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341 lines
11 KiB
341 lines
11 KiB
import sys
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from struct import pack
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from . import consts
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def align_int(i: int, align: int):
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return (-i) % align
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def align_int_add(i: int, align: int):
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return i + align_int(i, align)
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def align_data(data, align: int, padding: bytes = b"\x00"):
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return data + padding * align_int(len(data), align)
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class Norcow:
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def __init__(self):
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self.sectors = None
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self.active_sector = 0
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def init(self):
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if self.sectors:
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for sector in range(consts.NORCOW_SECTOR_COUNT):
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if self.sectors[sector][: len(self.magic)] == self.magic:
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self.active_sector = sector
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self.active_offset = self.find_free_offset()
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break
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else:
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self.wipe()
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def find_free_offset(self):
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offset = len(self.magic)
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while True:
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try:
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k, v = self._read_item(offset)
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except ValueError:
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break
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offset = offset + self._norcow_item_length(len(v))
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return offset
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def wipe(self, sector: int = None):
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if sector is None:
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sector = self.active_sector
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self.sectors = [
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bytearray([0xFF] * consts.NORCOW_SECTOR_SIZE)
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for _ in range(consts.NORCOW_SECTOR_COUNT)
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]
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self.sectors[sector][: len(self.magic)] = self.magic
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self.active_sector = sector
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self.active_offset = len(self.magic)
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def get(self, key: int) -> bytes:
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value, _ = self._find_item(key)
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return value
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def set(self, key: int, val: bytes):
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if key == consts.NORCOW_KEY_FREE:
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raise RuntimeError("Norcow: key 0xFFFF is not allowed")
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found_value, pos = self._find_item(key)
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if found_value is not None:
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if self._is_updatable(key, val):
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self._write(pos, key, val)
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return
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else:
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self._delete_old(pos, found_value)
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if (
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self.active_offset
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+ align_int_add(self.item_prefix_len + len(val), self.block_size)
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> consts.NORCOW_SECTOR_SIZE
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):
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self._compact()
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if (
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self.active_offset
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+ align_int_add(self.item_prefix_len + len(val), self.block_size)
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> consts.NORCOW_SECTOR_SIZE
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):
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raise RuntimeError("Norcow: no space left")
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self._append(key, val)
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def delete(self, key: int):
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if key == consts.NORCOW_KEY_FREE:
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raise RuntimeError("Norcow: key 0xFFFF is not allowed")
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found_value, pos = self._find_item(key)
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if found_value is None:
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return False
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self._delete_old(pos, found_value)
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return True
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def replace(self, key: int, new_value: bytes) -> bool:
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old_value, offset = self._find_item(key)
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if old_value is None:
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raise RuntimeError("Norcow: key not found")
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if len(old_value) != len(new_value):
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raise RuntimeError(
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"Norcow: replace works only with items of the same length"
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)
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self._write(offset, key, new_value)
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def _delete_old(self, pos: int, value: bytes):
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wiped_data = b"\x00" * len(value)
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self._write(pos, 0x0000, wiped_data)
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def _append(self, key: int, value: bytes):
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self.active_offset += self._write(self.active_offset, key, value)
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def _find_item(self, key: int) -> (bytes, int):
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offset = len(self.magic)
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value = None
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pos = offset
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while True:
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try:
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k, v = self._read_item(offset)
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if k == key:
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value = v
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pos = offset
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except ValueError:
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break
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offset = offset + self._norcow_item_length(len(v))
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return value, pos
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def _get_all_keys(self) -> (bytes, int):
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offset = len(self.magic)
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keys = set()
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while True:
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try:
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k, v = self._read_item(offset)
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keys.add(k)
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except ValueError:
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break
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offset = offset + self._norcow_item_length(len(v))
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return keys
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def _compact(self):
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offset = len(self.magic)
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data = list()
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while True:
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try:
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k, v = self._read_item(offset)
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if k != 0x00:
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data.append((k, v))
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except ValueError:
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break
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offset = offset + self._norcow_item_length(len(v))
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sector = self.active_sector
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self.wipe((sector + 1) % consts.NORCOW_SECTOR_COUNT)
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for key, value in data:
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self._append(key, value)
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def _set_sectors(self, data):
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if list(map(len, data)) != [
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consts.NORCOW_SECTOR_SIZE,
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consts.NORCOW_SECTOR_SIZE,
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]:
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raise RuntimeError("Norcow: set_sectors called with invalid data length")
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self.sectors = [bytearray(sector) for sector in data]
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def _dump(self):
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return [bytes(sector) for sector in self.sectors]
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class NorcowBitwise(Norcow):
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def __init__(self):
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super().__init__()
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self.block_size = consts.WORD_SIZE
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self.magic = consts.NORCOW_MAGIC_AND_VERSION
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self.item_prefix_len = 4
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self.lib_name = "libtrezor-storage.so"
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def get_lib_name(self):
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return self.lib_name
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def is_byte_access(self):
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return True
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def _is_updatable(self, key: int, new: bytes) -> bool:
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"""
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Item is updatable if the new value is the same or
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it changes 1 to 0 only (the flash memory does not
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allow to flip 0 to 1 unless you wipe it).
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"""
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old, _ = self._find_item(key)
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if old is None:
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return False
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if len(old) != len(new):
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return False
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for a, b in zip(old, new):
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if a & b != b:
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return False
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return True
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def _write(self, pos: int, key: int, new_value: bytes) -> int:
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data = pack("<HH", key, len(new_value)) + align_data(new_value, self.block_size)
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if pos + len(data) > consts.NORCOW_SECTOR_SIZE:
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raise RuntimeError("Norcow: item too big")
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self.sectors[self.active_sector][pos : pos + len(data)] = data
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return len(data)
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def _norcow_item_length(self, data_len: int) -> int:
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# APP_ID, KEY_ID, LENGTH, DATA, ALIGNMENT
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return self.item_prefix_len + data_len + align_int(data_len, self.block_size)
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def _read_item(self, offset: int) -> (int, bytes):
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if offset >= consts.NORCOW_SECTOR_SIZE:
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raise ValueError("Norcow: no data on this offset")
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key = self.sectors[self.active_sector][offset : offset + 2]
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key = int.from_bytes(key, sys.byteorder)
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if key == consts.NORCOW_KEY_FREE:
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raise ValueError("Norcow: no data on this offset")
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length = self.sectors[self.active_sector][offset + 2 : offset + 4]
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length = int.from_bytes(length, sys.byteorder)
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value = self.sectors[self.active_sector][offset + 4 : offset + 4 + length]
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return key, value
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class NorcowBlockwise(Norcow):
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def __init__(self):
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super().__init__()
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self.block_size = 4 * consts.WORD_SIZE
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self.small_item_size = 12
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self.magic = consts.NORCOW_MAGIC_AND_VERSION + bytes([0x00] * 8)
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self.item_prefix_len = 4 * consts.WORD_SIZE + 1
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self.lib_name = "libtrezor-storage-qw.so"
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def get_lib_name(self):
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return self.lib_name
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def is_byte_access(self):
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return False
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def _is_updatable(self, key: int, new: bytes) -> bool:
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"""
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The item is only deemed updatable if the new value is the same as the old one.
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"""
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old, _ = self._find_item(key)
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if old is None:
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return False
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if len(old) != len(new):
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return False
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for a, b in zip(old, new):
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if a != b:
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return False
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return True
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def _write(self, pos: int, key: int, new_value: bytes) -> int:
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if len(new_value) <= self.small_item_size:
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if key == 0:
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self.sectors[self.active_sector][pos : pos + self.block_size] = [
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0
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] * self.block_size
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else:
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if len(new_value) == 0:
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data = pack("<HH", key, len(new_value)) + bytes(
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[0] * self.small_item_size
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)
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else:
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data = pack("<HH", key, len(new_value)) + align_data(
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new_value, self.small_item_size
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)
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if pos + len(data) > consts.NORCOW_SECTOR_SIZE:
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raise RuntimeError("Norcow: item too big")
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self.sectors[self.active_sector][pos : pos + self.block_size] = data
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return len(data)
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else:
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if key == 0:
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old_key = self.sectors[self.active_sector][pos + 0 : pos + 2]
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old_key = int.from_bytes(old_key, sys.byteorder)
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data = align_data(
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pack("<HH", old_key, len(new_value)), self.block_size, b"\x00"
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)
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data += align_data(new_value + bytes([0]), self.block_size, b"\x00")
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else:
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data = align_data(
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pack("<HH", key, len(new_value)), self.block_size, b"\x00"
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)
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data += align_data(new_value + bytes([0xFF]), self.block_size, b"\xFF")
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if pos + len(data) > consts.NORCOW_SECTOR_SIZE:
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raise RuntimeError("Norcow: item too big")
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self.sectors[self.active_sector][pos : pos + len(data)] = data
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return len(data)
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def _norcow_item_length(self, data_len: int) -> int:
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if data_len <= 12:
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return self.block_size
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else:
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# APP_ID, KEY_ID, LENGTH, DATA, ALIGNMENT
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return (
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self.block_size
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+ 1
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+ data_len
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+ align_int(1 + data_len, self.block_size)
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)
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def _read_item(self, offset: int) -> (int, bytes):
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if offset >= consts.NORCOW_SECTOR_SIZE:
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raise ValueError("Norcow: no data on this offset")
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length = self.sectors[self.active_sector][offset + 2 : offset + 4]
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length = int.from_bytes(length, sys.byteorder)
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if length <= self.small_item_size:
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key = self.sectors[self.active_sector][offset : offset + 2]
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key = int.from_bytes(key, sys.byteorder)
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if key == consts.NORCOW_KEY_FREE:
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raise ValueError("Norcow: no data on this offset")
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value = self.sectors[self.active_sector][offset + 4 : offset + 4 + length]
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else:
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key = self.sectors[self.active_sector][offset : offset + 2]
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key = int.from_bytes(key, sys.byteorder)
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if key == consts.NORCOW_KEY_FREE:
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raise ValueError("Norcow: no data on this offset")
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deleted = self.sectors[self.active_sector][
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offset + self.block_size + length
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]
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value = self.sectors[self.active_sector][
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offset + self.block_size : offset + self.block_size + length
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]
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if deleted == 0:
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key = 0
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else:
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if key == consts.NORCOW_KEY_FREE:
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raise ValueError("Norcow: no data on this offset")
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return key, value
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NC_CLASSES = [NorcowBitwise, NorcowBlockwise]
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