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Gsub buffer limit #120

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Gsub buffer limit #120

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bb302a0
RawGlyph field clarification
zeonzip Jul 23, 2025
ef26e3b
Add glyph substituion limit in GSUB for all multiplesubst substitutions
zeonzip Jul 24, 2025
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9 changes: 7 additions & 2 deletions src/gsub.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,10 +23,11 @@ use crate::layout::{
};
use crate::scripts::{self, ScriptType};
use crate::tables::variable_fonts::Tuple;
use crate::tag;
use crate::unicode::VariationSelector;
use crate::{tag, GlyphId};

const SUBST_RECURSION_LIMIT: usize = 2;
const MAX_GLYPHS: usize = 10_000;

#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub struct FeatureInfo {
Expand Down Expand Up @@ -123,7 +124,7 @@ impl Ligature {
#[derive(Clone, Debug)]
pub struct RawGlyph<T> {
pub unicodes: TinyVec<[char; 1]>,
pub glyph_index: u16,
pub glyph_index: GlyphId,
pub liga_component_pos: u16,
pub glyph_origin: GlyphOrigin,
pub flags: RawGlyphFlags,
Expand Down Expand Up @@ -462,6 +463,10 @@ fn multiplesubst<T: GlyphData>(
) -> Result<Option<usize>, ParseError> {
match multiplesubst_would_apply(subtables, i, glyphs)? {
Some(sequence_table) => {
if sequence_table.substitute_glyphs.len() + glyphs.len() >= MAX_GLYPHS {
return Err(ParseError::LimitExceeded);
}

if !sequence_table.substitute_glyphs.is_empty() {
let first_glyph_index = sequence_table.substitute_glyphs[0];
glyphs[i].glyph_index = first_glyph_index;
Expand Down
2 changes: 1 addition & 1 deletion src/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1448,7 +1448,7 @@ pub struct MultipleSubst {
}

pub struct SequenceTable {
pub substitute_glyphs: Vec<u16>,
pub substitute_glyphs: Vec<GlyphId>,
}

impl ReadBinaryDep for MultipleSubst {
Expand Down
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