CasperSecurity
# Copyright 2013-2017 Donald Stufft and individual contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import nacl.exceptions as exc
from nacl._sodium import ffi, lib
from nacl.exceptions import ensure
def sodium_memcmp(inp1: bytes, inp2: bytes) -> bool:
"""
Compare contents of two memory regions in constant time
"""
ensure(isinstance(inp1, bytes), raising=exc.TypeError)
ensure(isinstance(inp2, bytes), raising=exc.TypeError)
ln = max(len(inp1), len(inp2))
buf1 = ffi.new("char []", ln)
buf2 = ffi.new("char []", ln)
ffi.memmove(buf1, inp1, len(inp1))
ffi.memmove(buf2, inp2, len(inp2))
eqL = len(inp1) == len(inp2)
eqC = lib.sodium_memcmp(buf1, buf2, ln) == 0
return eqL and eqC
def sodium_pad(s: bytes, blocksize: int) -> bytes:
"""
Pad the input bytearray ``s`` to a multiple of ``blocksize``
using the ISO/IEC 7816-4 algorithm
:param s: input bytes string
:type s: bytes
:param blocksize:
:type blocksize: int
:return: padded string
:rtype: bytes
"""
ensure(isinstance(s, bytes), raising=exc.TypeError)
ensure(isinstance(blocksize, int), raising=exc.TypeError)
if blocksize <= 0:
raise exc.ValueError
s_len = len(s)
m_len = s_len + blocksize
buf = ffi.new("unsigned char []", m_len)
p_len = ffi.new("size_t []", 1)
ffi.memmove(buf, s, s_len)
rc = lib.sodium_pad(p_len, buf, s_len, blocksize, m_len)
ensure(rc == 0, "Padding failure", raising=exc.CryptoError)
return ffi.buffer(buf, p_len[0])[:]
def sodium_unpad(s: bytes, blocksize: int) -> bytes:
"""
Remove ISO/IEC 7816-4 padding from the input byte array ``s``
:param s: input bytes string
:type s: bytes
:param blocksize:
:type blocksize: int
:return: unpadded string
:rtype: bytes
"""
ensure(isinstance(s, bytes), raising=exc.TypeError)
ensure(isinstance(blocksize, int), raising=exc.TypeError)
s_len = len(s)
u_len = ffi.new("size_t []", 1)
rc = lib.sodium_unpad(u_len, s, s_len, blocksize)
if rc != 0:
raise exc.CryptoError("Unpadding failure")
return s[: u_len[0]]
def sodium_increment(inp: bytes) -> bytes:
"""
Increment the value of a byte-sequence interpreted
as the little-endian representation of a unsigned big integer.
:param inp: input bytes buffer
:type inp: bytes
:return: a byte-sequence representing, as a little-endian
unsigned big integer, the value ``to_int(inp)``
incremented by one.
:rtype: bytes
"""
ensure(isinstance(inp, bytes), raising=exc.TypeError)
ln = len(inp)
buf = ffi.new("unsigned char []", ln)
ffi.memmove(buf, inp, ln)
lib.sodium_increment(buf, ln)
return ffi.buffer(buf, ln)[:]
def sodium_add(a: bytes, b: bytes) -> bytes:
"""
Given a couple of *same-sized* byte sequences, interpreted as the
little-endian representation of two unsigned integers, compute
the modular addition of the represented values, in constant time for
a given common length of the byte sequences.
:param a: input bytes buffer
:type a: bytes
:param b: input bytes buffer
:type b: bytes
:return: a byte-sequence representing, as a little-endian big integer,
the integer value of ``(to_int(a) + to_int(b)) mod 2^(8*len(a))``
:rtype: bytes
"""
ensure(isinstance(a, bytes), raising=exc.TypeError)
ensure(isinstance(b, bytes), raising=exc.TypeError)
ln = len(a)
ensure(len(b) == ln, raising=exc.TypeError)
buf_a = ffi.new("unsigned char []", ln)
buf_b = ffi.new("unsigned char []", ln)
ffi.memmove(buf_a, a, ln)
ffi.memmove(buf_b, b, ln)
lib.sodium_add(buf_a, buf_b, ln)
return ffi.buffer(buf_a, ln)[:]