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From 797226335ec47573f80e84d0fbdf1536292868d0 Mon Sep 17 00:00:00 2001
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From: Jan Wielemaker <J.Wielemaker@cs.vu.nl>
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Date: Wed, 24 Aug 2011 14:08:17 +0200
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Subject: [PATCH 1/2] SECURITY: Bug#9: Loading incomplete GIF files causes an
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invalid read. Petr Pisar.
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An incomplete image file causes part of the pixels to be uninitialised.
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As the pixels are entries in a colormap, this causes invalid reads.
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---
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src/img/gifread.c | 19 ++++++++++++-------
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1 files changed, 12 insertions(+), 7 deletions(-)
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diff --git a/src/img/gifread.c b/src/img/gifread.c
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index 0e24e27..9c35f63 100644
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--- a/src/img/gifread.c
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+++ b/src/img/gifread.c
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@@ -553,7 +553,9 @@ ReadImage(IOSTREAM *fd,
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UCHAR c;
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int color;
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int xpos = 0, ypos = 0, pass = 0;
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+ int lines = 0;
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long curidx;
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+ int last;
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if ( !ReadOK(fd, &c, 1) || c > MAX_LZW_BITS )
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{ return GIF_INVALID;
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@@ -606,20 +608,23 @@ ReadImage(IOSTREAM *fd,
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}
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}
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} else
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- {
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- ++ypos;
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+ { ++ypos;
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}
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+ ++lines;
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}
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if (ypos >= height)
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- break;
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+ goto fini;
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}
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+ return GIF_INVALID; /* short file */
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fini:
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+ if ( lines != height )
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+ return GIF_INVALID;
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- if (LZWReadByte(fd, FALSE, c) >= 0)
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- {
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+ if ( (last=LZWReadByte(fd, FALSE, c)) >= 0 )
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+ { return GIF_OK; /* end is 0x3B, but we only read the */
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+ } /* first image of animated GIFs */
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- }
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- return GIF_OK;
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+ return GIF_INVALID;
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}
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--
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1.7.6
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