fix(jpeg2000): reject corrupt component geometry and subsampling#5270
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lgritz wants to merge 1 commit into
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fix(jpeg2000): reject corrupt component geometry and subsampling#5270lgritz wants to merge 1 commit into
lgritz wants to merge 1 commit into
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…canline A fuzzed JPEG2000 caused a heap-buffer-overflow (caught by ASan) under `iinfo -stats`: copy_scanline read past the end of openjpeg's decoded component buffer. Root cause: the file's image canvas is 32x32, but one of its three components reports a horizontal subsampling factor dx=249 (a step larger than the entire image). OIIO derives the ImageSpec size from the union of each component's x0+w*dx / y0+h*dy window, so that bogus component inflated the spec to 249x32. copy_scanline then iterated x over the inflated width while indexing a component whose data array only held 1 column, walking off the end. The per-sample guard was also broken: it compared the component row index against reference-grid offsets (wrong units) and used `>` instead of `>=` on the column. Two fixes: 1. Detect the corruption at open(): the JPEG2000 canvas (x1-x0, y1-y0) is the authoritative image size, and a component's subsampling factor must be nonzero and no larger than the canvas. Reject files that violate this instead of decoding a nonsensical, inflated image. 2. Harden copy_scanline as defense in depth: bounds-check each access against the actual component array geometry -- row in [0, comp.h) and column in [0, comp.w) -- and skip the channel (zero-fill) when comp.data is null or a subsampling factor is zero, which also closes a latent divide-by-zero on comp.dx/comp.dy. Verified that the openjpeg conformance suite (jpeg2000-j2kp4files), which includes chroma-subsampled images, still decodes correctly. Assisted-by: Claude Code / Claude Opus 4.8 Signed-off-by: Larry Gritz <lg@larrygritz.com>
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A fuzzed JPEG2000 caused a heap-buffer-overflow (caught by ASan) when copy_scanline read past the end of openjpeg's decoded component buffer. The file's image canvas was 32x32, but one of its three components had a horizontal subsampling factor dx=249 (larger than the entire image). OIIO derives the ImageSpec size from the union of each component's x0+wdx / y0+hdy window, so that bogus component inflated the spec to 249x32. copy_scanline then iterated x over the inflated width while indexing a component whose data array only held 1 column, walking off the end. The per-sample guard was also broken: it compared the component row index against reference-grid offsets (wrong units) and used
>instead of>=on the column.Two fixes:
Detect the corruption at open(): the JPEG2000 canvas (x1-x0, y1-y0) is the authoritative image size, and a component's subsampling factor must be nonzero and no larger than the canvas. Reject files that violate this instead of decoding a nonsensical, inflated image.
Harden copy_scanline by bounds-checking each access against the actual component array geometry and skip the channel (zero-fill) when comp.data is null or a subsampling factor is zero, which also closes a latent divide-by-zero on comp.dx/comp.dy.
Assisted-by: Claude Code / Claude Opus 4.8