StrategyManager.md

StrategyManager

File	Type	Proxy
StrategyManager.sol	Singleton	Transparent proxy
StrategyBaseTVLLimits.sol	3 instances (for cbETH, rETH, stETH)	Transparent proxy

The primary function of the StrategyManager is to handle accounting for individual Stakers as they deposit and withdraw LSTs from their corresponding strategies. It is responsible for (i) allowing Stakers to deposit LSTs into the corresponding strategy, (ii) allowing the DelegationManager to remove shares when a Staker queues a withdrawal, and (iii) allowing the DelegationManager to complete a withdrawal by either adding shares back to the Staker or withdrawing the shares as tokens via the corresponding strategy.

As of M2, several LSTs are supported and each has its own instance of StrategyBaseTVLLimits. Each StrategyBaseTVLLimits has two main functions (deposit and withdraw), both of which can only be called by the StrategyManager. These StrategyBaseTVLLimits contracts are fairly simple deposit/withdraw contracts that hold tokens deposited by Stakers. Because these strategies are essentially extensions of the StrategyManager, their functions are documented in this file (see below).

High-level Concepts

This document organizes methods according to the following themes (click each to be taken to the relevant section):

• Depositing Into Strategies
• Withdrawal Processing
• Strategies
• System Configuration

Important state variables

• mapping(address => mapping(IStrategy => uint256)) public stakerStrategyShares: Tracks the current balance a Staker holds in a given strategy. Updated on deposit/withdraw.
• mapping(address => IStrategy[]) public stakerStrategyList: Maintains a list of the strategies a Staker holds a nonzero number of shares in.
  • Updated as needed when Stakers deposit and withdraw: if a Staker has a zero balance in a Strategy, it is removed from the list. Likewise, if a Staker deposits into a Strategy and did not previously have a balance, it is added to the list.
• mapping(IStrategy => bool) public strategyIsWhitelistedForDeposit: The strategyWhitelister is (as of M2) a permissioned role that can be changed by the contract owner. The strategyWhitelister has currently whitelisted 3 StrategyBaseTVLLimits contracts in this mapping, one for each supported LST.
• mapping(IStrategy => bool) public thirdPartyTransfersForbidden: The strategyWhitelister can disable third party transfers for a given strategy. If thirdPartyTransfersForbidden[strategy] == true:
  • Users cannot deposit on behalf of someone else (see depositIntoStrategyWithSignature).
  • Users cannot withdraw on behalf of someone else. (see DelegationManager.queueWithdrawals)

Helpful definitions

• stakerStrategyListLength(address staker) -> (uint):
  • Gives stakerStrategyList[staker].length
  • Used (especially by the DelegationManager) to determine whether a Staker has shares in any strategy in the StrategyManager (will be 0 if not)

---

Depositing Into Strategies

The following methods are called by Stakers as they (i) deposit LSTs into strategies to receive shares:

• StrategyManager.depositIntoStrategy
• StrategyManager.depositIntoStrategyWithSignature

Withdrawals are performed through the DelegationManager (see DelegationManager.md).

depositIntoStrategy

function depositIntoStrategy(
    IStrategy strategy, 
    IERC20 token, 
    uint256 amount
)
    external
    onlyWhenNotPaused(PAUSED_DEPOSITS)
    onlyNotFrozen(msg.sender)
    nonReentrant
    returns (uint256 shares)

Allows a Staker to deposit some amount of token into the specified strategy in exchange for shares of that strategy. The underlying strategy must be one of the whitelisted StrategyBaseTVLLimits instances, and the token being deposited must correspond to that strategy's underlying token (cbETH, rETH, or stETH).

The number of shares received is calculated by the strategy using an internal exchange rate that depends on the previous number of tokens deposited.

If the Staker is delegated to an Operator, the Operator's delegated shares are increased in the DelegationManager.

Effects:

• token.safeTransferFrom: Transfers amount of token to strategy on behalf of the caller.
• See StrategyBaseTVLLimits.deposit
• StrategyManager awards the Staker with the newly-created shares
• See DelegationManager.increaseDelegatedShares

Requirements:

• Pause status MUST NOT be set: PAUSED_DEPOSITS
• Caller MUST allow at least amount of token to be transferred by StrategyManager to the strategy
• strategy in question MUST be whitelisted for deposits.
• See StrategyBaseTVLLimits.deposit

depositIntoStrategyWithSignature

function depositIntoStrategyWithSignature(
    IStrategy strategy,
    IERC20 token,
    uint256 amount,
    address staker,
    uint256 expiry,
    bytes memory signature
)
    external
    onlyWhenNotPaused(PAUSED_DEPOSITS)
    onlyNotFrozen(staker)
    nonReentrant
    returns (uint256 shares)

Effects: See depositIntoStrategy above. Additionally:

• The Staker's nonce is incremented

Requirements: See depositIntoStrategy above. Additionally:

• Caller MUST provide a valid, unexpired signature over the correct fields
• thirdPartyTransfersForbidden[strategy] MUST be false

---

Withdrawal Processing

These methods are callable ONLY by the DelegationManager, and are used when processing undelegations and withdrawals:

• StrategyManager.removeShares
• StrategyManager.addShares
• StrategyManager.withdrawSharesAsTokens

See DelegationManager.md for more context on how these methods are used.

removeShares

function removeShares(
    address staker,
    IStrategy strategy,
    uint256 shares
)
    external
    onlyDelegationManager

The DelegationManager calls this method when a Staker queues a withdrawal (or undelegates, which also queues a withdrawal). The shares are removed while the withdrawal is in the queue, and when the queue completes, the shares will either be re-awarded or withdrawn as tokens (addShares and withdrawSharesAsTokens, respectively).

The Staker's share balance for the strategy is decreased by the removed shares. If this causes the Staker's share balance to hit zero, the strategy is removed from the Staker's strategy list.

Entry Points:

• DelegationManager.undelegate
• DelegationManager.queueWithdrawals

Effects:

• The Staker's share balance for the given strategy is decreased by the given shares
  • If this causes the balance to hit zero, the strategy is removed from the Staker's strategy list

Requirements:

• Caller MUST be the DelegationManager
• staker parameter MUST NOT be zero
• shares parameter MUST NOT be zero
• staker MUST have at least shares balance for the given strategy

addShares

function addShares(
    address staker,
    IStrategy strategy,
    uint256 shares
) 
    external 
    onlyDelegationManager

The DelegationManager calls this method when a queued withdrawal is completed and the withdrawer specifies that they want to receive the withdrawal as "shares" (rather than as the underlying tokens). In this case, the shares originally removed (via removeShares) are awarded to the staker passed in by the DelegationManager.

Entry Points:

• DelegationManager.completeQueuedWithdrawal
• DelegationManager.completeQueuedWithdrawals

Effects:

• The staker's share balance for the given strategy is increased by shares
  • If the prior balance was zero, the strategy is added to the staker's strategy list

Requirements:

• Caller MUST be the DelegationManager
• staker parameter MUST NOT be zero
• shares parameter MUST NOT be zero

withdrawSharesAsTokens

function withdrawSharesAsTokens(
    address recipient,
    IStrategy strategy,
    uint shares,
    IERC20 token
)
    external
    onlyDelegationManager

The DelegationManager calls this method when a queued withdrawal is completed and the withdrawer specifies that they want to receive the withdrawal as the tokens underlying the shares. In this case, the shares originally removed (via removeShares) are converted to tokens within the strategy and sent to the recipient.

Entry Points:

• DelegationManager.completeQueuedWithdrawal
• DelegationManager.completeQueuedWithdrawals

Effects:

• Calls StrategyBaseTVLLimits.withdraw

Requirements:

• Caller MUST be the DelegationManager
• See StrategyBaseTVLLimits.withdraw

---

Strategies

StrategyBaseTVLLimits only has two methods of note, and both can only be called by the StrategyManager. Documentation for these methods are included below, rather than in a separate file:

• StrategyBaseTVLLimits.deposit
• StrategyBaseTVLLimits.withdraw

StrategyBaseTVLLimits.deposit

function deposit(
    IERC20 token, 
    uint256 amount
)
    external
    onlyWhenNotPaused(PAUSED_DEPOSITS)
    onlyStrategyManager
    returns (uint256 newShares)

The StrategyManager calls this method when Stakers deposit LSTs into a strategy. At the time this method is called, the tokens have already been transferred to the strategy. The role of this method is to (i) calculate the number of shares the deposited tokens represent according to the exchange rate, and (ii) add the new shares to the strategy's recorded total shares.

The new shares created are returned to the StrategyManager to be added to the Staker's strategy share balance.

Entry Points:

• StrategyManager.depositIntoStrategy
• StrategyManager.depositIntoStrategyWithSignature

Effects:

• StrategyBaseTVLLimits.totalShares is increased to account for the new shares created by the deposit

Requirements:

• Caller MUST be the StrategyManager
• Pause status MUST NOT be set: PAUSED_DEPOSITS
• The passed-in token MUST match the strategy's underlyingToken
• The token amount being deposited MUST NOT exceed the per-deposit cap
• After deposit, the strategy's current token balance MUST NOT exceed the total-deposit cap
• When converted to shares via the strategy's exchange rate, the amount of token deposited MUST represent at least 1 new share for the depositor

StrategyBaseTVLLimits.withdraw

function withdraw(
    address recipient, 
    IERC20 token, 
    uint256 amountShares
)
    external
    onlyWhenNotPaused(PAUSED_WITHDRAWALS)
    onlyStrategyManager

The StrategyManager calls this method when a queued withdrawal is completed and the withdrawer has specified they would like to convert their withdrawn shares to tokens.

This method converts the withdrawal shares back into tokens using the strategy's exchange rate. The strategy's total shares are decreased to reflect the withdrawal before transferring the tokens to the recipient.

Entry Points:

• DelegationManager.completeQueuedWithdrawal
• DelegationManager.completeQueuedWithdrawals

Effects:

• StrategyBaseTVLLimits.totalShares is decreased to account for the shares being withdrawn
• underlyingToken.safeTransfer is called to transfer the tokens to the recipient

Requirements:

• Caller MUST be the StrategyManager
• Pause status MUST NOT be set: PAUSED_WITHDRAWALS
• The passed-in token MUST match the strategy's underlyingToken
• The amountShares being withdrawn MUST NOT exceed the totalShares in the strategy
• The tokens represented by amountShares MUST NOT exceed the strategy's token balance

---

System Configuration

• StrategyManager.setStrategyWhitelister
• StrategyManager.addStrategiesToDepositWhitelist
• StrategyManager.removeStrategiesFromDepositWhitelist
• StrategyManager.setThirdPartyTransfersForbidden

setStrategyWhitelister

function setStrategyWhitelister(address newStrategyWhitelister) external onlyOwner

Allows the owner to update the Strategy Whitelister address.

Effects:

• Updates StrategyManager.strategyWhitelister

Requirements:

• Caller MUST be the owner

addStrategiesToDepositWhitelist

function addStrategiesToDepositWhitelist(
    IStrategy[] calldata strategiesToWhitelist,
    bool[] calldata thirdPartyTransfersForbiddenValues
) 
    external 
    onlyStrategyWhitelister

Allows the Strategy Whitelister to add any number of strategies to the StrategyManager whitelist, and configure whether third party transfers are enabled or disabled for each. Strategies on the whitelist are eligible for deposit via depositIntoStrategy.

Effects:

• Adds entries to StrategyManager.strategyIsWhitelistedForDeposit
• Sets thirdPartyTransfersForbidden for each added strategy

Requirements:

• Caller MUST be the strategyWhitelister

removeStrategiesFromDepositWhitelist

function removeStrategiesFromDepositWhitelist(
    IStrategy[] calldata strategiesToRemoveFromWhitelist
) 
    external 
    onlyStrategyWhitelister

Allows the Strategy Whitelister to remove any number of strategies from the StrategyManager whitelist. The removed strategies will no longer be eligible for deposit via depositIntoStrategy. However, withdrawals for previously-whitelisted strategies may still be initiated and completed, as long as the Staker has shares to withdraw.

Effects:

• Removes entries from StrategyManager.strategyIsWhitelistedForDeposit

Requirements:

• Caller MUST be the strategyWhitelister

setThirdPartyTransfersForbidden

function setThirdPartyTransfersForbidden(
    IStrategy strategy,
    bool value
) 
    external 
    onlyStrategyWhitelister

Allows the Strategy Whitelister to enable or disable third-party transfers for any strategy. If third-party transfers are disabled:

• Deposits via depositIntoStrategyWithSiganture are disabled.
• Withdrawals to a different address via DelegationManager.queueWithdrawals are disabled.

Effects:

• Sets thirdPartyTransfersForbidden[strategy], even if that strategy is not currently whitelisted

Requirements:

• Caller MUST be the strategyWhitelister