bug: `blockHash()` reverts with error for `block.number-1`

[swetshaw]

Bug Report

Kakarot version

v0.9.6

Current behavior

Calculating blockHash for previous block reverts with error:

execution reverted: Provider errror StarknetError(ContractError(ContractErrorData { revert_error: "Error at pc=0:49:\nGot an exception while executing a hint: Execution failed. Failure reason: 0x426c6f636b206e756d626572206f7574206f662072616e6765 ('Block number out of range').\nCairo traceback (most recent call last):\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23794)\nUnknown location (pc=0:22982)\nUnknown location (pc=0:9986)\nUnknown location (pc=0:10171)\nUnknown location (pc=0:5927)\n" })).

Expected behavior

It should return blockhash in bytes32

Steps to reproduce

1. Copy and paste the following contract in Remix or any contract tooling of your choice:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract TestBlockNumber {

    function getPreviousBlockHash() public  view  returns (bytes32) {
        return blockhash(block.number - 1);
    }

    function getCurrentBlockHash() public view returns (bytes32) {
        return blockhash(block.number);
    }
}

2. Deploy the contract on kakarot starknet sepolia
3. Call getCurrentBlockHash() --- it will return valid hash
4. Call getPreviousBlockHash() --- it will revert with error:

execution reverted: Provider errror StarknetError(ContractError(ContractErrorData { revert_error: "Error at pc=0:49:\nGot an exception while executing a hint: Execution failed. Failure reason: 0x426c6f636b206e756d626572206f7574206f662072616e6765 ('Block number out of range').\nCairo traceback (most recent call last):\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23796)\nUnknown location (pc=0:23794)\nUnknown location (pc=0:22982)\nUnknown location (pc=0:9986)\nUnknown location (pc=0:10171)\nUnknown location (pc=0:5927)\n" })).

[enitrat]

known and addressed as part of C4 mitigation plan

HOWEVER https://docs.kakarot.org/starknet/architecture/differences note that the expected behavior is that it returns 0

[enitrat]

Closed by: #1593

@swetshaw can you follow up with layerswap to let them know of this behavior?