From 974b6b063b652317f1a2df12834c829415529bc5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Tue, 11 Jun 2019 06:28:12 -0700
Subject: [PATCH 09/11] CVE-2019-7635: Reject BMP images with pixel colors out
the palette 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.
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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>
--HG--
branch : SDL-1.2
---
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 d56cfd83a..8acae3bcb 100644
--- a/src/video/SDL_bmp.c
+++ b/src/video/SDL_bmp.c
@@ -296,6 +296,12 @@ 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;
@@ -306,6 +312,16 @@ 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. */
--
2.21.0