ChainSecurity

Our audit report for Spool is out. Thanks for your trust! Below we highlight one interesting finding and its fix. 🌐 Context on the System: Spool V2 introduces a system for deploying meta-strategies known as Smart Vaults. These vaults engage with multiple yield-generating strategies. Notably, the vaults operate with automated management that aligns with the set risk parameters of each Smart Vault. The protocol further differentiates itself by handling user investments and investments into the underlying protocols asynchronously, effectively reducing the gas consumption for the users. 🐞The Bug: DOS Synchronization by Dividing With Zero Redeemed Shares In the initially audited version, attackers could have exploited the system by making small withdrawals so that division-by-zero happens in the synchronization of a Smart Vault. 🔍 Scenario Breakdown: 1. 🧠 Preparation: By withdrawing just one Smart Vault share, rounding errors occur, prompting the Smart Vault to attempt a zero strategy share withdrawal. It's vital at this stage that no other vault has made non-zero withdrawals for at least one of the strategies of the attacked Smart Vault. That is due to strategies being shared among Smart Vaults. If at least one Smart Vault would have tried to redeem one strategy share, the computation would not revert due to the attacked Smart Vault trying to claim the underlying assets on synchronization for zero out of one shares instead of zero out of zero shares. 2. ⌛️ Waiting: The attacked Smart Vault awaits the results of the strategies. 3. 🔄 Synchronization: Post strategy investments, the Smart Vault initiates synchronization. The Smart Vault will report to the strategy registry that zero of its shares have been redeemed so that the vault should receive a zero out of zero share of the assets withdrawn for that strategy - leading to a division-by-zero and a DOS on synchronization. 💸 Impact: This vulnerability could have been exploitable under certain plausible conditions, potentially resulting in the freezing of Smart Vault funds due to synchronization being an intrinsic part of the Smart Vault processes. 🛠 Resolution: The flaw was addressed by omitting the claiming process when there's nothing to claim. Thus, in scenarios where there's genuinely nothing to claim, the division-by-zero error is evaded. 💡 Conclusion: Due to tiny inaccuracies with small numbers, the protocol funds could have been rendered inaccessible. By skipping parts of the synchronization when a particular corner case occurs, the protocol now evades the issue. https://lnkd.in/dp5z4DXk