update to python3.7

lib/python3.7/site-packages/asn1crypto/_int.py

@@ -0,0 +1,159 @@
+# coding: utf-8
+
+"""
+Function for calculating the modular inverse. Exports the following items:
+
+ - inverse_mod()
+
+Source code is derived from
+http://webpages.charter.net/curryfans/peter/downloads.html, but has been heavily
+modified to fit into this projects lint settings. The original project license
+is listed below:
+
+Copyright (c) 2014 Peter Pearson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+
+from __future__ import unicode_literals, division, absolute_import, print_function
+
+import math
+import platform
+
+from .util import int_to_bytes, int_from_bytes
+
+# First try to use ctypes with OpenSSL for better performance
+try:
+    from ._ffi import (
+        buffer_from_bytes,
+        bytes_from_buffer,
+        FFIEngineError,
+        LibraryNotFoundError,
+        null,
+    )
+
+    # Some versions of PyPy have segfault issues, so we just punt on PyPy
+    if platform.python_implementation() == 'PyPy':
+        raise EnvironmentError()
+
+    try:
+        from ._perf._big_num_ctypes import libcrypto
+
+        def inverse_mod(a, p):
+            """
+            Compute the modular inverse of a (mod p)
+
+            :param a:
+                An integer
+
+            :param p:
+                An integer
+
+            :return:
+                An integer
+            """
+
+            ctx = libcrypto.BN_CTX_new()
+
+            a_bytes = int_to_bytes(abs(a))
+            p_bytes = int_to_bytes(abs(p))
+
+            a_buf = buffer_from_bytes(a_bytes)
+            a_bn = libcrypto.BN_bin2bn(a_buf, len(a_bytes), null())
+            if a < 0:
+                libcrypto.BN_set_negative(a_bn, 1)
+
+            p_buf = buffer_from_bytes(p_bytes)
+            p_bn = libcrypto.BN_bin2bn(p_buf, len(p_bytes), null())
+            if p < 0:
+                libcrypto.BN_set_negative(p_bn, 1)
+
+            r_bn = libcrypto.BN_mod_inverse(null(), a_bn, p_bn, ctx)
+            r_len_bits = libcrypto.BN_num_bits(r_bn)
+            r_len = int(math.ceil(r_len_bits / 8))
+            r_buf = buffer_from_bytes(r_len)
+            libcrypto.BN_bn2bin(r_bn, r_buf)
+            r_bytes = bytes_from_buffer(r_buf, r_len)
+            result = int_from_bytes(r_bytes)
+
+            libcrypto.BN_free(a_bn)
+            libcrypto.BN_free(p_bn)
+            libcrypto.BN_free(r_bn)
+            libcrypto.BN_CTX_free(ctx)
+
+            return result
+    except (LibraryNotFoundError, FFIEngineError):
+        raise EnvironmentError()
+
+# If there was an issue using ctypes or OpenSSL, we fall back to pure python
+except (EnvironmentError, ImportError):
+
+    def inverse_mod(a, p):
+        """
+        Compute the modular inverse of a (mod p)
+
+        :param a:
+            An integer
+
+        :param p:
+            An integer
+
+        :return:
+            An integer
+        """
+
+        if a < 0 or p <= a:
+            a = a % p
+
+        # From Ferguson and Schneier, roughly:
+
+        c, d = a, p
+        uc, vc, ud, vd = 1, 0, 0, 1
+        while c != 0:
+            q, c, d = divmod(d, c) + (c,)
+            uc, vc, ud, vd = ud - q * uc, vd - q * vc, uc, vc
+
+        # At this point, d is the GCD, and ud*a+vd*p = d.
+        # If d == 1, this means that ud is a inverse.
+
+        assert d == 1
+        if ud > 0:
+            return ud
+        else:
+            return ud + p
+
+
+def fill_width(bytes_, width):
+    """
+    Ensure a byte string representing a positive integer is a specific width
+    (in bytes)
+
+    :param bytes_:
+        The integer byte string
+
+    :param width:
+        The desired width as an integer
+
+    :return:
+        A byte string of the width specified
+    """
+
+    while len(bytes_) < width:
+        bytes_ = b'\x00' + bytes_
+    return bytes_