✨ BlockHashLib (#1470)

Co-authored-by: Developer Uche <[email protected]>

Author: Vectorized

foundry.toml

@@ -10,7 +10,7 @@ auto_detect_solc = false
 optimizer = true
 optimizer_runs = 1_000
 gas_limit = 100_000_000 # ETH is 30M, but we use a higher value.
-skip = ["*/*7702*", "*/*Transient*", "*/ext/ithaca/*", "*/ext/zksync/*"]
+skip = ["*/*7702*", "*/*BlockHashLib*", "*/*Transient*", "*/ext/ithaca/*", "*/ext/zksync/*"]
 fs_permissions = [{ access = "read", path = "./test/data"}]
 remappings = [
   "forge-std=test/utils/forge-std/"

src/utils/BlockHashLib.sol

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+/// @notice Library for accessing block hashes way beyond the 256-block limit. ref: EIP-2935
+/// @author Solady (https://github.com/vectorized/solady/blob/main/src/utils/BlockHashLib.sol)
+/// @author Modified from OpenZeppelin (https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Blockhash.sol)
+library BlockHashLib {
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                         CONSTANTS                          */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    /// @dev Address of the EIP-2935 history storage contract.
+    /// See: https://eips.ethereum.org/EIPS/eip-2935
+    address internal constant HISTORY_STORAGE_ADDRESS = 0x0000F90827F1C53a10cb7A02335B175320002935;
+
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                         OPERATIONS                         */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    /// @dev Retrieves the block hash for any historical block within the supported range.
+    /// The function gracefully handles future blocks and blocks beyond the history window by returning zero,
+    /// consistent with the EVM's native `BLOCKHASH` behavior.
+    function blockHash(uint256 blockNumber) internal view returns (bytes32 result) {
+        unchecked {
+            // If `blockNumber + 256` overflows:
+            // - Typical chain height (`block.number > 255`) -> `staticcall` -> 0.
+            // - Very early chain (`block.number <= 255`) -> `blockhash` -> 0.
+            if (block.number <= blockNumber + 256) return blockhash(blockNumber);
+        }
+        /// @solidity memory-safe-assembly
+        assembly {
+            mstore(0x20, blockNumber)
+            mstore(0x00, 0)
+            pop(staticcall(gas(), HISTORY_STORAGE_ADDRESS, 0x20, 0x20, 0x00, 0x20))
+            result := mload(0x00)
+        }
+    }
+}

test/BlockHashLib.t.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+import "./utils/SoladyTest.sol";
+import {BlockHashLib} from "../src/utils/BlockHashLib.sol";
+
+contract BlockHashLibTest is SoladyTest {
+    uint256 internal startingBlock;
+
+    address internal constant SYSTEM_ADDRESS = 0xffffFFFfFFffffffffffffffFfFFFfffFFFfFFfE;
+
+    bytes private constant _HISTORY_STORAGE_BYTECODE =
+        hex"3373fffffffffffffffffffffffffffffffffffffffe14604657602036036042575f35600143038111604257611fff81430311604257611fff9006545f5260205ff35b5f5ffd5b5f35611fff60014303065500";
+
+    function testBlockHash(
+        uint256 simulationBlockNumber,
+        uint256 queryBlockNumber,
+        uint256 savedBlockedNumber,
+        bytes32 h
+    ) public {
+        if (_randomChance(2)) {
+            vm.etch(BlockHashLib.HISTORY_STORAGE_ADDRESS, _HISTORY_STORAGE_BYTECODE);
+        }
+
+        savedBlockedNumber = _bound(savedBlockedNumber, 0, 2 ** 64 - 1);
+
+        vm.roll(savedBlockedNumber + 1);
+        vm.prank(SYSTEM_ADDRESS);
+        (bool success,) = BlockHashLib.HISTORY_STORAGE_ADDRESS.call(abi.encode(h));
+        require(success);
+
+        vm.setBlockhash(savedBlockedNumber, h);
+
+        vm.roll(simulationBlockNumber);
+
+        assertEq(BlockHashLib.blockHash(queryBlockNumber), _blockHash(queryBlockNumber));
+    }
+
+    function _blockHash(uint256 blockNumber) internal view returns (bytes32) {
+        (bool success, bytes memory result) =
+            address(this).staticcall(abi.encodeWithSignature("blockHash(uint256)", blockNumber));
+        if (!success) return 0;
+        return abi.decode(result, (bytes32));
+    }
+
+    function blockHash(uint256 blockNumber) public view returns (bytes32 result) {
+        if (block.number <= blockNumber + 256) return blockhash(blockNumber);
+        address a = BlockHashLib.HISTORY_STORAGE_ADDRESS;
+        if (a.code.length == 0) return 0;
+        /// @solidity memory-safe-assembly
+        assembly {
+            mstore(0x20, blockNumber)
+            mstore(0x00, 0)
+            pop(staticcall(gas(), a, 0x20, 0x20, 0x00, 0x20))
+            result := mload(0x00)
+        }
+    }
+}

test/utils/forge-std/Vm.sol

@@ -1988,4 +1988,7 @@ interface Vm is VmSafe {
 
     /// Stops all safe memory expectation in the current subcontext.
     function stopExpectSafeMemory() external;
+
+    /// Sets the blockhash for a given block number.
+    function setBlockhash(uint256 blockNumber, bytes32 blockHash) external;
 }