Edit File: ecdsakey.py
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com> # # This file is part of paramiko. # # Paramiko is free software; you can redistribute it and/or modify it under the # terms of the GNU Lesser General Public License as published by the Free # Software Foundation; either version 2.1 of the License, or (at your option) # any later version. # # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR # A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more # details. # # You should have received a copy of the GNU Lesser General Public License # along with Paramiko; if not, write to the Free Software Foundation, Inc., # 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. """ ECDSA keys """ from cryptography.exceptions import InvalidSignature from cryptography.hazmat.backends import default_backend from cryptography.hazmat.primitives import hashes, serialization from cryptography.hazmat.primitives.asymmetric import ec from cryptography.hazmat.primitives.asymmetric.utils import ( decode_dss_signature, encode_dss_signature ) from paramiko.common import four_byte from paramiko.message import Message from paramiko.pkey import PKey from paramiko.ssh_exception import SSHException from paramiko.util import deflate_long class _ECDSACurve(object): """ Represents a specific ECDSA Curve (nistp256, nistp384, etc). Handles the generation of the key format identifier and the selection of the proper hash function. Also grabs the proper curve from the 'ecdsa' package. """ def __init__(self, curve_class, nist_name): self.nist_name = nist_name self.key_length = curve_class.key_size # Defined in RFC 5656 6.2 self.key_format_identifier = "ecdsa-sha2-" + self.nist_name # Defined in RFC 5656 6.2.1 if self.key_length <= 256: self.hash_object = hashes.SHA256 elif self.key_length <= 384: self.hash_object = hashes.SHA384 else: self.hash_object = hashes.SHA512 self.curve_class = curve_class class _ECDSACurveSet(object): """ A collection to hold the ECDSA curves. Allows querying by oid and by key format identifier. The two ways in which ECDSAKey needs to be able to look up curves. """ def __init__(self, ecdsa_curves): self.ecdsa_curves = ecdsa_curves def get_key_format_identifier_list(self): return [curve.key_format_identifier for curve in self.ecdsa_curves] def get_by_curve_class(self, curve_class): for curve in self.ecdsa_curves: if curve.curve_class == curve_class: return curve def get_by_key_format_identifier(self, key_format_identifier): for curve in self.ecdsa_curves: if curve.key_format_identifier == key_format_identifier: return curve def get_by_key_length(self, key_length): for curve in self.ecdsa_curves: if curve.key_length == key_length: return curve class ECDSAKey(PKey): """ Representation of an ECDSA key which can be used to sign and verify SSH2 data. """ _ECDSA_CURVES = _ECDSACurveSet([ _ECDSACurve(ec.SECP256R1, 'nistp256'), _ECDSACurve(ec.SECP384R1, 'nistp384'), _ECDSACurve(ec.SECP521R1, 'nistp521'), ]) def __init__(self, msg=None, data=None, filename=None, password=None, vals=None, file_obj=None, validate_point=True): self.verifying_key = None self.signing_key = None if file_obj is not None: self._from_private_key(file_obj, password) return if filename is not None: self._from_private_key_file(filename, password) return if (msg is None) and (data is not None): msg = Message(data) if vals is not None: self.signing_key, self.verifying_key = vals c_class = self.signing_key.curve.__class__ self.ecdsa_curve = self._ECDSA_CURVES.get_by_curve_class(c_class) else: if msg is None: raise SSHException('Key object may not be empty') self.ecdsa_curve = self._ECDSA_CURVES.get_by_key_format_identifier( msg.get_text()) if self.ecdsa_curve is None: raise SSHException('Invalid key') curvename = msg.get_text() if curvename != self.ecdsa_curve.nist_name: raise SSHException("Can't handle curve of type %s" % curvename) pointinfo = msg.get_binary() try: numbers = ec.EllipticCurvePublicNumbers.from_encoded_point( self.ecdsa_curve.curve_class(), pointinfo ) except ValueError: raise SSHException("Invalid public key") self.verifying_key = numbers.public_key(backend=default_backend()) @classmethod def supported_key_format_identifiers(cls): return cls._ECDSA_CURVES.get_key_format_identifier_list() def asbytes(self): key = self.verifying_key m = Message() m.add_string(self.ecdsa_curve.key_format_identifier) m.add_string(self.ecdsa_curve.nist_name) numbers = key.public_numbers() key_size_bytes = (key.curve.key_size + 7) // 8 x_bytes = deflate_long(numbers.x, add_sign_padding=False) x_bytes = b'\x00' * (key_size_bytes - len(x_bytes)) + x_bytes y_bytes = deflate_long(numbers.y, add_sign_padding=False) y_bytes = b'\x00' * (key_size_bytes - len(y_bytes)) + y_bytes point_str = four_byte + x_bytes + y_bytes m.add_string(point_str) return m.asbytes() def __str__(self): return self.asbytes() def __hash__(self): h = hash(self.get_name()) h = h * 37 + hash(self.verifying_key.public_numbers().x) h = h * 37 + hash(self.verifying_key.public_numbers().y) return hash(h) def get_name(self): return self.ecdsa_curve.key_format_identifier def get_bits(self): return self.ecdsa_curve.key_length def can_sign(self): return self.signing_key is not None def sign_ssh_data(self, data): ecdsa = ec.ECDSA(self.ecdsa_curve.hash_object()) signer = self.signing_key.signer(ecdsa) signer.update(data) sig = signer.finalize() r, s = decode_dss_signature(sig) m = Message() m.add_string(self.ecdsa_curve.key_format_identifier) m.add_string(self._sigencode(r, s)) return m def verify_ssh_sig(self, data, msg): if msg.get_text() != self.ecdsa_curve.key_format_identifier: return False sig = msg.get_binary() sigR, sigS = self._sigdecode(sig) signature = encode_dss_signature(sigR, sigS) verifier = self.verifying_key.verifier( signature, ec.ECDSA(self.ecdsa_curve.hash_object()) ) verifier.update(data) try: verifier.verify() except InvalidSignature: return False else: return True def write_private_key_file(self, filename, password=None): self._write_private_key_file( filename, self.signing_key, serialization.PrivateFormat.TraditionalOpenSSL, password=password ) def write_private_key(self, file_obj, password=None): self._write_private_key( file_obj, self.signing_key, serialization.PrivateFormat.TraditionalOpenSSL, password=password ) @classmethod def generate(cls, curve=ec.SECP256R1(), progress_func=None, bits=None): """ Generate a new private ECDSA key. This factory function can be used to generate a new host key or authentication key. :param function progress_func: Not used for this type of key. :returns: A new private key (`.ECDSAKey`) object """ if bits is not None: curve = cls._ECDSA_CURVES.get_by_key_length(bits) if curve is None: raise ValueError("Unsupported key length: %d"%(bits)) curve = curve.curve_class() private_key = ec.generate_private_key(curve, backend=default_backend()) return ECDSAKey(vals=(private_key, private_key.public_key())) ### internals... def _from_private_key_file(self, filename, password): data = self._read_private_key_file('EC', filename, password) self._decode_key(data) def _from_private_key(self, file_obj, password): data = self._read_private_key('EC', file_obj, password) self._decode_key(data) def _decode_key(self, data): try: key = serialization.load_der_private_key( data, password=None, backend=default_backend() ) except (ValueError, AssertionError) as e: raise SSHException(str(e)) self.signing_key = key self.verifying_key = key.public_key() curve_class = key.curve.__class__ self.ecdsa_curve = self._ECDSA_CURVES.get_by_curve_class(curve_class) def _sigencode(self, r, s): msg = Message() msg.add_mpint(r) msg.add_mpint(s) return msg.asbytes() def _sigdecode(self, sig): msg = Message(sig) r = msg.get_mpint() s = msg.get_mpint() return r, s