From 604bc8a9c3179d8f394c7f44155ddb7e9293cbb1 Mon Sep 17 00:00:00 2001
From: Leonardo Amaral <leonardo.pedrozo@hotmail.com>
Date: Wed, 8 Jan 2025 09:44:15 -0300
Subject: [PATCH] ec recover precompile implemented

---
 src/contract/contracthost.cpp | 52 ++++++++++++++++++++++++++++++++++-
 src/contract/contracthost.h   |  8 ++++++
 src/utils/dynamicexception.h  |  1 +
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/src/contract/contracthost.cpp b/src/contract/contracthost.cpp
index 08e64dfb..3e59ce5a 100644
--- a/src/contract/contracthost.cpp
+++ b/src/contract/contracthost.cpp
@@ -14,6 +14,29 @@ static inline bool isCall(const evmc_message& msg) {
   return msg.kind == EVMC_CALL || msg.kind == EVMC_DELEGATECALL;
 }
 
+static Address ecrecover(const Hash& hash, uint8_t v, const Hash& r, const Hash& s) {
+  if (v == 27) {
+    v = 0;
+  } else if (v == 28) {
+    v = 1;
+  } else {
+    return Address{};
+  }
+
+  Signature sig;
+  auto it = std::copy(r.begin(), r.end(), sig.begin());
+  it = std::copy(s.begin(), s.end(), it);
+  *it = v;
+
+  auto pubkey = Secp256k1::recover(sig, hash);
+
+  if (!pubkey) {
+    return Address{};
+  }
+
+  return Secp256k1::toAddress(pubkey);
+}
+
 void ContractHost::transfer(const Address& from, const Address& to, const uint256_t& value) {
   // the from account **Must exist** on the unordered_map.
   // unordered_map references to values are valid **until** you insert a new element
@@ -243,6 +266,11 @@ evmc::Result ContractHost::processBDKPrecompile(const evmc_message& msg) {
    *    function getRandom() external view returns (uint256);
    *  }
    */
+  
+  if (msg.recipient == ECRECOVER_PRECOMPILE) {
+    return this->processEcRecoverPrecompile(msg);
+  }
+
   try {
     this->leftoverGas_ = msg.gas;
     this->deduceGas(1000); // CPP contract call is 1000 gas
@@ -261,6 +289,21 @@ evmc::Result ContractHost::processBDKPrecompile(const evmc_message& msg) {
   return evmc::Result(EVMC_PRECOMPILE_FAILURE, this->leftoverGas_, 0, nullptr, 0);
 }
 
+evmc::Result ContractHost::processEcRecoverPrecompile(const evmc_message& msg) {
+  try {
+    this->deduceGas(3000); // The cost for a ecrecover call: https://www.evm.codes/precompiled
+    const auto [hash, v, r, s] = ABI::Decoder::decodeData<Hash, uint8_t, Hash, Hash>(bytes::View(msg.input_data, msg.input_size));
+    const Address result = ecrecover(hash, v, r, s);
+    const Bytes resultEncoded = ABI::Encoder::encodeData(result);
+    return evmc::Result{EVMC_SUCCESS, this->leftoverGas_, 0, resultEncoded.data(), resultEncoded.size()};
+  } catch (const std::exception& e) {
+    this->evmcThrows_.emplace_back(e.what());
+    this->evmcThrow_ = true;
+  }
+
+  return evmc::Result(EVMC_PRECOMPILE_FAILURE, this->leftoverGas_, 0, nullptr, 0);
+}
+
 void ContractHost::execute(const evmc_message& msg, const ContractType& type) {
   const Address from(msg.sender);
   const Address to(msg.recipient);
@@ -619,7 +662,14 @@ ContractType ContractHost::decodeContractCallType(const evmc_message& msg) const
       return ContractType::CREATE2;
     }
     default:
-      if (msg.recipient == BDK_PRECOMPILE) return ContractType::PRECOMPILED;
+      if (msg.recipient == BDK_PRECOMPILE) {
+        return ContractType::PRECOMPILED;
+      }
+
+      if (msg.recipient == ECRECOVER_PRECOMPILE) {
+        return ContractType::PRECOMPILED;
+      }
+
       Address recipient(msg.recipient);
       // we need to take a reference to the account, not a reference to the pointer
       const auto& recipientAccount = *accounts_[recipient];
diff --git a/src/contract/contracthost.h b/src/contract/contracthost.h
index c2d74820..542783f0 100644
--- a/src/contract/contracthost.h
+++ b/src/contract/contracthost.h
@@ -44,6 +44,7 @@ See the LICENSE.txt file in the project root for more information.
 using namespace evmc::literals;
 const auto ZERO_ADDRESS = 0x0000000000000000000000000000000000000000_address;
 const auto BDK_PRECOMPILE = 0x1000000000000000000000000000100000000001_address;
+const auto ECRECOVER_PRECOMPILE = 0x0000000000000000000000000000000000000001_address;
 
 /// Abstraction for a contract host.
 class ContractHost : public evmc::Host {
@@ -152,6 +153,13 @@ class ContractHost : public evmc::Host {
      */
     evmc::Result processBDKPrecompile(const evmc_message& msg);
 
+    /**
+     * Process a call to EC RECOVER precompile.
+     * @param msg The call message to process.
+     * @return The result of the call.
+     */
+    evmc::Result processEcRecoverPrecompile(const evmc_message& msg);
+
     /**
      * Process an EVM CREATE call.
      * @param msg The call message to process.
diff --git a/src/utils/dynamicexception.h b/src/utils/dynamicexception.h
index 9a29bf6d..7e58b626 100644
--- a/src/utils/dynamicexception.h
+++ b/src/utils/dynamicexception.h
@@ -9,6 +9,7 @@ See the LICENSE.txt file in the project root for more information.
 #define DYNAMIC_EXCEPTION_H
 
 #include <chrono> // ctime
+#include <iomanip>
 #include <sstream> // ostringstream
 
 /// Abstraction of a custom exception class for dynamic message building and timestamping.