This file is indexed.

/usr/lib/python3/dist-packages/paramiko/ecdsakey.py is in python3-paramiko 2.0.0-1ubuntu1.2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
# 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 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