144 lines
5.1 KiB
Python
144 lines
5.1 KiB
Python
import binascii
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import logging
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from twisted.internet import defer
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from cryptography.hazmat.primitives.ciphers import Cipher, modes
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from cryptography.hazmat.primitives.ciphers.algorithms import AES
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from cryptography.hazmat.primitives.padding import PKCS7
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from cryptography.hazmat.backends import default_backend
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from lbrynet import conf
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from lbrynet.core.BlobInfo import BlobInfo
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log = logging.getLogger(__name__)
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backend = default_backend()
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class CryptBlobInfo(BlobInfo):
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def __init__(self, blob_hash, blob_num, length, iv):
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BlobInfo.__init__(self, blob_hash, blob_num, length)
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self.iv = iv
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class StreamBlobDecryptor(object):
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def __init__(self, blob, key, iv, length):
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"""
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This class decrypts blob
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blob - object which implements read() function.
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key = encryption_key
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iv = initialization vector
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blob_num = blob number (has no effect on encryption)
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length = length in bytes of blob
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"""
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self.blob = blob
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self.key = key
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self.iv = iv
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self.length = length
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self.buff = b''
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self.len_read = 0
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cipher = Cipher(AES(self.key), modes.CBC(self.iv), backend=backend)
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self.unpadder = PKCS7(AES.block_size).unpadder()
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self.cipher = cipher.decryptor()
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def decrypt(self, write_func):
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"""
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Decrypt blob and write its content useing write_func
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write_func - function that takes decrypted string as
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arugment and writes it somewhere
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"""
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def remove_padding(data):
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return self.unpadder.update(data) + self.unpadder.finalize()
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def write_bytes():
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if self.len_read < self.length:
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num_bytes_to_decrypt = greatest_multiple(len(self.buff), (AES.block_size / 8))
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data_to_decrypt, self.buff = split(self.buff, num_bytes_to_decrypt)
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write_func(self.cipher.update(data_to_decrypt))
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def finish_decrypt():
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bytes_left = len(self.buff) % (AES.block_size / 8)
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if bytes_left != 0:
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log.warning(self.buff[-1 * (AES.block_size / 8):].encode('hex'))
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raise Exception("blob %s has incorrect padding: %i bytes left" %
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(self.blob.blob_hash, bytes_left))
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data_to_decrypt, self.buff = self.buff, b''
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last_chunk = self.cipher.update(data_to_decrypt) + self.cipher.finalize()
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write_func(remove_padding(last_chunk))
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def decrypt_bytes(data):
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self.buff += data
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self.len_read += len(data)
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write_bytes()
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d = self.blob.read(decrypt_bytes)
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d.addCallback(lambda _: finish_decrypt())
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return d
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class CryptStreamBlobMaker(object):
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def __init__(self, key, iv, blob_num, blob):
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"""
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This class encrypts data and writes it to a new blob
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key = encryption_key
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iv = initialization vector
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blob_num = blob number (has no effect on encryption)
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blob = object which implements write(), close() function , close() function must
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be a deferred. (Will generally be of HashBlobCreator type)
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"""
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self.key = key
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self.iv = iv
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self.blob_num = blob_num
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self.blob = blob
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cipher = Cipher(AES(self.key), modes.CBC(self.iv), backend=backend)
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self.padder = PKCS7(AES.block_size).padder()
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self.cipher = cipher.encryptor()
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self.length = 0
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def write(self, data):
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"""
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encrypt and write string data
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Returns:
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tuple (done, num_bytes_to_write) where done is True if
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max bytes are written. num_bytes_to_write is the number
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of bytes that will be written from data in this call
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"""
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max_bytes_to_write = conf.settings['BLOB_SIZE'] - self.length - 1
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done = False
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if max_bytes_to_write <= len(data):
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num_bytes_to_write = max_bytes_to_write
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done = True
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else:
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num_bytes_to_write = len(data)
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data_to_write = data[:num_bytes_to_write]
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self.length += len(data_to_write)
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padded_data = self.padder.update(data_to_write)
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encrypted_data = self.cipher.update(padded_data)
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self.blob.write(encrypted_data)
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return done, num_bytes_to_write
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@defer.inlineCallbacks
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def close(self):
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log.debug("closing blob %s with plaintext len %s", str(self.blob_num), str(self.length))
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if self.length != 0:
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self.length += (AES.block_size / 8) - (self.length % (AES.block_size / 8))
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padded_data = self.padder.finalize()
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encrypted_data = self.cipher.update(padded_data) + self.cipher.finalize()
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self.blob.write(encrypted_data)
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blob_hash = yield self.blob.close()
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log.debug("called the finished_callback from CryptStreamBlobMaker.close")
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blob = CryptBlobInfo(blob_hash, self.blob_num, self.length, binascii.hexlify(self.iv))
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defer.returnValue(blob)
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def greatest_multiple(a, b):
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"""return the largest value `c`, that is a multiple of `b` and is <= `a`"""
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return (a // b) * b
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def split(buff, cutoff):
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return buff[:cutoff], buff[cutoff:]
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