Skip to content

Commit

Permalink
Add more transparency into some EC structures.
Browse files Browse the repository at this point in the history
This adds the ability to create ECDH keys from raw bytes and export
signatures as raw bytes.
  • Loading branch information
zhalvorsen committed Aug 8, 2023
1 parent 8868752 commit f192b77
Show file tree
Hide file tree
Showing 5 changed files with 20 additions and 7 deletions.
11 changes: 11 additions & 0 deletions libraries/crypto/src/ecdh.rs
Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,17 @@ impl SecKey {
p.getx().to_int().to_bin(&mut x);
x
}

/// Creates a private key from the exponent's bytes, or None if checks fail.
pub fn from_bytes(bytes: &[u8; 32]) -> Option<SecKey> {
let a = NonZeroExponentP256::from_int_checked(Int256::from_bin(bytes));
// The branching here is fine because all this reveals is whether the key was invalid.
if bool::from(a.is_none()) {
return None;
}
let a = a.unwrap();
Some(SecKey { a })
}
}

impl PubKey {
Expand Down
5 changes: 1 addition & 4 deletions libraries/crypto/src/ecdsa.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,7 @@ use super::ec::point::PointP256;
use super::Hash256;
use alloc::vec;
use alloc::vec::Vec;
#[cfg(feature = "std")]
use arrayref::array_mut_ref;
use arrayref::{array_ref, mut_array_refs};
use arrayref::{array_mut_ref, array_ref, mut_array_refs};
use core::marker::PhantomData;
use rand_core::RngCore;
use zeroize::Zeroize;
Expand Down Expand Up @@ -220,7 +218,6 @@ impl Signature {
Some(Signature { r, s })
}

#[cfg(feature = "std")]
pub fn to_bytes(&self, bytes: &mut [u8; Signature::BYTES_LENGTH]) {
self.r
.to_int()
Expand Down
5 changes: 4 additions & 1 deletion libraries/opensk/src/api/crypto/ecdh.rs
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ pub trait Ecdh {
}

/// ECDH ephemeral key.
pub trait SecretKey {
pub trait SecretKey: Sized {
type PublicKey: PublicKey;
type SharedSecret: SharedSecret;

Expand All @@ -35,6 +35,9 @@ pub trait SecretKey {

/// Computes the shared secret when using Elliptic-curve Diffie–Hellman.
fn diffie_hellman(&self, public_key: &Self::PublicKey) -> Self::SharedSecret;

/// Creates a secret key from its representation in bytes.
fn from_slice(bytes: &[u8; EC_FIELD_SIZE]) -> Option<Self>;
}

/// ECDH public key.
Expand Down
1 change: 0 additions & 1 deletion libraries/opensk/src/api/crypto/ecdsa.rs
Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,6 @@ pub trait Signature: Sized {
fn from_slice(bytes: &[u8; EC_SIGNATURE_SIZE]) -> Option<Self>;

/// Writes the signature bytes into the passed in parameter.
#[cfg(feature = "std")]
fn to_slice(&self, bytes: &mut [u8; EC_SIGNATURE_SIZE]);

/// Encodes the signatures as ASN1 DER.
Expand Down
5 changes: 4 additions & 1 deletion libraries/opensk/src/api/crypto/software_crypto.rs
Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,10 @@ impl ecdh::SecretKey for SoftwareEcdhSecretKey {
let shared_secret = self.sec_key.exchange_x(&public_key.pub_key);
SoftwareEcdhSharedSecret { shared_secret }
}

fn from_slice(bytes: &[u8; EC_FIELD_SIZE]) -> Option<Self> {
crypto::ecdh::SecKey::from_bytes(bytes).map(|k| Self { sec_key: k })
}
}

pub struct SoftwareEcdhPublicKey {
Expand Down Expand Up @@ -169,7 +173,6 @@ impl ecdsa::Signature for SoftwareEcdsaSignature {
crypto::ecdsa::Signature::from_bytes(bytes).map(|s| SoftwareEcdsaSignature { signature: s })
}

#[cfg(feature = "std")]
fn to_slice(&self, bytes: &mut [u8; EC_SIGNATURE_SIZE]) {
self.signature.to_bytes(bytes);
}
Expand Down

0 comments on commit f192b77

Please sign in to comment.