Merge pull request #569 from keep-network/fully-backed-member-ban

Ban members of FullyBackedBondedECDSAKeep in case of signature fraud

Added functionality of banning keep members in case of a signature fraud 
for FullyBackedECDSAKeeps.

Once a signature fraud is discovered a keep will call the associated factory to 
ban its members. The factory will ban all members in a sortition pool the given keep
has been created for.

solidity/contracts/fully-backed/FullyBackedECDSAKeep.sol

@@ -52,9 +52,12 @@ contract FullyBackedECDSAKeep is AbstractBondedECDSAKeep {
         bonding.claimDelegatedAuthority(_keepFactory);
     }
 
+    /// @notice Punishes keep members after proving a signature fraud.
+    /// @dev Calls the keep factory to ban members of the keep. The owner of the
+    /// keep is able to seize the members bonds, so no action is necessary to be
+    /// taken from perspective of this function.
     function slashForSignatureFraud() internal {
-        // TODO: We don't need to do anything as keep owner is able to seize the bonds
-        // TODO: Ban members (remove from sortition pool and don't let to rejoin)
+        keepFactory.banKeepMembers();
     }
 
     /// @notice Gets the beneficiary for the specified member address.

solidity/contracts/fully-backed/FullyBackedECDSAKeepFactory.sol

@@ -68,14 +68,18 @@ contract FullyBackedECDSAKeepFactory is
     // in `FullyBackedBonding` contract. Minimum delegation deposit determines
     // a minimum value of ether that should be transferred to the bonding contract
     // by an owner when delegating to an operator.
-    uint256 public constant minimumBond = 20 ether;
+    uint256 public constant defaultMinimumBond = 20 ether;
 
     // Signer candidates in bonded sortition pool are weighted by their eligible
     // stake divided by a constant divisor. The divisor is set to 1 ETH so that
     // all ETHs in available unbonded value matter when calculating operator's
     // eligible weight for signer selection.
     uint256 public constant bondWeightDivisor = 1 ether;
 
+    // Maps a keep to an application for which the keep was created.
+    // keep address -> application address
+    mapping(address => address) keepApplication;
+
     // Notification that a new keep has been created.
     event FullyBackedECDSAKeepCreated(
         address indexed keepAddress,
@@ -85,6 +89,10 @@ contract FullyBackedECDSAKeepFactory is
         uint256 honestThreshold
     );
 
+    // Notification when an operator gets banned in a sortition pool for
+    // an application.
+    event OperatorBanned(address indexed operator, address indexed application);
+
     constructor(
         address _masterKeepAddress,
         address _sortitionPoolFactoryAddress,
@@ -194,6 +202,8 @@ contract FullyBackedECDSAKeepFactory is
             );
         }
 
+        keepApplication[keepAddress] = application;
+
         emit FullyBackedECDSAKeepCreated(
             keepAddress,
             members,
@@ -236,11 +246,34 @@ contract FullyBackedECDSAKeepFactory is
         return bonding.isAuthorizedForOperator(_operator, address(this));
     }
 
+    /// @notice Bans members of a calling keep in a sortition pool associated
+    /// with the application for which the keep was created.
+    /// @dev The function can be called only by a keep created by this factory.
+    function banKeepMembers() public onlyKeep() {
+        FullyBackedECDSAKeep keep = FullyBackedECDSAKeep(msg.sender);
+
+        address[] memory members = keep.getMembers();
+
+        address application = keepApplication[address(keep)];
+
+        FullyBackedSortitionPool sortitionPool = FullyBackedSortitionPool(
+            getSortitionPool(application)
+        );
+
+        for (uint256 i = 0; i < members.length; i++) {
+            address operator = members[i];
+
+            sortitionPool.ban(operator);
+
+            emit OperatorBanned(operator, application);
+        }
+    }
+
     function newSortitionPool(address _application) internal returns (address) {
         return
             sortitionPoolFactory.createSortitionPool(
                 IFullyBackedBonding(address(bonding)),
-                minimumBond,
+                defaultMinimumBond,
                 bondWeightDivisor
             );
     }
@@ -262,4 +295,13 @@ contract FullyBackedECDSAKeepFactory is
         // Ex. (100 + 3 - 1) / 3 = 34
         return (_keepBond.add(_groupSize).sub(1)).div(_groupSize);
     }
+
+    /// @notice Checks if caller is a keep created by this factory.
+    modifier onlyKeep() {
+        require(
+            keepOpenedTimestamp[msg.sender] > 0,
+            "Caller is not a keep created by the factory"
+        );
+        _;
+    }
 }

solidity/contracts/test/FullyBackedECDSAKeepCloneFactoryStub.sol

@@ -15,6 +15,8 @@ contract FullyBackedECDSAKeepCloneFactoryStub is
 {
     address public masterKeepAddress;
 
+    mapping(address => uint256) public banKeepMembersCalledCount;
+
     constructor(address _masterKeepAddress) public {
         masterKeepAddress = _masterKeepAddress;
     }
@@ -49,4 +51,8 @@ contract FullyBackedECDSAKeepCloneFactoryStub is
     {
         return true;
     }
+
+    function banKeepMembers() public {
+        banKeepMembersCalledCount[msg.sender]++;
+    }
 }

solidity/contracts/test/FullyBackedECDSAKeepStub.sol

@@ -13,6 +13,10 @@ contract FullyBackedECDSAKeepStub is FullyBackedECDSAKeep {
         markAsTerminated();
     }
 
+    function publicSlashForSignatureFraud() public {
+        slashForSignatureFraud();
+    }
+
     function isFradulentPreimageSet(bytes memory preimage)
         public
         view

solidity/test/BondedECDSAKeepFactoryTest.js

@@ -29,6 +29,8 @@ chai.use(require("bn-chai")(BN))
 const expect = chai.expect
 const assert = chai.assert
 
+// TODO: Refactor tests by pulling common parts of BondedECDSAKeepFactory and
+// FullyBackedBondedECDSAKeepFactory to one file.
 describe("BondedECDSAKeepFactory", function () {
   let registry
   let tokenStaking

solidity/test/BondedECDSAKeepTest.js

@@ -31,6 +31,8 @@ chai.use(require("bn-chai")(BN))
 const expect = chai.expect
 const assert = chai.assert
 
+// TODO: Refactor tests by pulling common parts of BondedECDSAKeep and
+// FullyBackedBondedECDSAKeep to one file.
 describe("BondedECDSAKeep", function () {
   const bondCreator = accounts[0]
   const owner = accounts[1]