File libpng12-CVE-2015-8126.patch of Package libpng12.3388

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
Index: pngwutil.c
===================================================================
--- pngwutil.c.orig	2015-11-16 14:39:45.517740820 +0100
+++ pngwutil.c	2015-11-16 14:46:45.926414642 +0100
@@ -575,17 +575,20 @@
 #ifdef PNG_USE_LOCAL_ARRAYS
    PNG_PLTE;
 #endif
-   png_uint_32 i;
+   png_uint_32 max_palette_length, i;
    png_colorp pal_ptr;
    png_byte buf[3];
 
    png_debug(1, "in png_write_PLTE");
 
+   max_palette_length = (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_palette_length)
    {
      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
Index: pngrutil.c
===================================================================
--- pngrutil.c.orig	2014-02-06 04:52:35.000000000 +0100
+++ pngrutil.c	2015-11-16 14:39:45.518740834 +0100
@@ -503,7 +503,7 @@
 png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
    png_color palette[PNG_MAX_PALETTE_LENGTH];
-   int num, i;
+   int max_palette_length, num, i;
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    png_colorp pal_ptr;
 #endif
@@ -557,6 +557,19 @@
 
    num = (int)length / 3;
 
+   /* If the palette has 256 or fewer entries but is too large for the bit
+    * depth, we don't issue an error, to preserve the behavior of previous
+    * libpng versions. We silently truncate the unused extra palette entries
+    * here.
+    */
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      max_palette_length = (1 << png_ptr->bit_depth);
+   else
+      max_palette_length = PNG_MAX_PALETTE_LENGTH;
+
+   if (num > max_palette_length)
+      num = max_palette_length;
+
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
    {
Index: pngset.c
===================================================================
--- pngset.c.orig	2015-11-16 14:39:45.509740712 +0100
+++ pngset.c	2015-11-16 14:39:45.518740834 +0100
@@ -446,12 +446,17 @@
    png_colorp palette, int num_palette)
 {
 
+   png_uint_32 max_palette_length;
+
    png_debug1(1, "in %s storage function", "PLTE");
 
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 
-   if (num_palette < 0 || num_palette > PNG_MAX_PALETTE_LENGTH)
+   max_palette_length = (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
+      (1 << png_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
+
+   if (num_palette < 0 || num_palette > (int) max_palette_length)
    {
       if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
          png_error(png_ptr, "Invalid palette length");