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