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309 lines
10 KiB
Python
309 lines
10 KiB
Python
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
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#
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# This file is part of paramiko.
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#
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# Paramiko is free software; you can redistribute it and/or modify it under the
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# terms of the GNU Lesser General Public License as published by the Free
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# Software Foundation; either version 2.1 of the License, or (at your option)
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# any later version.
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#
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# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
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# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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"""
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ECDSA keys
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"""
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from cryptography.exceptions import InvalidSignature
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import hashes, serialization
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from cryptography.hazmat.primitives.asymmetric import ec
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from cryptography.hazmat.primitives.asymmetric.utils import (
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decode_dss_signature,
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encode_dss_signature,
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)
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from paramiko.common import four_byte
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from paramiko.message import Message
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from paramiko.pkey import PKey
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from paramiko.ssh_exception import SSHException
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from paramiko.util import deflate_long
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class _ECDSACurve(object):
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"""
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Represents a specific ECDSA Curve (nistp256, nistp384, etc).
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Handles the generation of the key format identifier and the selection of
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the proper hash function. Also grabs the proper curve from the 'ecdsa'
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package.
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"""
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def __init__(self, curve_class, nist_name):
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self.nist_name = nist_name
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self.key_length = curve_class.key_size
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# Defined in RFC 5656 6.2
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self.key_format_identifier = "ecdsa-sha2-" + self.nist_name
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# Defined in RFC 5656 6.2.1
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if self.key_length <= 256:
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self.hash_object = hashes.SHA256
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elif self.key_length <= 384:
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self.hash_object = hashes.SHA384
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else:
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self.hash_object = hashes.SHA512
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self.curve_class = curve_class
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class _ECDSACurveSet(object):
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"""
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A collection to hold the ECDSA curves. Allows querying by oid and by key
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format identifier. The two ways in which ECDSAKey needs to be able to look
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up curves.
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"""
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def __init__(self, ecdsa_curves):
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self.ecdsa_curves = ecdsa_curves
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def get_key_format_identifier_list(self):
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return [curve.key_format_identifier for curve in self.ecdsa_curves]
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def get_by_curve_class(self, curve_class):
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for curve in self.ecdsa_curves:
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if curve.curve_class == curve_class:
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return curve
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def get_by_key_format_identifier(self, key_format_identifier):
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for curve in self.ecdsa_curves:
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if curve.key_format_identifier == key_format_identifier:
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return curve
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def get_by_key_length(self, key_length):
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for curve in self.ecdsa_curves:
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if curve.key_length == key_length:
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return curve
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class ECDSAKey(PKey):
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"""
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Representation of an ECDSA key which can be used to sign and verify SSH2
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data.
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"""
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_ECDSA_CURVES = _ECDSACurveSet(
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[
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_ECDSACurve(ec.SECP256R1, "nistp256"),
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_ECDSACurve(ec.SECP384R1, "nistp384"),
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_ECDSACurve(ec.SECP521R1, "nistp521"),
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]
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)
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def __init__(
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self,
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msg=None,
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data=None,
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filename=None,
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password=None,
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vals=None,
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file_obj=None,
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validate_point=True,
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):
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self.verifying_key = None
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self.signing_key = None
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self.public_blob = None
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if file_obj is not None:
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self._from_private_key(file_obj, password)
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return
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if filename is not None:
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self._from_private_key_file(filename, password)
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return
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if (msg is None) and (data is not None):
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msg = Message(data)
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if vals is not None:
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self.signing_key, self.verifying_key = vals
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c_class = self.signing_key.curve.__class__
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self.ecdsa_curve = self._ECDSA_CURVES.get_by_curve_class(c_class)
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else:
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# Must set ecdsa_curve first; subroutines called herein may need to
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# spit out our get_name(), which relies on this.
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key_type = msg.get_text()
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# But this also means we need to hand it a real key/curve
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# identifier, so strip out any cert business. (NOTE: could push
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# that into _ECDSACurveSet.get_by_key_format_identifier(), but it
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# feels more correct to do it here?)
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suffix = "-cert-v01@openssh.com"
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if key_type.endswith(suffix):
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key_type = key_type[: -len(suffix)]
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self.ecdsa_curve = self._ECDSA_CURVES.get_by_key_format_identifier(
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key_type
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)
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key_types = self._ECDSA_CURVES.get_key_format_identifier_list()
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cert_types = [
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"{}-cert-v01@openssh.com".format(x) for x in key_types
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]
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self._check_type_and_load_cert(
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msg=msg, key_type=key_types, cert_type=cert_types
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)
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curvename = msg.get_text()
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if curvename != self.ecdsa_curve.nist_name:
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raise SSHException(
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"Can't handle curve of type {}".format(curvename)
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)
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pointinfo = msg.get_binary()
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try:
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numbers = ec.EllipticCurvePublicNumbers.from_encoded_point(
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self.ecdsa_curve.curve_class(), pointinfo
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)
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except ValueError:
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raise SSHException("Invalid public key")
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self.verifying_key = numbers.public_key(backend=default_backend())
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@classmethod
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def supported_key_format_identifiers(cls):
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return cls._ECDSA_CURVES.get_key_format_identifier_list()
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def asbytes(self):
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key = self.verifying_key
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m = Message()
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m.add_string(self.ecdsa_curve.key_format_identifier)
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m.add_string(self.ecdsa_curve.nist_name)
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numbers = key.public_numbers()
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key_size_bytes = (key.curve.key_size + 7) // 8
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x_bytes = deflate_long(numbers.x, add_sign_padding=False)
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x_bytes = b"\x00" * (key_size_bytes - len(x_bytes)) + x_bytes
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y_bytes = deflate_long(numbers.y, add_sign_padding=False)
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y_bytes = b"\x00" * (key_size_bytes - len(y_bytes)) + y_bytes
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point_str = four_byte + x_bytes + y_bytes
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m.add_string(point_str)
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return m.asbytes()
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def __str__(self):
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return self.asbytes()
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def __hash__(self):
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return hash(
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(
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self.get_name(),
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self.verifying_key.public_numbers().x,
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self.verifying_key.public_numbers().y,
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)
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)
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def get_name(self):
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return self.ecdsa_curve.key_format_identifier
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def get_bits(self):
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return self.ecdsa_curve.key_length
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def can_sign(self):
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return self.signing_key is not None
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def sign_ssh_data(self, data):
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ecdsa = ec.ECDSA(self.ecdsa_curve.hash_object())
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sig = self.signing_key.sign(data, ecdsa)
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r, s = decode_dss_signature(sig)
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m = Message()
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m.add_string(self.ecdsa_curve.key_format_identifier)
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m.add_string(self._sigencode(r, s))
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return m
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def verify_ssh_sig(self, data, msg):
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if msg.get_text() != self.ecdsa_curve.key_format_identifier:
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return False
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sig = msg.get_binary()
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sigR, sigS = self._sigdecode(sig)
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signature = encode_dss_signature(sigR, sigS)
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try:
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self.verifying_key.verify(
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signature, data, ec.ECDSA(self.ecdsa_curve.hash_object())
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)
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except InvalidSignature:
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return False
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else:
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return True
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def write_private_key_file(self, filename, password=None):
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self._write_private_key_file(
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filename,
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self.signing_key,
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serialization.PrivateFormat.TraditionalOpenSSL,
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password=password,
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)
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def write_private_key(self, file_obj, password=None):
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self._write_private_key(
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file_obj,
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self.signing_key,
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serialization.PrivateFormat.TraditionalOpenSSL,
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password=password,
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)
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@classmethod
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def generate(cls, curve=ec.SECP256R1(), progress_func=None, bits=None):
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"""
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Generate a new private ECDSA key. This factory function can be used to
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generate a new host key or authentication key.
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:param progress_func: Not used for this type of key.
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:returns: A new private key (`.ECDSAKey`) object
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"""
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if bits is not None:
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curve = cls._ECDSA_CURVES.get_by_key_length(bits)
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if curve is None:
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raise ValueError("Unsupported key length: {:d}".format(bits))
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curve = curve.curve_class()
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private_key = ec.generate_private_key(curve, backend=default_backend())
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return ECDSAKey(vals=(private_key, private_key.public_key()))
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# ...internals...
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def _from_private_key_file(self, filename, password):
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data = self._read_private_key_file("EC", filename, password)
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self._decode_key(data)
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def _from_private_key(self, file_obj, password):
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data = self._read_private_key("EC", file_obj, password)
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self._decode_key(data)
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def _decode_key(self, data):
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try:
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key = serialization.load_der_private_key(
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data, password=None, backend=default_backend()
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)
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except (ValueError, AssertionError) as e:
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raise SSHException(str(e))
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self.signing_key = key
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self.verifying_key = key.public_key()
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curve_class = key.curve.__class__
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self.ecdsa_curve = self._ECDSA_CURVES.get_by_curve_class(curve_class)
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def _sigencode(self, r, s):
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msg = Message()
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msg.add_mpint(r)
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msg.add_mpint(s)
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return msg.asbytes()
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def _sigdecode(self, sig):
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msg = Message(sig)
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r = msg.get_mpint()
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s = msg.get_mpint()
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return r, s
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