Add isValidSignatureAndData to Bouncer to verify method calls (#973)

contracts/access/SignatureBouncer.sol

@@ -20,12 +20,25 @@ import "../ECRecovery.sol";
  * @dev Then restrict access to your crowdsale/whitelist/airdrop using the
  * @dev `onlyValidSignature` modifier (or implement your own using isValidSignature).
  * @dev
+ * @dev In addition to `onlyValidSignature`, `onlyValidSignatureAndMethod` and
+ * @dev `onlyValidSignatureAndData` can be used to restrict access to only a given method
+ * @dev or a given method with given parameters respectively.
+ * @dev
  * @dev See the tests Bouncer.test.js for specific usage examples.
+ * @notice A method that uses the `onlyValidSignatureAndData` modifier must make the _sig
+ * @notice parameter the "last" parameter. You cannot sign a message that has its own
+ * @notice signature in it so the last 128 bytes of msg.data (which represents the
+ * @notice length of the _sig data and the _sig data itself) is ignored when validating.
+ * @notice Also non fixed sized parameters make constructing the data in the signature
+ * @notice much more complex. See https://ethereum.stackexchange.com/a/50616 for more details.
  */
 contract SignatureBouncer is Ownable, RBAC {
   using ECRecovery for bytes32;
 
   string public constant ROLE_BOUNCER = "bouncer";
+  uint constant METHOD_ID_SIZE = 4;
+  // (signature length size) 32 bytes + (signature size 65 bytes padded) 96 bytes
+  uint constant SIGNATURE_SIZE = 128;
 
   /**
    * @dev requires that a valid signature of a bouncer was provided
@@ -36,6 +49,24 @@ contract SignatureBouncer is Ownable, RBAC {
     _;
   }
 
+  /**
+   * @dev requires that a valid signature with a specifed method of a bouncer was provided
+   */
+  modifier onlyValidSignatureAndMethod(bytes _sig)
+  {
+    require(isValidSignatureAndMethod(msg.sender, _sig));
+    _;
+  }
+
+  /**
+   * @dev requires that a valid signature with a specifed method and params of a bouncer was provided
+   */
+  modifier onlyValidSignatureAndData(bytes _sig)
+  {
+    require(isValidSignatureAndData(msg.sender, _sig));
+    _;
+  }
+
   /**
    * @dev allows the owner to add additional bouncer addresses
    */
@@ -73,6 +104,46 @@ contract SignatureBouncer is Ownable, RBAC {
     );
   }
 
+  /**
+   * @dev is the signature of `this + sender + methodId` from a bouncer?
+   * @return bool
+   */
+  function isValidSignatureAndMethod(address _address, bytes _sig)
+    internal
+    view
+    returns (bool)
+  {
+    bytes memory data = new bytes(METHOD_ID_SIZE);
+    for (uint i = 0; i < data.length; i++) {
+      data[i] = msg.data[i];
+    }
+    return isValidDataHash(
+      keccak256(address(this), _address, data),
+      _sig
+    );
+  }
+
+  /**
+    * @dev is the signature of `this + sender + methodId + params(s)` from a bouncer?
+    * @notice the _sig parameter of the method being validated must be the "last" parameter
+    * @return bool
+    */
+  function isValidSignatureAndData(address _address, bytes _sig)
+    internal
+    view
+    returns (bool)
+  {
+    require(msg.data.length > SIGNATURE_SIZE);
+    bytes memory data = new bytes(msg.data.length - SIGNATURE_SIZE);
+    for (uint i = 0; i < data.length; i++) {
+      data[i] = msg.data[i];
+    }
+    return isValidDataHash(
+      keccak256(address(this), _address, data),
+      _sig
+    );
+  }
+
   /**
    * @dev internal function to convert a hash to an eth signed message
    * @dev and then recover the signature and check it against the bouncer role

contracts/mocks/BouncerMock.sol

@@ -19,4 +19,36 @@ contract SignatureBouncerMock is SignatureBouncer {
   {
 
   }
+
+  function checkValidSignatureAndMethod(address _address, bytes _sig)
+    public
+    view
+    returns (bool)
+  {
+    return isValidSignatureAndMethod(_address, _sig);
+  }
+
+  function onlyWithValidSignatureAndMethod(bytes _sig)
+    onlyValidSignatureAndMethod(_sig)
+    public
+    view
+  {
+
+  }
+
+  function checkValidSignatureAndData(address _address, bytes _bytes, uint _val, bytes _sig)
+    public
+    view
+    returns (bool)
+  {
+    return isValidSignatureAndData(_address, _sig);
+  }
+
+  function onlyWithValidSignatureAndData(uint _val, bytes _sig)
+    onlyValidSignatureAndData(_sig)
+    public
+    view
+  {
+
+  }
 }