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Add SRS bounds check in KZG commit to prevent out-of-bounds slicing #1030

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Add SRS bounds check in KZG commit to prevent out-of-bounds slicing #1030

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11 changes: 11 additions & 0 deletions crates/crypto/src/commitments/kzg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -166,11 +166,22 @@ impl<const N: usize, F: IsPrimeField<RepresentativeType = UnsignedInteger<N>>, P
/// The commitment is p(s) g1, evaluated as \sum_i c_i srs.powers_main_group[i], where c_i are the coefficients
/// of the polynomial.
fn commit(&self, p: &Polynomial<FieldElement<F>>) -> Self::Commitment {
// Guard against SRS underprovisioning: if the polynomial degree exceeds the
// available SRS powers, limit MSM inputs to the SRS size to avoid out-of-bounds
// slicing. Callers should ensure the SRS has at least as many powers as the
// number of polynomial coefficients.
let coeffs_to_use = p
.coefficients
.len()
.min(self.srs.powers_main_group.len());

let coefficients: Vec<_> = p
.coefficients
.iter()
.take(coeffs_to_use)
.map(|coefficient| coefficient.representative())
.collect();

msm(
&coefficients,
&self.srs.powers_main_group[..coefficients.len()],
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