Implement signature of arbitrary data for Account

ethcontract/src/transaction.rs

@@ -14,7 +14,9 @@ pub use self::gas_price::GasPrice;
 pub use self::send::TransactionResult;
 use crate::errors::ExecutionError;
 use crate::secret::{Password, PrivateKey};
+use primitive_types::H256;
 use web3::api::Web3;
+use web3::signing::Signature;
 use web3::types::{AccessList, Address, Bytes, CallRequest, TransactionCondition, U256};
 use web3::Transport;
 
@@ -44,6 +46,35 @@ impl Account {
             Account::Kms(kms, _) => kms.public_address(),
         }
     }
+
+    /// Signs the given data
+    pub async fn sign<T: Transport>(&self, web3: Web3<T>, data: [u8; 32]) -> Option<Signature> {
+        match self {
+            Account::Local(_, _) => None,
+            Account::Locked(account, password, _) => {
+                let signature = web3
+                    .personal()
+                    .sign(Bytes::from(data), *account, password)
+                    .await
+                    .ok()?;
+                Some(Signature {
+                    v: signature[0].into(),                  // The first byte is V
+                    r: H256::from_slice(&signature[1..33]),  // Next 32 bytes are R
+                    s: H256::from_slice(&signature[33..65]), // Last 32 bytes are S
+                })
+            }
+            Account::Offline(key, _) => {
+                let signature = web3.accounts().sign(data, key);
+                Some(Signature {
+                    v: signature.v.into(),
+                    r: signature.r,
+                    s: signature.s,
+                })
+            }
+            #[cfg(feature = "aws-kms")]
+            Account::Kms(account, _) => account.sign(data).await.ok(),
+        }
+    }
 }
 
 /// The condition on which a transaction's `SendFuture` gets resolved.