From d0f32d186502f4c8d675f3cd0000852366e942da Mon Sep 17 00:00:00 2001
From: Remco Bloemen <remco@wicked.ventures>
Date: Tue, 6 Feb 2018 23:13:26 -0800
Subject: Add 'caller' signature type

---
 .../protocol/Exchange/MixinSignatureValidator.sol  | 52 +++++++++++++++-------
 1 file changed, 35 insertions(+), 17 deletions(-)

diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
index 919dbe312..959300753 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
@@ -26,6 +26,7 @@ contract MixinSignatureValidator is
 {
     enum SignatureType {
         Invalid,
+        Caller,
         Ecrecover
     }
   
@@ -36,27 +37,44 @@ contract MixinSignatureValidator is
         public view
         returns (bool isValid)
     {
-        require(signature.length >= 1);
+        // TODO: Domain separation: make hash depend on role. (Taker sig should not be valid as maker sig, etc.)
         
-        // Select signature type
+        require(signature.length >= 1);
         SignatureType signatureType = SignatureType(uint8(signature[0]));
-        if (signatureType != SignatureType.Ecrecover) {
-            valid = false;
+        
+        // Zero is always an invalid signature
+        if (signatureType == SignatureType.Invalid) {
+            require(signature.length == 1);
+            isValid = false;
             return;
-        }
         
-        // Verify using ecrecover
-        require(signature.length == 66);
-        uint8 v = uint8(signature[1]);
-        bytes32 r = get32(signature, 2);
-        bytes32 s = get32(signature, 34);
-        address recovered = ecrecover(
-            keccak256("\x19Ethereum Signed Message:\n32", hash),
-            v,
-            r,
-            s
-        );
-        isValid = signer == recovered;
+        // Implicitly signed by caller
+        } else if (signatureType == SignatureType.Caller) {
+            require(signature.length == 1);
+            isValid = signer == msg.sender;
+            return;
+        
+        // Signed using web3.eth_sign
+        } else if (signatureType == SignatureType.Ecrecover) {
+            require(signature.length == 66);
+            uint8 v = uint8(signature[1]);
+            bytes32 r = get32(signature, 2);
+            bytes32 s = get32(signature, 34);
+            address recovered = ecrecover(
+                keccak256("\x19Ethereum Signed Message:\n32", hash),
+                v,
+                r,
+                s
+            );
+            isValid = signer == recovered;
+            return;
+        
+        // Anything else is illegal
+        } else {
+            revert();
+          
+        }
+        return false;
     }
     
     function get32(bytes b, uint256 index)
-- 
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