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Add check for positive xsize/ysize in ImagingFliDecode #8406

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Add check for positive xsize/ysize in ImagingFliDecode #8406

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Yay295
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@Yay295 Yay295 commented Sep 23, 2024

Fixes #8405

I put the check near the top, but is there any valid reason xsize or ysize would be 0, and the check would need to be later in the code?

@radarhere radarhere mentioned this pull request Sep 23, 2024
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is there any valid reason xsize or ysize would be 0

No. Images that say one of their dimensions are zero will be stopped at

Pillow/src/PIL/ImageFile.py

Lines 154 to 156 in 731bcda

if not self.mode or self.size[0] <= 0 or self.size[1] <= 0:
msg = "not identified by this driver"
raise SyntaxError(msg)

Even if you consider just the C decoding process, we have

Pillow/src/decode.c

Lines 189 to 192 in 731bcda

if (state->xsize <= 0 || state->xsize + state->xoff > (int)im->xsize ||
state->ysize <= 0 || state->ysize + state->yoff > (int)im->ysize) {
PyErr_SetString(PyExc_ValueError, "tile cannot extend outside image");
return NULL;

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My minor concern with this strategy is that we could make someone reading the code think that xsize might be zero, which as I've said, shouldn't happen.

I've created #8408 as an alternative to this.

@radarhere radarhere mentioned this pull request Sep 23, 2024
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#8408 has been merged instead.

@radarhere radarhere closed this Sep 30, 2024
@Yay295 Yay295 deleted the patch-1 branch September 30, 2024 12:45
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Successfully merging this pull request may close these issues.

Unused code in FliDecode.c and _imaging.c has SAST security issue
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@Yay295 @radarhere