182 lines
7.6 KiB
Solidity
182 lines
7.6 KiB
Solidity
// SPDX-License-Identifier: Apache-2.0
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pragma solidity 0.6.8;
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// This interface is designed to be compatible with the Vyper version.
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/// @notice This is the Ethereum 2.0 deposit contract interface.
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/// For more information see the Phase 0 specification under https://github.com/ethereum/eth2.0-specs
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interface IDepositContract {
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/// @notice A processed deposit event.
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event DepositEvent(
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bytes pubkey,
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bytes withdrawal_credentials,
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bytes amount,
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bytes signature,
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bytes index
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);
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/// @notice Submit a Phase 0 DepositData object.
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/// @param pubkey A BLS12-381 public key.
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/// @param withdrawal_credentials Commitment to a public key for withdrawals.
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/// @param signature A BLS12-381 signature.
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/// @param deposit_data_root The SHA-256 hash of the SSZ-encoded DepositData object.
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/// Used as a protection against malformed input.
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function deposit(
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bytes calldata pubkey,
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bytes calldata withdrawal_credentials,
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bytes calldata signature,
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bytes32 deposit_data_root
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) external payable;
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/// @notice Query the current deposit root hash.
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/// @return The deposit root hash.
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function get_deposit_root() external view returns (bytes32);
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/// @notice Query the current deposit count.
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/// @return The deposit count encoded as a little endian 64-bit number.
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function get_deposit_count() external view returns (bytes memory);
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}
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// Based on official specification in https://eips.ethereum.org/EIPS/eip-165
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interface ERC165 {
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/// @notice Query if a contract implements an interface
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/// @param interfaceId The interface identifier, as specified in ERC-165
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/// @dev Interface identification is specified in ERC-165. This function
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/// uses less than 30,000 gas.
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/// @return `true` if the contract implements `interfaceId` and
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/// `interfaceId` is not 0xffffffff, `false` otherwise
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function supportsInterface(bytes4 interfaceId) external pure returns (bool);
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}
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// This is a rewrite of the Vyper Eth2.0 deposit contract in Solidity.
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// It tries to stay as close as possible to the original source code.
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/// @notice This is the Ethereum 2.0 deposit contract interface.
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/// For more information see the Phase 0 specification under https://github.com/ethereum/eth2.0-specs
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contract DepositContract is IDepositContract, ERC165 {
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uint constant GWEI = 1e9;
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uint constant DEPOSIT_CONTRACT_TREE_DEPTH = 32;
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// NOTE: this also ensures `deposit_count` will fit into 64-bits
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uint constant MAX_DEPOSIT_COUNT = 2**DEPOSIT_CONTRACT_TREE_DEPTH - 1;
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bytes32[DEPOSIT_CONTRACT_TREE_DEPTH] branch;
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uint256 deposit_count;
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bytes32[DEPOSIT_CONTRACT_TREE_DEPTH] zero_hashes;
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constructor() public {
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// Compute hashes in empty sparse Merkle tree
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for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH - 1; height++)
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zero_hashes[height + 1] = sha256(abi.encodePacked(zero_hashes[height], zero_hashes[height]));
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}
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/// @notice Query the current deposit root hash.
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/// @return The deposit root hash.
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function get_deposit_root() override external view returns (bytes32) {
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bytes32 node;
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uint size = deposit_count;
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for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH; height++) {
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if ((size & 1) == 1)
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node = sha256(abi.encodePacked(branch[height], node));
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else
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node = sha256(abi.encodePacked(node, zero_hashes[height]));
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size /= 2;
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}
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return sha256(abi.encodePacked(
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node,
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to_little_endian_64(uint64(deposit_count)),
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bytes24(0)
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));
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}
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/// @notice Query the current deposit count.
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/// @return The deposit count encoded as a little endian 64-bit number.
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function get_deposit_count() override external view returns (bytes memory) {
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return to_little_endian_64(uint64(deposit_count));
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}
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/// @notice Submit a Phase 0 DepositData object.
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/// @param pubkey A BLS12-381 public key.
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/// @param withdrawal_credentials Commitment to a public key for withdrawals.
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/// @param signature A BLS12-381 signature.
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/// @param deposit_data_root The SHA-256 hash of the SSZ-encoded DepositData object.
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/// Used as a protection against malformed input.
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function deposit(
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bytes calldata pubkey,
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bytes calldata withdrawal_credentials,
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bytes calldata signature,
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bytes32 deposit_data_root
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) override external payable {
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// Extended ABI length checks since dynamic types are used.
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require(pubkey.length == 48, "DepositContract: invalid pubkey length");
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require(withdrawal_credentials.length == 32, "DepositContract: invalid withdrawal_credentials length");
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require(signature.length == 96, "DepositContract: invalid signature length");
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// Check deposit amount
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require(msg.value >= 1 ether, "DepositContract: deposit value too low");
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require(msg.value % GWEI == 0, "DepositContract: deposit value not multiple of gwei");
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uint deposit_amount = msg.value / GWEI;
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require(deposit_amount <= type(uint64).max, "DepositContract: deposit value too high");
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// Emit `DepositEvent` log
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bytes memory amount = to_little_endian_64(uint64(deposit_amount));
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emit DepositEvent(
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pubkey,
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withdrawal_credentials,
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amount,
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signature,
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to_little_endian_64(uint64(deposit_count))
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);
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// Compute deposit data root (`DepositData` hash tree root)
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bytes32 pubkey_root = sha256(abi.encodePacked(pubkey, bytes16(0)));
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bytes32 signature_root = sha256(abi.encodePacked(
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sha256(abi.encodePacked(signature[:64])),
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sha256(abi.encodePacked(signature[64:], bytes32(0)))
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));
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bytes32 node = sha256(abi.encodePacked(
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sha256(abi.encodePacked(pubkey_root, withdrawal_credentials)),
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sha256(abi.encodePacked(amount, bytes24(0), signature_root))
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));
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// Verify computed and expected deposit data roots match
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require(node == deposit_data_root, "DepositContract: reconstructed DepositData does not match supplied deposit_data_root");
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// Avoid overflowing the Merkle tree (and prevent edge case in computing `branch`)
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require(deposit_count < MAX_DEPOSIT_COUNT, "DepositContract: merkle tree full");
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// Add deposit data root to Merkle tree (update a single `branch` node)
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deposit_count += 1;
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uint size = deposit_count;
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for (uint height = 0; height < DEPOSIT_CONTRACT_TREE_DEPTH; height++) {
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if ((size & 1) == 1) {
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branch[height] = node;
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return;
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}
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node = sha256(abi.encodePacked(branch[height], node));
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size /= 2;
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}
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// As the loop should always end prematurely with the `return` statement,
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// this code should be unreachable. We assert `false` just to be safe.
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assert(false);
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}
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function supportsInterface(bytes4 interfaceId) override external pure returns (bool) {
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return interfaceId == type(ERC165).interfaceId || interfaceId == type(IDepositContract).interfaceId;
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}
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function to_little_endian_64(uint64 value) internal pure returns (bytes memory ret) {
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ret = new bytes(8);
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bytes8 bytesValue = bytes8(value);
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// Byteswapping during copying to bytes.
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ret[0] = bytesValue[7];
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ret[1] = bytesValue[6];
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ret[2] = bytesValue[5];
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ret[3] = bytesValue[4];
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ret[4] = bytesValue[3];
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ret[5] = bytesValue[2];
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ret[6] = bytesValue[1];
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ret[7] = bytesValue[0];
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}
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}
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