[tahoe-lafs-trac-stream] [tahoe-lafs] #2120: Change counter value for AES-CTR

[tahoe-lafs]

#2120: Change counter value for AES-CTR
------------------------+---------------------------
 Reporter:  markberger  |          Owner:  daira
     Type:  defect      |         Status:  new
 Priority:  normal      |      Milestone:  undecided
Component:  unknown     |        Version:  1.10.0
 Keywords:              |  Launchpad Bug:
------------------------+---------------------------
 In `immutable/upload.py` we have the following code:

 {{{
 def _hash_and_encrypt_plaintext(self, data, hash_only):
         assert isinstance(data, (tuple, list)), type(data)
         data = list(data)
         cryptdata = []
         # we use data.pop(0) instead of 'for chunk in data' to save
         # memory: each chunk is destroyed as soon as we're done with it.
         bytes_processed = 0
         while data:
             chunk = data.pop(0)
             self.log(" read_encrypted handling %dB-sized chunk" %
 len(chunk),
                      level=log.NOISY)
             bytes_processed += len(chunk)
             self._plaintext_hasher.update(chunk)
             self._update_segment_hash(chunk)
             # TODO: we have to encrypt the data (even if hash_only==True)
             # because pycryptopp's AES-CTR implementation doesn't offer a
             # way to change the counter value. Once pycryptopp acquires
             # this ability, change this to simply update the counter
             # before each call to (hash_only==False) _encryptor.process()
             ciphertext = self._encryptor.process(chunk)
             if hash_only:
                 self.log("  skipping encryption", level=log.NOISY)
             else:
                 cryptdata.append(ciphertext)
             del ciphertext
             del chunk
         self._ciphertext_bytes_read += bytes_processed
         if self._status:
             progress = float(self._ciphertext_bytes_read) /
 self._file_size
             self._status.set_progress(1, progress)
         return cryptdata
 }}}

 As part of #1382 I am removing the TODO and creating a ticket for this
 instead.

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2120>
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