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From a11f47475e6443b7f32d21f2271f28f417e2ac04 Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Wed, 29 Nov 2017 19:37:38 +0100
Subject: [PATCH] Fix #420: Potential infinite loop in gdImageCreateFromGifCtx
Due to a signedness confusion in `GetCode_` a corrupt GIF file can
trigger an infinite loop. Furthermore we make sure that a GIF without
any palette entries is treated as invalid *after* open palette entries
have been removed.
CVE-2018-5711
See also https://bugs.php.net/bug.php?id=75571.
---
src/gd_gif_in.c | 12 ++++++------
tests/gif/.gitignore | 1 +
tests/gif/CMakeLists.txt | 1 +
tests/gif/Makemodule.am | 2 ++
tests/gif/php_bug_75571.c | 28 ++++++++++++++++++++++++++++
tests/gif/php_bug_75571.gif | Bin 0 -> 1731 bytes
6 files changed, 38 insertions(+), 6 deletions(-)
create mode 100644 tests/gif/php_bug_75571.c
create mode 100644 tests/gif/php_bug_75571.gif
diff --git a/src/gd_gif_in.c b/src/gd_gif_in.c
index daf26e79..0a8bd717 100644
--- a/src/gd_gif_in.c
+++ b/src/gd_gif_in.c
@@ -335,11 +335,6 @@ BGD_DECLARE(gdImagePtr) gdImageCreateFromGifCtx(gdIOCtxPtr fd)
return 0;
}
- if(!im->colorsTotal) {
- gdImageDestroy(im);
- return 0;
- }
-
/* Check for open colors at the end, so
* we can reduce colorsTotal and ultimately
* BitsPerPixel */
@@ -351,6 +346,11 @@ BGD_DECLARE(gdImagePtr) gdImageCreateFromGifCtx(gdIOCtxPtr fd)
}
}
+ if(!im->colorsTotal) {
+ gdImageDestroy(im);
+ return 0;
+ }
+
return im;
}
@@ -447,7 +447,7 @@ static int
GetCode_(gdIOCtx *fd, CODE_STATIC_DATA *scd, int code_size, int flag, int *ZeroDataBlockP)
{
int i, j, ret;
- unsigned char count;
+ int count;
if(flag) {
scd->curbit = 0;
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