Extra check for balance increase (#479)

contracts/libraries/SafeERC20.sol

@@ -0,0 +1,49 @@
+pragma solidity 0.4.24;
+
+import "openzeppelin-solidity/contracts/math/SafeMath.sol";
+import "../interfaces/ERC677.sol";
+
+/**
+ * @title SafeERC20
+ * @dev Helper methods for safe token transfers.
+ * Functions perform additional checks to be sure that token transfer really happened.
+ */
+library SafeERC20 {
+    using SafeMath for uint256;
+
+    /**
+    * @dev Same as ERC20.transfer(address,uint256) but with extra consistency checks.
+    * @param _token address of the token contract
+    * @param _to address of the receiver
+    * @param _value amount of tokens to send
+    */
+    function safeTransfer(address _token, address _to, uint256 _value) internal {
+        LegacyERC20(_token).transfer(_to, _value);
+        assembly {
+            if returndatasize {
+                returndatacopy(0, 0, 32)
+                if iszero(mload(0)) {
+                    revert(0, 0)
+                }
+            }
+        }
+    }
+
+    /**
+    * @dev Same as ERC20.transferFrom(address,address,uint256) but with extra consistency checks.
+    * @param _token address of the token contract
+    * @param _from address of the sender
+    * @param _value amount of tokens to send
+    */
+    function safeTransferFrom(address _token, address _from, uint256 _value) internal {
+        LegacyERC20(_token).transferFrom(_from, address(this), _value);
+        assembly {
+            if returndatasize {
+                returndatacopy(0, 0, 32)
+                if iszero(mload(0)) {
+                    revert(0, 0)
+                }
+            }
+        }
+    }
+}

contracts/upgradeable_contracts/amb_erc20_to_native/BasicAMBErc20ToNative.sol

@@ -51,7 +51,7 @@ contract BasicAMBErc20ToNative is Initializable, Upgradeable, Claimable, Version
     * @return patch value of the version
     */
     function getBridgeInterfacesVersion() external pure returns (uint64 major, uint64 minor, uint64 patch) {
-        return (1, 1, 0);
+        return (1, 1, 1);
     }
 
     /**

contracts/upgradeable_contracts/amb_erc20_to_native/ForeignAMBErc20ToNative.sol

@@ -3,13 +3,16 @@ pragma solidity 0.4.24;
 import "./BasicAMBErc20ToNative.sol";
 import "../BaseERC677Bridge.sol";
 import "../ReentrancyGuard.sol";
+import "../../libraries/SafeERC20.sol";
 
 /**
 * @title ForeignAMBErc20ToNative
 * @dev Foreign mediator implementation for erc20-to-native bridge intended to work on top of AMB bridge.
 * It is design to be used as implementation contract of EternalStorageProxy contract.
 */
 contract ForeignAMBErc20ToNative is BasicAMBErc20ToNative, ReentrancyGuard, BaseERC677Bridge {
+    using SafeERC20 for ERC677;
+
     bytes32 internal constant MEDIATOR_BALANCE = 0x3db340e280667ee926fa8c51e8f9fcf88a0ff221a66d84d63b4778127d97d139; // keccak256(abi.encodePacked("mediatorBalance"))
 
     /**
@@ -70,13 +73,12 @@ contract ForeignAMBErc20ToNative is BasicAMBErc20ToNative, ReentrancyGuard, Base
         // which will call passMessage.
         require(!lock());
         ERC677 token = _erc677token();
-        address to = address(this);
         require(withinLimit(_value));
         addTotalSpentPerDay(getCurrentDay(), _value);
         _setMediatorBalance(mediatorBalance().add(_value));
 
         setLock(true);
-        token.transferFrom(msg.sender, to, _value);
+        token.safeTransferFrom(msg.sender, _value);
         setLock(false);
         bridgeSpecificActionsOnTokenTransfer(token, msg.sender, _value, abi.encodePacked(_receiver));
     }
@@ -150,7 +152,7 @@ contract ForeignAMBErc20ToNative is BasicAMBErc20ToNative, ReentrancyGuard, Base
         bytes32 _messageId = messageId();
 
         _setMediatorBalance(mediatorBalance().sub(valueToTransfer));
-        _erc677token().transfer(_receiver, valueToTransfer);
+        _erc677token().safeTransfer(_receiver, valueToTransfer);
         emit TokensBridged(_receiver, valueToTransfer, _messageId);
     }
 
@@ -161,7 +163,7 @@ contract ForeignAMBErc20ToNative is BasicAMBErc20ToNative, ReentrancyGuard, Base
     */
     function executeActionOnFixedTokens(address _receiver, uint256 _value) internal {
         _setMediatorBalance(mediatorBalance().sub(_value));
-        _erc677token().transfer(_receiver, _value);
+        _erc677token().safeTransfer(_receiver, _value);
     }
 
     /**

contracts/upgradeable_contracts/amb_erc677_to_erc677/BasicAMBErc677ToErc677.sol

@@ -62,6 +62,12 @@ contract BasicAMBErc677ToErc677 is
         return mediatorContractOnOtherSide();
     }
 
+    /**
+    * @dev Initiates the bridge operation that will lock the amount of tokens transferred and mint the tokens on
+    * the other network. The user should first call Approve method of the ERC677 token.
+    * @param _receiver address that will receive the minted tokens on the other network.
+    * @param _value amount of tokens to be transferred to the other network.
+    */
     function relayTokens(address _receiver, uint256 _value) external {
         // This lock is to prevent calling passMessage twice if a ERC677 token is used.
         // When transferFrom is called, after the transfer, the ERC677 token will call onTokenTransfer from this contract
@@ -90,7 +96,7 @@ contract BasicAMBErc677ToErc677 is
     }
 
     function getBridgeInterfacesVersion() external pure returns (uint64 major, uint64 minor, uint64 patch) {
-        return (1, 2, 0);
+        return (1, 2, 1);
     }
 
     function getBridgeMode() external pure returns (bytes4 _data) {

contracts/upgradeable_contracts/amb_erc677_to_erc677/ForeignAMBErc677ToErc677.sol

@@ -1,13 +1,16 @@
 pragma solidity 0.4.24;
 
 import "./BasicAMBErc677ToErc677.sol";
+import "../../libraries/SafeERC20.sol";
 
 /**
 * @title ForeignAMBErc677ToErc677
 * @dev Foreign side implementation for erc677-to-erc677 mediator intended to work on top of AMB bridge.
 * It is designed to be used as an implementation contract of EternalStorageProxy contract.
 */
 contract ForeignAMBErc677ToErc677 is BasicAMBErc677ToErc677 {
+    using SafeERC20 for ERC677;
+
     /**
      * @dev Executes action on the request to withdraw tokens relayed from the other network
      * @param _recipient address of tokens receiver
@@ -16,10 +19,31 @@ contract ForeignAMBErc677ToErc677 is BasicAMBErc677ToErc677 {
     function executeActionOnBridgedTokens(address _recipient, uint256 _value) internal {
         uint256 value = _unshiftValue(_value);
         bytes32 _messageId = messageId();
-        erc677token().transfer(_recipient, value);
+        erc677token().safeTransfer(_recipient, value);
         emit TokensBridged(_recipient, value, _messageId);
     }
 
+    /**
+    * @dev Initiates the bridge operation that will lock the amount of tokens transferred and mint the tokens on
+    * the other network. The user should first call Approve method of the ERC677 token.
+    * @param _receiver address that will receive the minted tokens on the other network.
+    * @param _value amount of tokens to be transferred to the other network.
+    */
+    function relayTokens(address _receiver, uint256 _value) external {
+        // This lock is to prevent calling passMessage twice if a ERC677 token is used.
+        // When transferFrom is called, after the transfer, the ERC677 token will call onTokenTransfer from this contract
+        // which will call passMessage.
+        require(!lock());
+        ERC677 token = erc677token();
+        require(withinLimit(_value));
+        addTotalSpentPerDay(getCurrentDay(), _value);
+
+        setLock(true);
+        token.safeTransferFrom(msg.sender, _value);
+        setLock(false);
+        bridgeSpecificActionsOnTokenTransfer(token, msg.sender, _value, abi.encodePacked(_receiver));
+    }
+
     /**
      * @dev Executes action on deposit of bridged tokens
      * @param _from address of tokens sender
@@ -38,6 +62,6 @@ contract ForeignAMBErc677ToErc677 is BasicAMBErc677ToErc677 {
     }
 
     function executeActionOnFixedTokens(address _recipient, uint256 _value) internal {
-        erc677token().transfer(_recipient, _value);
+        erc677token().safeTransfer(_recipient, _value);
     }
 }

contracts/upgradeable_contracts/multi_amb_erc20_to_erc677/BasicMultiAMBErc20ToErc677.sol

@@ -58,7 +58,7 @@ contract BasicMultiAMBErc20ToErc677 is
     * @return patch value of the version
     */
     function getBridgeInterfacesVersion() external pure returns (uint64 major, uint64 minor, uint64 patch) {
-        return (1, 1, 0);
+        return (1, 1, 1);
     }
 
     /**

contracts/upgradeable_contracts/multi_amb_erc20_to_erc677/ForeignMultiAMBErc20ToErc677.sol

@@ -4,13 +4,17 @@ import "openzeppelin-solidity/contracts/token/ERC20/DetailedERC20.sol";
 import "./BasicMultiAMBErc20ToErc677.sol";
 import "./HomeMultiAMBErc20ToErc677.sol";
 import "../../libraries/TokenReader.sol";
+import "../../libraries/SafeERC20.sol";
 
 /**
  * @title ForeignMultiAMBErc20ToErc677
  * @dev Foreign side implementation for multi-erc20-to-erc677 mediator intended to work on top of AMB bridge.
  * It is designed to be used as an implementation contract of EternalStorageProxy contract.
  */
 contract ForeignMultiAMBErc20ToErc677 is BasicMultiAMBErc20ToErc677 {
+    using SafeERC20 for address;
+    using SafeERC20 for ERC677;
+
     /**
     * @dev Stores the initial parameters of the mediator.
     * @param _bridgeContract the address of the AMB bridge contract.
@@ -53,7 +57,7 @@ contract ForeignMultiAMBErc20ToErc677 is BasicMultiAMBErc20ToErc677 {
      */
     function executeActionOnBridgedTokens(address _token, address _recipient, uint256 _value) internal {
         bytes32 _messageId = messageId();
-        LegacyERC20(_token).transfer(_recipient, _value);
+        _token.safeTransfer(_recipient, _value);
         _setMediatorBalance(_token, mediatorBalance(_token).sub(_value));
         emit TokensBridged(_token, _recipient, _value, _messageId);
     }
@@ -97,10 +101,9 @@ contract ForeignMultiAMBErc20ToErc677 is BasicMultiAMBErc20ToErc677 {
         // When transferFrom is called, after the transfer, the ERC677 token will call onTokenTransfer from this contract
         // which will call passMessage.
         require(!lock());
-        address to = address(this);
 
         setLock(true);
-        LegacyERC20(token).transferFrom(msg.sender, to, _value);
+        token.safeTransferFrom(msg.sender, _value);
         setLock(false);
         bridgeSpecificActionsOnTokenTransfer(token, msg.sender, _value, abi.encodePacked(_receiver));
     }
@@ -189,7 +192,7 @@ contract ForeignMultiAMBErc20ToErc677 is BasicMultiAMBErc20ToErc677 {
     */
     function executeActionOnFixedTokens(address _token, address _recipient, uint256 _value) internal {
         _setMediatorBalance(_token, mediatorBalance(_token).sub(_value));
-        LegacyERC20(_token).transfer(_recipient, _value);
+        _token.safeTransfer(_recipient, _value);
     }
 
     /**