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From 28b1433b4bd7982524f2418420e8cc01786df5c4 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
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Date: Fri, 15 Feb 2019 16:52:27 +0100
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Subject: [PATCH] CVE-2019-7638, CVE-2019-7636: Refuse loading BMP images with
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too high number of colors
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If a BMP file that defines more colors than can fit into
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a palette of color depth defined in the same BMP file is loaded by
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SDL_LoadBMP_RW() function, invalid number of colors is set into
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resulting SDL surface.
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Then if the SDL surface is passed to SDL_DisplayFormat() function to
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convert the surface format into a native video format, a buffer
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overread will happen in Map1to1() or Map1toN() function
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(CVE-2019-7638). (The choice of the mapping function depends on
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a actual video hardware.)
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In addition SDL_GetRGB() called indirectly from SDL_DisplayFormat()
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performs the same buffer overread (CVE-2019-7636).
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There is also probably a buffer overwrite when the SDL_LoadBMP_RW()
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loads colors from a file.
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This patch fixes it by refusing loading such badly damaged BMP files.
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CVE-2019-7638
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https://bugzilla.libsdl.org/show_bug.cgi?id=4500
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CVE-2019-7636
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https://bugzilla.libsdl.org/show_bug.cgi?id=4499
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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src/video/SDL_bmp.c | 4 ++++
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1 file changed, 4 insertions(+)
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diff --git a/src/video/SDL_bmp.c b/src/video/SDL_bmp.c
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index d56cfd8..3accded 100644
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--- a/src/video/SDL_bmp.c
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+++ b/src/video/SDL_bmp.c
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@@ -233,6 +233,10 @@ SDL_Surface * SDL_LoadBMP_RW (SDL_RWops *src, int freesrc)
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if ( palette ) {
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if ( biClrUsed == 0 ) {
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biClrUsed = 1 << biBitCount;
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+ } else if ( biClrUsed > (1 << biBitCount) ) {
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+ SDL_SetError("BMP file has an invalid number of colors");
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+ was_error = SDL_TRUE;
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+ goto done;
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}
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if ( biSize == 12 ) {
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for ( i = 0; i < (int)biClrUsed; ++i ) {
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--
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2.20.1
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