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authorVictor Shyba <victor1984@riseup.net>2016-11-24 21:09:33 -0300
committerdrebs <drebs@leap.se>2016-12-12 09:17:51 -0200
commit8b091951e8adebadc4be4dc5b2fb4f8b63c6900e (patch)
tree9cfe8d0a946ed123e04830b27dc37d40ffec0015 /client
parent89d5c898527c32baec8454d6e3c749935d00a313 (diff)
[docs] add docstrings for _crypto
Also explaining how we are using Twisted's consumer interfaces.
Diffstat (limited to 'client')
-rw-r--r--client/src/leap/soledad/client/_crypto.py109
1 files changed, 101 insertions, 8 deletions
diff --git a/client/src/leap/soledad/client/_crypto.py b/client/src/leap/soledad/client/_crypto.py
index d8d37f55..4a59159c 100644
--- a/client/src/leap/soledad/client/_crypto.py
+++ b/client/src/leap/soledad/client/_crypto.py
@@ -75,11 +75,30 @@ docinfo = namedtuple('docinfo', 'doc_id rev')
class SoledadCrypto(object):
-
+ """
+ This class provides convenient methods for document encryption and
+ decryption using BlobEncryptor and BlobDecryptor classes.
+ """
def __init__(self, secret):
+ """
+ Initialize the crypto object.
+
+ :param secret: The Soledad remote storage secret.
+ :type secret: str
+ """
self.secret = secret
def encrypt_doc(self, doc):
+ """
+ Creates and configures a BlobEncryptor, asking it to start encryption
+ and wrapping the result as a simple JSON string with a "raw" key.
+
+ :param doc: the document to be encrypted.
+ :type doc: SoledadDocument
+ :return: A deferred whose callback will be invoked with a JSON string
+ containing the ciphertext as the value of "raw" key.
+ :rtype: twisted.internet.defer.Deferred
+ """
def put_raw(blob):
raw = blob.getvalue()
@@ -95,6 +114,15 @@ class SoledadCrypto(object):
return d
def decrypt_doc(self, doc):
+ """
+ Creates and configures a BlobDecryptor, asking it decrypt and returning
+ the decrypted cleartext content from the encrypted document.
+
+ :param doc: the document to be decrypted.
+ :type doc: SoledadDocument
+ :return: The decrypted cleartext content of the document.
+ :rtype: str
+ """
info = docinfo(doc.doc_id, doc.rev)
ciphertext = BytesIO()
payload = doc.content['raw']
@@ -106,6 +134,18 @@ class SoledadCrypto(object):
def encrypt_sym(data, key):
+ """
+ Encrypt data using AES-256 cipher in CTR mode.
+
+ :param data: The data to be encrypted.
+ :type data: str
+ :param key: The key used to encrypt data (must be 256 bits long).
+ :type key: str
+
+ :return: A tuple with the initialization vector and the ciphertext, both
+ encoded as base64.
+ :rtype: (str, str)
+ """
iv = os.urandom(16)
encryptor = AESEncryptor(key, iv)
encryptor.write(data)
@@ -115,6 +155,20 @@ def encrypt_sym(data, key):
def decrypt_sym(data, key, iv):
+ """
+ Decrypt data using AES-256 cipher in CTR mode.
+
+ :param data: The data to be decrypted.
+ :type data: str
+ :param key: The symmetric key used to decrypt data (must be 256 bits
+ long).
+ :type key: str
+ :param iv: The base64 encoded initialization vector.
+ :type iv: str
+
+ :return: The decrypted data.
+ :rtype: str
+ """
_iv = base64.b64decode(str(iv))
decryptor = AESDecryptor(key, _iv)
decryptor.write(data)
@@ -124,11 +178,16 @@ def decrypt_sym(data, key, iv):
class BlobEncryptor(object):
-
"""
- Encrypts a payload associated with a given Document.
+ Produces encrypted data from the cleartext data associated with a given
+ SoledadDocument using AES-256 cipher in CTR mode, together with a
+ HMAC-SHA512 Message Authentication Code.
+ The production happens using a Twisted's FileBodyProducer, which uses a
+ Cooperator to schedule calls and can be paused/resumed. Each call takes at
+ most 65536 bytes from the input.
+ Both the production input and output are file descriptors, so they can be
+ applied to a stream of data.
"""
-
def __init__(self, doc_info, content_fd, result=None, secret=None,
iv=None):
if iv is None:
@@ -162,11 +221,25 @@ class BlobEncryptor(object):
self._crypter = VerifiedEncrypter(self._aes, self._hmac)
def encrypt(self):
+ """
+ Starts producing encrypted data from the cleartext data.
+
+ :return: A deferred which will be fired when encryption ends and whose
+ callback will be invoked with the resulting ciphertext.
+ :rtype: twisted.internet.defer.Deferred
+ """
d = self._producer.startProducing(self._crypter)
d.addCallback(self._end_crypto_stream)
return d
def encrypt_whole(self):
+ """
+ Encrypts the input data at once and returns the resulting ciphertext
+ wrapped into a JSON string under the "raw" key.
+
+ :return: The resulting ciphertext JSON string.
+ :rtype: str
+ """
self._crypter.write(self._content_fd.getvalue())
self._end_crypto_stream(None)
return '{"raw":"' + self.result.getvalue() + '"}'
@@ -281,7 +354,10 @@ class BlobDecryptor(object):
class AESEncryptor(object):
-
+ """
+ A Twisted's Consumer implementation that takes an input file descriptor and
+ applies AES-256 cipher in CTR mode.
+ """
implements(interfaces.IConsumer)
def __init__(self, key, iv, fd=None):
@@ -311,7 +387,10 @@ class AESEncryptor(object):
class HMACWriter(object):
-
+ """
+ A Twisted's Consumer implementation that takes an input file descriptor and
+ produces a HMAC-SHA512 Message Authentication Code.
+ """
implements(interfaces.IConsumer)
hashtype = 'sha512'
@@ -327,7 +406,10 @@ class HMACWriter(object):
class VerifiedEncrypter(object):
-
+ """
+ A Twisted's Consumer implementation combining AESEncryptor and HMACWriter.
+ It directs the resulting ciphertext into HMAC-SHA512 processing.
+ """
implements(interfaces.IConsumer)
def __init__(self, crypter, hmac):
@@ -340,7 +422,10 @@ class VerifiedEncrypter(object):
class AESDecryptor(object):
-
+ """
+ A Twisted's Consumer implementation that consumes data encrypted with
+ AES-256 in CTR mode from a file descriptor and generates decrypted data.
+ """
implements(interfaces.IConsumer)
def __init__(self, key, iv, fd=None):
@@ -373,6 +458,14 @@ class AESDecryptor(object):
def is_symmetrically_encrypted(doc):
+ """
+ Return True if the document was symmetrically encrypted.
+
+ :param doc: The document to check.
+ :type doc: SoledadDocument
+
+ :rtype: bool
+ """
payload = doc.content
if not payload or 'raw' not in payload:
return False