From 81f44665cce4cb1373f049a76f3904e981b7a766 Mon Sep 17 00:00:00 2001
From: Glenn Randers-Pehrson <glennrp at users.sourceforge.net>
Date: Thu, 29 Oct 2015 09:26:41 -0500
Subject: [PATCH] [libpng16] Reject attempt to write over-length PLTE chunk

Upstream-Status: Backport
https://github.com/glennrp/libpng/commit/81f44665cce4cb1373f049a76f3904e981b7a766

CVE: CVE-2015-8126 patch #1

Signed-off-by: Armin Kuster <akuster@mvista.com>
Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>

diff -ruN a/libpng.3 b/libpng.3
--- a/libpng.3	2014-08-21 12:53:36.000000000 +0200
+++ b/libpng.3	2016-03-14 12:32:29.071935164 +0100
@@ -5611,6 +5611,11 @@
 chunk.  This error was fixed in libpng-1.6.3, and a tool (called
 contrib/tools/png-fix-itxt) has been added to the libpng distribution.
 
+Starting with libpng-1.6.19, attempting to write an over-length PLTE chunk
+is an error. Previously this requirement of the PNG specification was not
+enforced. Libpng continues to accept over-length PLTE chunks when reading,
+but does not make any use of the extra entries.
+
 .SH XIII.  Detecting libpng
 
 The png_get_io_ptr() function has been present since libpng-0.88, has never
diff -ruN a/libpng-manual.txt b/libpng-manual.txt
--- a/libpng-manual.txt	2014-08-21 12:53:36.000000000 +0200
+++ b/libpng-manual.txt	2016-03-14 12:32:29.067935336 +0100
@@ -5107,6 +5107,11 @@
 chunk.  This error was fixed in libpng-1.6.3, and a tool (called
 contrib/tools/png-fix-itxt) has been added to the libpng distribution.
 
+Starting with libpng-1.6.19, attempting to write an over-length PLTE chunk
+is an error. Previously this requirement of the PNG specification was not
+enforced. Libpng continues to accept over-length PLTE chunks when reading,
+but does not make any use of the extra entries.
+
 XIII.  Detecting libpng
 
 The png_get_io_ptr() function has been present since libpng-0.88, has never
diff -ruN a/pngwutil.c b/pngwutil.c
--- a/pngwutil.c	2014-08-21 12:53:37.000000000 +0200
+++ b/pngwutil.c	2016-03-14 12:35:00.001454124 +0100
@@ -919,17 +919,20 @@
 png_write_PLTE(png_structrp png_ptr, png_const_colorp palette,
     png_uint_32 num_pal)
 {
-   png_uint_32 i;
+   png_uint_32 max_num_pal, i;
    png_const_colorp pal_ptr;
    png_byte buf[3];
 
    png_debug(1, "in png_write_PLTE");
 
+   max_num_pal = (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
+      (1 << png_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
+
    if ((
 #ifdef PNG_MNG_FEATURES_SUPPORTED
        !(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) &&
 #endif
-       num_pal == 0) || num_pal > 256)
+       num_pal == 0) || num_pal > max_num_pal)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {