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gifdec,Remap: avoid out of bounds colormap read

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make this function return success/failure.
an empty map or out of bounds read is treated as an error.

BUG=webp:316

Change-Id: Ic8651836915ea4dd8e0dc81ca8d5d3f247be1ff8
This commit is contained in:
James Zern 2016-11-01 21:30:13 -07:00
parent 4595e01fd0
commit cac9a36a23
1 changed files with 15 additions and 8 deletions
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23
examples/gifdec.c
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@ -81,20 +81,27 @@ int GIFReadGraphicsExtension(const GifByteType* const buf, int* const duration,
return 1;
}
static void Remap(const GifFileType* const gif, const uint8_t* const src,
int len, int transparent_index, uint32_t* dst) {
static int Remap(const GifFileType* const gif, const uint8_t* const src,
int len, int transparent_index, uint32_t* dst) {
int i;
const GifColorType* colors;
const ColorMapObject* const cmap =
gif->Image.ColorMap ? gif->Image.ColorMap : gif->SColorMap;
if (cmap == NULL) return;
if (cmap == NULL) return 1;
if (cmap->Colors == NULL || cmap->ColorCount <= 0) return 0;
colors = cmap->Colors;
for (i = 0; i < len; ++i) {
const GifColorType c = colors[src[i]];
dst[i] = (src[i] == transparent_index) ? GIF_TRANSPARENT_COLOR
: c.Blue | (c.Green << 8) | (c.Red << 16) | (0xffu << 24);
if (src[i] == transparent_index) {
dst[i] = GIF_TRANSPARENT_COLOR;
} else if (src[i] < cmap->ColorCount) {
const GifColorType c = colors[src[i]];
dst[i] = c.Blue | (c.Green << 8) | (c.Red << 16) | (0xffu << 24);
} else {
return 0;
}
}
return 1;
}
int GIFReadFrame(GifFileType* const gif, int transparent_index,
@ -139,7 +146,7 @@ int GIFReadFrame(GifFileType* const gif, int transparent_index,
const size_t jump = interlace_jumps[pass] * stride;
for (; y < rect.height; y += interlace_jumps[pass], row += jump) {
if (DGifGetLine(gif, tmp, rect.width) == GIF_ERROR) goto End;
Remap(gif, tmp, rect.width, transparent_index, row);
if (!Remap(gif, tmp, rect.width, transparent_index, row)) goto End;
}
}
} else { // Non-interlaced image.
@ -147,7 +154,7 @@ int GIFReadFrame(GifFileType* const gif, int transparent_index,
uint32_t* ptr = dst;
for (y = 0; y < rect.height; ++y, ptr += sub_image.argb_stride) {
if (DGifGetLine(gif, tmp, rect.width) == GIF_ERROR) goto End;
Remap(gif, tmp, rect.width, transparent_index, ptr);
if (!Remap(gif, tmp, rect.width, transparent_index, ptr)) goto End;
}
}
ok = 1;