From 3479c6ea8db9f3fc7fffc75617acd009fbe548c1 Mon Sep 17 00:00:00 2001
From: Kay Kurokawa <kay@lbry.io>
Date: Mon, 26 Jun 2017 17:50:51 -0400
Subject: [PATCH] add docstring and unit test for CryptBlob.py

---
 lbrynet/cryptstream/CryptBlob.py         | 33 +++++++++-
 tests/unit/cryptstream/__init__.py       |  0
 tests/unit/cryptstream/test_cryptblob.py | 79 ++++++++++++++++++++++++
 3 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/cryptstream/__init__.py
 create mode 100644 tests/unit/cryptstream/test_cryptblob.py

diff --git a/lbrynet/cryptstream/CryptBlob.py b/lbrynet/cryptstream/CryptBlob.py
index 1aa2f4f1f..0b26d6f89 100644
--- a/lbrynet/cryptstream/CryptBlob.py
+++ b/lbrynet/cryptstream/CryptBlob.py
@@ -16,6 +16,15 @@ class CryptBlobInfo(BlobInfo):
 
 class StreamBlobDecryptor(object):
     def __init__(self, blob, key, iv, length):
+        """
+        This class decrypts blob
+
+        blob - object which implements read() function.
+        key = encryption_key
+        iv = initialization vector
+        blob_num = blob number (has no effect on encryption)
+        length = length in bytes of blob
+        """
         self.blob = blob
         self.key = key
         self.iv = iv
@@ -25,6 +34,12 @@ class StreamBlobDecryptor(object):
         self.cipher = AES.new(self.key, AES.MODE_CBC, self.iv)
 
     def decrypt(self, write_func):
+        """
+        Decrypt blob and write its content useing write_func
+
+        write_func - function that takes decrypted string as
+            arugment and writes it somewhere
+        """
 
         def remove_padding(data):
             pad_len = ord(data[-1])
@@ -55,8 +70,16 @@ class StreamBlobDecryptor(object):
 
 
 class CryptStreamBlobMaker(object):
-    """This class encrypts data and writes it to a new blob"""
     def __init__(self, key, iv, blob_num, blob):
+        """
+        This class encrypts data and writes it to a new blob
+
+        key = encryption_key
+        iv = initialization vector
+        blob_num = blob number (has no effect on encryption)
+        blob = object which implements write(), close() function , close() function must
+            be a deferred. (Will generally be of HashBlobCreator type)
+        """
         self.key = key
         self.iv = iv
         self.blob_num = blob_num
@@ -66,6 +89,14 @@ class CryptStreamBlobMaker(object):
         self.length = 0
 
     def write(self, data):
+        """
+        encrypt and write string data
+
+        Returns:
+        tuple (done, num_bytes_to_write) where done is True if
+        max bytes are written. num_bytes_to_write is the number
+        of bytes that will be written from data in this call
+        """
         max_bytes_to_write = conf.settings['BLOB_SIZE'] - self.length - 1
         done = False
         if max_bytes_to_write <= len(data):
diff --git a/tests/unit/cryptstream/__init__.py b/tests/unit/cryptstream/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/unit/cryptstream/test_cryptblob.py b/tests/unit/cryptstream/test_cryptblob.py
new file mode 100644
index 000000000..cb1110d77
--- /dev/null
+++ b/tests/unit/cryptstream/test_cryptblob.py
@@ -0,0 +1,79 @@
+from twisted.trial import unittest
+from twisted.internet import defer
+from lbrynet.cryptstream import CryptBlob
+from lbrynet.core.HashBlob import TempBlobCreator
+from lbrynet import conf
+
+from tests.mocks import mock_conf_settings
+
+from Crypto import Random
+from Crypto.Cipher import AES
+import tempfile
+import random
+import string
+import StringIO
+import time
+
+class MocBlob(object):
+    def __init__(self):
+        self.data = ''
+
+    def read(self, write_func):
+        data = self.data
+        write_func(data)
+        return defer.succeed(True)
+
+    def write(self, data):
+        self.data += data
+
+    def close(self):
+        return defer.succeed(True)
+
+
+def random_string(length):
+   return ''.join(random.choice(string.lowercase) for i in range(length))
+
+
+class TestCryptBlob(unittest.TestCase):
+    def setUp(self):
+        mock_conf_settings(self)
+
+
+    @defer.inlineCallbacks
+    def _test_encrypt_decrypt(self, size_of_data):
+        # max blob size is 2*2**20 -1 ( -1 due to required padding in the end )
+        blob = MocBlob()
+        blob_num = 0
+        key = Random.new().read(AES.block_size)
+        iv = Random.new().read(AES.block_size)
+        maker = CryptBlob.CryptStreamBlobMaker(key, iv, blob_num, blob)
+        write_size = size_of_data
+        string_to_encrypt = random_string(size_of_data)
+
+        # encrypt string
+        done,num_bytes = maker.write(string_to_encrypt)
+        yield maker.close()
+        self.assertEqual(size_of_data,num_bytes)
+        expected_encrypted_blob_size = ((size_of_data / AES.block_size) + 1) * AES.block_size
+        self.assertEqual(expected_encrypted_blob_size, len(blob.data))
+
+        if size_of_data < conf.settings['BLOB_SIZE']-1:
+            self.assertFalse(done)
+        else:
+            self.assertTrue(done)
+        self.data_buf = ''
+
+        def write_func(data):
+            self.data_buf += data
+
+        # decrypt string
+        decryptor = CryptBlob.StreamBlobDecryptor(blob, key, iv, size_of_data)
+        decryptor.decrypt(write_func)
+        self.assertEqual(self.data_buf,string_to_encrypt)
+
+    @defer.inlineCallbacks
+    def test_encrypt_decrypt(self):
+        yield self._test_encrypt_decrypt(1)
+        yield self._test_encrypt_decrypt(16*2)
+        yield self._test_encrypt_decrypt(2000)
+        yield self._test_encrypt_decrypt(2*2**20-1)