async def handle_download(self, offset, length, file_number):
# let them read from where we store the signed txn
# - filenumber can be 0 or 1: uploaded txn, or result
from sflash import SF
# limiting memory use here, should be MAX_BLK_LEN really
length = min(length, MAX_BLK_LEN)
assert 0 <= file_number < 2, 'bad fnum'
assert 0 <= offset <= MAX_TXN_LEN, "bad offset"
assert 1 <= length, 'len'
# maintain a running SHA256 over what's sent
if offset == 0:
self.file_checksum = sha256()
pos = (MAX_TXN_LEN * file_number) + offset
resp = bytearray(4 + length)
resp[0:4] = b'biny'
SF.read(pos, memoryview(resp)[4:])
self.file_checksum.update(memoryview(resp)[4:])
return resp
def read_into(self, b):
# limitation: this will read past end of file, but not tell the caller
actual = min(self.length - self.pos, len(b))
if actual <= 0:
return 0
SF.read(self.start + self.pos, b)
self.pos += actual
return actual
def count_busy():
from nvstore import SLOTS
from sflash import SF
busy = 0
b = bytearray(4096)
for pos in SLOTS:
SF.read(pos, b)
if len(set(b)) > 200:
busy += 1
return busy
def find_spot(self, not_here=0):
# search for a blank sector to use
# - check randomly and pick first blank one (wear leveling, deniability)
# - we will write and then erase old slot
# - if "full", blow away a random one
options = [s for s in SLOTS if s != not_here]
shuffle(options)
buf = bytearray(16)
for pos in options:
SF.read(pos, buf)
if set(buf) == {0xff}:
# blank
return pos
# No where to write! (probably a bug because we have lots of slots)
# ... so pick a random slot and kill what it had
#print("ERROR: nvram full?")
victem = options[0]
SF.sector_erase(victem)
SF.wait_done()
return victem
def read(self, ll=None):
if ll == 0:
return b''
elif ll is None:
ll = self.length - self.pos
else:
ll = min(ll, self.length - self.pos)
if ll <= 0:
# at EOF
return b''
rv = bytearray(ll)
SF.read(self.start + self.pos, rv)
self.pos += ll
if self.message and ll > 1:
from glob import dis
dis.progress_bar_show(self.pos / self.length)
# altho tempting to return a bytearray (which we already have) many
# callers expect return to be bytes and have those methods, like "find"
return bytes(rv)
async def test_sflash():
dis.clear()
dis.text(None, 18, 'Serial Flash')
dis.show()
from sflash import SF
from ustruct import pack
import ngu
msize = 1024 * 1024
SF.chip_erase()
for phase in [0, 1]:
steps = 7 * 4
for i in range(steps):
dis.progress_bar(i / steps)
dis.show()
await sleep_ms(250)
if not SF.is_busy(): break
assert not SF.is_busy() # "didn't finish"
# leave chip blank
if phase == 1: break
buf = bytearray(32)
for addr in range(0, msize, 1024):
SF.read(addr, buf)
assert set(buf) == {255} # "not blank"
rnd = ngu.hash.sha256s(pack('I', addr))
SF.write(addr, rnd)
SF.read(addr, buf)
assert buf == rnd # "write failed"
dis.progress_bar_show(addr / msize)
# check no aliasing, also right size part
for addr in range(0, msize, 1024):
expect = ngu.hash.sha256s(pack('I', addr))
SF.read(addr, buf)
assert buf == expect # "readback failed"
dis.progress_bar_show(addr / msize)
def load(self, dis=None):
# Search all slots for any we can read, decrypt that,
# and pick the newest one (in unlikely case of dups)
# reset
self.current.clear()
self.overrides.clear()
self.my_pos = 0
self.is_dirty = 0
self.capacity = 0
# 4k, but last 32 bytes are a SHA (itself encrypted)
global _tmp
buf = bytearray(4)
empty = 0
for pos in SLOTS:
if dis:
dis.progress_bar_show(
(pos - SLOTS.start) / (SLOTS.stop - SLOTS.start))
gc.collect()
SF.read(pos, buf)
if buf[0] == buf[1] == buf[2] == buf[3] == 0xff:
# erased (probably)
empty += 1
continue
# check if first 2 bytes makes sense for JSON
aes = self.get_aes(pos)
chk = aes.copy().cipher(b'{"')
if chk != buf[0:2]:
# doesn't look like JSON meant for me
continue
# probably good, read it
chk = sha256()
aes = aes.cipher
expect = None
with SFFile(pos, length=4096, pre_erased=True) as fd:
for i in range(4096 / 32):
b = aes(fd.read(32))
if i != 127:
_tmp[i * 32:(i * 32) + 32] = b
chk.update(b)
else:
expect = b
try:
# verify checksum in last 32 bytes
assert expect == chk.digest()
# loads() can't work from a byte array, and converting to
# bytes here would copy it; better to use file emulation.
fd = BytesIO(_tmp)
d = ujson.load(fd)
self.capacity = fd.seek(0, 1) / 4096 # .tell() is missing
except:
# One in 65k or so chance to come here w/ garbage decoded, so
# not an error.
continue
got_age = d.get('_age', 0)
if got_age > self.current.get('_age', -1):
# likely winner
self.current = d
self.my_pos = pos
#print("NV: data @ %d w/ age=%d" % (pos, got_age))
else:
# stale data seen; clean it up.
assert self.current['_age'] > 0
#print("NV: cleanup @ %d" % pos)
SF.sector_erase(pos)
SF.wait_done()
# 4k is a large object, sigh, for us right now. cleanup
gc.collect()
# done, if we found something
if self.my_pos:
return
# nothing found.
self.my_pos = 0
self.current = self.default_values()
if empty == len(SLOTS):
# Whole thing is blank. Bad for plausible deniability. Write 3 slots
# with garbage. They will be wasted space until it fills.
blks = list(SLOTS)
shuffle(blks)
for pos in blks[0:3]:
for i in range(0, 4096, 256):
h = ngu.random.bytes(256)
SF.wait_done()
SF.write(pos + i, h)
# everything should be encrypted now
assert count_busy() == len(SLOTS)
# check we hide initial values
SF.chip_erase()
settings.load()
settings.save()
assert count_busy() == 4
# check checksum/age stuff works
settings.set('wrecked', 768)
settings.save()
b = bytearray(4096)
SF.read(settings.my_pos, b)
was_age = settings.get('_age')
settings.set('wrecked', 123)
settings.save()
assert settings.get('_age') == was_age+1
was_pos = settings.my_pos
# write old data everywhere else
for pos in SLOTS:
if pos != was_pos:
for i in range(0, 4096, 256):
SF.write(pos+i, b[i:i+256])
settings.load()
assert was_pos == settings.my_pos