mirror of
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248 lines
7.7 KiB
Python
248 lines
7.7 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 distributed 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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DSS 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 dsa
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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 import util
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from paramiko.common import zero_byte
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from paramiko.ssh_exception import SSHException
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from paramiko.message import Message
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from paramiko.ber import BER, BERException
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from paramiko.pkey import PKey
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class DSSKey(PKey):
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"""
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Representation of a DSS key which can be used to sign an verify SSH2
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data.
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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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):
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self.p = None
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self.q = None
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self.g = None
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self.y = None
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self.x = 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.p, self.q, self.g, self.y = vals
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else:
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self._check_type_and_load_cert(
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msg=msg,
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key_type="ssh-dss",
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cert_type="ssh-dss-cert-v01@openssh.com",
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)
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self.p = msg.get_mpint()
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self.q = msg.get_mpint()
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self.g = msg.get_mpint()
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self.y = msg.get_mpint()
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self.size = util.bit_length(self.p)
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def asbytes(self):
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m = Message()
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m.add_string("ssh-dss")
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m.add_mpint(self.p)
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m.add_mpint(self.q)
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m.add_mpint(self.g)
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m.add_mpint(self.y)
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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((self.get_name(), self.p, self.q, self.g, self.y))
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def get_name(self):
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return "ssh-dss"
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def get_bits(self):
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return self.size
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def can_sign(self):
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return self.x is not None
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def sign_ssh_data(self, data):
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key = dsa.DSAPrivateNumbers(
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x=self.x,
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public_numbers=dsa.DSAPublicNumbers(
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y=self.y,
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parameter_numbers=dsa.DSAParameterNumbers(
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p=self.p, q=self.q, g=self.g
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),
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),
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).private_key(backend=default_backend())
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sig = key.sign(data, hashes.SHA1())
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r, s = decode_dss_signature(sig)
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m = Message()
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m.add_string("ssh-dss")
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# apparently, in rare cases, r or s may be shorter than 20 bytes!
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rstr = util.deflate_long(r, 0)
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sstr = util.deflate_long(s, 0)
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if len(rstr) < 20:
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rstr = zero_byte * (20 - len(rstr)) + rstr
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if len(sstr) < 20:
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sstr = zero_byte * (20 - len(sstr)) + sstr
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m.add_string(rstr + sstr)
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return m
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def verify_ssh_sig(self, data, msg):
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if len(msg.asbytes()) == 40:
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# spies.com bug: signature has no header
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sig = msg.asbytes()
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else:
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kind = msg.get_text()
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if kind != "ssh-dss":
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return 0
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sig = msg.get_binary()
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# pull out (r, s) which are NOT encoded as mpints
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sigR = util.inflate_long(sig[:20], 1)
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sigS = util.inflate_long(sig[20:], 1)
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signature = encode_dss_signature(sigR, sigS)
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key = dsa.DSAPublicNumbers(
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y=self.y,
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parameter_numbers=dsa.DSAParameterNumbers(
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p=self.p, q=self.q, g=self.g
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),
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).public_key(backend=default_backend())
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try:
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key.verify(signature, data, hashes.SHA1())
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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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key = dsa.DSAPrivateNumbers(
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x=self.x,
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public_numbers=dsa.DSAPublicNumbers(
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y=self.y,
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parameter_numbers=dsa.DSAParameterNumbers(
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p=self.p, q=self.q, g=self.g
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),
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),
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).private_key(backend=default_backend())
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self._write_private_key_file(
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filename,
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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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key = dsa.DSAPrivateNumbers(
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x=self.x,
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public_numbers=dsa.DSAPublicNumbers(
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y=self.y,
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parameter_numbers=dsa.DSAParameterNumbers(
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p=self.p, q=self.q, g=self.g
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),
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),
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).private_key(backend=default_backend())
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self._write_private_key(
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file_obj,
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key,
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serialization.PrivateFormat.TraditionalOpenSSL,
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password=password,
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)
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@staticmethod
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def generate(bits=1024, progress_func=None):
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"""
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Generate a new private DSS 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 int bits: number of bits the generated key should be.
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:param progress_func: Unused
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:return: new `.DSSKey` private key
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"""
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numbers = dsa.generate_private_key(
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bits, backend=default_backend()
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).private_numbers()
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key = DSSKey(
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vals=(
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numbers.public_numbers.parameter_numbers.p,
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numbers.public_numbers.parameter_numbers.q,
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numbers.public_numbers.parameter_numbers.g,
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numbers.public_numbers.y,
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)
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)
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key.x = numbers.x
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return 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("DSA", 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("DSA", file_obj, password)
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self._decode_key(data)
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def _decode_key(self, data):
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# private key file contains:
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# DSAPrivateKey = { version = 0, p, q, g, y, x }
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try:
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keylist = BER(data).decode()
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except BERException as e:
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raise SSHException("Unable to parse key file: " + str(e))
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if type(keylist) is not list or len(keylist) < 6 or keylist[0] != 0:
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raise SSHException(
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"not a valid DSA private key file (bad ber encoding)"
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)
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self.p = keylist[1]
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self.q = keylist[2]
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self.g = keylist[3]
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self.y = keylist[4]
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self.x = keylist[5]
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self.size = util.bit_length(self.p)
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