# 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
self.public_blob = 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:
# Must set ecdsa_curve first; subroutines called herein may need to
# spit out our get_name(), which relies on this.
key_type = msg.get_text()
# But this also means we need to hand it a real key/curve
# identifier, so strip out any cert business. (NOTE: could push
# that into _ECDSACurveSet.get_by_key_format_identifier(), but it
# feels more correct to do it here?)
suffix = "-cert-v01@openssh.com"
if key_type.endswith(suffix):
key_type = key_type[: -len(suffix)]
self.ecdsa_curve = self._ECDSA_CURVES.get_by_key_format_identifier(
key_type
)
key_types = self._ECDSA_CURVES.get_key_format_identifier_list()
cert_types = [
"{}-cert-v01@openssh.com".format(x) for x in key_types
]
self._check_type_and_load_cert(
msg=msg, key_type=key_types, cert_type=cert_types
)
curvename = msg.get_text()
if curvename != self.ecdsa_curve.nist_name:
raise SSHException(
"Can't handle curve of type {}".format(curvename)
)
pointinfo = msg.get_binary()
try:
key = ec.EllipticCurvePublicKey.from_encoded_point(
self.ecdsa_curve.curve_class(), pointinfo
)
self.verifying_key = key
except ValueError:
raise SSHException("Invalid public key")
@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):
return hash(
(
self.get_name(),
self.verifying_key.public_numbers().x,
self.verifying_key.public_numbers().y,
)
)
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())
sig = self.signing_key.sign(data, ecdsa)
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)
try:
self.verifying_key.verify(
signature, data, ec.ECDSA(self.ecdsa_curve.hash_object())
)
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 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}".format(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