PySecretHandshake/secret_handshake/util.py
Pedro Ferreira 59de8c3ce0 Refactor server code (use connections)
Past version was unusable with >1 client.
2018-02-04 15:41:30 +01:00

118 lines
3.6 KiB
Python

# Copyright (c) 2017 PySecretHandshake contributors (see AUTHORS for more details)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import struct
from io import BytesIO
NONCE_SIZE = 24
MAX_NONCE = (8 * NONCE_SIZE)
class AsyncBuffer(BytesIO):
"""Just a BytesIO with an async read method."""
async def read(self, n=None):
v = super(AsyncBuffer, self).read(n)
return v
readexactly = read
def append(self, data):
"""Append data to the buffer without changing the current position."""
pos = self.tell()
self.write(data)
self.seek(pos)
async def async_comprehend(generator):
"""Emulate ``[elem async for elem in generator]``."""
results = []
async for msg in generator:
results.append(msg)
return results
def inc_nonce(nonce):
num = bytes_to_long(nonce) + 1
if num > 2 ** MAX_NONCE:
num = 0
bnum = long_to_bytes(num)
bnum = b'\x00' * (NONCE_SIZE - len(bnum)) + bnum
return bnum
def split_chunks(seq, n):
"""Split sequence in equal-sized chunks.
The last chunk is not padded."""
while seq:
yield seq[:n]
seq = seq[n:]
# Stolen from PyCypto (Public Domain)
def b(s):
return s.encode("latin-1") # utf-8 would cause some side-effects we don't want
def long_to_bytes(n, blocksize=0):
"""long_to_bytes(n:long, blocksize:int) : string
Convert a long integer to a byte string.
If optional blocksize is given and greater than zero, pad the front of the
byte string with binary zeros so that the length is a multiple of
blocksize.
"""
# after much testing, this algorithm was deemed to be the fastest
s = b('')
pack = struct.pack
while n > 0:
s = pack('>I', n & 0xffffffff) + s
n = n >> 32
# strip off leading zeros
for i in range(len(s)):
if s[i] != b('\000')[0]:
break
else:
# only happens when n == 0
s = b('\000')
i = 0
s = s[i:]
# add back some pad bytes. this could be done more efficiently w.r.t. the
# de-padding being done above, but sigh...
if blocksize > 0 and len(s) % blocksize:
s = (blocksize - len(s) % blocksize) * b('\000') + s
return s
def bytes_to_long(s):
"""bytes_to_long(string) : long
Convert a byte string to a long integer.
This is (essentially) the inverse of long_to_bytes().
"""
acc = 0
unpack = struct.unpack
length = len(s)
if length % 4:
extra = (4 - length % 4)
s = b('\000') * extra + s
length = length + extra
for i in range(0, length, 4):
acc = (acc << 32) + unpack('>I', s[i:i+4])[0]
return acc