Fix abi decoding of 0x transaction data

contracts/tec/contracts/src/MixinTECApprovalVerifier.sol

@@ -45,7 +45,7 @@ contract MixinTECApprovalVerifier is
     /// @param transactionSignature Proof that the transaction has been signed by the signer.
     /// @param approvalExpirationTimeSeconds Array of expiration times in seconds for which each corresponding approval signature expires.
     /// @param approvalSignatures Array of signatures that correspond to the feeRecipients of each order in the transaction's Exchange calldata.
-    function assertValidTECApproval(
+    function assertValidTECApprovals(
         LibZeroExTransaction.ZeroExTransaction memory transaction,
         bytes memory transactionSignature,
         uint256[] memory approvalExpirationTimeSeconds,
@@ -67,7 +67,7 @@ contract MixinTECApprovalVerifier is
         ) {
             // Decode single order
             (LibOrder.Order memory order) = abi.decode(
-                transaction.data,
+                transaction.data.slice(4, transaction.data.length),
                 (LibOrder.Order)
             );
 
@@ -90,7 +90,7 @@ contract MixinTECApprovalVerifier is
         ) {
             // Decode all orders
             (LibOrder.Order[] memory orders) = abi.decode(
-                transaction.data,
+                transaction.data.slice(4, transaction.data.length),
                 (LibOrder.Order[])
             );
 
@@ -105,7 +105,7 @@ contract MixinTECApprovalVerifier is
         } else if (exchangeFunctionSelector == MATCH_ORDERS_SELECTOR) {
             // Decode left and right orders
             (LibOrder.Order memory leftOrder, LibOrder.Order memory rightOrder) = abi.decode(
-                transaction.data,
+                transaction.data.slice(4, transaction.data.length),
                 (LibOrder.Order, LibOrder.Order)
             );
 
@@ -182,7 +182,7 @@ contract MixinTECApprovalVerifier is
         );
     }
 
-    /// @dev Validates that the feeRecipient of a single order has approved a 0x transaction.
+    /// @dev Validates that the feeRecipients of a batch of order have approved a 0x transaction.
     /// @param orders Array of order structs containing order specifications.
     /// @param transactionHash EIP712 hash of the 0x transaction.
     /// @param transactionSignature Proof that the transaction has been signed by the signer.
@@ -223,7 +223,7 @@ contract MixinTECApprovalVerifier is
             address approvalSignerAddress = getSignerAddress(approvalHash, approvalSignatures[i]);
     
             // Add approval signer to list of signers
-            approvalSignerAddresses.append(approvalSignerAddress);
+            approvalSignerAddresses = approvalSignerAddresses.append(approvalSignerAddress);
         }
         
         uint256 ordersLength = orders.length;

contracts/tec/contracts/src/MixinTECCore.sol

@@ -43,8 +43,15 @@ contract MixinTECCore is
     )
         public
     {
+        // Ethereum transaction signer must be the same as 0x transaction signer
+        require(
+            // solhint-disable-next-line avoid-tx-origin
+            transaction.signerAddress == tx.origin,
+            "INVALID_TX_SIGNER"
+        );
+
         // Validate that the 0x transaction has been approves by each feeRecipient
-        assertValidTECApproval(
+        assertValidTECApprovals(
             transaction,
             transactionSignature,
             approvalExpirationTimeSeconds,

contracts/tec/contracts/src/interfaces/ITECApprovalVerifier.sol

@@ -31,7 +31,7 @@ contract ITECApprovalVerifier {
     /// @param transactionSignature Proof that the transaction has been signed by the signer.
     /// @param approvalExpirationTimeSeconds Array of expiration times in seconds for which each corresponding approval signature expires.
     /// @param approvalSignatures Array of signatures that correspond to the feeRecipients of each order in the transaction's Exchange calldata.
-    function assertValidTECApproval(
+    function assertValidTECApprovals(
         LibZeroExTransaction.ZeroExTransaction memory transaction,
         bytes memory transactionSignature,
         uint256[] memory approvalExpirationTimeSeconds,

contracts/tec/contracts/src/interfaces/ITransactions.sol

@@ -18,7 +18,7 @@
 pragma solidity ^0.5.3;
 
 
-contract IExchange {
+contract ITransactions {
 
     /// @dev Executes an exchange method call in the context of signer.
     /// @param salt Arbitrary number to ensure uniqueness of transaction hash.

contracts/tec/contracts/src/libs/LibConstants.sol

@@ -18,17 +18,17 @@
 
 pragma solidity ^0.5.3;
 
-import "../interfaces/IExchange.sol";
+import "../interfaces/ITransactions.sol";
 
 
 contract LibConstants {
 
      // solhint-disable-next-line var-name-mixedcase
-    IExchange internal EXCHANGE;
+    ITransactions internal EXCHANGE;
 
     constructor (address _exchange)
         public
     {
-        EXCHANGE = IExchange(_exchange);
+        EXCHANGE = ITransactions(_exchange);
     }
 }

contracts/tec/src/artifacts.ts

@@ -9,7 +9,7 @@ import * as TEC from '../generated-artifacts/TEC.json';
 import * as TestLibs from '../generated-artifacts/TestLibs.json';
 import * as TestMixins from '../generated-artifacts/TestMixins.json';
 export const artifacts = {
-    TestMixins: TestMixins as ContractArtifact,
     TEC: TEC as ContractArtifact,
     TestLibs: TestLibs as ContractArtifact,
+    TestMixins: TestMixins as ContractArtifact,
 };