Merge pull request #2225 from poanetwork/ab-fix-metadata-decoding-for-smart-contracts

fix metadata decoding in smart contract verification

CHANGELOG.md

@@ -45,8 +45,9 @@
 - [#2173](https://github.com/poanetwork/blockscout/pull/2173) - handle correctly empty transactions
 - [#2174](https://github.com/poanetwork/blockscout/pull/2174) - fix reward channel joining
 - [#2186](https://github.com/poanetwork/blockscout/pull/2186) - fix net version test
+- [#2167](https://github.com/poanetwork/blockscout/pull/2167) - feat: document eth rpc api mimicking endpoints
+- [#2225](https://github.com/poanetwork/blockscout/pull/2225) - fix metadata decoding in Solidity 0.5.9 smart contract verification
 - [#2204](https://github.com/poanetwork/blockscout/pull/2204) - fix large contract verification
-- [#2167](https://github.com/poanetwork/blockscout/pull/2168) - feat: document eth rpc api mimicking endpoints 
 
 ### Chore
 - [#2127](https://github.com/poanetwork/blockscout/pull/2127) - use previouse chromedriver version

apps/explorer/lib/explorer/smart_contract/verifier.ex

@@ -107,6 +107,13 @@ defmodule Explorer.SmartContract.Verifier do
         |> Enum.reverse()
         |> :binary.list_to_bin()
 
+      # Solidity >= 0.5.9; https://github.com/ethereum/solidity/blob/aa4ee3a1559ebc0354926af962efb3fcc7dc15bd/docs/metadata.rst
+      "a265627a7a72305820" <>
+          <<_::binary-size(64)>> <> "64736f6c6343" <> <<_::binary-size(6)>> <> "0032" <> _constructor_arguments ->
+        extracted
+        |> Enum.reverse()
+        |> :binary.list_to_bin()
+
       <<next::binary-size(2)>> <> rest ->
         do_extract_bytecode([next | extracted], rest)
     end

apps/explorer/lib/explorer/smart_contract/verifier/constructor_arguments.ex

@@ -21,6 +21,14 @@ defmodule Explorer.SmartContract.Verifier.ConstructorArguments do
     constructor_arguments
   end
 
+  # Solidity >= 0.5.9; https://github.com/ethereum/solidity/blob/aa4ee3a1559ebc0354926af962efb3fcc7dc15bd/docs/metadata.rst
+  defp extract_constructor_arguments(
+         "a265627a7a72305820" <>
+           <<_::binary-size(64)>> <> "64736f6c6343" <> <<_::binary-size(6)>> <> "0032" <> constructor_arguments
+       ) do
+    constructor_arguments
+  end
+
   defp extract_constructor_arguments(<<_::binary-size(2)>> <> rest) do
     extract_constructor_arguments(rest)
   end

apps/explorer/test/support/fixture/smart_contract/solidity_0.5.9_smart_contract.sol

@@ -0,0 +1,76 @@
+pragma solidity ^0.5.9;
+contract Token {
+    function totalSupply() public view returns (uint256 supply) {}
+    function balanceOf(address _owner) public view returns (uint256 balance) {}
+    function transfer(address _to, uint256 _value) public returns (bool success) {}
+    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {}
+    function approve(address _spender, uint256 _value) public returns (bool success) {}
+    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {}
+    event Transfer(address indexed _from, address indexed _to, uint256 _value);
+    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
+}
+
+
+contract StandardToken is Token {
+    function transfer(address _to, uint256 _value) public returns (bool success) {
+        //if (balances[msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
+        if (balances[msg.sender] >= _value && _value > 0) {
+            balances[msg.sender] -= _value;
+            balances[_to] += _value;
+            emit Transfer(msg.sender, _to, _value);
+            return true;
+        } else { return false; }
+    }
+    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
+        //if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
+        if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0) {
+            balances[_to] += _value;
+            balances[_from] -= _value;
+            allowed[_from][msg.sender] -= _value;
+            emit Transfer(_from, _to, _value);
+            return true;
+        } else { return false; }
+    }
+    function balanceOf(address _owner) public view returns (uint256 balance) {
+        return balances[_owner];
+    }
+    function approve(address _spender, uint256 _value) public returns (bool success) {
+        allowed[msg.sender][_spender] = _value;
+        emit Approval(msg.sender, _spender, _value);
+        return true;
+    }
+    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
+      return allowed[_owner][_spender];
+    }
+    mapping (address => uint256) balances;
+    mapping (address => mapping (address => uint256)) allowed;
+    uint256 totalTokenSupply;
+}
+
+contract TestToken is StandardToken {
+
+    /* Public variables */
+    string public name;
+    uint8 public decimals;
+    string public symbol;
+    string public version = '0.1';
+
+    constructor(
+        uint256 _initialAmount,
+        string memory _tokenName,
+        uint8 _decimalUnits,
+        string memory _tokenSymbol
+        ) public {
+        balances[msg.sender] = _initialAmount;
+        totalTokenSupply = _initialAmount;
+        name = _tokenName;
+        decimals = _decimalUnits;
+        symbol = _tokenSymbol;
+    }
+
+    function approveAndCall(address _spender, uint256 _value) public returns (bool success) {
+        allowed[msg.sender][_spender] = _value;
+        emit Approval(msg.sender, _spender, _value);
+        return true;
+    }
+}