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Created Dec 30, 2018

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Fix PHP bug #77270
From 23d0a0bc3c0b858e5b491373e59b7c3e5c7d7ed5 Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Sun, 30 Dec 2018 13:59:26 +0100
Subject: [PATCH] Fix #77270: 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()`.
---
ext/gd/libgd/gd_color_match.c | 4 ++--
ext/gd/tests/bug77270.phpt | 18 ++++++++++++++++++
2 files changed, 20 insertions(+), 2 deletions(-)
create mode 100644 ext/gd/tests/bug77270.phpt
diff --git a/ext/gd/libgd/gd_color_match.c b/ext/gd/libgd/gd_color_match.c
index a4e56b1c40..e6f539bc75 100644
--- a/ext/gd/libgd/gd_color_match.c
+++ b/ext/gd/libgd/gd_color_match.c
@@ -33,8 +33,8 @@ int gdImageColorMatch (gdImagePtr im1, gdImagePtr im2)
return -4; /* At least 1 color must be allocated */
}
- buf = (unsigned long *)safe_emalloc(sizeof(unsigned long), 5 * im2->colorsTotal, 0);
- memset( buf, 0, sizeof(unsigned long) * 5 * im2->colorsTotal );
+ buf = (unsigned long *)safe_emalloc(sizeof(unsigned long), 5 * gdMaxColors, 0);
+ 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/ext/gd/tests/bug77270.phpt b/ext/gd/tests/bug77270.phpt
new file mode 100644
index 0000000000..1c4555a64d
--- /dev/null
+++ b/ext/gd/tests/bug77270.phpt
@@ -0,0 +1,18 @@
+--TEST--
+Bug #77270 (imagecolormatch Out Of Bounds Write on Heap)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+if (!GD_BUNDLED && version_compare(GD_VERSION, '2.2.5', '<=')) die('skip upstream bugfix has not been released');
+?>
+--FILE--
+<?php
+$img1 = imagecreatetruecolor(0xfff, 0xfff);
+$img2 = imagecreate(0xfff, 0xfff);
+imagecolorallocate($img2, 0, 0, 0);
+imagesetpixel($img2, 0, 0, 255);
+imagecolormatch($img1, $img2);
+?>
+===DONE===
+--EXPECT--
+===DONE===
--
2.17.0.windows.1
@setharnold

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commented Jan 30, 2019

Is there code to prevent sizeof(unsigned long) * 5 * gdMaxColors from overflowing?

Thanks

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