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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 - Matt Sarett
- Mike Klein - Mike Klein
- Sami Boukortt - Sami Boukortt
- Wan-Teh Chang
The build projects, the build scripts, the test scripts, and other The build projects, the build scripts, the test scripts, and other
files in the "ci", "projects", "scripts" and "tests" directories, have files in the "ci", "projects", "scripts" and "tests" directories, have

13
pngget.c
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@ -1,7 +1,7 @@
/* pngget.c - retrieval of values from info struct /* 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) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger * Copyright (c) 1996-1997 Andreas Dilger
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. * 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) png_uint_32 flag)
{ {
if (png_ptr != NULL && info_ptr != NULL) 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(info_ptr->valid & flag);
}
return(0); return(0);
} }