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deposit_contract.sol
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deposit_contract.sol
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// ┏━━━┓━┏┓━┏┓━━┏━━━┓━━┏━━━┓━━━━┏━━━┓━━━━━━━━━━━━━━━━━━━┏┓━━━━━┏━━━┓━━━━━━━━━┏┓━━━━━━━━━━━━━━┏┓━
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// ┗━━━┛━┗━┛┗┛┗┛┗━━━┛┗┛┗━━━┛━━━━┗━━━┛┗━━┛┃┏━┛┗━━┛┗━━┛┗┛━┗━┛━━━━┗━━━┛┗━━┛┗┛┗┛━┗━┛┗┛━┗━━━┛┗━━┛━┗━┛
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// ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┗┛━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
// SPDX-License-Identifier: CC0-1.0
pragma solidity 0.6.11;
// This interface is designed to be compatible with the Vyper version.
/// @notice This is the Ethereum 2.0 deposit contract interface.
/// For more information see the Phase 0 specification under https://github.com/ethereum/eth2.0-specs
interface IDepositContract {
/// @notice A processed deposit event.
event DepositEvent(
bytes pubkey,
bytes withdrawal_credentials,
bytes amount,
bytes signature,
bytes index
);
/// @notice Submit a Phase 0 DepositData object.
/// @param pubkey A BLS12-381 public key.
/// @param withdrawal_credentials Commitment to a public key for withdrawals.
/// @param signature A BLS12-381 signature.
/// @param deposit_data_root The SHA-256 hash of the SSZ-encoded DepositData object.
/// Used as a protection against malformed input.
function deposit(
bytes calldata pubkey,
bytes calldata withdrawal_credentials,
bytes calldata signature,
bytes32 deposit_data_root
) external payable;
/// @notice Query the current deposit root hash.
/// @return The deposit root hash.
function get_deposit_root() external view returns (bytes32);
/// @notice Query the current deposit count.
/// @return The deposit count encoded as a little endian 64-bit number.
function get_deposit_count() external view returns (bytes memory);
}
// Based on official specification in https://eips.ethereum.org/EIPS/eip-165
interface ERC165 {
/// @notice Query if a contract implements an interface
/// @param interfaceId The interface identifier, as specified in ERC-165
/// @dev Interface identification is specified in ERC-165. This function
/// uses less than 30,000 gas.
/// @return `true` if the contract implements `interfaceId` and
/// `interfaceId` is not 0xffffffff, `false` otherwise
function supportsInterface(bytes4 interfaceId) external pure returns (bool);
}
// This is a rewrite of the Vyper Eth2.0 deposit contract in Solidity.
// It tries to stay as close as possible to the original source code.
/// @notice This is the Ethereum 2.0 deposit contract interface.
/// For more information see the Phase 0 specification under https://github.com/ethereum/eth2.0-specs
contract DepositContract is IDepositContract, ERC165 {
uint constant DEPOSIT_CONTRACT_TREE_DEPTH = 32;
// NOTE: this also ensures `deposit_count` will fit into 64-bits
uint constant MAX_DEPOSIT_COUNT = 2**DEPOSIT_CONTRACT_TREE_DEPTH - 1;
bytes32[DEPOSIT_CONTRACT_TREE_DEPTH] branch;
uint256 deposit_count;
bytes32[DEPOSIT_CONTRACT_TREE_DEPTH] zero_hashes;
constructor() public {
// Compute hashes in empty sparse Merkle tree
for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH - 1; height++)
zero_hashes[height + 1] = sha256(abi.encodePacked(zero_hashes[height], zero_hashes[height]));
}
function get_deposit_root() override external view returns (bytes32) {
bytes32 node;
uint size = deposit_count;
for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH; height++) {
if ((size & 1) == 1)
node = sha256(abi.encodePacked(branch[height], node));
else
node = sha256(abi.encodePacked(node, zero_hashes[height]));
size /= 2;
}
return sha256(abi.encodePacked(
node,
to_little_endian_64(uint64(deposit_count)),
bytes24(0)
));
}
function get_deposit_count() override external view returns (bytes memory) {
return to_little_endian_64(uint64(deposit_count));
}
function deposit(
bytes calldata pubkey,
bytes calldata withdrawal_credentials,
bytes calldata signature,
bytes32 deposit_data_root
) override external payable {
// Extended ABI length checks since dynamic types are used.
require(pubkey.length == 48, "DepositContract: invalid pubkey length");
require(withdrawal_credentials.length == 32, "DepositContract: invalid withdrawal_credentials length");
require(signature.length == 96, "DepositContract: invalid signature length");
// Check deposit amount
require(msg.value >= 1 ether, "DepositContract: deposit value too low");
require(msg.value % 1 gwei == 0, "DepositContract: deposit value not multiple of gwei");
uint deposit_amount = msg.value / 1 gwei;
require(deposit_amount <= type(uint64).max, "DepositContract: deposit value too high");
// Emit `DepositEvent` log
bytes memory amount = to_little_endian_64(uint64(deposit_amount));
emit DepositEvent(
pubkey,
withdrawal_credentials,
amount,
signature,
to_little_endian_64(uint64(deposit_count))
);
// Compute deposit data root (`DepositData` hash tree root)
bytes32 pubkey_root = sha256(abi.encodePacked(pubkey, bytes16(0)));
bytes32 signature_root = sha256(abi.encodePacked(
sha256(abi.encodePacked(signature[:64])),
sha256(abi.encodePacked(signature[64:], bytes32(0)))
));
bytes32 node = sha256(abi.encodePacked(
sha256(abi.encodePacked(pubkey_root, withdrawal_credentials)),
sha256(abi.encodePacked(amount, bytes24(0), signature_root))
));
// Verify computed and expected deposit data roots match
require(node == deposit_data_root, "DepositContract: reconstructed DepositData does not match supplied deposit_data_root");
// Avoid overflowing the Merkle tree (and prevent edge case in computing `branch`)
require(deposit_count < MAX_DEPOSIT_COUNT, "DepositContract: merkle tree full");
// Add deposit data root to Merkle tree (update a single `branch` node)
deposit_count += 1;
uint size = deposit_count;
for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH; height++) {
if ((size & 1) == 1) {
branch[height] = node;
return;
}
node = sha256(abi.encodePacked(branch[height], node));
size /= 2;
}
// As the loop should always end prematurely with the `return` statement,
// this code should be unreachable. We assert `false` just to be safe.
assert(false);
}
function supportsInterface(bytes4 interfaceId) override external pure returns (bool) {
return interfaceId == type(ERC165).interfaceId || interfaceId == type(IDepositContract).interfaceId;
}
function to_little_endian_64(uint64 value) internal pure returns (bytes memory ret) {
ret = new bytes(8);
bytes8 bytesValue = bytes8(value);
// Byteswapping during copying to bytes.
ret[0] = bytesValue[7];
ret[1] = bytesValue[6];
ret[2] = bytesValue[5];
ret[3] = bytesValue[4];
ret[4] = bytesValue[3];
ret[5] = bytesValue[2];
ret[6] = bytesValue[1];
ret[7] = bytesValue[0];
}
}