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Sanitize the glyph bounding box

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- if the contours count is lower than -1, the glyph is really likely wrong
so just remove it from the font;
- if a contour has the repeat flag then repeats count mustn't be 0.
This commit is contained in:
Calixte Denizet 2023-05-21 13:42:11 +02:00
parent 65e23432cd
commit ca12bca276
4 changed files with 55 additions and 7 deletions
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43
src/core/fonts.js
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@ -1859,16 +1859,41 @@ class Font {
length: 0,
sizeOfInstructions: 0,
};
if (sourceEnd - sourceStart <= 12) {
// glyph with data less than 12 is invalid one
if (
sourceStart < 0 ||
sourceStart >= source.length ||
sourceEnd > source.length ||
sourceEnd - sourceStart <= 12
) {
// If the offsets are wrong or the glyph is too small, remove it.
return glyphProfile;
}
const glyf = source.subarray(sourceStart, sourceEnd);
let contoursCount = signedInt16(glyf[0], glyf[1]);
// Sanitize the glyph bounding box.
const xMin = signedInt16(glyf[2], glyf[3]);
const yMin = signedInt16(glyf[4], glyf[5]);
const xMax = signedInt16(glyf[6], glyf[7]);
const yMax = signedInt16(glyf[8], glyf[9]);
if (xMin > xMax) {
writeSignedInt16(glyf, 2, xMax);
writeSignedInt16(glyf, 6, xMin);
}
if (yMin > yMax) {
writeSignedInt16(glyf, 4, yMax);
writeSignedInt16(glyf, 8, yMin);
}
const contoursCount = signedInt16(glyf[0], glyf[1]);
if (contoursCount < 0) {
// OTS doesn't like contour count to be less than -1.
contoursCount = -1;
writeSignedInt16(glyf, 0, contoursCount);
if (contoursCount < -1) {
// OTS doesn't like contour count to be less than -1.
// The glyph data offsets are very likely wrong and
// having something lower than -1, very likely, implies
// to have some garbage data.
return glyphProfile;
}
// complex glyph, writing as is
dest.set(glyf, destStart);
glyphProfile.length = glyf.length;
@ -1913,6 +1938,10 @@ class Font {
coordinatesLength += xyLength;
if (flag & 8) {
const repeat = glyf[j++];
if (repeat === 0) {
// The repeat count should be non-zero when the repeat flag is set.
glyf[j - 1] ^= 8;
}
i += repeat;
coordinatesLength += repeat * xyLength;
}
@ -2763,7 +2792,7 @@ class Font {
// hhea tables; yMin and descent value are always negative.
const metricsOverride = {
unitsPerEm: int16(tables.head.data[18], tables.head.data[19]),
yMax: int16(tables.head.data[42], tables.head.data[43]),
yMax: signedInt16(tables.head.data[42], tables.head.data[43]),
yMin: signedInt16(tables.head.data[38], tables.head.data[39]),
ascent: signedInt16(tables.hhea.data[4], tables.hhea.data[5]),
descent: signedInt16(tables.hhea.data[6], tables.hhea.data[7]),