From 5b026e3cc05d7041cbe47a8702f1b51ffbf0a99b Mon Sep 17 00:00:00 2001
From: Ondrej Dubaj <odubaj@redhat.com>
Date: Thu, 5 Mar 2020 11:02:27 +0100
Subject: [PATCH] Imagecolormatch Out Of Bounds Write on Heap

At least some of the image reading functions may return images which
use color indexes greater than or equal to im->colorsTotal.  We cater
to this by always using a buffer size which is sufficient for
`gdMaxColors` in `gdImageColorMatch()`.

Resolves: #1678104
Version: 2.2.5-7
---
 src/gd_color_match.c                    |  4 ++--
 tests/CMakeLists.txt                    |  1 +
 tests/Makefile.am                       |  1 +
 tests/gdimagecolormatch/CMakeLists.txt  |  5 +++++
 tests/gdimagecolormatch/Makemodule.am   |  5 +++++
 tests/gdimagecolormatch/cve_2019_6977.c | 25 +++++++++++++++++++++++++
 6 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 tests/gdimagecolormatch/CMakeLists.txt
 create mode 100644 tests/gdimagecolormatch/Makemodule.am
 create mode 100644 tests/gdimagecolormatch/cve_2019_6977.c

diff --git a/src/gd_color_match.c b/src/gd_color_match.c
index f0842b6..a94a841 100755
--- a/src/gd_color_match.c
+++ b/src/gd_color_match.c
@@ -31,8 +31,8 @@ BGD_DECLARE(int) gdImageColorMatch (gdImagePtr im1, gdImagePtr im2)
 		return -4; /* At least 1 color must be allocated */
 	}
 
-	buf = (unsigned long *)gdMalloc(sizeof(unsigned long) * 5 * im2->colorsTotal);
-	memset (buf, 0, sizeof(unsigned long) * 5 * im2->colorsTotal );
+	buf = (unsigned long *)gdMalloc(sizeof(unsigned long) * 5 * gdMaxColors);
+	memset (buf, 0, sizeof(unsigned long) * 5 * gdMaxColors );
 
 	for (x=0; x < im1->sx; x++) {
 		for( y=0; y<im1->sy; y++ ) {
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 7eef4bf..6979416 100755
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -31,6 +31,7 @@ if (BUILD_TEST)
 		gdimagecolordeallocate
 		gdimagecolorexact
 		gdimagecolorreplace
+		gdimagecolormatch
 		gdimagecolorresolve
 		gdimagecolortransparent
 		gdimagecontrast
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 5f8b624..1a44112 100755
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -26,6 +26,7 @@ include gdimagecolorclosest/Makemodule.am
 include gdimagecolordeallocate/Makemodule.am
 include gdimagecolorexact/Makemodule.am
 include gdimagecolorreplace/Makemodule.am
+include gdimagecolormatch/Makemodule.am
 include gdimagecolorresolve/Makemodule.am
 include gdimagecolortransparent/Makemodule.am
 include gdimagecontrast/Makemodule.am
diff --git a/tests/gdimagecolormatch/CMakeLists.txt b/tests/gdimagecolormatch/CMakeLists.txt
new file mode 100644
index 0000000..591938f
--- /dev/null
+++ b/tests/gdimagecolormatch/CMakeLists.txt
@@ -0,0 +1,5 @@
+LIST(APPEND TESTS_FILES
+	cve_2019_6977
+)
+
+ADD_GD_TESTS()
diff --git a/tests/gdimagecolormatch/Makemodule.am b/tests/gdimagecolormatch/Makemodule.am
new file mode 100644
index 0000000..e8e09a9
--- /dev/null
+++ b/tests/gdimagecolormatch/Makemodule.am
@@ -0,0 +1,5 @@
+libgd_test_programs += \
+	gdimagecolormatch/cve_2019_6977
+
+EXTRA_DIST += \
+	gdimagecolormatch/CMakeLists.txt
diff --git a/tests/gdimagecolormatch/cve_2019_6977.c b/tests/gdimagecolormatch/cve_2019_6977.c
new file mode 100644
index 0000000..fdd7af5
--- /dev/null
+++ b/tests/gdimagecolormatch/cve_2019_6977.c
@@ -0,0 +1,25 @@
+/**
+ * Test for CVE-2019-6977
+ */
+
+#include "gd.h"
+
+int main()
+{
+	gdImagePtr im1;
+	gdImagePtr im2;
+
+	im1 = gdImageCreateTrueColor(0xfff, 0xfff);
+	im2 = gdImageCreate(0xfff, 0xfff);
+	if (gdImageColorAllocate(im2, 0, 0, 0) < 0)
+	{
+		gdImageDestroy(im1);
+		gdImageDestroy(im2);
+		return 1;
+	}
+	gdImageSetPixel(im2, 0, 0, 255);
+	gdImageColorMatch(im1, im2);
+	gdImageDestroy(im1);
+	gdImageDestroy(im2);
+	return 0;
+}
-- 
2.24.1