def test_get_base64_invalid_length(self):
"""
Test that trying to read a number of bits that is not a multiple of 8
as base64 data raises an exception.
"""
bitstream = BitStream()
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
self.assertRaises(ValueError,
bitstream.get_base64, 26) # read 3.25 bytes?
def test_get_base64_invalid_length(self):
"""
Test that trying to read a number of bits that is not a multiple of 8
as base64 data raises an exception.
"""
bitstream = BitStream()
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
self.assertRaises(ValueError, bitstream.get_base64,
26) # read 3.25 bytes?
def test_base64_basic(self):
"""
This method tests put_base64's and get_base64's basic functionality.
"""
bitstream = BitStream()
# We use the Base64 Test Vectors defined in RFC4648.
# http://www.ietf.org/rfc/rfc4648.txt
test_vectors = [("",""),
("f","Zg=="),
("fo","Zm8="),
("foo","Zm9v"),
("foob","Zm9vYg=="),
("fooba","Zm9vYmE="),
("foobar","Zm9vYmFy")]
# STEP 1:
# For each test vector, we write its value to the bitstream as a string
# then read it as base64 data.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val)*8
bitstream.put_string(str_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(vector_bit_length),
base64_val)
bitstream.seek(0)
# NOTE that we are overwriting multiple times our bitstream, this is
# also a feature of BitStream we are testing in this test case.
# STEP 2:
# For each test vector, we write its value to the bitstream as base64
# data, then read it as string *and* base64 data.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val)*8
bitstream.put_base64(base64_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_string(vector_bit_length),
str_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(vector_bit_length),
base64_val)
bitstream.seek(0)
# STEP 3:
# For each test vector, we write its value to a NEW bitstream as base64
# data, and make sure the length of the stream is the expected one.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val)*8
new_bs = BitStream()
new_bs.put_base64(base64_val)
self.assertEquals(new_bs.get_length(), vector_bit_length)
self.assertEquals(new_bs.get_current_pos(), vector_bit_length)
def test_get_base64_zero_bits(self):
"""
Test that reading zero bits from the stream as base64 data results in
getting the empty string: \"\".
"""
bitstream = BitStream()
self.assertEquals(bitstream.get_base64(0), "")
# Store some base64 data in the stream.
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(0), "")
def test_get_base64_zero_bits(self):
"""
Test that reading zero bits from the stream as base64 data results in
getting the empty string: \"\".
"""
bitstream = BitStream()
self.assertEquals(bitstream.get_base64(0), "")
# Store some base64 data in the stream.
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(0), "")
def test_base64_basic(self):
"""
This method tests put_base64's and get_base64's basic functionality.
"""
bitstream = BitStream()
# We use the Base64 Test Vectors defined in RFC4648.
# http://www.ietf.org/rfc/rfc4648.txt
test_vectors = [("", ""), ("f", "Zg=="), ("fo", "Zm8="),
("foo", "Zm9v"), ("foob", "Zm9vYg=="),
("fooba", "Zm9vYmE="), ("foobar", "Zm9vYmFy")]
# STEP 1:
# For each test vector, we write its value to the bitstream as a string
# then read it as base64 data.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val) * 8
bitstream.put_string(str_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(vector_bit_length),
base64_val)
bitstream.seek(0)
# NOTE that we are overwriting multiple times our bitstream, this is
# also a feature of BitStream we are testing in this test case.
# STEP 2:
# For each test vector, we write its value to the bitstream as base64
# data, then read it as string *and* base64 data.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val) * 8
bitstream.put_base64(base64_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_string(vector_bit_length), str_val)
bitstream.seek(0)
self.assertEquals(bitstream.get_base64(vector_bit_length),
base64_val)
bitstream.seek(0)
# STEP 3:
# For each test vector, we write its value to a NEW bitstream as base64
# data, and make sure the length of the stream is the expected one.
for (str_val, base64_val) in test_vectors:
vector_bit_length = len(str_val) * 8
new_bs = BitStream()
new_bs.put_base64(base64_val)
self.assertEquals(new_bs.get_length(), vector_bit_length)
self.assertEquals(new_bs.get_current_pos(), vector_bit_length)
def test_get_base64_beyond_eos(self):
"""
Test that trying to read beyond the end of the stream raises an
exception when calling get_base64(...).
"""
bitstream = BitStream()
self.assertRaises(NotEnoughBitsInStreamError, bitstream.get_base64, 8)
# Current position should not have been changed
self.assertEquals(bitstream.get_current_pos(), 0)
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
# Read beyond EOS
self.assertRaises(NotEnoughBitsInStreamError, bitstream.get_base64, 48)
# Current position should not have been changed
self.assertEquals(bitstream.get_current_pos(), 0)
def test_get_base64_beyond_eos(self):
"""
Test that trying to read beyond the end of the stream raises an
exception when calling get_base64(...).
"""
bitstream = BitStream()
self.assertRaises(NotEnoughBitsInStreamError,
bitstream.get_base64, 8)
# Current position should not have been changed
self.assertEquals(bitstream.get_current_pos(),0)
bitstream.put_base64("Zm9vYmE=") # 40 bits
bitstream.seek(0)
# Read beyond EOS
self.assertRaises(NotEnoughBitsInStreamError,
bitstream.get_base64, 48)
# Current position should not have been changed
self.assertEquals(bitstream.get_current_pos(),0)
def from_file(cls, filename, SerializerClass=serialize.XMLSerializer):
"""
Loads an instance of Ciphertext from the given file.
Arguments:
filename::string -- The name of a file containing the ciphertext
in serialized form.
SerializerClass::class --
The class that provides the deserialization. XMLSerializer by
default. Must inherit from serialize.BaseSerializer and provide
an adequate deserialize_from_file method.
Note that often the same class used to serialize the data must
be used to deserialize it.
(see utilities/serialize.py documentation for more information)
Throws:
InvalidPloneVoteCryptoFileError -- If the file is not a valid
PloneVoteCryptoLib stored
ciphertext file.
"""
# Create a new serializer object for the Ciphertext structure definition
serializer = SerializerClass(Ciphertext_serialize_structure_definition)
# Deserialize the Ciphertext instance from file
try:
data = serializer.deserialize_from_file(filename)
except serialize.InvalidSerializeDataError as e:
# Convert the exception to an InvalidPloneVoteCryptoFileError
raise InvalidPloneVoteCryptoFileError(filename,
"File \"%s\" does not contain a valid ciphertext. The " \
"following error occurred while trying to deserialize the " \
"file contents: %s" % (filename, str(e)))
# Get the values from the deserialized data
try:
nbits = int(data["PloneVoteCiphertext"]["nbits"])
except ValueError:
raise InvalidPloneVoteCryptoFileError(filename,
"File \"%s\" does not contain a valid ciphertext. The " \
"stored value for nbits is not a valid (decimal) integer." \
% filename)
fingerprint_str = data["PloneVoteCiphertext"]["PKFingerprint"]
enc_data_str = data["PloneVoteCiphertext"]["EncryptedData"]
# Construct a new Ciphertext object with the given nbits and fingerprint
ciphertext = cls(nbits, fingerprint_str)
# Load the encrypted data
bitstream = BitStream()
bitstream.put_base64(enc_data_str)
bitstream.seek(0)
length = bitstream.get_length()
# number of gamma and delta blocks in the bitstream:
blocks = length // (nbits * 2)
for i in range(0, blocks):
gamma_val = bitstream.get_num(nbits)
delta_val = bitstream.get_num(nbits)
ciphertext.append(gamma_val, delta_val)
# Return the ciphertext
return ciphertext
