> For the complete documentation index, see [llms.txt](https://reports.immunefi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://reports.immunefi.com/alchemix/31078-sc-high-withdraw-doesnt-claim-all-rewards-before-burnin....md). # 31078 - \[SC - High] withdraw doesnt claim all rewards before burnin... Submitted on May 12th 2024 at 11:07:38 UTC by @Holterhus for [Boost | Alchemix](https://immunefi.com/bounty/alchemix-boost/) Report ID: #31078 Report type: Smart Contract Report severity: High Target: Impacts: * Permanent freezing of unclaimed yield ## Description ## Brief/Intro The `claim()` function in the `RewardsDistributor` does not always claim all of the pending rewards for a given `tokenId`. This is because the `_claimable()` function has a finite `for` loop that does 50 iterations. However, the `withdraw()` function in `veALCX` only calls `claim()` once before permanently burning the token. This can lead to a permanent freezing of unclaimed yield if the 50 iterations are not sufficient. ## Vulnerability Details The `_claimable()` function in the `RewardsDistributor` has the following main loop: ```solidity for (uint256 i = 0; i < 50; i++) { if (weekCursor >= _lastTokenTime) break; if (weekCursor >= userPoint.ts && userEpoch <= maxUserEpoch) { userEpoch += 1; oldUserPoint = userPoint; if (userEpoch > maxUserEpoch) { userPoint = IVotingEscrow.Point(0, 0, 0, 0); } else { userPoint = IVotingEscrow(_ve).getUserPointHistory(_tokenId, userEpoch); } } else { int256 dt = int256(weekCursor - oldUserPoint.ts); int256 calc = oldUserPoint.bias - dt * oldUserPoint.slope > int256(0) ? oldUserPoint.bias - dt * oldUserPoint.slope : int256(0); uint256 balanceOf = uint256(calc); if (balanceOf == 0 && userEpoch > maxUserEpoch) break; if (balanceOf != 0) { toDistribute += (balanceOf * tokensPerWeek[weekCursor]) / veSupply[weekCursor]; } weekCursor += WEEK; } } ``` Notice that this loop only does a maximum of 50 iterations. This is fine on its own, because calling `claim()` multiple times will progress the rewards claiming in multiples of 50 iterations. However, consider the following code in the `withdraw()` function of the `veALCX` contract: ```solidity // Claim any unclaimed ALCX rewards and FLUX IRewardsDistributor(distributor).claim(_tokenId, false); IFluxToken(FLUX).claimFlux(_tokenId, IFluxToken(FLUX).getUnclaimedFlux(_tokenId)); // Burn the token _burn(_tokenId, value); ``` Since this only calls `claim()` once, this will only do 50 iterations within the `_claimable()` calculation, which can be insufficient for claiming all of the user's unclaimed `ALCX` rewards. ## Impact Details Yield is permanently frozen whenever a user calls `withdraw()` on a `tokenId` that needs more than 50 iterations to claim remaining rewards. This can happen if the `tokenId` has been deposited and left alone for a long time (perhaps with `maxLockEnabled == true`). It can also happen if the user has checkpointed many times before (notice that `weekCursor += WEEK` only happens in the `else` case of the main loop, so `claim()` may not even progress a single week). ## References See the PoC below. ## Proof of Concept I have created the following test file and added it to the `tests/` directory: ```solidity // SPDX-License-Identifier: GPL-3.0 pragma solidity ^0.8.15; import "./BaseTest.sol"; contract NotFullClaimBugTest is BaseTest { constructor() { setupContracts(block.timestamp); } function testNotFullClaimBug() public { vm.startPrank(admin); uint256 tokenId1 = createVeAlcx(admin, TOKEN_100K, MAXTIME, true); uint256 tokenId2 = createVeAlcx(admin, TOKEN_100K, MAXTIME, true); for (uint256 i; i < 100; ++i) { vm.warp(newEpoch()); voter.distribute(); } veALCX.updateUnlockTime(tokenId1, 365 days, false); veALCX.updateUnlockTime(tokenId2, 365 days, false); for (uint256 i; i < 30; ++i) { vm.warp(newEpoch()); voter.distribute(); } veALCX.startCooldown(tokenId1); veALCX.startCooldown(tokenId2); vm.warp(block.timestamp + 1 weeks); address rewardsToken = distributor.rewardsToken(); uint256 balBefore; uint256 balAfter; console.log("claimable 1:", distributor.claimable(tokenId1)); console.log("claimable 2:", distributor.claimable(tokenId2)); /************************************************************* Amount from withdraw() *************************************************************/ balBefore = IERC20(rewardsToken).balanceOf(admin); veALCX.withdraw(tokenId1); balAfter = IERC20(rewardsToken).balanceOf(admin); console.log("claimed from withdraw():", balAfter - balBefore); /************************************************************* Amount from claim() *************************************************************/ balBefore = IERC20(rewardsToken).balanceOf(admin); for (uint256 i; i < 20; ++i) distributor.claim(tokenId2, false); balAfter = IERC20(rewardsToken).balanceOf(admin); console.log("claimed from claim():", balAfter - balBefore); vm.stopPrank(); } } ``` Running the command `forge test -vvv --match-test testNotFullClaimBug --rpc-url $ETH_RPC_URL` gives the following result: ``` [PASS] testNotFullClaimBug() (gas: 109527243) Logs: claimable 1: 85548935342535580780653 claimable 2: 85548935342535580780653 claimed from withdraw(): 85548935342535580780653 claimed from claim(): 113317958706345737195718 ``` which shows that calling `withdraw()` will permanently freeze unclaimed yield. --- # Agent Instructions This documentation is published with GitBook. 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