Colin/deposit priority (#90)

* updated deposit priority, added test

* formatting

* finalizing fix provided by eric, tx test provided by kevin

* deleted unnecessary comments

* updated comments

* forogot to save all comments from last commit

* updated assert comment

Author: colin-axner

contracts/PlasmaMVP.sol

@@ -152,7 +152,8 @@ contract PlasmaMVP {
 
         uint amount = deposits[nonce].amount;
         address owner = deposits[nonce].owner;
-        depositExitQueue.insert(nonce);
+        uint256 priority = block.timestamp << 128 | nonce;
+        depositExitQueue.insert(priority);
         depositExits[nonce] = exit({
             owner: owner,
             amount: amount,
@@ -408,15 +409,12 @@ contract PlasmaMVP {
         uint256 priority = queue[0];
         exit memory currentExit;
         uint256 position;
-        if (isDeposits) {
-            currentExit = depositExits[priority];
-        } else {
-            // retrieve the right 128 bits from the priority to obtain the position
-            assembly {
-   			    position := and(priority, div(not(0x0), exp(256, 16)))
-		    }
-            currentExit = txExits[position];
-        }
+        // retrieve the right 128 bits from the priority to obtain the position
+        assembly {
+   	        position := and(priority, div(not(0x0), exp(256, 16)))
+		}
+
+        currentExit = isDeposits ? depositExits[position] : txExits[position];
 
         /*
         * Conditions:
@@ -439,7 +437,7 @@ contract PlasmaMVP {
                 totalWithdrawBalance = totalWithdrawBalance.add(amountToAdd);
 
                 if (isDeposits)
-                    depositExits[priority].state = ExitState.Finalized;
+                    depositExits[position].state = ExitState.Finalized;
                 else
                     txExits[position].state = ExitState.Finalized;
 
@@ -456,15 +454,13 @@ contract PlasmaMVP {
 
             // move onto the next oldest exit
             priority = queue[0];
-            if (isDeposits) {
-                currentExit = depositExits[priority];
-            } else {
-                // retrieve the right 128 bits from the priority to obtain the position
-                assembly {
-   			        position := and(priority, div(not(0x0), exp(256, 16)))
-		        }
-                currentExit = txExits[position];
-            }
+            
+            // retrieve the right 128 bits from the priority to obtain the position
+            assembly {
+   			    position := and(priority, div(not(0x0), exp(256, 16)))
+		    }
+             
+            currentExit = isDeposits ? depositExits[position] : txExits[position];
         }
     }
 

test/plasmamvp/deposits.js

@@ -224,4 +224,42 @@ contract('[PlasmaMVP] Deposits', async (accounts) => {
         if (!err)
             assert.fail("operator challenged exit with correct committed fee");
     });
+
+    it("Attempts a withdrawal delay attack on exiting deposits", async () => {
+        
+        /* 1. Start exit for nonce_2 (newest) 
+         * 2. Start exit for nonce_1, nonce_0 in the same eth block
+         * 3. Check exit ordering:  nonce_2, nonce_0, nonce_1
+         */
+
+        let nonce_0 = (await instance.depositNonce.call()).toNumber();
+        await instance.deposit(accounts[2], {from: accounts[2], value: 100});
+
+        let nonce_1 = (await instance.depositNonce.call()).toNumber();
+        await instance.deposit(accounts[2], {from: accounts[2], value: 100});
+
+        let nonce_2 = (await instance.depositNonce.call()).toNumber();
+        await instance.deposit(accounts[2], {from: accounts[2], value: 100});
+
+        // exit nonce_2 
+        await instance.startDepositExit(nonce_2, 0, {from: accounts[2], value: minExitBond});
+        
+        // first exit should be in a different eth block
+        fastForward(10);
+        
+        // exit nonce_1 then nonce_0 in the same ethereum block
+        async function exits(nonce_1, nonce_0) {
+            let p1 = instance.startDepositExit(nonce_1, 0, {from: accounts[2], value: minExitBond});
+            let p2 = instance.startDepositExit(nonce_0, 0, {from: accounts[2], value: minExitBond});
+            return Promise.all([p1, p2]);
+        }
+        await exits(nonce_1, nonce_0);
+       
+        fastForward(one_week);
+        let depositExits = await instance.finalizeDepositExits({from: authority});
+        assert.equal(depositExits.logs[0].args.position.toString(), [0, 0, 0, nonce_2].toString(), "nonce_2 was not finalized first");
+        
+        assert.equal(depositExits.logs[2].args.position.toString(), [0, 0, 0, nonce_0].toString(), "nonce_0 was not finalized second");
+        assert.equal(depositExits.logs[4].args.position.toString(), [0, 0, 0, nonce_1].toString(), "nonce_1 was not finalized last");
+    });
 });

test/plasmamvp/transactions.js

@@ -278,7 +278,7 @@ contract('[PlasmaMVP] Transactions', async (accounts) => {
         let secondOutput = [txPos[0], txPos[1], 1, 0];
         await instance.startTransactionExit(secondOutput, toHex(txBytes), toHex(proof),
             toHex(confirmSignatures), 0, {from: authority, value: minExitBond});
-        
+
         // operator will challenge with second output
         let err;
         [err] = await catchError(instance.challengeFeeMismatch(secondOutput, txPos2, toHex(txBytes2), proof2));
@@ -738,4 +738,60 @@ contract('[PlasmaMVP] Transactions', async (accounts) => {
         exit = await instance.txExits.call(position);
         assert.equal(exit[4].toNumber(), 1, "exit has been challenged or finalized");
     });
+
+    it("Does finalize two transaction exits if given enough gas", async () => {
+        depositNonce = (await instance.depositNonce.call()).toNumber();
+        await instance.deposit(authority, {from: authority, value: amount});
+
+        // deposit is the first input. authority sends entire deposit to accounts[1]
+        let txList2 = Array(17).fill(0);
+        txList2[3] = depositNonce; txList2[12] = accounts[1]; txList2[13] = amount;
+        let txHash2 = web3.sha3(RLP.encode(txList2).toString('hex'), {encoding: 'hex'});
+
+        let sigs2 = [toHex(await web3.eth.sign(authority, txHash2)), toHex(Buffer.alloc(65).toString('hex'))];
+
+        txBytes2 = [txList2, sigs2];
+        txBytes2 = RLP.encode(txBytes2).toString('hex');
+
+        // submit the block
+        let merkleHash2 = sha256String(txBytes2);
+        let merkleRoot2, proof2;
+        [merkleRoot2, proof2] = generateMerkleRootAndProof([merkleHash2], 0);
+        let blockNum2 = (await instance.lastCommittedBlock.call()).toNumber() + 1;
+        await instance.submitBlock([toHex(merkleRoot2)], [1], [0], blockNum2, {from: authority});
+
+        // construct the confirm signature
+        let confirmHash2 = sha256String(merkleHash2 + merkleRoot2.slice(2));
+        confirmSignatures2 = await web3.eth.sign(authority, confirmHash2);
+
+        txPos2 = [blockNum2, 0, 0];
+
+        // Start txn exit on both utxos
+        await instance.startTransactionExit(txPos,
+            toHex(txBytes), toHex(proof), toHex(confirmSignatures), 0,
+            {from: accounts[1], value: minExitBond});
+
+        await instance.startTransactionExit(txPos2,
+            toHex(txBytes2), toHex(proof2), toHex(confirmSignatures2), 0,
+            {from: accounts[1], value: minExitBond});
+
+        fastForward(one_week + 1000);
+
+        // Provide enough gas for both txns to be finalized
+        await instance.finalizeTransactionExits({gas: 200000});
+
+        // The both utxo should have been exited correctly
+        let balance = (await instance.balanceOf.call(accounts[1])).toNumber();
+        assert.equal(balance, 2 * (amount + minExitBond));
+
+        // Verify that txn1 has been exited
+        let position = 1000000*txPos[0];
+        let exit = await instance.txExits.call(position);
+        assert.equal(exit[4].toNumber(), 3, "exit's state not set to finalized");
+
+        // Verify that txn2 has been exited
+        position = 1000000*txPos2[0];
+        exit = await instance.txExits.call(position);
+        assert.equal(exit[4].toNumber(), 3, "exit's state not set to finalized");
+    });
 });