mirror of
https://github.com/Legrandin/pycryptodome.git
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438 lines
17 KiB
Python
438 lines
17 KiB
Python
# -*- coding: utf-8 -*-
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#
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# PublicKey/RSA.py : RSA public key 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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"""RSA public-key cryptography algorithm.
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:sort: generate,construct,importKey,error
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:undocumented: _fastmath, __revision__, _impl
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"""
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__revision__ = "$Id$"
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__all__ = ['generate', 'construct', 'error', 'importKey' ]
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from Crypto.Util.python_compat import *
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from Crypto.Util.number import getRandomRange, bytes_to_long, long_to_bytes
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from Crypto.PublicKey import _RSA, _slowmath, pubkey
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from Crypto import Random
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from Crypto.Util.asn1 import DerObject, DerSequence
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import binascii
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import struct
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from Crypto.Util.number import inverse
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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 _RSAobj(pubkey.pubkey):
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"""Class defining an actual RSA key."""
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#: Dictionary of RSA parameters.
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#:
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#: A public key will only have the following entries:
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#:
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#: - **n**, the modulus.
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#: - **e**, the public exponent.
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#:
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#: A private key will also have:
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#:
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#: - **d**, the private exponent.
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#: - **p**, the first factor of n.
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#: - **q**, the second factor of n.
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#: - **u**, the CRT coefficient (1/p) mod q.
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keydata = ['n', 'e', 'd', 'p', 'q', 'u']
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def __init__(self, implementation, key, randfunc=None):
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self.implementation = implementation
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self.key = key
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if randfunc is None:
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randfunc = Random.new().read
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self._randfunc = randfunc
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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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# RSA 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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return (self.key._encrypt(c),)
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def _decrypt(self, c):
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#(ciphertext,) = c
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(ciphertext,) = c[:1] # HACK - We should use the previous line
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# instead, but this is more compatible and we're
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# going to replace the Crypto.PublicKey API soon
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# anyway.
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# Blinded RSA decryption (to prevent timing attacks):
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# Step 1: Generate random secret blinding factor r, such that 0 < r < n-1
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r = getRandomRange(1, self.key.n-1, randfunc=self._randfunc)
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# Step 2: Compute c' = c * r**e mod n
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cp = self.key._blind(ciphertext, r)
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# Step 3: Compute m' = c'**d mod n (ordinary RSA decryption)
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mp = self.key._decrypt(cp)
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# Step 4: Compute m = m**(r-1) mod n
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return self.key._unblind(mp, r)
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def _blind(self, m, r):
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return self.key._blind(m, r)
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def _unblind(self, m, r):
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return self.key._unblind(m, r)
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def _sign(self, m, K=None):
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return (self.key._sign(m),)
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def _verify(self, m, sig):
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#(s,) = sig
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(s,) = sig[:1] # HACK - We should use the previous line instead, but
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# this is more compatible and we're going to replace
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# the Crypto.PublicKey API soon anyway.
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return self.key._verify(m, 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 True
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def can_encrypt(self):
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return True
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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.n, self.key.e))
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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 = RSAImplementation()
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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.rsa_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 == 'n':
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attrs.append("n(%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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def exportKey(self, format='PEM'):
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"""Export this RSA key.
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:Parameter format: The encoding to use to wrap the key.
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- *'DER'* for PKCS#1
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- *'OpenSSH'* for OpenSSH public keys (no private key)
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- *'PEM'* for RFC1421
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:Type format: string
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:Return: A string with the encoded public or private half.
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:Raise ValueError:
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When the format is unknown.
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"""
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if format=='OpenSSH':
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eb = long_to_bytes(self.e)
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nb = long_to_bytes(self.n)
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if ord(eb[0]) & 0x80: eb='\x00'+nb
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if ord(nb[0]) & 0x80: nb='\x00'+nb
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keyparts = [ 'ssh-rsa', eb, nb ]
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keystring = ''.join([ struct.pack(">I",len(kp))+kp for kp in keyparts])
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return 'ssh-rsa '+binascii.b2a_base64(keystring)[:-1]
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# PKCS#1 is a direct DER encoding. PEM uses it as well, but
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# wraps in an ASCII envelope.
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der = DerSequence()
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if self.has_private():
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keyType = "RSA PRIVATE"
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der[:] = [ 0, self.n, self.e, self.d, self.p, self.q,
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self.d % (self.p-1), self.d % (self.q-1),
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inverse(self.q, self.p) ]
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else:
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keyType = "PUBLIC"
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der.append('\x30\x0D\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01\x05\x00')
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bitmap = DerObject('BIT STRING')
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derPK = DerSequence()
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derPK[:] = [ self.n, self.e ]
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bitmap.payload = '\x00' + derPK.encode()
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der.append(bitmap.encode())
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if format=='DER':
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return der.encode()
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if format=='PEM':
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pem = "-----BEGIN %s KEY-----\n" % keyType
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binaryKey = der.encode()
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# Each BASE64 line can take up to 64 characters (=48 bytes of data)
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chunks = [ binascii.b2a_base64(binaryKey[i:i+48]) for i in range(0, len(binaryKey), 48) ]
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pem += ''.join(chunks)
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pem += "-----END %s KEY-----" % keyType
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return pem
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return ValueError("Unknown key format '%s'. Cannot export the RSA key." % format)
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class RSAImplementation(object):
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"""
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An RSA key factory.
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This class is only internally used to implement the methods of the `Crypto.PublicKey.RSA` modulule.
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:sort: __init__,generate,construct,importKey
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:undocumented: _g*, _i*
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"""
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def __init__(self, **kwargs):
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"""Create a new RSA key factory.
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:Keywords:
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use_fast_math : bool
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Specify which mathematic library to use:
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- *None* (default). Use fastest math available.
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- *True* . Use fast math.
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- *False* . Use slow math.
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default_randfunc : callable
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Specify how to collect random data:
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- *None* (default). Use Random.new().read().
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- not *Note* . Use the specified function directly.
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:Raise RuntimeError:
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When **use_fast_math** =True but fast math is not available.
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"""
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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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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, e=65537):
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"""Randomly generate a fresh, new RSA key object.
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:Parameters:
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bits : int
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Key length, or size (in bits) of the RSA modulus.
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It must be a multiple of 256, and no smaller than 1024.
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randfunc : callable
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Random number generation function; it should accept
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a single integer N and return a string of random data
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N bytes long.
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progress_func : callable
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Optional function that will be called with a short string
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containing the key parameter currently being generated;
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it's useful for interactive applications where a user is
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waiting for a key to be generated.
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e : int
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Public RSA exponent. It must be an odd positive integer.
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It is typically a small number with very few ones in its
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binary representation.
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The default value 65537 (= ``0b10000000000000001`` ) is a safe
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choice: other common values are 5, 7, 17, and 257.
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:attention: You should always use a cryptographically secure random number generator,
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such as the one defined in the ``Crypto.Random`` module; **don't** just use the
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current time and the ``random`` module.
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:attention: Exponent 3 is also widely used, but it requires very special care when padding
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the message.
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:Raise ValueError:
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When **bits** is too little or not a multiple of 256, or when
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**e** is not odd or smaller than 2.
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"""
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if bits < 1024 or (bits & 0xff) != 0:
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# pubkey.getStrongPrime doesn't like anything that's not a multiple of 128 and > 512
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raise ValueError("RSA modulus length must be a multiple of 256 and >= 1024")
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if e%2==0 or e<3:
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raise ValueError("RSA public exponent must be a positive, odd integer larger than 2.")
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rf = self._get_randfunc(randfunc)
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obj = _RSA.generate_py(bits, rf, progress_func, e) # TODO: Don't use legacy _RSA module
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key = self._math.rsa_construct(obj.n, obj.e, obj.d, obj.p, obj.q, obj.u)
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return _RSAobj(self, key)
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def construct(self, tup):
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"""Construct an RSA key object from a tuple of valid RSA components.
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The modulus **n** must be the product of two primes.
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The public exponent **e** must be odd and larger than 1.
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In case of a private key, the following equations must apply:
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- e != 1
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- p*q = n
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- e*d = 1 mod (p-1)(q-1)
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- p*u = 1 mod q
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:Parameters:
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tup : tuple
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A tuple of long integers, with at least 2 and no
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more than 6 items. The items come in the following order:
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1. RSA modulus (n).
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2. Public exponent (e).
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3. Private exponent (d). Only required if the key is private.
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4. First factor of n (p). Optional.
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5. Second factor of n (q). Optional.
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6. CRT coefficient, (1/p) mod q (u). Optional.
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"""
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key = self._math.rsa_construct(*tup)
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return _RSAobj(self, key)
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def _importKeyDER(self, externKey):
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"""Import an RSA key (public or private half), encoded in DER form."""
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der = DerSequence()
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der.decode(externKey, True)
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if len(der)==9 and der.hasOnlyInts() and der[0]==0:
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# ASN.1 RSAPrivateKey element
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del der[6:] # Remove d mod (p-1), d mod (q-1), and q^{-1} mod p
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der.append(inverse(der[4],der[5])) # Add p^{-1} mod q
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del der[0] # Remove version
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return self.construct(der[:])
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if len(der)==2:
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# The DER object is a SubjectPublicKeyInfo SEQUENCE with two elements:
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# an algorithm SEQUENCE (or algorithmIdentifier) and a subjectPublicKey BIT STRING.
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#
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# The first element is always the same. It contains the oid of
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# the RSA algorithm and its parameters (none).
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# 0x30 0x0D SEQUENCE, 12 bytes of payload
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# 0x06 0x09 OBJECT IDENTIFIER, 9 bytes of payload
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# 0x2A 0x86 0x48 0x86 0xF7 0x0D 0x01 0x01 0x01
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# rsaEncryption (1 2 840 113549 1 1 1) (PKCS #1)
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# 0x05 0x00 NULL
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#
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# subjectPublicKey encapsulates the actual ASN.1 RSAPublicKey element.
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if der[0]=='\x30\x0D\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01\x05\x00':
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bitmap = DerObject()
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bitmap.decode(der[1], True)
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if bitmap.typeTag=='\x03' and bitmap.payload[0]=='\x00':
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der.decode(bitmap.payload[1:], True)
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if len(der)==2 and der.hasOnlyInts():
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return self.construct(der[:])
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raise ValueError("RSA key format is not supported")
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def importKey(self, externKey):
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"""Import an RSA key (public or private half), encoded in standard form.
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:Parameter externKey:
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The RSA key to import, encoded as a string.
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The key can be in DER (PKCS#1), OpenSSH or in unencrypted PEM format (RFC1421).
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:Type externKey: string
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:Raise ValueError/IndexError:
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When the given key cannot be parsed.
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"""
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if externKey.startswith('-----'):
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# This is probably a PEM encoded key
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lines = externKey.replace(" ",'').split()
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der = binascii.a2b_base64(''.join(lines[1:-1]))
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return self._importKeyDER(der)
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if externKey.startswith('ssh-rsa '):
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# This is probably an OpenSSH key
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keystring = binascii.a2b_base64(externKey.split(' ')[1])
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keyparts = []
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while len(keystring)>4:
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l = struct.unpack(">I",keystring[:4])[0]
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keyparts.append(keystring[4:4+l])
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keystring = keystring[4+l:]
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e = bytes_to_long(keyparts[1])
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n = bytes_to_long(keyparts[2])
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return self.construct([n, e])
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if externKey[0]=='\x30':
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# This is probably a DER encoded key
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return self._importKeyDER(externKey)
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raise ValueError("RSA key format is not supported")
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_impl = RSAImplementation()
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#:
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#: Randomly generate a fresh, new RSA key object.
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#:
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#: See `RSAImplementation.generate`.
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#:
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generate = _impl.generate
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#:
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#: Construct an RSA key object from a tuple of valid RSA components.
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#:
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#: See `RSAImplementation.construct`.
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#:
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construct = _impl.construct
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#:
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#: Import an RSA key (public or private half), encoded in standard form.
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#:
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#: See `RSAImplementation.importKey`.
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#:
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importKey = _impl.importKey
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error = _impl.error
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# vim:set ts=4 sw=4 sts=4 expandtab:
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