✨ Add Support for Nested Safes

[ipatka]

🕓 Changelog

This PR adds support for calculating the Safe transaction hashes for nested Safe (i.e. use a Safe as a signatory to another Safe) approval transactions. When a nested Safe needs to approve a transaction on the primary Safe, it must call the approveHash(bytes32) function on the target Safe with the Safe transaction hash to approve:

/**
 * @inheritdoc ISafe
 */
function approveHash(bytes32 hashToApprove) external override {
    if (owners[msg.sender] == address(0)) revertWithError("GS030");
    approvedHashes[msg.sender][hashToApprove] = 1;
    emit ApproveHash(hashToApprove, msg.sender);
}

Reference: https://github.com/safe-global/safe-smart-account/blob/bdcfce3a76c4d1dfb256ac2ca971be7cfd6e493a/contracts/Safe.sol#L372-L379.

    /**
     * @inheritdoc ISafe
     */
    function execTransaction(
        address to,
        uint256 value,
        bytes calldata data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver,
        bytes memory signatures
    ) external payable override returns (bool success) {
        onBeforeExecTransaction(to, value, data, operation, safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, signatures);
        bytes32 txHash;
        // Use scope here to limit variable lifetime and prevent `stack too deep` errors
        {
            = getTransactionHash( // Transaction info
                to,
                value,
                data,
                operation,
                safeTxGas,
                // Payment info
                baseGas,
                gasPrice,
                gasToken,
                refundReceiver,
                // Signature info
                // We use the post-increment here, so the current nonce value is used and incremented afterwards.
                nonce++
            );
            checkSignatures(msg.sender, txHash, signatures); // <-- For a nested Safe `txHash` is used as input for `approveHash(bytes32)`.
        }
...

Reference: https://github.com/safe-global/safe-smart-account/blob/bdcfce3a76c4d1dfb256ac2ca971be7cfd6e493a/contracts/Safe.sol#L108-L143.

...
} else if (v == 1) {
    // If v is 1 then it is an approved hash
    // When handling approved hashes the address of the approver is encoded into r
    currentOwner = address(uint160(uint256(r)));
    // Hashes are automatically approved by the sender of the message or when they have been pre-approved via a separate transaction
    if (executor != currentOwner && approvedHashes[currentOwner][dataHash] == 0) revertWithError("GS025");
...

Reference: https://github.com/safe-global/safe-smart-account/blob/bdcfce3a76c4d1dfb256ac2ca971be7cfd6e493a/contracts/Safe.sol#L318-L323.

New Features

• New Command-Line Arguments:

  • --nested-safe-address: Specifies the address of the nested Safe approving the transaction.
  • --nested-safe-nonce: Defines the nonce for the nested Safe's approval transaction.

• Updated Transaction Flow:
  When these arguments are provided, the script:

  1. Computes and displays the primary Safe transaction hashes as usual.
  2. Constructs an approveHash transaction with:
     • to: The primary Safe multisig address,
     • data: Encoded approveHash(bytes32) function call with the Safe transaction hash as argument,
     • value: Set to 0,
     • operation: Set to 0 (i.e. CALL),
     • All other parameters are set to their default values (0 or the zero address 0x0000000000000000000000000000000000000000).
  3. Calculates and displays the hashes for the approval transaction.

• Additional Improvements:

  • Adds validation for nested Safe parameters.
  • Enhances the --interactive mode support to override the nested Safe version.
  • Updates the help documentation with the new parameters and an example usage for nested Safes.
  • Adds a CI Bash formatting step using shfmt.
  • Add support of nested Safes for calculating Safe message hashes.

Example Usage

./safe_hashes.sh --network sepolia --address 0x657ff0D4eC65D82b2bC1247b0a558bcd2f80A0f1 --nonce 4 --nested-safe-address 0x6bc56d6CE87C86CB0756c616bECFD3Cd32b09251 --nested-safe-nonce 4

This will calculate and return both the primary Safe transaction hashes and the nested Safe approval transaction hashes, displaying all relevant details for each.

[pcaversaccio]

Thx for this!