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keyfork-derive-util: allow zeroable input for key derivation

This commit is contained in:
Ryan Heywood 2024-04-14 23:08:25 -04:00
parent 57354fc714
commit 5ff5643887
Signed by: ryan
GPG Key ID: 8E401478A3FBEF72
2 changed files with 30 additions and 23 deletions
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31
crates/derive/keyfork-derive-util/src/private_key.rs
View File

@ -102,6 +102,10 @@ pub enum PrivateKeyError {
/// For the given algorithm, the private key must be nonzero.
#[error("The provided private key must be nonzero, but is not")]
NonZero,
/// A scalar could not be constructed for the given algorithm.
#[error("A scalar could not be constructed for the given algorithm")]
InvalidScalar,
}
#[cfg(feature = "secp256k1")]
@ -130,20 +134,19 @@ impl PrivateKey for k256::SecretKey {
}
fn derive_child(&self, other: &PrivateKeyBytes) -> Result<Self, Self::Err> {
if other.iter().all(|n| n == &0) {
return Err(PrivateKeyError::NonZero);
}
let other = *other;
// Checked: See above nonzero check
let scalar = Option::<NonZeroScalar>::from(NonZeroScalar::from_repr(other.into()))
.expect(bug!("Should have been able to get a NonZeroScalar"));
use k256::elliptic_curve::ScalarPrimitive;
use k256::{Scalar, Secp256k1};
// Construct a scalar from bytes
let scalar = ScalarPrimitive::<Secp256k1>::from_bytes(other.into());
let scalar = Option::<ScalarPrimitive<Secp256k1>>::from(scalar);
let scalar = scalar.ok_or(PrivateKeyError::InvalidScalar)?;
let scalar = Scalar::from(scalar);
let derived_scalar = self.to_nonzero_scalar().as_ref() + scalar.as_ref();
Ok(
Option::<NonZeroScalar>::from(NonZeroScalar::new(derived_scalar))
.map(Into::into)
.expect(bug!("Should be able to make Key")),
)
let nonzero_scalar = Option::<NonZeroScalar>::from(NonZeroScalar::new(derived_scalar))
.ok_or(PrivateKeyError::NonZero)?;
Ok(Self::from(nonzero_scalar))
}
}
@ -202,9 +205,7 @@ impl PrivateKey for TestPrivateKey {
type Err = PrivateKeyError;
fn from_bytes(b: &PrivateKeyBytes) -> Self {
Self {
key: *b
}
Self { key: *b }
}
fn to_bytes(&self) -> PrivateKeyBytes {

22
crates/derive/keyfork-derive-util/src/public_key.rs
View File

@ -77,6 +77,10 @@ pub enum PublicKeyError {
#[error("The provided public key must be nonzero, but is not")]
NonZero,
/// A scalar could not be constructed for the given algorithm.
#[error("A scalar could not be constructed for the given algorithm")]
InvalidScalar,
/// Public key derivation is unsupported for this algorithm.
#[error("Public key derivation is unsupported for this algorithm")]
DerivationUnsupported,
@ -85,7 +89,7 @@ pub enum PublicKeyError {
#[cfg(feature = "secp256k1")]
use k256::{
elliptic_curve::{group::prime::PrimeCurveAffine, sec1::ToEncodedPoint},
AffinePoint, NonZeroScalar,
AffinePoint,
};
#[cfg(feature = "secp256k1")]
@ -105,14 +109,16 @@ impl PublicKey for k256::PublicKey {
}
fn derive_child(&self, other: PrivateKeyBytes) -> Result<Self, Self::Err> {
if other.iter().all(|n| n == &0) {
return Err(PublicKeyError::NonZero);
}
// Checked: See above
let scalar = Option::<NonZeroScalar>::from(NonZeroScalar::from_repr(other.into()))
.expect(bug!("Should have been able to get a NonZeroScalar"));
use k256::elliptic_curve::ScalarPrimitive;
use k256::{Secp256k1, Scalar};
let point = self.to_projective() + (AffinePoint::generator() * *scalar);
// Construct a scalar from bytes
let scalar = ScalarPrimitive::<Secp256k1>::from_bytes(&other.into());
let scalar = Option::<ScalarPrimitive<Secp256k1>>::from(scalar);
let scalar = scalar.ok_or(PublicKeyError::InvalidScalar)?;
let scalar = Scalar::from(scalar);
let point = self.to_projective() + (AffinePoint::generator() * scalar);
Ok(Self::from_affine(point.into())
.expect(bug!("Could not from_affine after scalar arithmetic")))
}