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From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Wed, 29 Nov 2017 19:37:38 +0100
Subject: Fix #420: Potential infinite loop in gdImageCreateFromGifCtx
origin: https://github.com/libgd/libgd/commit/a11f47475e6443b7f32d21f2271f28f417e2ac04
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-5711
Bug-Debian: https://bugs.debian.org/887485
Bug: https://github.com/libgd/libgd/issues/420
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.
---
--- a/src/gd_gif_in.c
+++ b/src/gd_gif_in.c
@@ -335,11 +335,6 @@ terminated:
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 @@ terminated:
}
}
+ 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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