Merge pull request #561 from 0xProject/feature/contracts/txorigin

Add Validator signature type

40 files changed, 669 insertions, 149 deletions

diff --git a/packages/contracts/compiler.json b/packages/contracts/compiler.json
index 7d469d2c3..ed59069fe 100644
--- a/packages/contracts/compiler.json
+++ b/packages/contracts/compiler.json
@@ -33,6 +33,7 @@
         "TestLibs",
         "TestSignatureValidator",
         "TokenRegistry",
+        "Whitelist",
         "WETH9",
         "ZRXToken"
     ]
diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index 037cb7a04..7bd0cf571 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -29,7 +29,7 @@
         "test:circleci": "yarn test"
     },
     "config": {
-        "abis": "../migrations/artifacts/2.0.0/@(AssetProxyOwner|DummyERC20Token|DummyERC721Token|ERC20Proxy|ERC721Proxy|Exchange|MixinAuthorizable|MultiSigWallet|MultiSigWalletWithTimeLock||TestAssetProxyDispatcher|TestLibBytes|TestLibs|TestSignatureValidator|TokenRegistry|WETH9|ZRXToken).json"
+        "abis": "../migrations/artifacts/2.0.0/@(AssetProxyOwner|DummyERC20Token|DummyERC721Token|ERC20Proxy|ERC721Proxy|Exchange|MixinAuthorizable|MultiSigWallet|MultiSigWalletWithTimeLock|TestAssetProxyDispatcher|TestLibBytes|TestLibs|TestSignatureValidator|TokenRegistry|Whitelist|WETH9|ZRXToken).json"
     },
     "repository": {
         "type": "git",
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
index ee0c66fdc..79824fbbb 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
@@ -47,21 +47,25 @@ contract ERC20Proxy is
         bytes memory assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         internal
     {
         // Data must be intended for this proxy.
+        uint256 length = assetMetadata.length;
+
         require(
-            uint8(assetMetadata[0]) == PROXY_ID,
-            PROXY_ID_MISMATCH
+            length == 21,
+            INVALID_METADATA_LENGTH
         );
 
-        // Decode metadata.
         require(
-            assetMetadata.length == 21,
-            INVALID_METADATA_LENGTH
+            uint8(assetMetadata[length - 1]) == PROXY_ID,
+            PROXY_ID_MISMATCH
         );
-        address token = readAddress(assetMetadata, 1);
+
+        // Decode metadata.
+        address token = readAddress(assetMetadata, 0);
 
         // Transfer tokens.
         bool success = IERC20Token(token).transferFrom(from, to, amount);
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
index 94aab9139..ace3570bc 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
@@ -47,12 +47,20 @@ contract ERC721Proxy is
         bytes memory assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         internal
     {
         // Data must be intended for this proxy.
+        uint256 length = assetMetadata.length;
+
+        require(
+            length == 53,
+            INVALID_METADATA_LENGTH
+        );
+
         require(
-            uint8(assetMetadata[0]) == PROXY_ID,
+            uint8(assetMetadata[length - 1]) == PROXY_ID,
             PROXY_ID_MISMATCH
         );
 
@@ -63,12 +71,8 @@ contract ERC721Proxy is
         );
 
         // Decode metadata
-        require(
-            assetMetadata.length == 53,
-            INVALID_METADATA_LENGTH
-        );
-        address token = readAddress(assetMetadata, 1);
-        uint256 tokenId = readUint256(assetMetadata, 21);
+        address token = readAddress(assetMetadata, 0);
+        uint256 tokenId = readUint256(assetMetadata, 20);
 
         // Transfer token.
         // Either succeeds or throws.
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
index 4ec31304f..4bd533148 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
@@ -36,7 +36,8 @@ contract MixinAssetProxy is
         bytes assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         external
         onlyAuthorized
     {
@@ -57,7 +58,8 @@ contract MixinAssetProxy is
         bytes[] memory assetMetadata,
         address[] memory from,
         address[] memory to,
-        uint256[] memory amounts)
+        uint256[] memory amounts
+    )
         public
         onlyAuthorized
     {
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
index 0bbd3b318..4aaeb66d1 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
@@ -87,7 +87,10 @@ contract MixinAuthorizable is
     /// @dev Removes authorizion of an address.
     /// @param target Address to remove authorization from.
     /// @param index Index of target in authorities array.
-    function removeAuthorizedAddressAtIndex(address target, uint256 index)
+    function removeAuthorizedAddressAtIndex(
+        address target,
+        uint256 index
+    )
         external
     {
         require(
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
index 8b30dfabb..7e1848889 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
@@ -34,7 +34,8 @@ contract IAssetProxy is
         bytes assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         external;
     
     /// @dev Makes multiple transfers of assets. Either succeeds or throws.
@@ -46,7 +47,8 @@ contract IAssetProxy is
         bytes[] memory assetMetadata,
         address[] memory from,
         address[] memory to,
-        uint256[] memory amounts)
+        uint256[] memory amounts
+    )
         public;
 
     /// @dev Gets the proxy id associated with the proxy address.
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol
index d6fe03898..cedd1744c 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol
@@ -45,6 +45,9 @@ contract IAuthorizable is
     /// @dev Removes authorizion of an address.
     /// @param target Address to remove authorization from.
     /// @param index Index of target in authorities array.
-    function removeAuthorizedAddressAtIndex(address target, uint256 index)
+    function removeAuthorizedAddressAtIndex(
+        address target,
+        uint256 index
+    )
         external;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
index 3800bf04c..de9d65a53 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
@@ -34,6 +34,7 @@ contract MAssetProxy is
         bytes memory assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         internal;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol
index cdf60bdee..6f35bd7ec 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol
@@ -38,5 +38,5 @@ contract MAuthorizable is
     );
 
     /// @dev Only authorized addresses can invoke functions with this modifier.
-    modifier onlyAuthorized { _; }
+    modifier onlyAuthorized { revert(); _; }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index 3b38d1f37..d996f933c 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -39,7 +39,8 @@ contract MixinAssetProxyDispatcher is
     function registerAssetProxy(
         uint8 assetProxyId,
         address newAssetProxy,
-        address oldAssetProxy)
+        address oldAssetProxy
+    )
         external
         onlyOwner
     {
@@ -86,17 +87,20 @@ contract MixinAssetProxyDispatcher is
         bytes memory assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         internal
     {
         // Do nothing if no amount should be transferred.
         if (amount > 0) {
+
             // Lookup asset proxy
+            uint256 length = assetMetadata.length;
             require(
-                assetMetadata.length >= 1,
+                length > 0,
                 GT_ZERO_LENGTH_REQUIRED
             );
-            uint8 assetProxyId = uint8(assetMetadata[0]);
+            uint8 assetProxyId = uint8(assetMetadata[length - 1]);
             IAssetProxy assetProxy = assetProxies[assetProxyId];
 
             // transferFrom will either succeed or throw.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
index f7fcd36b6..d40974e5f 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
@@ -19,18 +19,24 @@
 pragma solidity ^0.4.24;
 
 import "./mixins/MSignatureValidator.sol";
-import "./interfaces/ISigner.sol";
+import "./mixins/MTransactions.sol";
+import "./interfaces/IWallet.sol";
+import "./interfaces/IValidator.sol";
 import "./libs/LibExchangeErrors.sol";
 import "../../utils/LibBytes/LibBytes.sol";
 
 contract MixinSignatureValidator is
     LibBytes,
     LibExchangeErrors,
-    MSignatureValidator
+    MSignatureValidator,
+    MTransactions
 {
 
     // Mapping of hash => signer => signed
-    mapping(bytes32 => mapping(address => bool)) preSigned;
+    mapping (bytes32 => mapping (address => bool)) public preSigned;
+
+    // Mapping of signer => validator => approved
+    mapping (address => mapping (address => bool)) public allowedValidators;
 
     /// @dev Approves a hash on-chain using any valid signature type.
     ///      After presigning a hash, the preSign signature type will become valid for that hash and signer.
@@ -39,7 +45,8 @@ contract MixinSignatureValidator is
     function preSign(
         bytes32 hash,
         address signer,
-        bytes signature)
+        bytes signature
+    )
         external
     {
         require(
@@ -49,6 +56,19 @@ contract MixinSignatureValidator is
         preSigned[hash][signer] = true;
     }
 
+    /// @dev Approves/unnapproves a Validator contract to verify signatures on signer's behalf.
+    /// @param validator Address of Validator contract.
+    /// @param approval Approval or disapproval of  Validator contract.
+    function setSignatureValidatorApproval(
+        address validator,
+        bool approval
+    )
+        external
+    {
+        address signer = getCurrentContextAddress();
+        allowedValidators[signer][validator] = approval;
+    }
+
     /// @dev Verifies that a hash has been signed by the given signer.
     /// @param hash Any 32 byte hash.
     /// @param signer Address that should have signed the given hash.
@@ -57,71 +77,69 @@ contract MixinSignatureValidator is
     function isValidSignature(
         bytes32 hash,
         address signer,
-        bytes memory signature)
+        bytes memory signature
+    )
         internal
         view
         returns (bool isValid)
     {
         // TODO: Domain separation: make hash depend on role. (Taker sig should not be valid as maker sig, etc.)
-
         require(
             signature.length >= 1,
             INVALID_SIGNATURE_LENGTH
         );
-        SignatureType signatureType = SignatureType(uint8(signature[0]));
 
-        // Variables are not scoped in Solidity
+        // Pop last byte off of signature byte array.
+        SignatureType signatureType = SignatureType(uint8(popByte(signature)));
+
+        // Variables are not scoped in Solidity.
         uint8 v;
         bytes32 r;
         bytes32 s;
         address recovered;
-
-        // Always illegal signature
+        
+        // Always illegal signature.
         // This is always an implicit option since a signer can create a
         // signature array with invalid type or length. We may as well make
         // it an explicit option. This aids testing and analysis. It is
         // also the initialization value for the enum type.
         if (signatureType == SignatureType.Illegal) {
-            // NOTE: Reason cannot be assigned to a variable because of https://github.com/ethereum/solidity/issues/4051
-            revert("Illegal signature type.");
+            revert(ILLEGAL_SIGNATURE_TYPE);
 
-        // Always invalid signature
+        // Always invalid signature.
         // Like Illegal, this is always implicitly available and therefore
         // offered explicitly. It can be implicitly created by providing
         // a correctly formatted but incorrect signature.
         } else if (signatureType == SignatureType.Invalid) {
             require(
-                signature.length == 1,
+                signature.length == 0,
                 INVALID_SIGNATURE_LENGTH
             );
             isValid = false;
             return isValid;
 
-        // Implicitly signed by caller
-        // The signer has initiated the call. In the case of non-contract
-        // accounts it means the transaction itself was signed.
-        // Example: let's say for a particular operation three signatures
-        // A, B and C are required. To submit the transaction, A and B can
-        // give a signature to C, who can then submit the transaction using
-        // `Caller` for his own signature. Or A and C can sign and B can
-        // submit using `Caller`. Having `Caller` allows this flexibility.
-        } else if (signatureType == SignatureType.Caller) {
+        // Signature using EIP712
+        } else if (signatureType == SignatureType.EIP712) {
             require(
-                signature.length == 1,
+                signature.length == 65,
                 INVALID_SIGNATURE_LENGTH
             );
-            isValid = signer == msg.sender;
+            v = uint8(signature[0]);
+            r = readBytes32(signature, 1);
+            s = readBytes32(signature, 33);
+            recovered = ecrecover(hash, v, r, s);
+            isValid = signer == recovered;
             return isValid;
 
         // Signed using web3.eth_sign
-        } else if (signatureType == SignatureType.Ecrecover) {
+        } else if (signatureType == SignatureType.EthSign) {
             require(
-                signature.length == 66,
+                signature.length == 65,
                 INVALID_SIGNATURE_LENGTH
             );
-            v = uint8(signature[1]);
-            r = readBytes32(signature, 2);
-            s = readBytes32(signature, 34);
+            v = uint8(signature[0]);
+            r = readBytes32(signature, 1);
+            s = readBytes32(signature, 33);
             recovered = ecrecover(
                 keccak256("\x19Ethereum Signed Message:\n32", hash),
                 v,
@@ -131,20 +149,55 @@ contract MixinSignatureValidator is
             isValid = signer == recovered;
             return isValid;
 
-        // Signature using EIP712
-        } else if (signatureType == SignatureType.EIP712) {
+        // Implicitly signed by caller.
+        // The signer has initiated the call. In the case of non-contract
+        // accounts it means the transaction itself was signed.
+        // Example: let's say for a particular operation three signatures
+        // A, B and C are required. To submit the transaction, A and B can
+        // give a signature to C, who can then submit the transaction using
+        // `Caller` for his own signature. Or A and C can sign and B can
+        // submit using `Caller`. Having `Caller` allows this flexibility.
+        } else if (signatureType == SignatureType.Caller) {
             require(
-                signature.length == 66,
+                signature.length == 0,
                 INVALID_SIGNATURE_LENGTH
             );
-            v = uint8(signature[1]);
-            r = readBytes32(signature, 2);
-            s = readBytes32(signature, 34);
-            recovered = ecrecover(hash, v, r, s);
-            isValid = signer == recovered;
+            isValid = signer == msg.sender;
             return isValid;
 
-        // Signature from Trezor hardware wallet
+        // Signature verified by wallet contract.
+        // If used with an order, the maker of the order is the wallet contract.
+        } else if (signatureType == SignatureType.Wallet) {
+            isValid = IWallet(signer).isValidSignature(hash, signature);
+            return isValid;
+
+        // Signature verified by validator contract.
+        // If used with an order, the maker of the order can still be an EOA.
+        // A signature using this type should be encoded as:
+        // | Offset   | Length | Contents                        |
+        // | 0x00     | x      | Signature to validate           |
+        // | 0x00 + x | 20     | Address of validator contract   |
+        // | 0x14 + x | 1      | Signature type is always "\x06" |
+        } else if (signatureType == SignatureType.Validator) {
+            // Pop last 20 bytes off of signature byte array.
+            address validator = popAddress(signature);
+            // Ensure signer has approved validator.
+            if (!allowedValidators[signer][validator]) {
+                return false;
+            }
+            isValid = IValidator(validator).isValidSignature(
+                hash,
+                signer,
+                signature
+            );
+            return isValid;
+
+        // Signer signed hash previously using the preSign function.
+        } else if (signatureType == SignatureType.PreSigned) {
+            isValid = preSigned[hash][signer];
+            return isValid;
+
+        // Signature from Trezor hardware wallet.
         // It differs from web3.eth_sign in the encoding of message length
         // (Bitcoin varint encoding vs ascii-decimal, the latter is not
         // self-terminating which leads to ambiguities).
@@ -154,12 +207,12 @@ contract MixinSignatureValidator is
         // https://github.com/trezor/trezor-mcu/blob/master/firmware/crypto.c#L36
         } else if (signatureType == SignatureType.Trezor) {
             require(
-                signature.length == 66,
+                signature.length == 65,
                 INVALID_SIGNATURE_LENGTH
             );
-            v = uint8(signature[1]);
-            r = readBytes32(signature, 2);
-            s = readBytes32(signature, 34);
+            v = uint8(signature[0]);
+            r = readBytes32(signature, 1);
+            s = readBytes32(signature, 33);
             recovered = ecrecover(
                 keccak256("\x19Ethereum Signed Message:\n\x41", hash),
                 v,
@@ -169,11 +222,6 @@ contract MixinSignatureValidator is
             isValid = signer == recovered;
             return isValid;
 
-        // Signature verified by signer contract
-        } else if (signatureType == SignatureType.Contract) {
-            isValid = ISigner(signer).isValidSignature(hash, signature);
-            return isValid;
-
         // Signer signed hash previously using the preSign function
         } else if (signatureType == SignatureType.PreSigned) {
             isValid = preSigned[hash][signer];
@@ -185,7 +233,6 @@ contract MixinSignatureValidator is
         // that we currently support. In this case returning false
         // may lead the caller to incorrectly believe that the
         // signature was invalid.)
-        // NOTE: Reason cannot be assigned to a variable because of https://github.com/ethereum/solidity/issues/4051
-        revert("Unsupported signature type.");
+        revert(UNSUPPORTED_SIGNATURE_TYPE);
     }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
index f93a80705..d153dfa5c 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
@@ -43,15 +43,20 @@ contract MixinTransactions is
         uint256 salt,
         address signer,
         bytes data,
-        bytes signature)
+        bytes signature
+    )
         external
     {
         // Prevent reentrancy
-        require(currentContextAddress == address(0));
+        require(
+            currentContextAddress == address(0),
+            REENTRANCY_NOT_ALLOWED
+        );
 
         // Calculate transaction hash
         bytes32 transactionHash = keccak256(
             address(this),
+            signer,
             salt,
             data
         );
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol
index fc428e9c0..9f21c18d7 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol
@@ -20,17 +20,15 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./IExchangeCore.sol";
-import "./IMatchOrders";
-import "./ISettlement";
-import "./ISignatureValidator";
-import "./ITransactions";
-import "./IAssetProxyDispatcher";
-import "./IWrapperFunctions";
+import "./IMatchOrders.sol";
+import "./ISignatureValidator.sol";
+import "./ITransactions.sol";
+import "./IAssetProxyDispatcher.sol";
+import "./IWrapperFunctions.sol";
 
 contract IExchange is
     IExchangeCore,
     IMatchOrders,
-    ISettlement,
     ISignatureValidator,
     ITransactions,
     IAssetProxyDispatcher,
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol
index 65ff45f7b..26e360c91 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol
@@ -27,6 +27,16 @@ contract ISignatureValidator {
     function preSign(
         bytes32 hash,
         address signer,
-        bytes signature)
+        bytes signature
+    )
+        external;
+    
+    /// @dev Approves/unnapproves a Validator contract to verify signatures on signer's behalf.
+    /// @param validator Address of Validator contract.
+    /// @param approval Approval or disapproval of  Validator contract.
+    function setSignatureValidatorApproval(
+        address validator,
+        bool approval
+    )
         external;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IValidator.sol
new file mode 100644
index 000000000..3e5ccc190
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IValidator.sol
@@ -0,0 +1,36 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.23;
+
+contract IValidator {
+
+    /// @dev Verifies that a signature is valid.
+    /// @param hash Message hash that is signed.
+    /// @param signer Address that should have signed the given hash.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        address signer,
+        bytes signature
+    )
+        external
+        view
+        returns (bool isValid);
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISigner.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWallet.sol
index 53c41d331..c86a2c057 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISigner.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWallet.sol
@@ -18,7 +18,7 @@
 
 pragma solidity ^0.4.24;
 
-contract ISigner {
+contract IWallet {
 
     /// @dev Verifies that a signature is valid.
     /// @param hash Message hash that is signed.
@@ -26,7 +26,8 @@ contract ISigner {
     /// @return Validity of order signature.
     function isValidSignature(
         bytes32 hash,
-        bytes signature)
+        bytes signature
+    )
         external
         view
         returns (bool isValid);
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
index 1eb1233ed..8682b394a 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
@@ -19,27 +19,23 @@
 pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "./libs/LibOrder.sol";
-import "./libs/LibFillResults.sol";
+import "../libs/LibOrder.sol";
+import "../libs/LibFillResults.sol";
 
 contract IWrapperFunctions is
-    LibBytes,
-    LibMath,
     LibOrder,
-    LibFillResults,
-    LibExchangeErrors,
-    MExchangeCore
+    LibFillResults
 {
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
     /// @param order LibOrder.Order struct containing order specifications.
     /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
     /// @param signature Proof that order has been created by maker.
     function fillOrKillOrder(
-        LibOrder.LibOrder.Order memory order,
+        LibOrder.Order memory order,
         uint256 takerAssetFillAmount,
         bytes memory signature)
         public
-        returns (LibFillResults.LibFillResults.FillResults memory fillResults);
+        returns (LibFillResults.FillResults memory fillResults);
 
     /// @dev Fills an order with specified parameters and ECDSA signature.
     ///      Returns false if the transaction would otherwise revert.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
index 4712ee36c..7d67e5080 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
@@ -32,6 +32,7 @@ contract LibExchangeErrors {
     string constant INVALID_ORDER_MAKER_ASSET_AMOUNT = "Invalid order maker asset amount: expected a non-zero value.";
 
     // Transaction revert reasons
+    string constant REENTRANCY_NOT_ALLOWED = "`executeTransaction` is not allowed to call itself recursively.";
     string constant DUPLICATE_TRANSACTION_HASH = "Transaction has already been executed.";
     string constant TRANSACTION_EXECUTION_FAILED = "Transaction execution failed.";
 
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index ccc960d6e..87c5f6361 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -41,6 +41,7 @@ contract MAssetProxyDispatcher is
         bytes memory assetMetadata,
         address from,
         address to,
-        uint256 amount)
+        uint256 amount
+    )
         internal;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
index 3658e7c6f..7eed453ff 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
@@ -25,14 +25,15 @@ contract MSignatureValidator is
 {
     // Allowed signature types.
     enum SignatureType {
-        Illegal,  // Default value
-        Invalid,
-        Caller,
-        Ecrecover,
-        EIP712,
-        Trezor,
-        Contract,
-        PreSigned
+        Illegal,    // 0x00, default value
+        Invalid,    // 0x01
+        EIP712,     // 0x02
+        EthSign,    // 0x03
+        Caller,     // 0x04
+        Wallet,     // 0x05
+        Validator,  // 0x06
+        PreSigned,  // 0x07
+        Trezor      // 0x08
     }
 
     /// @dev Verifies that a signature is valid.
@@ -43,7 +44,8 @@ contract MSignatureValidator is
     function isValidSignature(
         bytes32 hash,
         address signer,
-        bytes memory signature)
+        bytes memory signature
+    )
         internal
         view
         returns (bool isValid);
diff --git a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
index 5a6801262..69554605d 100644
--- a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
+++ b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
@@ -25,6 +25,30 @@ contract TestLibBytes is
     LibBytes
 {
 
+    /// @dev Pops the last byte off of a byte array by modifying its length.
+    /// @param b Byte array that will be modified.
+    /// @return The byte that was popped off.
+    function publicPopByte(bytes memory b)
+        public
+        pure
+        returns (bytes memory, bytes1 result)
+    {
+        result = popByte(b);
+        return (b, result);
+    }
+
+    /// @dev Pops the last 20 bytes off of a byte array by modifying its length.
+    /// @param b Byte array that will be modified.
+    /// @return The 20 byte address that was popped off.
+    function publicPopAddress(bytes memory b)
+        public
+        pure
+        returns (bytes memory, address result)
+    {
+        result = popAddress(b);
+        return (b, result);
+    }
+
     /// @dev Tests equality of two byte arrays.
     /// @param lhs First byte array to compare.
     /// @param rhs Second byte array to compare.
diff --git a/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol b/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
index 15d9ca189..0f84678cf 100644
--- a/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
@@ -20,13 +20,18 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "../../protocol/Exchange/MixinSignatureValidator.sol";
+import "../../protocol/Exchange/MixinTransactions.sol";
 
-contract TestSignatureValidator is MixinSignatureValidator {
+contract TestSignatureValidator is
+    MixinSignatureValidator,
+    MixinTransactions
+{
 
     function publicIsValidSignature(
         bytes32 hash,
         address signer,
-        bytes memory signature)
+        bytes memory signature
+    )
         public
         view
         returns (bool isValid)
diff --git a/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol b/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol
new file mode 100644
index 000000000..0594e2767
--- /dev/null
+++ b/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol
@@ -0,0 +1,133 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../utils/Ownable/Ownable.sol";
+
+contract Whitelist is 
+    Ownable
+{
+    // Revert reasons
+    string constant MAKER_NOT_WHITELISTED = "Maker address not whitelisted.";
+    string constant TAKER_NOT_WHITELISTED = "Taker address not whitelisted.";
+    string constant INVALID_SENDER = "Sender must equal transaction origin.";
+
+    // Mapping of address => whitelist status.
+    mapping (address => bool) public isWhitelisted;
+
+    // Exchange contract.
+    IExchange EXCHANGE;
+
+    byte constant VALIDATOR_SIGNATURE_BYTE = "\x06";
+    bytes TX_ORIGIN_SIGNATURE;
+
+    constructor (address _exchange)
+        public
+    {
+        EXCHANGE = IExchange(_exchange);
+        TX_ORIGIN_SIGNATURE = abi.encodePacked(address(this), VALIDATOR_SIGNATURE_BYTE);
+    }
+
+    /// @dev Adds or removes an address from the whitelist.
+    /// @param target Address to add or remove from whitelist.
+    /// @param isApproved Whitelist status to assign to address.
+    function updateWhitelistStatus(
+        address target,
+        bool isApproved
+    )
+        external
+        onlyOwner
+    {
+        isWhitelisted[target] = isApproved;
+    }
+
+    /// @dev Fills an order using `msg.sender` as the taker.
+    ///      The transaction will revert if both the maker and taker are not whitelisted.
+    ///      Orders should specify this contract as the `senderAddress` in order to gaurantee
+    ///      that both maker and taker have been whitelisted.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param salt Arbitrary value to gaurantee uniqueness of 0x transaction hash.
+    /// @param orderSignature Proof that order has been created by maker.
+    function fillOrderIfWhitelisted(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        uint256 salt,
+        bytes memory orderSignature
+    )
+        public
+    {
+        address takerAddress = msg.sender;
+    
+        // This contract must be the entry point for the transaction.
+        require(
+            takerAddress == tx.origin,
+            INVALID_SENDER
+        );
+
+        // Check if maker is on the whitelist.
+        require(
+            isWhitelisted[order.makerAddress],
+            MAKER_NOT_WHITELISTED
+        );
+
+        // Check if taker is on the whitelist.
+        require(
+            isWhitelisted[takerAddress],
+            TAKER_NOT_WHITELISTED
+        );
+
+        // Encode arguments into byte array.
+        bytes memory data = abi.encodeWithSelector(
+            EXCHANGE.fillOrder.selector,
+            order,
+            takerAssetFillAmount,
+            orderSignature
+        );
+
+        // Call `fillOrder` via `executeTransaction`.
+        EXCHANGE.executeTransaction(
+            salt,
+            takerAddress,
+            data,
+            TX_ORIGIN_SIGNATURE
+        );
+    }
+
+    /// @dev Verifies signer is same as signer of current Ethereum transaction.
+    ///      NOTE: This function can currently be used to validate signatures coming from outside of this contract.
+    ///      Extra safety checks can be added for a production contract.
+    /// @param signer Address that should have signed the given hash.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        address signer,
+        bytes signature
+    )
+        external
+        view
+        returns (bool isValid)
+    {
+        return signer == tx.origin;
+    }
+}
diff --git a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
index 975565773..df2221c93 100644
--- a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
@@ -21,15 +21,68 @@ pragma solidity ^0.4.24;
 contract LibBytes {
 
     // Revert reasons
+    string constant GT_ZERO_LENGTH_REQUIRED = "Length must be greater than 0.";
     string constant GTE_4_LENGTH_REQUIRED = "Length must be greater than or equal to 4.";
     string constant GTE_20_LENGTH_REQUIRED = "Length must be greater than or equal to 20.";
     string constant GTE_32_LENGTH_REQUIRED = "Length must be greater than or equal to 32.";
+    string constant INDEX_OUT_OF_BOUNDS = "Specified array index is out of bounds.";
+
+    /// @dev Pops the last byte off of a byte array by modifying its length.
+    /// @param b Byte array that will be modified.
+    /// @return The byte that was popped off.
+    function popByte(bytes memory b)
+        internal
+        pure
+        returns (bytes1 result)
+    {
+        require(
+            b.length > 0,
+            GT_ZERO_LENGTH_REQUIRED
+        );
+
+        // Store last byte.
+        result = b[b.length - 1];
+        
+        assembly {
+            // Decrement length of byte array.
+            let newLen := sub(mload(b), 1)
+            mstore(b, newLen)
+        }
+        return result;
+    }
+
+    /// @dev Pops the last 20 bytes off of a byte array by modifying its length.
+    /// @param b Byte array that will be modified.
+    /// @return The 20 byte address that was popped off.
+    function popAddress(bytes memory b)
+        internal
+        pure
+        returns (address result)
+    {
+        require(
+            b.length >= 20,
+            GTE_20_LENGTH_REQUIRED
+        );
+
+        // Store last 20 bytes.
+        result = readAddress(b, b.length - 20);
+
+        assembly {
+            // Subtract 20 from byte array length.
+            let newLen := sub(mload(b), 20)
+            mstore(b, newLen)
+        }
+        return result;
+    }
 
     /// @dev Tests equality of two byte arrays.
     /// @param lhs First byte array to compare.
     /// @param rhs Second byte array to compare.
     /// @return True if arrays are the same. False otherwise.
-    function areBytesEqual(bytes memory lhs, bytes memory rhs)
+    function areBytesEqual(
+        bytes memory lhs,
+        bytes memory rhs
+    )
         internal
         pure
         returns (bool equal)
@@ -63,7 +116,8 @@ contract LibBytes {
     /// @return address from byte array.
     function readAddress(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         internal
         pure
         returns (address result)
@@ -95,7 +149,8 @@ contract LibBytes {
     function writeAddress(
         bytes memory b,
         uint256 index,
-        address input)
+        address input
+    )
         internal
         pure
     {
@@ -132,7 +187,8 @@ contract LibBytes {
     /// @return bytes32 value from byte array.
     function readBytes32(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         internal
         pure
         returns (bytes32 result)
@@ -159,7 +215,8 @@ contract LibBytes {
     function writeBytes32(
         bytes memory b,
         uint256 index,
-        bytes32 input)
+        bytes32 input
+    )
         internal
         pure
     {
@@ -183,7 +240,8 @@ contract LibBytes {
     /// @return uint256 value from byte array.
     function readUint256(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         internal
         pure
         returns (uint256 result)
@@ -198,7 +256,8 @@ contract LibBytes {
     function writeUint256(
         bytes memory b,
         uint256 index,
-        uint256 input)
+        uint256 input
+    )
         internal
         pure
     {
diff --git a/packages/contracts/src/utils/artifacts.ts b/packages/contracts/src/utils/artifacts.ts
index fe74ea072..357c66a0a 100644
--- a/packages/contracts/src/utils/artifacts.ts
+++ b/packages/contracts/src/utils/artifacts.ts
@@ -15,6 +15,7 @@ import * as TestLibs from '../artifacts/TestLibs.json';
 import * as TestSignatureValidator from '../artifacts/TestSignatureValidator.json';
 import * as TokenRegistry from '../artifacts/TokenRegistry.json';
 import * as EtherToken from '../artifacts/WETH9.json';
+import * as Whitelist from '../artifacts/Whitelist.json';
 import * as ZRX from '../artifacts/ZRXToken.json';
 
 export const artifacts = {
@@ -33,5 +34,6 @@ export const artifacts = {
     TestLibs: (TestLibs as any) as ContractArtifact,
     TestSignatureValidator: (TestSignatureValidator as any) as ContractArtifact,
     TokenRegistry: (TokenRegistry as any) as ContractArtifact,
+    Whitelist: (Whitelist as any) as ContractArtifact,
     ZRX: (ZRX as any) as ContractArtifact,
 };
diff --git a/packages/contracts/src/utils/asset_proxy_utils.ts b/packages/contracts/src/utils/asset_proxy_utils.ts
index c042da5d0..a17d4cdfa 100644
--- a/packages/contracts/src/utils/asset_proxy_utils.ts
+++ b/packages/contracts/src/utils/asset_proxy_utils.ts
@@ -39,7 +39,7 @@ export const assetProxyUtils = {
     encodeERC20ProxyData(tokenAddress: string): string {
         const encodedAssetProxyId = assetProxyUtils.encodeAssetProxyId(AssetProxyId.ERC20);
         const encodedAddress = assetProxyUtils.encodeAddress(tokenAddress);
-        const encodedMetadata = Buffer.concat([encodedAssetProxyId, encodedAddress]);
+        const encodedMetadata = Buffer.concat([encodedAddress, encodedAssetProxyId]);
         const encodedMetadataHex = ethUtil.bufferToHex(encodedMetadata);
         return encodedMetadataHex;
     },
@@ -52,7 +52,7 @@ export const assetProxyUtils = {
                 }`,
             );
         }
-        const encodedAssetProxyId = encodedProxyMetadata.slice(0, 1);
+        const encodedAssetProxyId = encodedProxyMetadata.slice(-1);
         const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
         if (assetProxyId !== AssetProxyId.ERC20) {
             throw new Error(
@@ -61,7 +61,7 @@ export const assetProxyUtils = {
                 }), but got ${assetProxyId}`,
             );
         }
-        const encodedTokenAddress = encodedProxyMetadata.slice(1, 21);
+        const encodedTokenAddress = encodedProxyMetadata.slice(0, 20);
         const tokenAddress = assetProxyUtils.decodeAddress(encodedTokenAddress);
         const erc20ProxyData = {
             assetProxyId,
@@ -73,7 +73,7 @@ export const assetProxyUtils = {
         const encodedAssetProxyId = assetProxyUtils.encodeAssetProxyId(AssetProxyId.ERC721);
         const encodedAddress = assetProxyUtils.encodeAddress(tokenAddress);
         const encodedTokenId = assetProxyUtils.encodeUint256(tokenId);
-        const encodedMetadata = Buffer.concat([encodedAssetProxyId, encodedAddress, encodedTokenId]);
+        const encodedMetadata = Buffer.concat([encodedAddress, encodedTokenId, encodedAssetProxyId]);
         const encodedMetadataHex = ethUtil.bufferToHex(encodedMetadata);
         return encodedMetadataHex;
     },
@@ -86,7 +86,7 @@ export const assetProxyUtils = {
                 }`,
             );
         }
-        const encodedAssetProxyId = encodedProxyMetadata.slice(0, 1);
+        const encodedAssetProxyId = encodedProxyMetadata.slice(-1);
         const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
         if (assetProxyId !== AssetProxyId.ERC721) {
             throw new Error(
@@ -95,9 +95,9 @@ export const assetProxyUtils = {
                 }), but got ${assetProxyId}`,
             );
         }
-        const encodedTokenAddress = encodedProxyMetadata.slice(1, 21);
+        const encodedTokenAddress = encodedProxyMetadata.slice(0, 20);
         const tokenAddress = assetProxyUtils.decodeAddress(encodedTokenAddress);
-        const encodedTokenId = encodedProxyMetadata.slice(21, 53);
+        const encodedTokenId = encodedProxyMetadata.slice(20, 52);
         const tokenId = assetProxyUtils.decodeUint256(encodedTokenId);
         const erc721ProxyData = {
             assetProxyId,
@@ -115,7 +115,7 @@ export const assetProxyUtils = {
                 }`,
             );
         }
-        const encodedAssetProxyId = encodedProxyMetadata.slice(0, 1);
+        const encodedAssetProxyId = encodedProxyMetadata.slice(-1);
         const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
         return assetProxyId;
     },
diff --git a/packages/contracts/src/utils/constants.ts b/packages/contracts/src/utils/constants.ts
index 7a0e26a48..9b0b92545 100644
--- a/packages/contracts/src/utils/constants.ts
+++ b/packages/contracts/src/utils/constants.ts
@@ -28,6 +28,7 @@ export const constants = {
     DUMMY_TOKEN_SYMBOL: '',
     DUMMY_TOKEN_DECIMALS: new BigNumber(18),
     DUMMY_TOKEN_TOTAL_SUPPLY: new BigNumber(0),
+    NULL_BYTES: '0x',
     NUM_DUMMY_ERC20_TO_DEPLOY: 3,
     NUM_DUMMY_ERC721_TO_DEPLOY: 1,
     NUM_ERC721_TOKENS_TO_MINT: 2,
diff --git a/packages/contracts/src/utils/signing_utils.ts b/packages/contracts/src/utils/signing_utils.ts
index 61ab1f138..4c36c8310 100644
--- a/packages/contracts/src/utils/signing_utils.ts
+++ b/packages/contracts/src/utils/signing_utils.ts
@@ -8,19 +8,19 @@ export const signingUtils = {
             const prefixedMessage = ethUtil.hashPersonalMessage(message);
             const ecSignature = ethUtil.ecsign(prefixedMessage, privateKey);
             const signature = Buffer.concat([
-                ethUtil.toBuffer(signatureType),
                 ethUtil.toBuffer(ecSignature.v),
                 ecSignature.r,
                 ecSignature.s,
+                ethUtil.toBuffer(signatureType),
             ]);
             return signature;
         } else if (signatureType === SignatureType.EIP712) {
             const ecSignature = ethUtil.ecsign(message, privateKey);
             const signature = Buffer.concat([
-                ethUtil.toBuffer(signatureType),
                 ethUtil.toBuffer(ecSignature.v),
                 ecSignature.r,
                 ecSignature.s,
+                ethUtil.toBuffer(signatureType),
             ]);
             return signature;
         } else {
diff --git a/packages/contracts/src/utils/transaction_factory.ts b/packages/contracts/src/utils/transaction_factory.ts
index 941bff96d..65cdb3f89 100644
--- a/packages/contracts/src/utils/transaction_factory.ts
+++ b/packages/contracts/src/utils/transaction_factory.ts
@@ -7,26 +7,25 @@ import { signingUtils } from './signing_utils';
 import { SignatureType, SignedTransaction } from './types';
 
 export class TransactionFactory {
-    private _signer: string;
+    private _signerBuff: Buffer;
     private _exchangeAddress: string;
     private _privateKey: Buffer;
     constructor(privateKey: Buffer, exchangeAddress: string) {
         this._privateKey = privateKey;
         this._exchangeAddress = exchangeAddress;
-        const signerBuff = ethUtil.privateToAddress(this._privateKey);
-        this._signer = `0x${signerBuff.toString('hex')}`;
+        this._signerBuff = ethUtil.privateToAddress(this._privateKey);
     }
     public newSignedTransaction(
         data: string,
         signatureType: SignatureType = SignatureType.Ecrecover,
     ): SignedTransaction {
         const salt = generatePseudoRandomSalt();
-        const txHash = crypto.solSHA3([this._exchangeAddress, salt, ethUtil.toBuffer(data)]);
+        const txHash = crypto.solSHA3([this._exchangeAddress, this._signerBuff, salt, ethUtil.toBuffer(data)]);
         const signature = signingUtils.signMessage(txHash, this._privateKey, signatureType);
         const signedTx = {
             exchangeAddress: this._exchangeAddress,
             salt,
-            signer: this._signer,
+            signer: `0x${this._signerBuff.toString('hex')}`,
             data,
             signature: `0x${signature.toString('hex')}`,
         };
diff --git a/packages/contracts/src/utils/types.ts b/packages/contracts/src/utils/types.ts
index 90f90ec27..1eeffc70e 100644
--- a/packages/contracts/src/utils/types.ts
+++ b/packages/contracts/src/utils/types.ts
@@ -111,16 +111,19 @@ export enum ContractName {
     DummyERC721Token = 'DummyERC721Token',
     TestLibBytes = 'TestLibBytes',
     Authorizable = 'Authorizable',
+    Whitelist = 'Whitelist',
 }
 
 export enum SignatureType {
     Illegal,
     Invalid,
-    Caller,
-    Ecrecover,
     EIP712,
-    Trezor,
+    Ecrecover,
+    TxOrigin,
+    Caller,
     Contract,
+    PreSigned,
+    Trezor,
 }
 
 export interface SignedTransaction {
diff --git a/packages/contracts/src/utils/web3_wrapper.ts b/packages/contracts/src/utils/web3_wrapper.ts
index 02595506b..4b8512222 100644
--- a/packages/contracts/src/utils/web3_wrapper.ts
+++ b/packages/contracts/src/utils/web3_wrapper.ts
@@ -7,7 +7,7 @@ import { coverage } from './coverage';
 
 export const txDefaults = {
     from: devConstants.TESTRPC_FIRST_ADDRESS,
-    gas: devConstants.GAS_ESTIMATE,
+    gas: devConstants.GAS_LIMIT,
 };
 const providerConfigs = { shouldUseInProcessGanache: true };
 export const provider = web3Factory.getRpcProvider(providerConfigs);
diff --git a/packages/contracts/test/asset_proxy_owner.ts b/packages/contracts/test/asset_proxy_owner.ts
index db68b5678..43c5da512 100644
--- a/packages/contracts/test/asset_proxy_owner.ts
+++ b/packages/contracts/test/asset_proxy_owner.ts
@@ -36,6 +36,12 @@ describe('AssetProxyOwner', () => {
     let multiSigWrapper: MultiSigWrapper;
 
     before(async () => {
+        await blockchainLifecycle.startAsync();
+    });
+    after(async () => {
+        await blockchainLifecycle.revertAsync();
+    });
+    before(async () => {
         const accounts = await web3Wrapper.getAvailableAddressesAsync();
         owners = [accounts[0], accounts[1]];
         const initialOwner = (authorized = accounts[0]);
diff --git a/packages/contracts/test/exchange/core.ts b/packages/contracts/test/exchange/core.ts
index be8d14cb0..bc476a5ee 100644
--- a/packages/contracts/test/exchange/core.ts
+++ b/packages/contracts/test/exchange/core.ts
@@ -460,10 +460,11 @@ describe('Exchange core', () => {
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
             });
 
+            const v = ethUtil.toBuffer(signedOrder.signature.slice(0, 4));
             const invalidR = ethUtil.sha3('invalidR');
             const invalidS = ethUtil.sha3('invalidS');
-            const signatureTypeAndV = signedOrder.signature.slice(0, 6);
-            const invalidSigBuff = Buffer.concat([ethUtil.toBuffer(signatureTypeAndV), invalidR, invalidS]);
+            const signatureType = ethUtil.toBuffer(`0x${signedOrder.signature.slice(-2)}`);
+            const invalidSigBuff = Buffer.concat([v, invalidR, invalidS, signatureType]);
             const invalidSigHex = `0x${invalidSigBuff.toString('hex')}`;
             signedOrder.signature = invalidSigHex;
             return expect(exchangeWrapper.fillOrderAsync(signedOrder, takerAddress)).to.be.rejectedWith(
diff --git a/packages/contracts/test/exchange/libs.ts b/packages/contracts/test/exchange/libs.ts
index bbca54274..a3282876b 100644
--- a/packages/contracts/test/exchange/libs.ts
+++ b/packages/contracts/test/exchange/libs.ts
@@ -49,7 +49,6 @@ describe('Exchange libs', () => {
 
     beforeEach(async () => {
         await blockchainLifecycle.startAsync();
-        signedOrder = orderFactory.newSignedOrder();
     });
     afterEach(async () => {
         await blockchainLifecycle.revertAsync();
@@ -69,7 +68,8 @@ describe('Exchange libs', () => {
             });
         });
         describe('getOrderHash', () => {
-            it('should output the correct order hash', async () => {
+            it('should output the correct orderHash', async () => {
+                signedOrder = orderFactory.newSignedOrder();
                 const orderHashHex = await libs.publicGetOrderHash.callAsync(signedOrder);
                 expect(orderUtils.getOrderHashHex(signedOrder)).to.be.equal(orderHashHex);
             });
diff --git a/packages/contracts/test/exchange/signature_validator.ts b/packages/contracts/test/exchange/signature_validator.ts
index 376fff438..1f030b742 100644
--- a/packages/contracts/test/exchange/signature_validator.ts
+++ b/packages/contracts/test/exchange/signature_validator.ts
@@ -53,7 +53,6 @@ describe('MixinSignatureValidator', () => {
 
     beforeEach(async () => {
         await blockchainLifecycle.startAsync();
-        signedOrder = orderFactory.newSignedOrder();
     });
     afterEach(async () => {
         await blockchainLifecycle.revertAsync();
@@ -75,13 +74,11 @@ describe('MixinSignatureValidator', () => {
         });
 
         it('should return false with an invalid signature', async () => {
+            const v = ethUtil.toBuffer(signedOrder.signature.slice(0, 4));
             const invalidR = ethUtil.sha3('invalidR');
             const invalidS = ethUtil.sha3('invalidS');
-            const invalidSigBuff = Buffer.concat([
-                ethUtil.toBuffer(signedOrder.signature.slice(0, 6)),
-                invalidR,
-                invalidS,
-            ]);
+            const signatureType = ethUtil.toBuffer(`0x${signedOrder.signature.slice(-2)}`);
+            const invalidSigBuff = Buffer.concat([v, invalidR, invalidS, signatureType]);
             const invalidSigHex = `0x${invalidSigBuff.toString('hex')}`;
             signedOrder.signature = invalidSigHex;
             const orderHashHex = orderUtils.getOrderHashHex(signedOrder);
diff --git a/packages/contracts/test/exchange/transactions.ts b/packages/contracts/test/exchange/transactions.ts
index 33fe11bfa..6b3083ae5 100644
--- a/packages/contracts/test/exchange/transactions.ts
+++ b/packages/contracts/test/exchange/transactions.ts
@@ -1,4 +1,5 @@
 import { BlockchainLifecycle } from '@0xproject/dev-utils';
+import { generatePseudoRandomSalt } from '@0xproject/order-utils';
 import { Order, SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 import * as chai from 'chai';
@@ -8,6 +9,7 @@ import * as Web3 from 'web3';
 import { DummyERC20TokenContract } from '../../src/contract_wrappers/generated/dummy_e_r_c20_token';
 import { ERC20ProxyContract } from '../../src/contract_wrappers/generated/e_r_c20_proxy';
 import { ExchangeContract } from '../../src/contract_wrappers/generated/exchange';
+import { WhitelistContract } from '../../src/contract_wrappers/generated/whitelist';
 import { artifacts } from '../../src/utils/artifacts';
 import { assetProxyUtils } from '../../src/utils/asset_proxy_utils';
 import { chaiSetup } from '../../src/utils/chai_setup';
@@ -55,6 +57,8 @@ describe('Exchange transactions', () => {
 
     let defaultMakerTokenAddress: string;
     let defaultTakerTokenAddress: string;
+    let makerPrivateKey: Buffer;
+    let takerPrivateKey: Buffer;
 
     before(async () => {
         await blockchainLifecycle.startAsync();
@@ -98,8 +102,8 @@ describe('Exchange transactions', () => {
             makerAssetData: assetProxyUtils.encodeERC20ProxyData(defaultMakerTokenAddress),
             takerAssetData: assetProxyUtils.encodeERC20ProxyData(defaultTakerTokenAddress),
         };
-        const makerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddress)];
-        const takerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(takerAddress)];
+        makerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddress)];
+        takerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(takerAddress)];
         orderFactory = new OrderFactory(makerPrivateKey, defaultOrderParams);
         makerTransactionFactory = new TransactionFactory(makerPrivateKey, exchange.address);
         takerTransactionFactory = new TransactionFactory(takerPrivateKey, exchange.address);
@@ -203,4 +207,131 @@ describe('Exchange transactions', () => {
             });
         });
     });
+
+    describe('Whitelist', () => {
+        let whitelist: WhitelistContract;
+        let whitelistOrderFactory: OrderFactory;
+
+        before(async () => {
+            whitelist = await WhitelistContract.deployFrom0xArtifactAsync(
+                artifacts.Whitelist,
+                provider,
+                txDefaults,
+                exchange.address,
+            );
+            const isApproved = true;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await exchange.approveSignatureValidator.sendTransactionAsync(whitelist.address, isApproved, {
+                    from: takerAddress,
+                }),
+            );
+            const defaultOrderParams = {
+                ...constants.STATIC_ORDER_PARAMS,
+                senderAddress: whitelist.address,
+                exchangeAddress: exchange.address,
+                makerAddress,
+                feeRecipientAddress,
+                makerAssetData: assetProxyUtils.encodeERC20ProxyData(defaultMakerTokenAddress),
+                takerAssetData: assetProxyUtils.encodeERC20ProxyData(defaultTakerTokenAddress),
+            };
+            whitelistOrderFactory = new OrderFactory(makerPrivateKey, defaultOrderParams);
+        });
+
+        beforeEach(async () => {
+            signedOrder = whitelistOrderFactory.newSignedOrder();
+            erc20Balances = await erc20Wrapper.getBalancesAsync();
+        });
+
+        it('should revert if maker has not been whitelisted', async () => {
+            const isApproved = true;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await whitelist.updateWhitelistStatus.sendTransactionAsync(takerAddress, isApproved, { from: owner }),
+            );
+
+            const orderStruct = orderUtils.getOrderStruct(signedOrder);
+            const takerAssetFillAmount = signedOrder.takerAssetAmount;
+            const salt = generatePseudoRandomSalt();
+            return expect(
+                whitelist.fillOrderIfWhitelisted.sendTransactionAsync(
+                    orderStruct,
+                    takerAssetFillAmount,
+                    salt,
+                    signedOrder.signature,
+                    { from: takerAddress },
+                ),
+            ).to.be.rejectedWith(constants.REVERT);
+        });
+
+        it('should revert if taker has not been whitelisted', async () => {
+            const isApproved = true;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await whitelist.updateWhitelistStatus.sendTransactionAsync(makerAddress, isApproved, { from: owner }),
+            );
+
+            const orderStruct = orderUtils.getOrderStruct(signedOrder);
+            const takerAssetFillAmount = signedOrder.takerAssetAmount;
+            const salt = generatePseudoRandomSalt();
+            return expect(
+                whitelist.fillOrderIfWhitelisted.sendTransactionAsync(
+                    orderStruct,
+                    takerAssetFillAmount,
+                    salt,
+                    signedOrder.signature,
+                    { from: takerAddress },
+                ),
+            ).to.be.rejectedWith(constants.REVERT);
+        });
+
+        it('should fill the order if maker and taker have been whitelisted', async () => {
+            const isApproved = true;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await whitelist.updateWhitelistStatus.sendTransactionAsync(makerAddress, isApproved, { from: owner }),
+            );
+
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await whitelist.updateWhitelistStatus.sendTransactionAsync(takerAddress, isApproved, { from: owner }),
+            );
+
+            const orderStruct = orderUtils.getOrderStruct(signedOrder);
+            const takerAssetFillAmount = signedOrder.takerAssetAmount;
+            const salt = generatePseudoRandomSalt();
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await whitelist.fillOrderIfWhitelisted.sendTransactionAsync(
+                    orderStruct,
+                    takerAssetFillAmount,
+                    salt,
+                    signedOrder.signature,
+                    { from: takerAddress },
+                ),
+            );
+
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const makerAssetFillAmount = signedOrder.makerAssetAmount;
+            const makerFeePaid = signedOrder.makerFee;
+            const takerFeePaid = signedOrder.takerFee;
+
+            expect(newBalances[makerAddress][defaultMakerTokenAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerTokenAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][defaultTakerTokenAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultTakerTokenAddress].add(takerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][zrxToken.address].minus(makerFeePaid),
+            );
+            expect(newBalances[takerAddress][defaultTakerTokenAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultTakerTokenAddress].minus(takerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerTokenAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerTokenAddress].add(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][zrxToken.address].minus(takerFeePaid),
+            );
+            expect(newBalances[feeRecipientAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[feeRecipientAddress][zrxToken.address].add(makerFeePaid.add(takerFeePaid)),
+            );
+        });
+    });
 });
diff --git a/packages/contracts/test/libraries/lib_bytes.ts b/packages/contracts/test/libraries/lib_bytes.ts
index 968bac300..e817951ab 100644
--- a/packages/contracts/test/libraries/lib_bytes.ts
+++ b/packages/contracts/test/libraries/lib_bytes.ts
@@ -22,6 +22,7 @@ describe('LibBytes', () => {
     let owner: string;
     let libBytes: TestLibBytesContract;
     const byteArrayShorterThan32Bytes = '0x012345';
+    const byteArrayShorterThan20Bytes = byteArrayShorterThan32Bytes;
     const byteArrayLongerThan32Bytes =
         '0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef';
     const byteArrayLongerThan32BytesFirstBytesSwapped =
@@ -60,6 +61,36 @@ describe('LibBytes', () => {
         await blockchainLifecycle.revertAsync();
     });
 
+    describe('popByte', () => {
+        it('should revert if length is 0', async () => {
+            return expect(libBytes.publicPopByte.callAsync(constants.NULL_BYTES)).to.be.rejectedWith(constants.REVERT);
+        });
+
+        it('should pop the last byte from the input and return it', async () => {
+            const [newBytes, poppedByte] = await libBytes.publicPopByte.callAsync(byteArrayLongerThan32Bytes);
+            const expectedNewBytes = byteArrayLongerThan32Bytes.slice(0, -2);
+            const expectedPoppedByte = `0x${byteArrayLongerThan32Bytes.slice(-2)}`;
+            expect(newBytes).to.equal(expectedNewBytes);
+            expect(poppedByte).to.equal(expectedPoppedByte);
+        });
+    });
+
+    describe('popAddress', () => {
+        it('should revert if length is less than 20', async () => {
+            return expect(libBytes.publicPopAddress.callAsync(byteArrayShorterThan20Bytes)).to.be.rejectedWith(
+                constants.REVERT,
+            );
+        });
+
+        it('should pop the last 20 bytes from the input and return it', async () => {
+            const [newBytes, poppedAddress] = await libBytes.publicPopAddress.callAsync(byteArrayLongerThan32Bytes);
+            const expectedNewBytes = byteArrayLongerThan32Bytes.slice(0, -40);
+            const expectedPoppedAddress = `0x${byteArrayLongerThan32Bytes.slice(-40)}`;
+            expect(newBytes).to.equal(expectedNewBytes);
+            expect(poppedAddress).to.equal(expectedPoppedAddress);
+        });
+    });
+
     describe('areBytesEqual', () => {
         it('should return true if byte arrays are equal (both arrays < 32 bytes)', async () => {
             const areBytesEqual = await libBytes.publicAreBytesEqual.callAsync(
diff --git a/packages/contracts/test/multi_sig_with_time_lock.ts b/packages/contracts/test/multi_sig_with_time_lock.ts
index ace0f0045..7b7885a00 100644
--- a/packages/contracts/test/multi_sig_with_time_lock.ts
+++ b/packages/contracts/test/multi_sig_with_time_lock.ts
@@ -27,6 +27,12 @@ describe('MultiSigWalletWithTimeLock', () => {
     const SECONDS_TIME_LOCKED = new BigNumber(1000000);
 
     before(async () => {
+        await blockchainLifecycle.startAsync();
+    });
+    after(async () => {
+        await blockchainLifecycle.revertAsync();
+    });
+    before(async () => {
         const accounts = await web3Wrapper.getAvailableAddressesAsync();
         owners = [accounts[0], accounts[1]];
     });
diff --git a/packages/contracts/test/token_registry.ts b/packages/contracts/test/token_registry.ts
index 1cc519c53..7980977c8 100644
--- a/packages/contracts/test/token_registry.ts
+++ b/packages/contracts/test/token_registry.ts
@@ -23,6 +23,7 @@ describe('TokenRegistry', () => {
     let notOwner: string;
     let tokenReg: TokenRegistryContract;
     let tokenRegWrapper: TokenRegWrapper;
+
     before(async () => {
         await blockchainLifecycle.startAsync();
     });