/usr/lib/python3/dist-packages/asyncssh/ecdh.py is in python3-asyncssh 1.11.1-1.
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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 | # Copyright (c) 2013-2017 by Ron Frederick <ronf@timeheart.net>.
# All rights reserved.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v1.0 which accompanies this
# distribution and is available at:
#
# http://www.eclipse.org/legal/epl-v10.html
#
# Contributors:
# Ron Frederick - initial implementation, API, and documentation
"""Elliptic curve Diffie-Hellman key exchange handler"""
from hashlib import sha256, sha384, sha512
from .constants import DISC_KEY_EXCHANGE_FAILED, DISC_PROTOCOL_ERROR
from .kex import Kex, register_kex_alg
from .misc import DisconnectError
from .packet import Byte, MPInt, String
# pylint: disable=bad-whitespace
# SSH KEX ECDH message values
MSG_KEX_ECDH_INIT = 30
MSG_KEX_ECDH_REPLY = 31
# pylint: enable=bad-whitespace
class _KexECDH(Kex):
"""Handler for elliptic curve Diffie-Hellman key exchange"""
def __init__(self, alg, conn, hash_alg, ecdh_class, *args):
super().__init__(alg, conn, hash_alg)
self._priv = ecdh_class(*args)
pub = self._priv.get_public()
if conn.is_client():
self._client_pub = pub
else:
self._server_pub = pub
def start(self):
"""Start ECDH key exchange"""
self._conn.send_packet(Byte(MSG_KEX_ECDH_INIT),
String(self._client_pub))
def _compute_hash(self, host_key_data, k):
"""Compute a hash of key information associated with the connection"""
hash_obj = self._hash_alg()
hash_obj.update(self._conn.get_hash_prefix())
hash_obj.update(String(host_key_data))
hash_obj.update(String(self._client_pub))
hash_obj.update(String(self._server_pub))
hash_obj.update(MPInt(k))
return hash_obj.digest()
def _process_init(self, pkttype, packet):
"""Process an ECDH init message"""
# pylint: disable=unused-argument
if self._conn.is_client():
raise DisconnectError(DISC_PROTOCOL_ERROR,
'Unexpected kex init msg')
self._client_pub = packet.get_string()
packet.check_end()
try:
k = self._priv.get_shared(self._client_pub)
except (AssertionError, ValueError):
raise DisconnectError(DISC_PROTOCOL_ERROR,
'Invalid kex init msg') from None
host_key = self._conn.get_server_host_key()
h = self._compute_hash(host_key.public_data, k)
sig = host_key.sign(h)
self._conn.send_packet(Byte(MSG_KEX_ECDH_REPLY),
String(host_key.public_data),
String(self._server_pub), String(sig))
self._conn.send_newkeys(k, h)
def _process_reply(self, pkttype, packet):
"""Process an ECDH reply message"""
# pylint: disable=unused-argument
if self._conn.is_server():
raise DisconnectError(DISC_PROTOCOL_ERROR,
'Unexpected kex reply msg')
host_key_data = packet.get_string()
self._server_pub = packet.get_string()
sig = packet.get_string()
packet.check_end()
try:
k = self._priv.get_shared(self._server_pub)
except (AssertionError, ValueError):
raise DisconnectError(DISC_PROTOCOL_ERROR,
'Invalid kex reply msg') from None
host_key = self._conn.validate_server_host_key(host_key_data)
h = self._compute_hash(host_key_data, k)
if not host_key.verify(h, sig):
raise DisconnectError(DISC_KEY_EXCHANGE_FAILED,
'Key exchange hash mismatch')
self._conn.send_newkeys(k, h)
packet_handlers = {
MSG_KEX_ECDH_INIT: _process_init,
MSG_KEX_ECDH_REPLY: _process_reply
}
try:
# pylint: disable=wrong-import-position
from .crypto import Curve25519DH
except ImportError: # pragma: no cover
pass
else:
register_kex_alg(b'curve25519-sha256', _KexECDH, sha256, Curve25519DH)
register_kex_alg(b'curve25519-sha256@libssh.org', _KexECDH,
sha256, Curve25519DH)
try:
# pylint: disable=wrong-import-position
from .crypto import ECDH
except ImportError: # pragma: no cover
pass
else:
for _curve_id, _hash_alg in ((b'nistp521', sha512),
(b'nistp384', sha384),
(b'nistp256', sha256)):
register_kex_alg(b'ecdh-sha2-' + _curve_id, _KexECDH,
_hash_alg, ECDH, _curve_id)
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