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Fix silent corruption on malformed 3MF triangle indices #102

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Fix silent corruption on malformed 3MF triangle indices #102

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21 changes: 11 additions & 10 deletions js/stlLoader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -305,17 +305,18 @@ function parse3MF(data) {
vertices[i * 3 + 1] = parseFloat(vertEls[i].getAttribute('y'));
vertices[i * 3 + 2] = parseFloat(vertEls[i].getAttribute('z'));
}
const triangles = new Uint32Array(triEls.length * 3);
// Validate raw attrs before storing — Uint32Array coerces on write
// (NaN→0, negatives wrap), so post-hoc checks can't catch bad input.
const vertCount = vertEls.length;
const triangles = new Uint32Array(triEls.length * 3);
for (let i = 0; i < triEls.length; i++) {
triangles[i * 3] = parseInt(triEls[i].getAttribute('v1'), 10);
triangles[i * 3 + 1] = parseInt(triEls[i].getAttribute('v2'), 10);
triangles[i * 3 + 2] = parseInt(triEls[i].getAttribute('v3'), 10);
}

const vertCount = vertEls.length;
for (let i = 0; i < triangles.length; i++) {
if (triangles[i] < 0 || triangles[i] >= vertCount || isNaN(triangles[i])) {
throw new Error('Invalid triangle index in 3MF file');
for (let j = 0; j < 3; j++) {
const raw = triEls[i].getAttribute('v' + (j + 1));
const idx = (raw !== null && /^[0-9]+$/.test(raw.trim())) ? Number(raw) : NaN;
if (!Number.isInteger(idx) || idx >= vertCount) {
throw new Error('Invalid triangle index in 3MF file');
}
triangles[i * 3 + j] = idx;
}
}

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