else
{
png_alloc_size_t limit = PNG_SIZE_MAX;
# ifdef PNG_SET_USER_LIMITS_SUPPORTED
if (png_ptr->user_chunk_malloc_max > 0 &&
png_ptr->user_chunk_malloc_max < limit)
@@ -234,9 +245,9 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
if (PNG_USER_CHUNK_MALLOC_MAX < limit)
limit = PNG_USER_CHUNK_MALLOC_MAX;
# endif
if (png_ptr->push_length > limit)
png_chunk_error(png_ptr, "chunk data is too large");
}
if (png_ptr->push_length > limit)
png_chunk_error(png_ptr, "chunk data is too large");
if (chunk_name == png_IHDR)
{