/usr/lib/python2.7/dist-packages/paramiko/dsskey.py is in python-paramiko 2.0.0-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# 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 distributed 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.
"""
DSS 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 dsa
from cryptography.hazmat.primitives.asymmetric.utils import (
decode_dss_signature, encode_dss_signature
)
from paramiko import util
from paramiko.common import zero_byte
from paramiko.ssh_exception import SSHException
from paramiko.message import Message
from paramiko.ber import BER, BERException
from paramiko.pkey import PKey
class DSSKey(PKey):
"""
Representation of a DSS key which can be used to sign an verify SSH2
data.
"""
def __init__(self, msg=None, data=None, filename=None, password=None, vals=None, file_obj=None):
self.p = None
self.q = None
self.g = None
self.y = None
self.x = 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.p, self.q, self.g, self.y = vals
else:
if msg is None:
raise SSHException('Key object may not be empty')
if msg.get_text() != 'ssh-dss':
raise SSHException('Invalid key')
self.p = msg.get_mpint()
self.q = msg.get_mpint()
self.g = msg.get_mpint()
self.y = msg.get_mpint()
self.size = util.bit_length(self.p)
def asbytes(self):
m = Message()
m.add_string('ssh-dss')
m.add_mpint(self.p)
m.add_mpint(self.q)
m.add_mpint(self.g)
m.add_mpint(self.y)
return m.asbytes()
def __str__(self):
return self.asbytes()
def __hash__(self):
h = hash(self.get_name())
h = h * 37 + hash(self.p)
h = h * 37 + hash(self.q)
h = h * 37 + hash(self.g)
h = h * 37 + hash(self.y)
# h might be a long by now...
return hash(h)
def get_name(self):
return 'ssh-dss'
def get_bits(self):
return self.size
def can_sign(self):
return self.x is not None
def sign_ssh_data(self, data):
key = dsa.DSAPrivateNumbers(
x=self.x,
public_numbers=dsa.DSAPublicNumbers(
y=self.y,
parameter_numbers=dsa.DSAParameterNumbers(
p=self.p,
q=self.q,
g=self.g
)
)
).private_key(backend=default_backend())
signer = key.signer(hashes.SHA1())
signer.update(data)
r, s = decode_dss_signature(signer.finalize())
m = Message()
m.add_string('ssh-dss')
# apparently, in rare cases, r or s may be shorter than 20 bytes!
rstr = util.deflate_long(r, 0)
sstr = util.deflate_long(s, 0)
if len(rstr) < 20:
rstr = zero_byte * (20 - len(rstr)) + rstr
if len(sstr) < 20:
sstr = zero_byte * (20 - len(sstr)) + sstr
m.add_string(rstr + sstr)
return m
def verify_ssh_sig(self, data, msg):
if len(msg.asbytes()) == 40:
# spies.com bug: signature has no header
sig = msg.asbytes()
else:
kind = msg.get_text()
if kind != 'ssh-dss':
return 0
sig = msg.get_binary()
# pull out (r, s) which are NOT encoded as mpints
sigR = util.inflate_long(sig[:20], 1)
sigS = util.inflate_long(sig[20:], 1)
signature = encode_dss_signature(sigR, sigS)
key = dsa.DSAPublicNumbers(
y=self.y,
parameter_numbers=dsa.DSAParameterNumbers(
p=self.p,
q=self.q,
g=self.g
)
).public_key(backend=default_backend())
verifier = key.verifier(signature, hashes.SHA1())
verifier.update(data)
try:
verifier.verify()
except InvalidSignature:
return False
else:
return True
def write_private_key_file(self, filename, password=None):
key = dsa.DSAPrivateNumbers(
x=self.x,
public_numbers=dsa.DSAPublicNumbers(
y=self.y,
parameter_numbers=dsa.DSAParameterNumbers(
p=self.p,
q=self.q,
g=self.g
)
)
).private_key(backend=default_backend())
self._write_private_key_file(
filename,
key,
serialization.PrivateFormat.TraditionalOpenSSL,
password=password
)
def write_private_key(self, file_obj, password=None):
key = dsa.DSAPrivateNumbers(
x=self.x,
public_numbers=dsa.DSAPublicNumbers(
y=self.y,
parameter_numbers=dsa.DSAParameterNumbers(
p=self.p,
q=self.q,
g=self.g
)
)
).private_key(backend=default_backend())
self._write_private_key(
file_obj,
key,
serialization.PrivateFormat.TraditionalOpenSSL,
password=password
)
@staticmethod
def generate(bits=1024, progress_func=None):
"""
Generate a new private DSS key. This factory function can be used to
generate a new host key or authentication key.
:param int bits: number of bits the generated key should be.
:param function progress_func: Unused
:return: new `.DSSKey` private key
"""
numbers = dsa.generate_private_key(
bits, backend=default_backend()
).private_numbers()
key = DSSKey(vals=(
numbers.public_numbers.parameter_numbers.p,
numbers.public_numbers.parameter_numbers.q,
numbers.public_numbers.parameter_numbers.g,
numbers.public_numbers.y
))
key.x = numbers.x
return key
### internals...
def _from_private_key_file(self, filename, password):
data = self._read_private_key_file('DSA', filename, password)
self._decode_key(data)
def _from_private_key(self, file_obj, password):
data = self._read_private_key('DSA', file_obj, password)
self._decode_key(data)
def _decode_key(self, data):
# private key file contains:
# DSAPrivateKey = { version = 0, p, q, g, y, x }
try:
keylist = BER(data).decode()
except BERException as e:
raise SSHException('Unable to parse key file: ' + str(e))
if (type(keylist) is not list) or (len(keylist) < 6) or (keylist[0] != 0):
raise SSHException('not a valid DSA private key file (bad ber encoding)')
self.p = keylist[1]
self.q = keylist[2]
self.g = keylist[3]
self.y = keylist[4]
self.x = keylist[5]
self.size = util.bit_length(self.p)
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