From 1842d7c86574e5ac6494423a5e3205c3fedd74b4 Mon Sep 17 00:00:00 2001
From: Glenn Randers-Pehrson <glennrp at users.sourceforge.net>
Date: Sun, 11 Sep 2016 22:02:05 -0500
Subject: [PATCH] [libpng16] Issue a png_benign_error instead of a png_error on
 ADLER32 mismatch

while decoding compressed data chunks.
---
 ANNOUNCE   | 4 +++-
 CHANGES    | 4 +++-
 pngpread.c | 7 ++++++-
 pngrutil.c | 7 ++++++-
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/ANNOUNCE b/ANNOUNCE
index 294faa99b..d3fd78005 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -30,7 +30,9 @@ Version 1.6.26beta01 [September 12, 2016]
     bugfix by John Bowler).
   Do not issue a png_error() on read in png_set_pCAL() because png_handle_pCAL
     has allocated memory that libpng needs to free.
-  Conditionally compile png_set_benign_errors() in pngread.c
+  Conditionally compile png_set_benign_errors() in pngread.c and pngtest.c
+  Issue a png_benign_error instead of a png_error on ADLER32 mismatch
+    while decoding compressed data chunks.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 5c6af71fc..2b318c790 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5708,7 +5708,9 @@ Version 1.6.26beta01 [September 12, 2016]
     bugfix by John Bowler).
   Do not issue a png_error() on read in png_set_pCAL() because png_handle_pCAL
     has allocated memory that libpng needs to free.
-  Conditionally compile png_set_benign_errors() in pngread.c
+  Conditionally compile png_set_benign_errors() in pngread.c and pngtest.c
+  Issue a png_benign_error instead of a png_error on ADLER32 mismatch
+    while decoding compressed data chunks.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngpread.c b/pngpread.c
index 794352f42..c3637b5f0 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -684,7 +684,12 @@ png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
             png_warning(png_ptr, "Truncated compressed data in IDAT");
 
          else
-            png_error(png_ptr, "Decompression error in IDAT");
+         {
+            if (ret == Z_DATA_ERROR)
+               png_benign_error(png_ptr, "ADLER32 checksum mismatch in IDAT");
+            else
+               png_error(png_ptr, "Decompression error in IDAT");
+         }
 
          /* Skip the check on unprocessed input */
          return;
diff --git a/pngrutil.c b/pngrutil.c
index 3eaa635ad..c619cbb5e 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -4101,7 +4101,12 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
          png_zstream_error(png_ptr, ret);
 
          if (output != NULL)
-            png_chunk_error(png_ptr, png_ptr->zstream.msg);
+         {
+            if(!strncmp(png_ptr->zstream.msg,"incorrect data check",20))
+               png_chunk_benign_error(png_ptr, png_ptr->zstream.msg);
+            else
+               png_chunk_error(png_ptr, png_ptr->zstream.msg);
+         }
 
          else /* checking */
          {