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https://github.com/Legrandin/pycryptodome.git
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386de1947b
In an attempt to simplify the copyright status of PyCrypto, I'm placing my
code into the public domain, and encouraging other contributors to do the
same.
I have used a public domain dedication that was recommended in a book on FOSS legal
issues[1], followed by the warranty disclaimer boilerplate from the MIT license.
[1] _Intellectual Property and Open Source: A Practical Guide to Protecting
Code_, a book written by Van Lindberg and published by O'Reilly Media.
(ISBN 978-0-596-51796-0)
189 lines
6.2 KiB
Python
189 lines
6.2 KiB
Python
# -*- coding: utf-8 -*-
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#
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# PublicKey/DSA.py : DSA signature primitive
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#
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# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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"""DSA public-key signature algorithm."""
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__revision__ = "$Id$"
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__all__ = ['generate', 'construct', 'error']
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from Crypto.Util.python_compat import *
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from Crypto.PublicKey import _DSA, _slowmath, pubkey
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from Crypto import Random
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try:
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from Crypto.PublicKey import _fastmath
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except ImportError:
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_fastmath = None
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class _DSAobj(pubkey.pubkey):
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keydata = ['y', 'g', 'p', 'q', 'x']
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def __init__(self, implementation, key):
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self.implementation = implementation
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self.key = key
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def __getattr__(self, attrname):
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if attrname in self.keydata:
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# For backward compatibility, allow the user to get (not set) the
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# DSA key parameters directly from this object.
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return getattr(self.key, attrname)
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else:
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raise AttributeError("%s object has no %r attribute" % (self.__class__.__name__, attrname,))
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def _encrypt(self, c, K):
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raise error("DSA cannot encrypt")
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def _decrypt(self, c):
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raise error("DSA cannot decrypt")
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def _blind(self, m, r):
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raise error("DSA cannot blind")
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def _unblind(self, m, r):
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raise error("DSA cannot unblind")
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def _sign(self, m, k):
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return self.key._sign(m, k)
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def _verify(self, m, sig):
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(r, s) = sig
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return self.key._verify(m, r, s)
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def has_private(self):
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return self.key.has_private()
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def size(self):
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return self.key.size()
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def can_blind(self):
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return False
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def can_encrypt(self):
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return False
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def can_sign(self):
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return True
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def publickey(self):
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return self.implementation.construct((self.key.y, self.key.g, self.key.p, self.key.q))
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def __getstate__(self):
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d = {}
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for k in self.keydata:
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try:
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d[k] = getattr(self.key, k)
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except AttributeError:
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pass
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return d
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def __setstate__(self, d):
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if not hasattr(self, 'implementation'):
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self.implementation = DSAImplementation()
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t = []
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for k in self.keydata:
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if not d.has_key(k):
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break
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t.append(d[k])
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self.key = self.implementation._math.dsa_construct(*tuple(t))
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def __repr__(self):
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attrs = []
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for k in self.keydata:
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if k == 'p':
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attrs.append("p(%d)" % (self.size()+1,))
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elif hasattr(self.key, k):
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attrs.append(k)
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if self.has_private():
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attrs.append("private")
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return "<%s @0x%x %s>" % (self.__class__.__name__, id(self), ",".join(attrs))
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class DSAImplementation(object):
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def __init__(self, **kwargs):
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# 'use_fast_math' parameter:
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# None (default) - Use fast math if available; Use slow math if not.
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# True - Use fast math, and raise RuntimeError if it's not available.
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# False - Use slow math.
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use_fast_math = kwargs.get('use_fast_math', None)
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if use_fast_math is None: # Automatic
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if _fastmath is not None:
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self._math = _fastmath
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else:
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self._math = _slowmath
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elif use_fast_math: # Explicitly select fast math
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if _fastmath is not None:
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self._math = _fastmath
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else:
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raise RuntimeError("fast math module not available")
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else: # Explicitly select slow math
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self._math = _slowmath
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self.error = self._math.error
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# 'default_randfunc' parameter:
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# None (default) - use Random.new().read
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# not None - use the specified function
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self._default_randfunc = kwargs.get('default_randfunc', None)
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self._current_randfunc = None
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def _get_randfunc(self, randfunc):
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if randfunc is not None:
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return randfunc
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elif self._current_randfunc is None:
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self._current_randfunc = Random.new().read
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return self._current_randfunc
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def generate(self, bits, randfunc=None, progress_func=None):
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# Check against FIPS 186-2, which says that the size of the prime p
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# must be a multiple of 64 bits between 512 and 1024
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for i in (0, 1, 2, 3, 4, 5, 6, 7, 8):
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if bits == 512 + 64*i:
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return self._generate(bits, randfunc, progress_func)
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# The March 2006 draft of FIPS 186-3 also allows 2048 and 3072-bit
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# primes, but only with longer q values. Since the current DSA
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# implementation only supports a 160-bit q, we don't support larger
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# values.
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raise ValueError("Number of bits in p must be a multiple of 64 between 512 and 1024, not %d bits" % (bits,))
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def _generate(self, bits, randfunc=None, progress_func=None):
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rf = self._get_randfunc(randfunc)
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obj = _DSA.generate_py(bits, rf, progress_func) # TODO: Don't use legacy _DSA module
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key = self._math.dsa_construct(obj.y, obj.g, obj.p, obj.q, obj.x)
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return _DSAobj(self, key)
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def construct(self, tup):
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key = self._math.dsa_construct(*tup)
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return _DSAobj(self, key)
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_impl = DSAImplementation()
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generate = _impl.generate
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construct = _impl.construct
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error = _impl.error
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# vim:set ts=4 sw=4 sts=4 expandtab:
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