def encrypt(buf, offset, fh, cuuid, suuid):
key = retrieve_key(cuuid, suuid)
# TODO incorporate nonce
ctr = Crypto.Util.Counter.new(128, initial_value=long(offset))
cipher = Crypto.Cipher.AES.new(key, Crypto.Cipher.AES.MODE_CTR, counter=ctr)
leftovers = len(buf) % block_size
# Pad the block for encrypting
if len(buf) == 0 or leftovers != 0:
padding_size = block_size - leftovers
buf += padding_size * chr(padding_size)
# Write to the file
fh.seek(offset)
fh.write(cipher.encrypt(buf))
return padding_size
def decrypt(buf, offset, fh, cuuid, suuid):
key = retrieve_key(cuuid, suuid)
# Return blank in the case of a blank buffer
if buf == "":
return ""
# TODO incorporate nonce
ctr = Crypto.Util.Counter.new(128, initial_value=long(offset))
cipher = Crypto.Cipher.AES.new(key, Crypto.Cipher.AES.MODE_CTR, counter=ctr)
buf = cipher.decrypt(buf)
# Undo the padding
padding_size = ord(buf[-1])
if padding_size < 1 or padding_size > block_size:
print("Bad padding value")
elif buf[-padding_size:] != (padding_size * chr(padding_size)):
print("Bad decrypt")
buf = buf[:-padding_size]
# Return decrypted text
return buf
