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Code Issues Releases Wiki Activity

core/sd_salt: decorate sd_salt functions to ensure proper finalization and power-off

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This commit is contained in:
matejcik 2019-11-08 12:42:30 +01:00
parent 33bd4d3ba9
commit f03562cca0
3 changed files with 107 additions and 96 deletions
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29
core/src/apps/common/sd_salt.py
View File

@ -1,5 +1,5 @@
import storage.sd_salt
from storage.sd_salt import SD_CARD_HOT_SWAPPABLE, SdSaltMismatch
from storage.sd_salt import SD_CARD_HOT_SWAPPABLE
from trezor import io, ui, wire
from trezor.ui.text import Text
@ -29,7 +29,7 @@ async def _wrong_card_dialog(ctx: wire.GenericContext) -> bool:
return await confirm(ctx, text, confirm=btn_confirm, cancel=btn_cancel)
async def _insert_card_dialog(ctx: wire.GenericContext) -> None:
async def insert_card_dialog(ctx: wire.GenericContext) -> bool:
text = Text("SD card protection", ui.ICON_WRONG)
text.bold("SD card required.")
text.br_half()
@ -42,20 +42,20 @@ async def _insert_card_dialog(ctx: wire.GenericContext) -> None:
btn_confirm = None
btn_cancel = "Close"
if not await confirm(ctx, text, confirm=btn_confirm, cancel=btn_cancel):
raise SdProtectCancelled
return await confirm(ctx, text, confirm=btn_confirm, cancel=btn_cancel)
async def sd_write_failed_dialog(ctx: wire.GenericContext) -> bool:
async def sd_problem_dialog(ctx: wire.GenericContext) -> bool:
text = Text("SD card protection", ui.ICON_WRONG, ui.RED)
text.normal("Failed to write data to", "the SD card.")
text.normal("There was a problem", "accessing the SD card.")
return await confirm(ctx, text, confirm="Retry", cancel="Abort")
async def ensure_sd_card(ctx: wire.GenericContext) -> None:
sd = io.SDCard()
while not sd.power(True):
await _insert_card_dialog(ctx)
while not sd.present():
if not await insert_card_dialog(ctx):
raise SdProtectCancelled
async def request_sd_salt(
@ -65,11 +65,14 @@ async def request_sd_salt(
ensure_sd_card(ctx)
try:
return storage.sd_salt.load_sd_salt()
except SdSaltMismatch as e:
except storage.sd_salt.WrongSdCard:
if not await _wrong_card_dialog(ctx):
raise SdProtectCancelled from e
raise SdProtectCancelled
except OSError:
# This happens when there is both old and new salt file, and we can't move
# new salt over the old salt. If the user clicks Retry, we will try again.
if not await sd_write_failed_dialog(ctx):
# Either the SD card did not power on, or the filesystem could not be
# mounted (card is not formatted?), or there is a staged salt file and
# we could not commit it.
# In either case, there is no good way to recover. If the user clicks Retry,
# we will try again.
if not await sd_problem_dialog(ctx):
raise

11
core/src/apps/management/sd_protect.py
View File

@ -14,7 +14,7 @@ from apps.common.request_pin import (
request_pin_and_sd_salt,
show_pin_invalid,
)
from apps.common.sd_salt import ensure_sd_card, sd_write_failed_dialog
from apps.common.sd_salt import ensure_sd_card, sd_problem_dialog
if False:
from typing import Awaitable, Tuple
@ -32,10 +32,11 @@ async def _set_salt(
ctx: wire.Context, salt: bytes, salt_tag: bytes, stage: bool = False
) -> None:
while True:
ensure_sd_card(ctx)
try:
return storage.sd_salt.set_sd_salt(salt, salt_tag, stage)
except OSError:
if not await sd_write_failed_dialog(ctx):
if not await sd_problem_dialog(ctx):
raise
@ -60,7 +61,7 @@ async def sd_protect_enable(ctx: wire.Context, msg: SdProtect) -> Success:
# Confirm that user wants to proceed with the operation.
await require_confirm_sd_protect(ctx, msg)
# Make sure SD card is available.
# Make sure SD card is present.
await ensure_sd_card(ctx)
# Get the current PIN.
@ -95,7 +96,7 @@ async def sd_protect_disable(ctx: wire.Context, msg: SdProtect) -> Success:
if not storage.sd_salt.is_enabled():
raise wire.ProcessError("SD card protection not enabled")
# Note that the SD card doesn't need to be accessible in order to disable SD
# Note that the SD card doesn't need to be present in order to disable SD
# protection. The cleanup will not happen in such case, but that does not matter.
# Confirm that user wants to proceed with the operation.
@ -131,7 +132,7 @@ async def sd_protect_refresh(ctx: wire.Context, msg: SdProtect) -> Success:
# Confirm that user wants to proceed with the operation.
await require_confirm_sd_protect(ctx, msg)
# Make sure SD card is available.
# Make sure SD card is present.
await ensure_sd_card(ctx)
# Get the current PIN and salt from the SD card.

163
core/src/storage/sd_salt.py
View File

@ -7,14 +7,16 @@ from trezor.crypto.hashlib import sha256
from trezor.utils import consteq
if False:
from typing import Optional
from typing import Optional, TypeVar, Callable
T = TypeVar("T", bound=Callable)
SD_CARD_HOT_SWAPPABLE = False
SD_SALT_LEN_BYTES = const(32)
SD_SALT_AUTH_TAG_LEN_BYTES = const(16)
class SdSaltMismatch(Exception):
class WrongSdCard(Exception):
pass
@ -35,6 +37,48 @@ def _get_salt_path(new: bool = False) -> str:
return "{}/salt{}".format(_get_device_dir(), ".new" if new else "")
_ensure_filesystem_nesting_counter = 0
def ensure_filesystem(func: T) -> T:
"""Ensure the decorated function has access to SD card filesystem.
Usage:
>>> @ensure_filesystem
>>> def do_something(arg):
>>> fs = io.FatFS()
>>> # the decorator guarantees that `fs` is mounted
>>> fs.unlink("/dir/" + arg)
"""
# XXX
# A slightly better design would be to make the decorated function take the `fs`
# as an argument, but that is currently untypeable with mypy.
# (see https://github.com/python/mypy/issues/3157)
def wrapped_func(*args, **kwargs): # type: ignore
global _ensure_filesystem_nesting_counter
sd = io.SDCard()
if _ensure_filesystem_nesting_counter == 0:
if not sd.power(True):
raise OSError
try:
_ensure_filesystem_nesting_counter += 1
fs = io.FatFS()
fs.mount()
# XXX do we need to differentiate failure types?
# If yes, can the problem be derived from the type of OSError raised?
return func(*args, **kwargs)
finally:
_ensure_filesystem_nesting_counter -= 1
assert _ensure_filesystem_nesting_counter >= 0
if _ensure_filesystem_nesting_counter == 0:
fs.unmount()
sd.power(False)
return wrapped_func # type: ignore
def _load_salt(fs: io.FatFS, auth_key: bytes, path: str) -> Optional[bytearray]:
# Load the salt file if it exists.
try:
@ -54,107 +98,70 @@ def _load_salt(fs: io.FatFS, auth_key: bytes, path: str) -> Optional[bytearray]:
return salt
@ensure_filesystem
def load_sd_salt() -> Optional[bytearray]:
salt_auth_key = storage.device.get_sd_salt_auth_key()
if salt_auth_key is None:
return None
sd = io.SDCard()
if not sd.power(True):
raise OSError
salt_path = _get_salt_path()
new_salt_path = _get_salt_path(new=True)
try:
fs = io.FatFS()
try:
fs.mount()
except OSError as e:
# SD card is probably not formatted. For purposes of loading SD salt, this
# is identical to having the wrong card in.
raise SdSaltMismatch from e
fs = io.FatFS()
salt = _load_salt(fs, salt_auth_key, salt_path)
if salt is not None:
return salt
# Check if there is a new salt.
salt = _load_salt(fs, salt_auth_key, new_salt_path)
if salt is None:
# No valid salt file on this SD card.
raise SdSaltMismatch
# Normal salt file does not exist, but new salt file exists. That means that
# SD salt regeneration was interrupted earlier. Bring into consistent state.
# TODO Possibly overwrite salt file with random data.
try:
fs.unlink(salt_path)
except OSError:
pass
# fs.rename can fail with a write error, which falls through as an OSError.
# This should be handled in calling code, by allowing the user to retry.
fs.rename(new_salt_path, salt_path)
salt = _load_salt(fs, salt_auth_key, salt_path)
if salt is not None:
return salt
finally:
fs.unmount()
sd.power(False)
# Check if there is a new salt.
salt = _load_salt(fs, salt_auth_key, new_salt_path)
if salt is None:
# No valid salt file on this SD card.
raise WrongSdCard
# Normal salt file does not exist, but new salt file exists. That means that
# SD salt regeneration was interrupted earlier. Bring into consistent state.
# TODO Possibly overwrite salt file with random data.
try:
fs.unlink(salt_path)
except OSError:
pass
# fs.rename can fail with a write error, which falls through as an OSError.
# This should be handled in calling code, by allowing the user to retry.
fs.rename(new_salt_path, salt_path)
return salt
@ensure_filesystem
def set_sd_salt(salt: bytes, salt_tag: bytes, stage: bool = False) -> None:
salt_path = _get_salt_path(stage)
sd = io.SDCard()
if not sd.power(True):
raise OSError
try:
fs = io.FatFS()
fs.mount()
fs.mkdir("/trezor", True)
fs.mkdir(_get_device_dir(), True)
with fs.open(salt_path, "w") as f:
f.write(salt)
f.write(salt_tag)
finally:
fs.unmount()
sd.power(False)
fs = io.FatFS()
fs.mount()
fs.mkdir("/trezor", True)
fs.mkdir(_get_device_dir(), True)
with fs.open(salt_path, "w") as f:
f.write(salt)
f.write(salt_tag)
@ensure_filesystem
def commit_sd_salt() -> None:
salt_path = _get_salt_path(new=False)
new_salt_path = _get_salt_path(new=True)
sd = io.SDCard()
fs = io.FatFS()
if not sd.power(True):
raise OSError
try:
fs.mount()
# TODO Possibly overwrite salt file with random data.
try:
fs.unlink(salt_path)
except OSError:
pass
fs.rename(new_salt_path, salt_path)
finally:
fs.unmount()
sd.power(False)
fs.unlink(salt_path)
except OSError:
pass
fs.rename(new_salt_path, salt_path)
@ensure_filesystem
def remove_sd_salt() -> None:
salt_path = _get_salt_path()
sd = io.SDCard()
fs = io.FatFS()
if not sd.power(True):
raise OSError
try:
fs.mount()
# TODO Possibly overwrite salt file with random data.
fs.unlink(salt_path)
finally:
fs.unmount()
sd.power(False)
# TODO Possibly overwrite salt file with random data.
fs.unlink(salt_path)