Fix heap-based buffer overflow in combineSeparateSamples16bits():

http://bugzilla.maptools.org/show_bug.cgi?id=2621

2016-12-03 Even Rouault <even.rouault at spatialys.com>

        * tools/tiffcrop.c: add 3 extra bytes at end of strip buffer in
        readSeparateStripsIntoBuffer() to avoid read outside of heap allocated
buffer.
        Reported by Agostina Sarubo.
        Fixes http://bugzilla.maptools.org/show_bug.cgi?id=2621

/cvs/maptools/cvsroot/libtiff/ChangeLog,v  <--  ChangeLog
new revision: 1.1179; previous revision: 1.1178
/cvs/maptools/cvsroot/libtiff/tools/tiffcrop.c,v  <--  tools/tiffcrop.c
new revision: 1.48; previous revision: 1.47

Index: libtiff/tools/tiffcrop.c
===================================================================
RCS file: /cvs/maptools/cvsroot/libtiff/tools/tiffcrop.c,v
retrieving revision 1.47
retrieving revision 1.48
diff -u -r1.47 -r1.48
--- libtiff/tools/tiffcrop.c	3 Dec 2016 11:35:56 -0000	1.47
+++ libtiff/tools/tiffcrop.c	3 Dec 2016 12:19:32 -0000	1.48
@@ -1,4 +1,4 @@
-/* $Id: tiffcrop.c,v 1.47 2016-12-03 11:35:56 erouault Exp $ */
+/* $Id: tiffcrop.c,v 1.48 2016-12-03 12:19:32 erouault Exp $ */
 
 /* tiffcrop.c -- a port of tiffcp.c extended to include manipulations of
  * the image data through additional options listed below
@@ -4815,10 +4815,17 @@
   nstrips = TIFFNumberOfStrips(in);
   strips_per_sample = nstrips /spp;
 
+  /* Add 3 padding bytes for combineSeparateSamples32bits */
+  if( (size_t) stripsize > 0xFFFFFFFFU - 3U )
+  {
+      TIFFError("readSeparateStripsIntoBuffer", "Integer overflow when calculating buffer size.");
+      exit(-1);
+  }
+
   for (s = 0; (s < spp) && (s < MAX_SAMPLES); s++)
     {
     srcbuffs[s] = NULL;
-    buff = _TIFFmalloc(stripsize);
+    buff = _TIFFmalloc(stripsize + 3);
     if (!buff)
       {
       TIFFError ("readSeparateStripsIntoBuffer", 
@@ -4827,6 +4834,9 @@
         _TIFFfree (srcbuffs[i]);
       return 0;
       }
+    buff[stripsize] = 0;
+    buff[stripsize+1] = 0;
+    buff[stripsize+2] = 0;
     srcbuffs[s] = buff;
     }