test_vector_push_in_immediate_masks_jumpdest()

Documentation for tests/amsterdam/eip8024_dupn_swapn_exchange/test_eip_vectors.py::test_vector_push_in_immediate_masks_jumpdest@26332146.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip8024_dupn_swapn_exchange/test_eip_vectors.py::test_vector_push_in_immediate_masks_jumpdest --fork Amsterdam

Test that a PUSH1 in the would-be immediate masks a following 0x5b.

Executable form of the e6605b assembly vector ([INVALID_DUPN, PUSH1 0x5b]), parametrized over all three opcodes. JUMPDEST analysis is unchanged by EIP-8024: the byte after the opcode is analyzed as PUSH1, whose data portion masks the 0x5b, so the jump to it must fail. A client that instead masks the opcode's immediate would leave the 0x5b at an instruction boundary, accept the jump, and succeed — diverging on bytecode that is valid before and after the fork.

Source code in tests/amsterdam/eip8024_dupn_swapn_exchange/test_eip_vectors.py

@pytest.mark.parametrize(
    "opcode",
    [Op.DUPN, Op.SWAPN, Op.EXCHANGE],
)
def test_vector_push_in_immediate_masks_jumpdest(
    pre: Alloc,
    state_test: StateTestFiller,
    opcode: Op,
) -> None:
    """
    Test that a PUSH1 in the would-be immediate masks a following 0x5b.

    Executable form of the `e6605b` assembly vector ([INVALID_DUPN,
    PUSH1 0x5b]), parametrized over all three opcodes. JUMPDEST analysis
    is unchanged by EIP-8024: the byte after the opcode is analyzed as
    PUSH1, whose data portion masks the 0x5b, so the jump to it must
    fail. A client that instead masks the opcode's immediate would leave
    the 0x5b at an instruction boundary, accept the jump, and succeed —
    diverging on bytecode that is valid before and after the fork.
    """
    sender = pre.fund_eoa()

    # 00 PUSH1 0x05
    # 02 JUMP
    # 03 <opcode>
    # 04 PUSH1 0x5b
    code = Op.PUSH1(5) + Op.JUMP + opcode[bytes(Op.PUSH1)] + Op.JUMPDEST
    expected_bytes = (
        bytes.fromhex("600556") + bytes(opcode) + bytes.fromhex("605b")
    )
    assert bytes(code) == expected_bytes

    # This should never execute: position 5 is PUSH1 data, not a
    # JUMPDEST, so the jump above aborts.
    code += Op.SSTORE(0, 0x42)
    code += Op.STOP

    contract_address = pre.deploy_contract(code=code, storage={0: 0xBA5E})
    tx = Transaction(to=contract_address, sender=sender)

    # Transaction fails on the invalid jump; the canary is untouched.
    post = {contract_address: Account(storage={0: 0xBA5E})}

    state_test(pre=pre, post=post, tx=tx)

Parametrized Test Cases

This test generates 3 parametrized test cases across 1 fork.