feat(cheatcodes): Add vm.signWithNonce(privateKey, digest, nonce) cheatcode (Crypto)

crates/cheatcodes/spec/src/vm.rs

@@ -2785,6 +2785,12 @@ interface Vm {
     #[cheatcode(group = Crypto)]
     function sign(uint256 privateKey, bytes32 digest) external pure returns (uint8 v, bytes32 r, bytes32 s);
 
+    /// Signs `digest` with `privateKey` on the secp256k1 curve, using the given `nonce`
+    /// as the raw ephemeral k value in ECDSA (instead of deriving it deterministically).
+    #[cheatcode(group = Crypto)]
+    function signWithNonce(uint256 privateKey, bytes32 digest, uint256 nonce) external pure returns (uint8 v, bytes32 r, bytes32 s);
+
+
     /// Signs `digest` with `privateKey` using the secp256k1 curve.
     ///
     /// Returns a compact signature (`r`, `vs`) as per EIP-2098, where `vs` encodes both the

crates/cheatcodes/src/crypto.rs

@@ -12,9 +12,11 @@ use alloy_signer_local::{
 };
 use alloy_sol_types::SolValue;
 use k256::{
-    ecdsa::SigningKey,
+    FieldBytes, Scalar,
+    ecdsa::{SigningKey, hazmat},
     elliptic_curve::{bigint::ArrayEncoding, sec1::ToEncodedPoint},
 };
+
 use p256::ecdsa::{
     Signature as P256Signature, SigningKey as P256SigningKey, signature::hazmat::PrehashSigner,
 };
@@ -51,6 +53,16 @@ impl Cheatcode for sign_0Call {
     }
 }
 
+impl Cheatcode for signWithNonceCall {
+    fn apply(&self, _state: &mut Cheatcodes) -> Result {
+        let pk: U256 = self.privateKey;
+        let digest: B256 = self.digest;
+        let nonce: U256 = self.nonce;
+        let sig: alloy_primitives::Signature = sign_with_nonce(&pk, &digest, &nonce)?;
+        Ok(encode_full_sig(sig))
+    }
+}
+
 impl Cheatcode for signCompact_0Call {
     fn apply(&self, _state: &mut Cheatcodes) -> Result {
         let Self { wallet, digest } = self;
@@ -241,6 +253,83 @@ fn sign(private_key: &U256, digest: &B256) -> Result<alloy_primitives::Signature
     Ok(sig)
 }
 
+// Signs `digest` on secp256k1 using a user-supplied ephemeral nonce `k` (no RFC6979).
+// - `private_key` and `nonce` must be in (0, n)
+// - `digest` is a 32-byte prehash.
+// WARNING: Use sign_with_nonce with extreme caution!
+// Reusing the same nonce (k) with the same private key in ECDSA will leak the private key.
+// Always generate `nonce` with a cryptographically secure RNG, and never reuse it across
+// signatures.
+fn sign_with_nonce(
+    private_key: &U256,
+    digest: &B256,
+    nonce: &U256,
+) -> Result<alloy_primitives::Signature> {
+    let d_scalar: Scalar =
+        <Scalar as k256::elliptic_curve::PrimeField>::from_repr(private_key.to_be_bytes().into())
+            .into_option()
+            .ok_or_else(|| fmt_err!("invalid private key scalar"))?;
+    if bool::from(d_scalar.is_zero()) {
+        return Err(fmt_err!("private key cannot be 0"));
+    }
+
+    let k_scalar: Scalar =
+        <Scalar as k256::elliptic_curve::PrimeField>::from_repr(nonce.to_be_bytes().into())
+            .into_option()
+            .ok_or_else(|| fmt_err!("invalid nonce scalar"))?;
+    if bool::from(k_scalar.is_zero()) {
+        return Err(fmt_err!("nonce cannot be 0"));
+    }
+
+    let mut z = [0u8; 32];
+    z.copy_from_slice(digest.as_slice());
+    let z_fb: FieldBytes = FieldBytes::from(z);
+
+    // Hazmat signing using the scalar `d` (SignPrimitive is implemented for `Scalar`)
+    // Note: returns (Signature, Option<RecoveryId>)
+    let (sig_raw, recid_opt) =
+        <Scalar as hazmat::SignPrimitive<k256::Secp256k1>>::try_sign_prehashed(
+            &d_scalar, k_scalar, &z_fb,
+        )
+        .map_err(|e| fmt_err!("sign_prehashed failed: {e}"))?;
+
+    // Enforce low-s; if mirrored, parity flips (we’ll account for it below if we use recid)
+    let (sig_low, flipped) =
+        if let Some(norm) = sig_raw.normalize_s() { (norm, true) } else { (sig_raw, false) };
+
+    let r_u256 = U256::from_be_bytes(sig_low.r().to_bytes().into());
+    let s_u256 = U256::from_be_bytes(sig_low.s().to_bytes().into());
+
+    // Determine v parity in {0,1}
+    let v_parity = if let Some(id) = recid_opt {
+        let mut v = id.to_byte() & 1;
+        if flipped {
+            v ^= 1;
+        }
+        v
+    } else {
+        // Fallback: choose parity by recovery to expected address
+        let expected_addr = {
+            let sk: SigningKey = parse_private_key(private_key)?;
+            alloy_signer::utils::secret_key_to_address(&sk)
+        };
+        // Try v = 0
+        let cand0 = alloy_primitives::Signature::new(r_u256, s_u256, false);
+        if cand0.recover_address_from_prehash(digest).ok() == Some(expected_addr) {
+            return Ok(cand0);
+        }
+        // Try v = 1
+        let cand1 = alloy_primitives::Signature::new(r_u256, s_u256, true);
+        if cand1.recover_address_from_prehash(digest).ok() == Some(expected_addr) {
+            return Ok(cand1);
+        }
+        return Err(fmt_err!("failed to determine recovery id for signature"));
+    };
+
+    let y_parity = v_parity != 0;
+    Ok(alloy_primitives::Signature::new(r_u256, s_u256, y_parity))
+}
+
 fn sign_with_wallet(
     state: &mut Cheatcodes,
     signer: Option<Address>,
@@ -393,6 +482,7 @@ fn derive_wallets<W: Wordlist>(
 mod tests {
     use super::*;
     use alloy_primitives::{FixedBytes, hex::FromHex};
+    use k256::elliptic_curve::Curve;
     use p256::ecdsa::signature::hazmat::PrehashVerifier;
 
     #[test]
@@ -438,4 +528,69 @@ mod tests {
         let result = sign_p256(&U256::ZERO, &digest);
         assert_eq!(result.err().unwrap().to_string(), "private key cannot be 0");
     }
+
+    #[test]
+    fn test_sign_with_nonce_varies_and_recovers() {
+        // Given a fixed private key and digest
+        let pk_u256: U256 = U256::from(1u64);
+        let digest = FixedBytes::from_hex(
+            "0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+        )
+        .unwrap();
+
+        // Two distinct nonces
+        let n1: U256 = U256::from(123u64);
+        let n2: U256 = U256::from(456u64);
+
+        // Sign with both nonces
+        let sig1 = sign_with_nonce(&pk_u256, &digest, &n1).expect("sig1");
+        let sig2 = sign_with_nonce(&pk_u256, &digest, &n2).expect("sig2");
+
+        // (r,s) must differ when nonce differs
+        assert!(
+            sig1.r() != sig2.r() || sig1.s() != sig2.s(),
+            "signatures should differ with different nonces"
+        );
+
+        // ecrecover must yield the address for both signatures
+        let sk = parse_private_key(&pk_u256).unwrap();
+        let expected = alloy_signer::utils::secret_key_to_address(&sk);
+
+        assert_eq!(sig1.recover_address_from_prehash(&digest).unwrap(), expected);
+        assert_eq!(sig2.recover_address_from_prehash(&digest).unwrap(), expected);
+    }
+
+    #[test]
+    fn test_sign_with_nonce_zero_nonce_errors() {
+        // nonce = 0 should be rejected
+        let pk_u256: U256 = U256::from(1u64);
+        let digest = FixedBytes::from_hex(
+            "0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
+        )
+        .unwrap();
+        let n0: U256 = U256::ZERO;
+
+        let err = sign_with_nonce(&pk_u256, &digest, &n0).unwrap_err();
+        let msg = err.to_string();
+        assert!(msg.contains("nonce cannot be 0"), "unexpected error: {msg}");
+    }
+
+    #[test]
+    fn test_sign_with_nonce_nonce_ge_order_errors() {
+        // nonce >= n should be rejected
+        use k256::Secp256k1;
+        // Curve order n as U256
+        let n_u256 = U256::from_be_slice(&Secp256k1::ORDER.to_be_byte_array());
+
+        let pk_u256: U256 = U256::from(1u64);
+        let digest = FixedBytes::from_hex(
+            "0xcccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
+        )
+        .unwrap();
+
+        // Try exactly n (>= n invalid)
+        let err = sign_with_nonce(&pk_u256, &digest, &n_u256).unwrap_err();
+        let msg = err.to_string();
+        assert!(msg.contains("invalid nonce scalar"), "unexpected error: {msg}");
+    }
 }

testdata/default/cheats/Sign.t.sol

@@ -44,4 +44,60 @@ contract SignTest is DSTest {
     function testSignCompactMessage(uint248 pk, bytes memory message) public {
         testSignCompactDigest(pk, keccak256(message));
     }
+
+    /// secp256k1 subgroup order n
+    function _secp256k1Order() internal pure returns (uint256) {
+        return 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141;
+    }
+
+    function testSignWithNonceDigestDifferentNonces(uint248 pk, bytes32 digest) public {
+        vm.assume(pk != 0);
+        uint256 n1 = 123;
+        uint256 n2 = 456;
+        vm.assume(n1 != 0 && n2 != 0 && n1 != n2);
+        (uint8 v1, bytes32 r1, bytes32 s1) = vm.signWithNonce(pk, digest, n1);
+        (uint8 v2, bytes32 r2, bytes32 s2) = vm.signWithNonce(pk, digest, n2);
+        assertTrue(r1 != r2 || s1 != s2, "signatures should differ for different nonces");
+        address expected = vm.addr(pk);
+        assertEq(ecrecover(digest, v1, r1, s1), expected, "recover for nonce n1 failed");
+        assertEq(ecrecover(digest, v2, r2, s2), expected, "recover for nonce n2 failed");
+    }
+
+    function testSignWithNonceDigestSameNonceDeterministic(uint248 pk, bytes32 digest) public {
+        vm.assume(pk != 0);
+        uint256 n = 777;
+        vm.assume(n != 0);
+        (uint8 v1, bytes32 r1, bytes32 s1) = vm.signWithNonce(pk, digest, n);
+        (uint8 v2, bytes32 r2, bytes32 s2) = vm.signWithNonce(pk, digest, n);
+        assertEq(v1, v2, "v should match");
+        assertEq(r1, r2, "r should match");
+        assertEq(s1, s2, "s should match");
+        address expected = vm.addr(pk);
+        assertEq(ecrecover(digest, v1, r1, s1), expected, "recover failed");
+    }
+
+    function testSignWithNonceInvalidNoncesRevert() public {
+        uint256 pk = 1;
+        bytes32 digest = 0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+        (bool ok, bytes memory data) =
+            HEVM_ADDRESS.call(abi.encodeWithSelector(Vm.signWithNonce.selector, pk, digest, 0));
+        assertTrue(!ok, "expected revert on nonce=0");
+        assertEq(_revertString(data), "vm.signWithNonce: nonce cannot be 0");
+        uint256 n = _secp256k1Order();
+        (ok, data) = HEVM_ADDRESS.call(abi.encodeWithSelector(Vm.signWithNonce.selector, pk, digest, n));
+        assertTrue(!ok, "expected revert on nonce >= n");
+        assertEq(_revertString(data), "vm.signWithNonce: invalid nonce scalar");
+    }
+
+    /// Decode revert payload
+    /// by stripping the 4-byte selector and ABI-decoding the tail as `string`.
+    function _revertString(bytes memory data) internal pure returns (string memory) {
+        if (data.length < 4) return "";
+        // copy data[4:] into a new bytes
+        bytes memory tail = new bytes(data.length - 4);
+        for (uint256 i = 0; i < tail.length; i++) {
+            tail[i] = data[i + 4];
+        }
+        return abi.decode(tail, (string));
+    }
 }