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From 974b6b063b652317f1a2df12834c829415529bc5 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: Tue, 11 Jun 2019 06:28:12 -0700
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Subject: [PATCH 09/11] CVE-2019-7635: Reject BMP images with pixel colors out
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the palette If a 1-, 4-, or 8-bit per pixel BMP image declares less used
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colors than the palette offers an SDL_Surface with a palette of the indicated
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number of used colors is created. If some of the image's pixel refer to a
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color number higher then the maximal used colors, a subsequent bliting
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operation on the surface will look up a color past a blit map (that is based
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on the palette) memory. I.e. passing such SDL_Surface to e.g. an
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SDL_DisplayFormat() function will result in a buffer overread in a blit
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function.
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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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This patch fixes it by validing each pixel's color to be less than the
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maximal color number in the palette. A validation failure raises an
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error from a SDL_LoadBMP_RW() function.
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CVE-2019-7635
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https://bugzilla.libsdl.org/show_bug.cgi?id=4498
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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--HG--
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branch : SDL-1.2
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---
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src/video/SDL_bmp.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/src/video/SDL_bmp.c b/src/video/SDL_bmp.c
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index d56cfd83a..8acae3bcb 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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@@ -296,6 +296,12 @@ SDL_Surface * SDL_LoadBMP_RW (SDL_RWops *src, int freesrc)
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}
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*(bits+i) = (pixel>>shift);
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pixel <<= ExpandBMP;
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+ if ( bits[i] >= biClrUsed ) {
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+ SDL_SetError(
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+ "A BMP image contains a pixel with a color out of the palette");
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+ was_error = SDL_TRUE;
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+ goto done;
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+ }
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} }
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break;
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@@ -306,6 +312,16 @@ SDL_Surface * SDL_LoadBMP_RW (SDL_RWops *src, int freesrc)
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was_error = SDL_TRUE;
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goto done;
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}
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+ if ( 8 == biBitCount && palette && biClrUsed < (1 << biBitCount ) ) {
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+ for ( i=0; i<surface->w; ++i ) {
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+ if ( bits[i] >= biClrUsed ) {
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+ SDL_SetError(
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+ "A BMP image contains a pixel with a color out of the palette");
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+ was_error = SDL_TRUE;
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+ goto done;
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+ }
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+ }
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+ }
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#if SDL_BYTEORDER == SDL_BIG_ENDIAN
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/* Byte-swap the pixels if needed. Note that the 24bpp
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case has already been taken care of above. */
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--
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2.21.0
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