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ecdsa: use FromDigest trait; RFC6979 fixups #134

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Merged
tarcieri merged 1 commit into from
Sep 1, 2020
Merged

ecdsa: use FromDigest trait; RFC6979 fixups #134

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45 changes: 33 additions & 12 deletions ecdsa/src/dev.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,19 +31,28 @@ pub struct TestVector {
#[macro_export]
#[cfg_attr(docsrs, doc(cfg(feature = "dev")))]
macro_rules! new_signing_test {
($vectors:expr) => {
($curve:path, $vectors:expr) => {
use core::convert::TryInto;
use $crate::generic_array::GenericArray;
use $crate::{
elliptic_curve::{Arithmetic, FromBytes},
generic_array::GenericArray,
hazmat::SignPrimitive,
};

#[test]
fn ecdsa_signing() {
for vector in $vectors {
let d = Scalar::from_bytes(vector.d.try_into().unwrap()).unwrap();
let k = Scalar::from_bytes(vector.k.try_into().unwrap()).unwrap();
let sig = d
.try_sign_prehashed(&k, GenericArray::from_slice(vector.m))
let d = <$curve as Arithmetic>::Scalar::from_bytes(vector.d.try_into().unwrap())
.unwrap();

let k = <$curve as Arithmetic>::Scalar::from_bytes(vector.k.try_into().unwrap())
.unwrap();

let z = <$curve as Arithmetic>::Scalar::from_bytes(vector.m.try_into().unwrap())
.unwrap();

let sig = d.try_sign_prehashed(&k, &z).unwrap();

assert_eq!(vector.r, sig.r().as_slice());
assert_eq!(vector.s, sig.s().as_slice());
}
Expand All @@ -55,8 +64,14 @@ macro_rules! new_signing_test {
#[macro_export]
#[cfg_attr(docsrs, doc(cfg(feature = "dev")))]
macro_rules! new_verification_test {
($vectors:expr) => {
use $crate::elliptic_curve::sec1::EncodedPoint;
($curve:path, $vectors:expr) => {
use core::convert::TryInto;
use $crate::{
elliptic_curve::{sec1::EncodedPoint, Arithmetic, FromBytes},
generic_array::GenericArray,
hazmat::VerifyPrimitive,
Signature,
};

#[test]
fn ecdsa_verify_success() {
Expand All @@ -67,14 +82,17 @@ macro_rules! new_verification_test {
false,
);

let q: AffinePoint = q_encoded.decode().unwrap();
let q: <$curve as Arithmetic>::AffinePoint = q_encoded.decode().unwrap();

let z = <$curve as Arithmetic>::Scalar::from_bytes(vector.m.try_into().unwrap())
.unwrap();

let sig = Signature::from_scalars(
GenericArray::from_slice(vector.r),
GenericArray::from_slice(vector.s),
);

let result = q.verify_prehashed(GenericArray::from_slice(vector.m), &sig);
let result = q.verify_prehashed(&z, &sig);
assert!(result.is_ok());
}
}
Expand All @@ -88,15 +106,18 @@ macro_rules! new_verification_test {
false,
);

let q: AffinePoint = q_encoded.decode().unwrap();
let q: <$curve as Arithmetic>::AffinePoint = q_encoded.decode().unwrap();

let z = <$curve as Arithmetic>::Scalar::from_bytes(vector.m.try_into().unwrap())
.unwrap();

// Flip a bit in `s`
let mut s_tweaked = GenericArray::clone_from_slice(vector.s);
s_tweaked[0] ^= 1;

let sig = Signature::from_scalars(GenericArray::from_slice(vector.r), &s_tweaked);

let result = q.verify_prehashed(GenericArray::from_slice(vector.m), &sig);
let result = q.verify_prehashed(&z, &sig);
assert!(result.is_err());
}
}
Expand Down
16 changes: 7 additions & 9 deletions ecdsa/src/hazmat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,9 +13,7 @@

use crate::{Signature, SignatureSize};
use core::borrow::Borrow;
use elliptic_curve::{
generic_array::ArrayLength, ops::Invert, weierstrass::Curve, Arithmetic, ElementBytes,
};
use elliptic_curve::{generic_array::ArrayLength, ops::Invert, weierstrass::Curve, Arithmetic};
use signature::Error;

#[cfg(feature = "digest")]
Expand All @@ -36,12 +34,12 @@ where
/// Accepts the following arguments:
///
/// - `ephemeral_scalar`: ECDSA `k` value. MUST BE UNIFORMLY RANDOM!!!
/// - `hashed_msg`: hashed message digest to be signed.
/// - `hashed_msg`: scalar computed from a hashed message digest to be signed.
/// MUST BE OUTPUT OF A CRYPTOGRAPHICALLY SECURE DIGEST ALGORITHM!!!
fn try_sign_prehashed<K: Borrow<C::Scalar> + Invert<Output = C::Scalar>>(
&self,
ephemeral_scalar: &K,
hashed_msg: &ElementBytes<C>,
hashed_msg: &C::Scalar,
) -> Result<Signature<C>, Error>;
}

Expand All @@ -64,7 +62,7 @@ where
fn try_sign_recoverable_prehashed<K: Borrow<C::Scalar> + Invert<Output = C::Scalar>>(
&self,
ephemeral_scalar: &K,
hashed_msg: &ElementBytes<C>,
hashed_msg: &C::Scalar,
) -> Result<Self::RecoverableSignature, Error>;
}

Expand All @@ -77,7 +75,7 @@ where
fn try_sign_prehashed<K: Borrow<C::Scalar> + Invert<Output = C::Scalar>>(
&self,
ephemeral_scalar: &K,
hashed_msg: &ElementBytes<C>,
hashed_msg: &C::Scalar,
) -> Result<Signature<C>, Error> {
self.try_sign_recoverable_prehashed(ephemeral_scalar, hashed_msg)
.map(Into::into)
Expand All @@ -91,7 +89,7 @@ where
/// particular curve's `AffinePoint` type.
pub trait VerifyPrimitive<C>
where
C: Curve,
C: Curve + Arithmetic,
SignatureSize<C>: ArrayLength<u8>,
{
/// Verify the prehashed message against the provided signature
Expand All @@ -103,7 +101,7 @@ where
/// - `signature`: signature to be verified against the key and message
fn verify_prehashed(
&self,
hashed_msg: &ElementBytes<C>,
hashed_msg: &C::Scalar,
signature: &Signature<C>,
) -> Result<(), Error>;
}
Expand Down
2 changes: 1 addition & 1 deletion ecdsa/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@
#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![forbid(unsafe_code)]
#![warn(missing_docs, rust_2018_idioms, intra_doc_link_resolution_failure)]
#![warn(missing_docs, rust_2018_idioms)]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo_small.png",
html_root_url = "https://docs.rs/ecdsa/0.7.2"
Expand Down
67 changes: 33 additions & 34 deletions ecdsa/src/signer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,32 +5,35 @@

// TODO(tarcieri): support for hardware crypto accelerators

mod rfc6979;
pub mod rfc6979;

use crate::{
hazmat::{DigestPrimitive, SignPrimitive},
Error, Signature, SignatureSize,
};
use elliptic_curve::{
generic_array::ArrayLength, ops::Invert, scalar::NonZeroScalar, weierstrass::Curve,
zeroize::Zeroize, Arithmetic, ElementBytes, FromBytes, FromDigest, SecretKey,
zeroize::Zeroize, Arithmetic, FromBytes, FromDigest, SecretKey,
};
use signature::{
digest::{BlockInput, Digest, FixedOutput, Reset, Update},
DigestSigner,
};

#[cfg(feature = "rand")]
use signature::{
rand_core::{CryptoRng, RngCore},
RandomizedDigestSigner, RandomizedSigner,
use {
elliptic_curve::ElementBytes,
signature::{
rand_core::{CryptoRng, RngCore},
RandomizedDigestSigner, RandomizedSigner,
},
};

/// ECDSA signer
pub struct Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
{
secret_scalar: NonZeroScalar<C>,
Expand All @@ -39,7 +42,7 @@ where
impl<C> Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
{
/// Create a new signer
Expand All @@ -48,9 +51,7 @@ where

// TODO(tarcieri): replace with into conversion when available (see subtle#73)
if scalar.is_some().into() {
Ok(Self {
secret_scalar: scalar.unwrap(),
})
Ok(Self::from(scalar.unwrap()))
} else {
Err(Error::new())
}
Expand All @@ -61,31 +62,25 @@ impl<C, D> DigestSigner<D, Signature<C>> for Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
D: BlockInput<BlockSize = C::ElementSize>
+ FixedOutput<OutputSize = C::ElementSize>
+ Clone
+ Default
+ Reset
+ Update,
ElementBytes<C>: Zeroize,
D: FixedOutput<OutputSize = C::ElementSize> + BlockInput + Clone + Default + Reset + Update,
SignatureSize<C>: ArrayLength<u8>,
{
/// Sign message prehash using a deterministic ephemeral scalar (`k`)
/// computed using the algorithm described in RFC 6979 (Section 3.2):
/// <https://tools.ietf.org/html/rfc6979#section-3>
fn try_sign_digest(&self, digest: D) -> Result<Signature<C>, Error> {
let ephemeral_scalar = rfc6979::generate_k(&self.secret_scalar, digest.clone(), &[]);
let msg_scalar = C::Scalar::from_digest(digest);

self.secret_scalar
.as_ref()
.try_sign_prehashed(ephemeral_scalar.as_ref(), &digest.finalize())
.try_sign_prehashed(ephemeral_scalar.as_ref(), &msg_scalar)
}
}

impl<C> signature::Signer<Signature<C>> for Signer<C>
where
C: Curve + Arithmetic + DigestPrimitive,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
Self: DigestSigner<C::Digest, Signature<C>>,
{
Expand All @@ -100,13 +95,7 @@ impl<C, D> RandomizedDigestSigner<D, Signature<C>> for Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
D: BlockInput<BlockSize = C::ElementSize>
+ FixedOutput<OutputSize = C::ElementSize>
+ Clone
+ Default
+ Reset
+ Update,
ElementBytes<C>: Zeroize,
D: FixedOutput<OutputSize = C::ElementSize> + BlockInput + Clone + Default + Reset + Update,
SignatureSize<C>: ArrayLength<u8>,
{
/// Sign message prehash using an ephemeral scalar (`k`) derived according
Expand All @@ -123,9 +112,10 @@ where
let ephemeral_scalar =
rfc6979::generate_k(&self.secret_scalar, digest.clone(), &added_entropy);

let msg_scalar = C::Scalar::from_digest(digest);

self.secret_scalar
.as_ref()
.try_sign_prehashed(ephemeral_scalar.as_ref(), &digest.finalize())
.try_sign_prehashed(ephemeral_scalar.as_ref(), &msg_scalar)
}
}

Expand All @@ -134,7 +124,7 @@ where
impl<C> RandomizedSigner<Signature<C>> for Signer<C>
where
C: Curve + Arithmetic + DigestPrimitive,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
Self: RandomizedDigestSigner<C::Digest, Signature<C>>,
{
Expand All @@ -147,11 +137,21 @@ where
}
}

impl<C> Zeroize for Signer<C>
impl<C> From<NonZeroScalar<C>> for Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
{
fn from(secret_scalar: NonZeroScalar<C>) -> Self {
Self { secret_scalar }
}
}

impl<C> Zeroize for Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
{
fn zeroize(&mut self) {
Expand All @@ -162,8 +162,7 @@ where
impl<C> Drop for Signer<C>
where
C: Curve + Arithmetic,
C::Scalar: Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,

C::Scalar: FromDigest<C> + Invert<Output = C::Scalar> + SignPrimitive<C> + Zeroize,
SignatureSize<C>: ArrayLength<u8>,
{
fn drop(&mut self) {
Expand Down
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