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De-golf some crypto functions.

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encrypt_key and decrypt_key were using a feature of sum() where
the second argument is a 'start' value and every futher value
is += onto that. Since it was a tuple, the final result is a tuple.
Replaced it with a tuple comprehension.
get_chunks just needed some variable names but I am not sure the
purpose of the increasing chunk size during iteration. It's probably
a feature of the MEGA webclient.
This commit is contained in:
Ethan Dalool 2020-03-23 20:35:22 -07:00
parent 1a7c3ea781
commit 85d4f9d6a3
1 changed files with 22 additions and 18 deletions
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40
src/mega/crypto.py
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@ -48,8 +48,8 @@ def stringhash(str, aeskey):
""" """
s32 = str_to_a32(str) s32 = str_to_a32(str)
h32 = [0, 0, 0, 0] h32 = [0, 0, 0, 0]
for i in range(len(s32)): for (index, word) in enumerate(s32):
h32[i % 4] ^= s32[i] h32[index % 4] ^= word
for r in range(0x4000): for r in range(0x4000):
h32 = aes_cbc_encrypt_a32(h32, aeskey) h32 = aes_cbc_encrypt_a32(h32, aeskey)
return a32_to_base64((h32[0], h32[2])) return a32_to_base64((h32[0], h32[2]))
@ -68,15 +68,20 @@ def prepare_key(arr):
def encrypt_key(a, key): def encrypt_key(a, key):
return sum( encrypted = tuple(
(aes_cbc_encrypt_a32(a[i:i + 4], key) for i in range(0, len(a), 4)), () piece
for i in range(0, len(a), 4)
for piece in aes_cbc_encrypt_a32(a[i:i + 4], key)
) )
return encrypted
def decrypt_key(a, key): def decrypt_key(a, key):
return sum( decrypted = tuple(
(aes_cbc_decrypt_a32(a[i:i + 4], key) for i in range(0, len(a), 4)), () piece
for i in range(0, len(a), 4)
for piece in aes_cbc_decrypt_a32(a[i:i + 4], key)
) )
return decrypted
def encrypt_attr(attr, key): def encrypt_attr(attr, key):
@ -160,19 +165,18 @@ def get_chunks(size):
Given the size of a file in bytes, return tuples (chunk_start, chunk_size) Given the size of a file in bytes, return tuples (chunk_start, chunk_size)
for the purposes of downloading or uploading a file in chunks. for the purposes of downloading or uploading a file in chunks.
""" """
p = 0 chunk_start = 0
s = 0x20000 chunk_size = 0x20000
while p + s < size: while chunk_start + chunk_size < size:
yield (p, s) yield (chunk_start, chunk_size)
p += s chunk_start += chunk_size
if s < 0x100000: # why?
s += 0x20000 if chunk_size < 0x100000:
yield (p, size - p) chunk_size += 0x20000
yield (chunk_start, size - chunk_start)
def make_id(length): def make_id(length):
text = ''
possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
for i in range(length): text = ''.join(random.choice(possible) for i in range(length))
text += random.choice(possible)
return text return text