core: replace secp256k with k256 in crypto::ecdsa

substrate/primitives/core/Cargo.toml

@@ -52,9 +52,9 @@ blake2 = { version = "0.10.4", default-features = false, optional = true }
 libsecp256k1 = { version = "0.7", default-features = false, features = ["static-context"], optional = true }
 schnorrkel = { version = "0.11.4", features = ["preaudit_deprecated"], default-features = false }
 merlin = { version = "3.0", default-features = false }
-secp256k1 = { version = "0.28.0", default-features = false, features = ["alloc", "recovery"], optional = true }
 sp-crypto-hashing = { path = "../crypto/hashing", default-features = false, optional = true }
 sp-runtime-interface = { path = "../runtime-interface", default-features = false }
+k256 = { version = "0.13.3", features = ["alloc", "ecdsa"], default-features = false }
 
 # bls crypto
 w3f-bls = { version = "0.1.3", default-features = false, optional = true }
@@ -94,6 +94,7 @@ std = [
 	"hash256-std-hasher/std",
 	"impl-serde/std",
 	"itertools",
+	"k256/std",
 	"libsecp256k1/std",
 	"log/std",
 	"merlin/std",
@@ -105,8 +106,6 @@ std = [
 	"rand",
 	"scale-info/std",
 	"schnorrkel/std",
-	"secp256k1/global-context",
-	"secp256k1/std",
 	"secrecy/alloc",
 	"serde/std",
 	"sp-crypto-hashing/std",
@@ -137,6 +136,7 @@ serde = [
 	"secrecy/alloc",
 	"sp-crypto-hashing",
 	"sp-storage/serde",
+	"k256/serde"
 ]
 
 # This feature enables all crypto primitives for `no_std` builds like microcontrollers
@@ -147,7 +147,6 @@ full_crypto = [
 	"blake2",
 	"ed25519-zebra",
 	"libsecp256k1",
-	"secp256k1",
 	"sp-crypto-hashing",
 	"sp-runtime-interface/disable_target_static_assertions",
 ]

substrate/primitives/core/src/ecdsa.rs

@@ -28,15 +28,9 @@ use crate::crypto::{
 };
 #[cfg(feature = "full_crypto")]
 use crate::crypto::{DeriveError, DeriveJunction, Pair as TraitPair, SecretStringError};
-#[cfg(all(feature = "full_crypto", not(feature = "std")))]
-use secp256k1::Secp256k1;
-#[cfg(feature = "std")]
-use secp256k1::SECP256K1;
+use k256::ecdsa::{VerifyingKey};
 #[cfg(feature = "full_crypto")]
-use secp256k1::{
-	ecdsa::{RecoverableSignature, RecoveryId},
-	Message, PublicKey, SecretKey,
-};
+use k256::ecdsa::{RecoveryId, SigningKey};
 #[cfg(feature = "serde")]
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 #[cfg(all(not(feature = "std"), feature = "serde"))]
@@ -53,7 +47,7 @@ pub const PUBLIC_KEY_SERIALIZED_SIZE: usize = 33;
 /// The byte length of signature
 pub const SIGNATURE_SERIALIZED_SIZE: usize = 65;
 
-/// A secret seed (which is bytewise essentially equivalent to a SecretKey).
+/// A secret seed (which is bytewise essentially equivalent to a SigningKey).
 ///
 /// We need it as a different type because `Seed` is expected to be AsRef<[u8]>.
 #[cfg(feature = "full_crypto")]
@@ -103,11 +97,11 @@ impl Public {
 			let mut tagged_full = [0u8; 65];
 			tagged_full[0] = 0x04;
 			tagged_full[1..].copy_from_slice(full);
-			secp256k1::PublicKey::from_slice(&tagged_full)
+			VerifyingKey::from_sec1_bytes(&tagged_full)
 		} else {
-			secp256k1::PublicKey::from_slice(full)
+			VerifyingKey::from_sec1_bytes(full)
 		};
-		pubkey.map(|k| Self(k.serialize())).map_err(|_| ())
+		pubkey.map(|k| k.into()).map_err(|_| ())
 	}
 }
 
@@ -131,6 +125,16 @@ impl AsMut<[u8]> for Public {
 	}
 }
 
+impl From<VerifyingKey> for Public {
+	fn from(pubkey: VerifyingKey) -> Self {
+		Self::unchecked_from(
+			pubkey.to_sec1_bytes()[..]
+				.try_into()
+				.expect("valid key is serializable to [u8,33]. qed."),
+		)
+	}
+}
+
 impl TryFrom<&[u8]> for Public {
 	type Error = ();
 
@@ -331,30 +335,19 @@ impl Signature {
 	/// Recover the public key from this signature and a pre-hashed message.
 	#[cfg(feature = "full_crypto")]
 	pub fn recover_prehashed(&self, message: &[u8; 32]) -> Option<Public> {
-		let rid = RecoveryId::from_i32(self.0[64] as i32).ok()?;
-		let sig = RecoverableSignature::from_compact(&self.0[..64], rid).ok()?;
-		let message = Message::from_digest_slice(message).expect("Message is 32 bytes; qed");
+		let rid = RecoveryId::from_byte(self.0[64])?;
+		let sig = k256::ecdsa::Signature::from_bytes((&self.0[..64]).into()).ok()?;
 
-		#[cfg(feature = "std")]
-		let context = SECP256K1;
-		#[cfg(not(feature = "std"))]
-		let context = Secp256k1::verification_only();
-
-		context
-			.recover_ecdsa(&message, &sig)
-			.ok()
-			.map(|pubkey| Public(pubkey.serialize()))
+		VerifyingKey::recover_from_prehash(message, &sig, rid).map(|p| p.into()).ok()
 	}
 }
 
 #[cfg(feature = "full_crypto")]
-impl From<RecoverableSignature> for Signature {
-	fn from(recsig: RecoverableSignature) -> Signature {
+impl From<(k256::ecdsa::Signature, RecoveryId)> for Signature {
+	fn from(recsig: (k256::ecdsa::Signature, RecoveryId)) -> Signature {
 		let mut r = Self::default();
-		let (recid, sig) = recsig.serialize_compact();
-		r.0[..64].copy_from_slice(&sig);
-		// This is safe due to the limited range of possible valid ids.
-		r.0[64] = recid.to_i32() as u8;
+		r.0[..64].copy_from_slice(&recsig.0.to_bytes());
+		r.0[64] = recsig.1.to_byte();
 		r
 	}
 }
@@ -370,7 +363,7 @@ fn derive_hard_junction(secret_seed: &Seed, cc: &[u8; 32]) -> Seed {
 #[derive(Clone)]
 pub struct Pair {
 	public: Public,
-	secret: SecretKey,
+	secret: SigningKey,
 }
 
 #[cfg(feature = "full_crypto")]
@@ -385,16 +378,8 @@ impl TraitPair for Pair {
 	/// You should never need to use this; generate(), generate_with_phrase
 	fn from_seed_slice(seed_slice: &[u8]) -> Result<Pair, SecretStringError> {
 		let secret =
-			SecretKey::from_slice(seed_slice).map_err(|_| SecretStringError::InvalidSeedLength)?;
-
-		#[cfg(feature = "std")]
-		let context = SECP256K1;
-		#[cfg(not(feature = "std"))]
-		let context = Secp256k1::signing_only();
-
-		let public = PublicKey::from_secret_key(&context, &secret);
-		let public = Public(public.serialize());
-		Ok(Pair { public, secret })
+			SigningKey::from_slice(seed_slice).map_err(|_| SecretStringError::InvalidSeedLength)?;
+		Ok(Pair { public: VerifyingKey::from(&secret).into(), secret })
 	}
 
 	/// Derive a child key from a series of given junctions.
@@ -438,7 +423,7 @@ impl TraitPair for Pair {
 impl Pair {
 	/// Get the seed for this key.
 	pub fn seed(&self) -> Seed {
-		self.secret.secret_bytes()
+		self.secret.to_bytes().into()
 	}
 
 	/// Exactly as `from_string` except that if no matches are found then, the the first 32
@@ -455,14 +440,10 @@ impl Pair {
 
 	/// Sign a pre-hashed message
 	pub fn sign_prehashed(&self, message: &[u8; 32]) -> Signature {
-		let message = Message::from_digest_slice(message).expect("Message is 32 bytes; qed");
-
-		#[cfg(feature = "std")]
-		let context = SECP256K1;
-		#[cfg(not(feature = "std"))]
-		let context = Secp256k1::signing_only();
-
-		context.sign_ecdsa_recoverable(&message, &self.secret).into()
+		self.secret
+			.sign_prehash_recoverable(message)
+			.expect("signing may not fail (???). qed.")
+			.into()
 	}
 
 	/// Verify a signature on a pre-hashed message. Return `true` if the signature is valid
@@ -498,18 +479,6 @@ impl Pair {
 	}
 }
 
-// The `secp256k1` backend doesn't implement cleanup for their private keys.
-// Currently we should take care of wiping the secret from memory.
-// NOTE: this solution is not effective when `Pair` is moved around memory.
-// The very same problem affects other cryptographic backends that are just using
-// `zeroize`for their secrets.
-#[cfg(feature = "full_crypto")]
-impl Drop for Pair {
-	fn drop(&mut self) {
-		self.secret.non_secure_erase()
-	}
-}
-
 impl CryptoType for Public {
 	#[cfg(feature = "full_crypto")]
 	type Pair = Pair;
@@ -770,8 +739,10 @@ mod test {
 		let msg = [0u8; 32];
 		let sig1 = pair.sign_prehashed(&msg);
 		let sig2: Signature = {
-			let message = Message::from_digest_slice(&msg).unwrap();
-			SECP256K1.sign_ecdsa_recoverable(&message, &pair.secret).into()
+			pair.secret
+				.sign_prehash_recoverable(&msg)
+				.expect("signing may not fail (???). qed.")
+				.into()
 		};
 		assert_eq!(sig1, sig2);