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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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20
pngrutil.c
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@@ -157,6 +157,7 @@ png_read_chunk_header(png_structrp png_ptr)
{
png_byte buf[8];
png_uint_32 length;
png_alloc_size_t limit = PNG_UINT_31_MAX;
#ifdef PNG_IO_STATE_SUPPORTED
png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
@@ -184,7 +185,6 @@ png_read_chunk_header(png_structrp png_ptr)
/* Check for too-large chunk length */
if (png_ptr->chunk_name != png_IDAT)
{
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)
@@ -193,8 +193,22 @@ png_read_chunk_header(png_structrp png_ptr)
if (PNG_USER_CHUNK_MALLOC_MAX < limit)
limit = PNG_USER_CHUNK_MALLOC_MAX;
# endif
if (length > limit)
png_chunk_error(png_ptr, "chunk data is too large");
}
else
{
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;
}
if (length > limit)
{
png_chunk_error(png_ptr, "chunk data is too large");
}
#ifdef PNG_IO_STATE_SUPPORTED