The Crow: City of Angels for Saturn - generate all level passwords

the_crow_saturn.py

LETTER_MAP = {"A": 2, "B": 3, "X": 0, "Y": 1}


def rotate_right(value, positions, bit_width=32):
    # This is the function at 06031e3c (NTSC-U Saturn verison)
    mask = (1 << bit_width) - 1
    value &= mask
    positions %= bit_width  # Handle positions > bit_width

    return ((value >> positions) | (value << (bit_width - positions))) & mask


def check_password_accumulator(acc):
    # Adapted from Ghidra's decompilation of the  functions at 06031718
    # and 06031eec (NTSC-U Saturn version)

    # Decrypt using fixed key
    acc = acc ^ 0xA5A5A

    # Extract low 4 bits
    uVar3 = acc & 0xF

    # Extract high 14 bits and XOR with low 4 bits, keep low 4 bits
    starting_stage = (uVar3 ^ (acc >> 0xE)) & 0xF

    # Extract bits 4-13: (acc & 0x3ff0) >> 4
    # Extract bits 0-1, shift to bits 8-9: (acc & 3) << 8
    # Low 4 bits shifted to bits 4-7: uVar3 << 4
    # Low 4 bits in bits 0-3: uVar3
    # XOR the extracted middle bits with the constructed value
    rotate_input = ((acc & 0x3FF0) >> 4) ^ ((acc & 3) << 8 | uVar3 << 4 | uVar3)

    # Rotate by the calculated amount
    uVar1 = rotate_right(rotate_input, starting_stage, 10)

    # Extract components from rotated result
    uVar3 = (uVar1 & 0xC) >> 2  # Bits 2-3

    # Validation check: sum of components should equal original high bits
    if (
        starting_stage == 0
        or ((uVar1 >> 4) + uVar3 + (uVar1 & 3) + starting_stage) & 0x3F != acc >> 0xE
    ):
        return ()

    # Store extracted components globally
    sVar2 = uVar1 >> 4
    lives = uVar3  # Bits 2-3 of rotated value
    difficulty_level = uVar1 & 3  # Bits 0-1 of rotated value

    # Calculate some derived value
    if sVar2 == 0:
        starting_health = 2
    else:
        starting_health = sVar2 * 2 + 1

    return (starting_stage, lives, difficulty_level, starting_health)


def check_password(password_letters):
    if len(password_letters) != 10:
        return ()

    accumulator = 0
    for i, letter in enumerate(password_letters):
        mapped_letter = LETTER_MAP.get(letter, -1) & 0xFFFFFFFF
        accumulator |= (mapped_letter << 2 * i) & 0xFFFFFFFF

    return check_password_accumulator(accumulator)


if __name__ == "__main__":
    from itertools import product

    seen = set()
    for prod in product("ABXY", repeat=10):
        password_letters = "".join(prod)
        params = check_password(password_letters)
        if not params:
            continue

        starting_stage, lives, difficulty_level, starting_health = params
        if (lives == 3) and (starting_health == 0x7F) and (1 <= difficulty_level <= 3):
            if (starting_stage, difficulty_level) not in seen:
                seen.add((starting_stage, difficulty_level))
                print(password_letters, *params, sep="\t")