lbry-sdk/lbrynet/cryptstream/CryptStreamCreator.py

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"""
Utility for creating Crypt Streams, which are encrypted blobs and associated metadata.
"""
import logging
from Crypto import Random
from Crypto.Cipher import AES
from twisted.internet import defer
from lbrynet.core.StreamCreator import StreamCreator
from lbrynet.cryptstream.CryptBlob import CryptStreamBlobMaker
log = logging.getLogger(__name__)
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class CryptStreamCreator(StreamCreator):
"""Create a new stream with blobs encrypted by a symmetric cipher.
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Each blob is encrypted with the same key, but each blob has its
own initialization vector which is associated with the blob when
the blob is associated with the stream.
"""
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def __init__(self, blob_manager, name=None, key=None, iv_generator=None):
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"""@param blob_manager: Object that stores and provides access to blobs.
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@type blob_manager: BlobManager
@param name: the name of the stream, which will be presented to the user
@type name: string
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@param key: the raw AES key which will be used to encrypt the
blobs. If None, a random key will be generated.
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@type key: string
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@param iv_generator: a generator which yields initialization
vectors for the blobs. Will be called once for each blob.
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@type iv_generator: a generator function which yields strings
@return: None
"""
StreamCreator.__init__(self, name)
self.blob_manager = blob_manager
self.key = key
if iv_generator is None:
self.iv_generator = self.random_iv_generator()
else:
self.iv_generator = iv_generator
@staticmethod
def random_iv_generator():
while 1:
yield Random.new().read(AES.block_size)
def setup(self):
"""Create the symmetric key if it wasn't provided"""
if self.key is None:
self.key = Random.new().read(AES.block_size)
return defer.succeed(True)
def _finalize(self):
"""
Finalize a stream by adding an empty
blob at the end, this is to indicate that
the stream has ended. This empty blob is not
saved to the blob manager
"""
log.debug("_finalize has been called")
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self.blob_count += 1
iv = self.iv_generator.next()
final_blob_creator = self.blob_manager.get_blob_creator()
final_blob = self._get_blob_maker(iv, final_blob_creator)
d = final_blob.close()
d.addCallback(self._blob_finished)
self.finished_deferreds.append(d)
def _write(self, data):
def close_blob(blob):
d = blob.close()
d.addCallback(self._blob_finished)
self.finished_deferreds.append(d)
while len(data) > 0:
if self.current_blob is None:
self.next_blob_creator = self.blob_manager.get_blob_creator()
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self.blob_count += 1
iv = self.iv_generator.next()
self.current_blob = self._get_blob_maker(iv, self.next_blob_creator)
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done, num_bytes_written = self.current_blob.write(data)
data = data[num_bytes_written:]
if done is True:
should_announce = self.blob_count == 0
d = self.current_blob.close()
d.addCallback(self._blob_finished)
d.addCallback(lambda _: self.blob_manager.creator_finished(
self.next_blob_creator, should_announce))
self.finished_deferreds.append(d)
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self.current_blob = None
def _get_blob_maker(self, iv, blob_creator):
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return CryptStreamBlobMaker(self.key, iv, self.blob_count, blob_creator)