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Diffstat (limited to 'paramiko/kex_group1.py')
| -rw-r--r-- | paramiko/kex_group1.py | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/paramiko/kex_group1.py b/paramiko/kex_group1.py new file mode 100644 index 0000000..a13cf3a --- /dev/null +++ b/paramiko/kex_group1.py @@ -0,0 +1,136 @@ +# Copyright (C) 2003-2005 Robey Pointer <robey@lag.net> +# +# 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. + +""" +Standard SSH key exchange ("kex" if you wanna sound cool). Diffie-Hellman of +1024 bit key halves, using a known "p" prime and "g" generator. +""" + +from Crypto.Hash import SHA + +from paramiko.common import * +from paramiko import util +from paramiko.message import Message +from paramiko.ssh_exception import SSHException + + +_MSG_KEXDH_INIT, _MSG_KEXDH_REPLY = range(30, 32) + +# draft-ietf-secsh-transport-09.txt, page 17 +P = 0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFFL +G = 2 + + +class KexGroup1(object): + + name = 'diffie-hellman-group1-sha1' + + def __init__(self, transport): + self.transport = transport + self.x = 0L + self.e = 0L + self.f = 0L + + def start_kex(self): + self._generate_x() + if self.transport.server_mode: + # compute f = g^x mod p, but don't send it yet + self.f = pow(G, self.x, P) + self.transport._expect_packet(_MSG_KEXDH_INIT) + return + # compute e = g^x mod p (where g=2), and send it + self.e = pow(G, self.x, P) + m = Message() + m.add_byte(chr(_MSG_KEXDH_INIT)) + m.add_mpint(self.e) + self.transport._send_message(m) + self.transport._expect_packet(_MSG_KEXDH_REPLY) + + def parse_next(self, ptype, m): + if self.transport.server_mode and (ptype == _MSG_KEXDH_INIT): + return self._parse_kexdh_init(m) + elif not self.transport.server_mode and (ptype == _MSG_KEXDH_REPLY): + return self._parse_kexdh_reply(m) + raise SSHException('KexGroup1 asked to handle packet type %d' % ptype) + + + ### internals... + + + def _generate_x(self): + # generate an "x" (1 < x < q), where q is (p-1)/2. + # p is a 128-byte (1024-bit) number, where the first 64 bits are 1. + # therefore q can be approximated as a 2^1023. we drop the subset of + # potential x where the first 63 bits are 1, because some of those will be + # larger than q (but this is a tiny tiny subset of potential x). + while 1: + self.transport.randpool.stir() + x_bytes = self.transport.randpool.get_bytes(128) + x_bytes = chr(ord(x_bytes[0]) & 0x7f) + x_bytes[1:] + if (x_bytes[:8] != '\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF') and \ + (x_bytes[:8] != '\x00\x00\x00\x00\x00\x00\x00\x00'): + break + self.x = util.inflate_long(x_bytes) + + def _parse_kexdh_reply(self, m): + # client mode + host_key = m.get_string() + self.f = m.get_mpint() + if (self.f < 1) or (self.f > P - 1): + raise SSHException('Server kex "f" is out of range') + sig = m.get_string() + K = pow(self.f, self.x, P) + # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) + hm = Message() + hm.add(self.transport.local_version, self.transport.remote_version, + self.transport.local_kex_init, self.transport.remote_kex_init) + hm.add_string(host_key) + hm.add_mpint(self.e) + hm.add_mpint(self.f) + hm.add_mpint(K) + self.transport._set_K_H(K, SHA.new(str(hm)).digest()) + self.transport._verify_key(host_key, sig) + self.transport._activate_outbound() + + def _parse_kexdh_init(self, m): + # server mode + self.e = m.get_mpint() + if (self.e < 1) or (self.e > P - 1): + raise SSHException('Client kex "e" is out of range') + K = pow(self.e, self.x, P) + key = str(self.transport.get_server_key()) + # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) + hm = Message() + hm.add(self.transport.remote_version, self.transport.local_version, + self.transport.remote_kex_init, self.transport.local_kex_init) + hm.add_string(key) + hm.add_mpint(self.e) + hm.add_mpint(self.f) + hm.add_mpint(K) + H = SHA.new(str(hm)).digest() + self.transport._set_K_H(K, H) + # sign it + sig = self.transport.get_server_key().sign_ssh_data(self.transport.randpool, H) + # send reply + m = Message() + m.add_byte(chr(_MSG_KEXDH_REPLY)) + m.add_string(key) + m.add_mpint(self.f) + m.add_string(str(sig)) + self.transport._send_message(m) + self.transport._activate_outbound() |