[libpng17] Added private png_check_chunk_name() and png_check_chunk_length()

functions.

ANNOUNCE

diff --git a/ANNOUNCE b/ANNOUNCE
index 4bd99f5..1b8bc19 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.7.0beta88 - April 1, 2017
+Libpng 1.7.0beta88 - August 6, 2017
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -1431,7 +1431,9 @@
     makefile.linux and makefile.solaris-x86 (Cosmin).
   Merged some recent changes from libpng-1.6.30beta01.
 
-Version 1.7.0beta88 [April 1, 2017]
+Version 1.7.0beta88 [August 6, 2017]
+  Added private png_check_chunk_name() and png_check_chunk_length()
+    functions.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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CHANGES

diff --git a/CHANGES b/CHANGES
index 0d196c7..4538d00 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5731,7 +5731,10 @@
     makefile.linux and makefile.solaris-x86 (Cosmin).
   Merged some recent changes from libpng-1.6.30beta01.
 
-Version 1.7.0beta88 [April 1, 2017]
+Version 1.7.0beta88 [August 6, 2017]
+  Initialized btoa[] in pngstest.c
+  Added private png_check_chunk_name() and png_check_chunk_length()
+    functions.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

pngpread.c

diff --git a/pngpread.c b/pngpread.c
index 3d25a43..c7e5425 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -743,6 +743,8 @@
    png_ptr->chunk_length = png_get_uint_31(png_ptr, chunk_header);
    png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_header+4);
    png_reset_crc(png_ptr, chunk_header+4);
+   png_check_chunk_name(png_ptr, png_ptr->chunk_name);
+   png_check_chunk_length(png_ptr, png_ptr->chunk_length);
    mode = png_ptr->mode;
    png_ptr->process_mode = png_check_bits(png_ptr,
       png_read_chunk+png_find_chunk_op(png_ptr), 4);

pngpriv.h

diff --git a/pngpriv.h b/pngpriv.h
index c0f2951..a322fae 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1737,6 +1737,12 @@
     * read state.
     */
 
+PNG_INTERNAL_FUNCTION(void,png_check_chunk_name,(png_const_structrp png_ptr,
+    const png_uint_32 chunk_name),PNG_EMPTY);
+
+PNG_INTERNAL_FUNCTION(void,png_check_chunk_length,(png_const_structrp png_ptr,
+    const png_uint_32 chunk_length),PNG_EMPTY);
+
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
 PNG_INTERNAL_FUNCTION(void,png_handle_unknown,(png_structrp png_ptr,
    png_inforp info_ptr, png_bytep chunk_data),PNG_EMPTY);

pngrutil.c

diff --git a/pngrutil.c b/pngrutil.c
index 2da883e..0d41e71 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -2,7 +2,7 @@
 /* pngrutil.c - utilities to read a PNG file
  *
  * Last changed in libpng 1.7.0 [(PENDING RELEASE)]
- * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -2198,6 +2198,9 @@
    }
 #endif /* USER_LIMITS */
 
+   /* Note, "length" is sufficient here; we won't be adding
+    * a null terminator later.
+    */
    buffer = png_read_buffer(png_ptr, length, 2/*silent*/);
 
    if (buffer == NULL)
@@ -2623,24 +2626,61 @@
  * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
  */
 
-static void
-png_check_chunk_name(png_structrp png_ptr, png_uint_32 chunk_name)
+void /* PRIVATE */
+png_check_chunk_name(png_const_structrp png_ptr, const png_uint_32 chunk_name)
 {
    int i;
+   png_uint_32 cn=chunk_name;
 
    png_debug(1, "in png_check_chunk_name");
 
    for (i=1; i<=4; ++i)
    {
-      int c = chunk_name & 0xff;
+      int c = cn & 0xff;
 
-      /* This is unrecoverable at present because it most likely indicates
-       * a broken stream.
-       */
       if (c < 65 || c > 122 || (c > 90 && c < 97))
          png_chunk_error(png_ptr, "invalid chunk type");
 
-      chunk_name >>= 8;
+      cn >>= 8;
+   }
+}
+void /* PRIVATE */
+png_check_chunk_length(png_const_structrp png_ptr, const png_uint_32 length)
+{
+   png_alloc_size_t limit = PNG_UINT_31_MAX;
+
+   if (png_ptr->chunk_name != png_IDAT)
+   {
+# ifdef PNG_SET_USER_LIMITS_SUPPORTED
+      if (png_ptr->user_chunk_malloc_max > 0 &&
+          png_ptr->user_chunk_malloc_max < limit)
+         limit = png_ptr->user_chunk_malloc_max;
+# elif PNG_USER_CHUNK_MALLOC_MAX > 0
+      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+         limit = PNG_USER_CHUNK_MALLOC_MAX;
+# endif
+   }
+   else
+   {
+      /* color_type   0 x 2 3 4 x 6 */
+      int channels[]={1,0,3,1,2,0,4};
+      size_t row_factor =
+         (png_ptr->width * channels[png_ptr->color_type] *
+             (png_ptr->bit_depth > 8? 2: 1)
+          + 1 + (png_ptr->interlaced? 6: 0));
+      if (png_ptr->height > PNG_UINT_32_MAX/row_factor)
+         limit=PNG_UINT_31_MAX;
+      else
+         limit = png_ptr->height * row_factor;
+      limit += 6 + 5*(limit/32566+1); /* zlib+deflate overhead */
+      limit=limit < PNG_UINT_31_MAX? limit : PNG_UINT_31_MAX;
+   }
+
+   if (length > limit)
+   {
+      png_debug2(0," length = %lu, limit = %lu",
+         (unsigned long)length,(unsigned long)limit);
+      png_chunk_error(png_ptr, "chunk data is too large");
    }
 }