Fix #72482: Ilegal write/read access caused by gdImageAALine overflow

Instead of rolling our own bounds check we use clip_1d() as it's done
in gdImageLine() and in external libgd. We must not pass the image
width and height, respectively, but rather the largest ordinate value
that is allowed to be accessed, i.e. width-1 and height-1,
respectively.

4 files changed, 43 insertions, 48 deletions

diff --git a/ext/gd/libgd/gd.c b/ext/gd/libgd/gd.c
index 033d4fa5f0..058f1c9759 100644
--- a/ext/gd/libgd/gd.c
+++ b/ext/gd/libgd/gd.c
@@ -1117,7 +1117,7 @@ void gdImageLine (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
 	}
 
 	/* 2.0.10: Nick Atty: clip to edges of drawing rectangle, return if no points need to be drawn */
-	if (!clip_1d(&x1,&y1,&x2,&y2,gdImageSX(im)) || !clip_1d(&y1,&x1,&y2,&x2,gdImageSY(im))) {
+	if (!clip_1d(&x1,&y1,&x2,&y2,gdImageSX(im)-1) || !clip_1d(&y1,&x1,&y2,&x2,gdImageSY(im)-1)) {
 		return;
 	}
 
@@ -1301,55 +1301,10 @@ void gdImageAALine (gdImagePtr im, int x1, int y1, int x2, int y2, int col)
 	long x, y, inc, frac;
 	long dx, dy,tmp;
 
-	if (y1 < 0 && y2 < 0) {
-		return;
-	}
-	if (y1 < 0) {
-		x1 += (y1 * (x1 - x2)) / (y2 - y1);
-		y1 = 0;
-	}
-	if (y2 < 0) {
-		x2 += (y2 * (x1 - x2)) / (y2 - y1);
-		y2 = 0;
-	}
-
-	/* bottom edge */
-	if (y1 >= im->sy && y2 >= im->sy) {
-		return;
-	}
-	if (y1 >= im->sy) {
-		x1 -= ((im->sy - y1) * (x1 - x2)) / (y2 - y1);
-		y1 = im->sy - 1;
-	}
-	if (y2 >= im->sy) {
-		x2 -= ((im->sy - y2) * (x1 - x2)) / (y2 - y1);
-		y2 = im->sy - 1;
-	}
-
-	/* left edge */
-	if (x1 < 0 && x2 < 0) {
-		return;
-	}
-	if (x1 < 0) {
-		y1 += (x1 * (y1 - y2)) / (x2 - x1);
-		x1 = 0;
-	}
-	if (x2 < 0) {
-		y2 += (x2 * (y1 - y2)) / (x2 - x1);
-		x2 = 0;
-	}
-	/* right edge */
-	if (x1 >= im->sx && x2 >= im->sx) {
+	/* 2.0.10: Nick Atty: clip to edges of drawing rectangle, return if no points need to be drawn */
+	if (!clip_1d(&x1,&y1,&x2,&y2,gdImageSX(im)-1) || !clip_1d(&y1,&x1,&y2,&x2,gdImageSY(im)-1)) {
 		return;
 	}
-	if (x1 >= im->sx) {
-		y1 -= ((im->sx - x1) * (y1 - y2)) / (x2 - x1);
-		x1 = im->sx - 1;
-	}
-	if (x2 >= im->sx) {
-		y2 -= ((im->sx - x2) * (y1 - y2)) / (x2 - x1);
-		x2 = im->sx - 1;
-	}
 
 	dx = x2 - x1;
 	dy = y2 - y1;
diff --git a/ext/gd/tests/bug72482.phpt b/ext/gd/tests/bug72482.phpt
new file mode 100644
index 0000000000..548921d559
--- /dev/null
+++ b/ext/gd/tests/bug72482.phpt
@@ -0,0 +1,19 @@
+--TEST--
+Bug #72482 (Ilegal write/read access caused by gdImageAALine overflow)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+?>
+--FILE--
+<?php
+$img = imagecreatetruecolor(13, 1007);
+imageantialias($img, true);
+imageline($img, 0, 0, 1073745919, 1073745919, 4096);
+
+$img = imagecreatetruecolor(100, 100);
+imageantialias($img, true);
+imageline($img, 1094795585, 0, 2147483647, 255, 0xff);
+?>
+===DONE===
+--EXPECT--
+===DONE===
diff --git a/ext/gd/tests/bug72482_2.phpt b/ext/gd/tests/bug72482_2.phpt
new file mode 100644
index 0000000000..a8a08faa53
--- /dev/null
+++ b/ext/gd/tests/bug72482_2.phpt
@@ -0,0 +1,21 @@
+--TEST--
+Bug 72482 (Ilegal write/read access caused by gdImageAALine overflow)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+?>
+--FILE--
+<?php
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'func.inc';
+
+$im = imagecreatetruecolor(10, 10);
+imagefilledrectangle($im, 0, 0, 9, 9, imagecolorallocate($im, 255, 255, 255));
+imageantialias($im, true);
+imageline($im, 0, 0, 10, 10, imagecolorallocate($im, 0, 0, 0));
+
+test_image_equals_file(__DIR__ . DIRECTORY_SEPARATOR . 'bug72482_2.png', $im);
+?>
+===DONE===
+--EXPECT--
+The images are equal.
+===DONE===
diff --git a/ext/gd/tests/bug72482_2.png b/ext/gd/tests/bug72482_2.png
new file mode 100644
index 0000000000..da90b2a267
--- /dev/null
+++ b/ext/gd/tests/bug72482_2.png