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From beef32b0e510371f3c968d22a1e3d48abbf366c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Tue, 19 Feb 2019 14:52:52 +0100
Subject: [PATCH] CVE-2019-7635: Reject BMP images with pixel colors out the
palette
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
If a 1-, 4-, or 8-bit per pixel BMP image declares less used colors
than the palette offers an SDL_Surface with a palette of the indicated
number of used colors is created. If some of the image's pixel
refer to a color number higher then the maximal used colors, a subsequent
bliting operation on the surface will look up a color past a blit map
(that is based on the palette) memory. I.e. passing such SDL_Surface
to e.g. an SDL_DisplayFormat() function will result in a buffer overread in
a blit function.
This patch fixes it by validing each pixel's color to be less than the
maximal color number in the palette. A validation failure raises an
error from a SDL_LoadBMP_RW() function.
CVE-2019-7635
https://bugzilla.libsdl.org/show_bug.cgi?id=4498
Signed-off-by: Petr Písař <ppisar@redhat.com>
---
src/video/SDL_bmp.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/src/video/SDL_bmp.c b/src/video/SDL_bmp.c
index 3accded..8eadc5f 100644
--- a/src/video/SDL_bmp.c
+++ b/src/video/SDL_bmp.c
@@ -300,6 +300,12 @@ SDL_Surface * SDL_LoadBMP_RW (SDL_RWops *src, int freesrc)
}
*(bits+i) = (pixel>>shift);
pixel <<= ExpandBMP;
+ if ( bits[i] >= biClrUsed ) {
+ SDL_SetError(
+ "A BMP image contains a pixel with a color out of the palette");
+ was_error = SDL_TRUE;
+ goto done;
+ }
} }
break;
@@ -310,6 +316,16 @@ SDL_Surface * SDL_LoadBMP_RW (SDL_RWops *src, int freesrc)
was_error = SDL_TRUE;
goto done;
}
+ if ( 8 == biBitCount && palette && biClrUsed < (1 << biBitCount ) ) {
+ for ( i=0; i<surface->w; ++i ) {
+ if ( bits[i] >= biClrUsed ) {
+ SDL_SetError(
+ "A BMP image contains a pixel with a color out of the palette");
+ was_error = SDL_TRUE;
+ goto done;
+ }
+ }
+ }
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
/* Byte-swap the pixels if needed. Note that the 24bpp
case has already been taken care of above. */
--
2.20.1
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