From 25f99f92536fe2c7bf8e1a7fe12f0145c67a0383 Mon Sep 17 00:00:00 2001
From: Thomas Bernard <miniupnp@free.fr>
Date: Mon, 11 Feb 2019 23:08:25 +0100
Subject: [PATCH] (CVE-2020-19131) tiffcrop.c: fix invertImage() for bps 2 and
 4

too much bytes were processed, causing a heap buffer overrun
    http://bugzilla.maptools.org/show_bug.cgi?id=2831
the loop counter must be
    for (col = 0; col < width; col += 8 / bps)

Also the values were not properly calculated. It should be
255-x, 15-x, 3-x for bps 8, 4, 2.

But anyway it is easyer to invert all bits as 255-x = ~x, etc.
(substracting from a binary number composed of all 1 is like inverting
the bits)

(cherry picked from commit 9cfa5c469109c207bf3b916c52e618d4400ba2c0)
---
 tools/tiffcrop.c | 37 ++++++-------------------------------
 1 file changed, 6 insertions(+), 31 deletions(-)

diff --git a/tools/tiffcrop.c b/tools/tiffcrop.c
index 3862b1ca..a6129148 100644
--- a/tools/tiffcrop.c
+++ b/tools/tiffcrop.c
@@ -9142,7 +9142,6 @@ static int
 invertImage(uint16 photometric, uint16 spp, uint16 bps, uint32 width, uint32 length, unsigned char *work_buff)
   {
   uint32   row, col;
-  unsigned char  bytebuff1, bytebuff2, bytebuff3, bytebuff4;
   unsigned char *src;
   uint16        *src_uint16;
   uint32        *src_uint32;
@@ -9172,7 +9171,7 @@ invertImage(uint16 photometric, uint16 spp, uint16 bps, uint32 width, uint32 len
              for (row = 0; row < length; row++)
                for (col = 0; col < width; col++)
                  {
-		 *src_uint32 = (uint32)0xFFFFFFFF - *src_uint32;
+		 *src_uint32 = ~(*src_uint32);
                   src_uint32++;
                  }
             break;
@@ -9180,39 +9179,15 @@ invertImage(uint16 photometric, uint16 spp, uint16 bps, uint32 width, uint32 len
              for (row = 0; row < length; row++)
                for (col = 0; col < width; col++)
                  {
-		 *src_uint16 = (uint16)0xFFFF - *src_uint16;
+		 *src_uint16 = ~(*src_uint16);
                   src_uint16++;
                  }
             break;
-    case 8: for (row = 0; row < length; row++)
-              for (col = 0; col < width; col++)
-                {
-		*src = (uint8)255 - *src;
-                 src++;
-                }
-            break;
-    case 4: for (row = 0; row < length; row++)
-              for (col = 0; col < width; col++)
-                {
-		bytebuff1 = 16 - (uint8)(*src & 240 >> 4);
-		bytebuff2 = 16 - (*src & 15);
-		*src = bytebuff1 << 4 & bytebuff2;
-                src++;
-                }
-            break;
-    case 2: for (row = 0; row < length; row++)
-              for (col = 0; col < width; col++)
-                {
-		bytebuff1 = 4 - (uint8)(*src & 192 >> 6);
-		bytebuff2 = 4 - (uint8)(*src & 48  >> 4);
-		bytebuff3 = 4 - (uint8)(*src & 12  >> 2);
-		bytebuff4 = 4 - (uint8)(*src & 3);
-		*src = (bytebuff1 << 6) || (bytebuff2 << 4) || (bytebuff3 << 2) || bytebuff4;
-                src++;
-                }
-            break;
+    case 8:
+    case 4:
+    case 2:
     case 1: for (row = 0; row < length; row++)
-              for (col = 0; col < width; col += 8 /(spp * bps))
+              for (col = 0; col < width; col += 8 / bps)
                 {
                 *src = ~(*src);
                 src++;