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Don't report a valid tRNS chunk if it was canceled

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Add special handling of the PNG_INFO_tRNS flag to png_get_valid() to
not report a canceled tRNS chunk as valid.

Fix https://github.com/glennrp/libpng/issues/482

Signed-off-by: Cosmin Truta <ctruta@gmail.com>
This commit is contained in:
Wan-Teh Chang 2023-06-15 11:34:22 -07:00 committed by Cosmin Truta
parent f7abe3c419
commit 8be5c147d5
2 changed files with 13 additions and 1 deletions
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1
AUTHORS
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@ -41,6 +41,7 @@ Authors, for copyright and licensing purposes.
- Matt Sarett
- Mike Klein
- Sami Boukortt
- Wan-Teh Chang
The build projects, the build scripts, the test scripts, and other
files in the "ci", "projects", "scripts" and "tests" directories, have

13
pngget.c
View File

@ -1,7 +1,7 @@
/* pngget.c - retrieval of values from info struct
*
* Copyright (c) 2018 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.
@ -21,7 +21,18 @@ png_get_valid(png_const_structrp png_ptr, png_const_inforp info_ptr,
png_uint_32 flag)
{
if (png_ptr != NULL && info_ptr != NULL)
{
#ifdef PNG_READ_tRNS_SUPPORTED
/* png_handle_PLTE() may have canceled a valid tRNS chunk but left the
* 'valid' flag for the detection of duplicate chunks. Do not report a
* valid tRNS chunk in this case.
*/
if (flag == PNG_INFO_tRNS && png_ptr->num_trans == 0)
return(0);
#endif
return(info_ptr->valid & flag);
}
return(0);
}