Add BoostManager slippage protection and create Permit2Manager (#201)

periphery/src/managers/BoostManager.sol

@@ -76,7 +76,12 @@ contract BoostManager is IManager, IUniswapV3SwapCallback {
         uint128 liquidity;
         // Leverage factor
         uint24 boost;
-        (tokenId, lower, upper, liquidity, boost) = abi.decode(args, (uint256, int24, int24, uint128, uint24));
+        // Packed maxBorrow0 and maxBorrow1; slippage protection
+        uint224 maxBorrows;
+        (tokenId, lower, upper, liquidity, boost, maxBorrows) = abi.decode(
+            args,
+            (uint256, int24, int24, uint128, uint24, uint224)
+        );
 
         require(owner == UNISWAP_NFT.ownerOf(tokenId), "Aloe: owners must match to import");
 
@@ -96,6 +101,7 @@ contract BoostManager is IManager, IUniswapV3SwapCallback {
                 amount1 = (needs1 + 1) > amount1 ? (needs1 + 1 - amount1) : 0;
             }
 
+            require(amount0 < uint112(maxBorrows) && amount1 < (maxBorrows >> 112), "slippage");
             borrower.borrow(amount0, amount1, msg.sender);
             borrower.uniswapDeposit(lower, upper, liquidity);
         }

periphery/src/managers/Permit2Manager.sol

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.17;
+
+import {IManager} from "aloe-ii-core/Borrower.sol";
+import {Factory} from "aloe-ii-core/Factory.sol";
+
+import {IPermit2} from "../interfaces/IPermit2.sol";
+
+/// @dev Permit2 signatures attest to {token, amount, spender, nonce, deadline}. Noticeable lacking is a `to`
+/// field. So given a signature, this contract would have permission to send the user's tokens *anywhere*. In
+/// this case the `to` address is part of the incoming calldata, so we must verify that the user is the creator
+/// of that calldata (or has authorized it somehow).
+/// Within `callback`, if `FACTORY.isBorrower(msg.sender) && owner == BORROWER_NFT`, then we can be sure
+/// that either the user themselves OR someone who's been approved to manage their NFT(s) is the source
+/// of the calldata.
+contract Permit2Manager is IManager {
+    error Permit2CallFailed();
+
+    error BorrowerCallFailed();
+
+    IPermit2 public immutable PERMIT2;
+
+    Factory public immutable FACTORY;
+
+    address public immutable BORROWER_NFT;
+
+    constructor(IPermit2 permit2, Factory factory, address borrowerNft) {
+        PERMIT2 = permit2;
+        FACTORY = factory;
+        BORROWER_NFT = borrowerNft;
+    }
+
+    function callback(bytes calldata data, address owner, uint208) external override returns (uint208) {
+        // Need to check that `msg.sender` is really a borrower and that its owner is `BORROWER_NFT`
+        // in order to be sure that incoming `data` is in the expected format
+        require(FACTORY.isBorrower(msg.sender) && owner == BORROWER_NFT, "Aloe: bad caller");
+
+        // `data` layout...
+        // -------------------------------------------
+        // | value            | start | end | length |
+        // | owner            |     0 |  20 |     20 |
+        // | permit2 selector |    20 |  24 |      4 |
+        // | permit2 args     |    24 | 248 |    224 |
+        // | permit2 sig      |   248 | 313 |     65 |
+        // | borrower call    |   313 |   ? |      ? |
+        // -------------------------------------------
+
+        // Get references to the calldata for the 2 calls we're going to make
+        bytes calldata dataPermit2 = data[20:313];
+        bytes calldata dataBorrower = data[313:];
+
+        // Before calling `PERMIT2`, verify
+        // (a) correct function selector
+        // (b) `to` field is the Borrower (`msg.sender`)
+        // (c) correct signer address, i.e. [claimed Permit2 signer] == [user who owns the Borrower]
+        // Note that data[:20] is the true owner prepended by the `BORROWER_NFT`
+        require(
+            bytes4(dataPermit2[:4]) == IPermit2.permitTransferFrom.selector &&
+                bytes20(dataPermit2[144:164]) == bytes20(msg.sender) &&
+                bytes20(dataPermit2[208:228]) == bytes20(data[:20])
+        );
+
+        // Make calls
+        bool success;
+        (success, ) = address(PERMIT2).call(dataPermit2); // solhint-disable-line avoid-low-level-calls
+        if (!success) revert Permit2CallFailed();
+
+        (success, ) = msg.sender.call(dataBorrower); // solhint-disable-line avoid-low-level-calls
+        if (!success) revert BorrowerCallFailed();
+
+        return 0;
+    }
+}

periphery/test/managers/BoostManager.t.sol

@@ -45,7 +45,7 @@ contract BoostManagerTest is Test {
         lender1.deposit(1e18, address(0));
     }
 
-    function test_mint() public { 
+    function test_mint() public {
         address owner = 0xde8E7d3fFada10dE2A57E7bAc090dB06596F51Cd;
 
         bytes memory mintCall;
@@ -67,7 +67,14 @@ contract BoostManagerTest is Test {
             managers[0] = boostManager;
             datas[0] = abi.encode(
                 uint8(0),
-                abi.encode(uint256(425835), int24(70020), int24(71700), uint128(344339104909795631), 10_000)
+                abi.encode(
+                    uint256(425835),
+                    int24(70020),
+                    int24(71700),
+                    uint128(344339104909795631),
+                    10_000,
+                    uint224(type(uint224).max)
+                )
             );
             antes[0] = 0.01 ether / 1e13;
             modifyCall = abi.encodeCall(borrowerNft.modify, (owner, indices, managers, datas, antes));