Source Code for Module paramiko.kex_group1

  1  # Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com> 
  2  # 
  3  # This file is part of paramiko. 
  4  # 
  5  # Paramiko is free software; you can redistribute it and/or modify it under the 
  6  # terms of the GNU Lesser General Public License as published by the Free 
  7  # Software Foundation; either version 2.1 of the License, or (at your option) 
  8  # any later version. 
  9  # 
 10  # Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY 
 11  # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR 
 12  # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more 
 13  # details. 
 14  # 
 15  # You should have received a copy of the GNU Lesser General Public License 
 16  # along with Paramiko; if not, write to the Free Software Foundation, Inc., 
 17  # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA. 
 18   
 19  """ 
 20  Standard SSH key exchange ("kex" if you wanna sound cool).  Diffie-Hellman of 
 21  1024 bit key halves, using a known "p" prime and "g" generator. 
 22  """ 
 23   
 24  import os 
 25  from hashlib import sha1 
 26   
 27  from paramiko import util 
 28  from paramiko.common import max_byte, zero_byte 
 29  from paramiko.message import Message 
 30  from paramiko.py3compat import byte_chr, long, byte_mask 
 31  from paramiko.ssh_exception import SSHException 
 32   
 33   
 34  _MSG_KEXDH_INIT, _MSG_KEXDH_REPLY = range(30, 32) 
 35  c_MSG_KEXDH_INIT, c_MSG_KEXDH_REPLY = [byte_chr(c) for c in range(30, 32)] 
 36   
 37  # draft-ietf-secsh-transport-09.txt, page 17 
 38  P = 0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF 
 39  G = 2 
 40   
 41  b7fffffffffffffff = byte_chr(0x7f) + max_byte * 7 
 42  b0000000000000000 = zero_byte * 8 
 43   
 44   
 45 -class KexGroup1(object): 
 46   
 47      name = 'diffie-hellman-group1-sha1' 
 48   
 49 -    def __init__(self, transport): 
 50          self.transport = transport 
 51          self.x = long(0) 
 52          self.e = long(0) 
 53          self.f = long(0) 
 54   
 55 -    def start_kex(self): 
 56          self._generate_x() 
 57          if self.transport.server_mode: 
 58              # compute f = g^x mod p, but don't send it yet 
 59              self.f = pow(G, self.x, P) 
 60              self.transport._expect_packet(_MSG_KEXDH_INIT) 
 61              return 
 62          # compute e = g^x mod p (where g=2), and send it 
 63          self.e = pow(G, self.x, P) 
 64          m = Message() 
 65          m.add_byte(c_MSG_KEXDH_INIT) 
 66          m.add_mpint(self.e) 
 67          self.transport._send_message(m) 
 68          self.transport._expect_packet(_MSG_KEXDH_REPLY) 
 69   
 70 -    def parse_next(self, ptype, m): 
 71          if self.transport.server_mode and (ptype == _MSG_KEXDH_INIT): 
 72              return self._parse_kexdh_init(m) 
 73          elif not self.transport.server_mode and (ptype == _MSG_KEXDH_REPLY): 
 74              return self._parse_kexdh_reply(m) 
 75          raise SSHException('KexGroup1 asked to handle packet type %d' % ptype) 
 76   
 77      ###  internals... 
 78   
 79 -    def _generate_x(self): 
 80          # generate an "x" (1 < x < q), where q is (p-1)/2. 
 81          # p is a 128-byte (1024-bit) number, where the first 64 bits are 1.  
 82          # therefore q can be approximated as a 2^1023.  we drop the subset of 
 83          # potential x where the first 63 bits are 1, because some of those will be 
 84          # larger than q (but this is a tiny tiny subset of potential x). 
 85          while 1: 
 86              x_bytes = os.urandom(128) 
 87              x_bytes = byte_mask(x_bytes[0], 0x7f) + x_bytes[1:] 
 88              if (x_bytes[:8] != b7fffffffffffffff and 
 89                      x_bytes[:8] != b0000000000000000): 
 90                  break 
 91          self.x = util.inflate_long(x_bytes) 
 92   
 93 -    def _parse_kexdh_reply(self, m): 
 94          # client mode 
 95          host_key = m.get_string() 
 96          self.f = m.get_mpint() 
 97          if (self.f < 1) or (self.f > P - 1): 
 98              raise SSHException('Server kex "f" is out of range') 
 99          sig = m.get_binary() 
100          K = pow(self.f, self.x, P) 
101          # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) 
102          hm = Message() 
103          hm.add(self.transport.local_version, self.transport.remote_version, 
104                 self.transport.local_kex_init, self.transport.remote_kex_init) 
105          hm.add_string(host_key) 
106          hm.add_mpint(self.e) 
107          hm.add_mpint(self.f) 
108          hm.add_mpint(K) 
109          self.transport._set_K_H(K, sha1(hm.asbytes()).digest()) 
110          self.transport._verify_key(host_key, sig) 
111          self.transport._activate_outbound() 
112   
113 -    def _parse_kexdh_init(self, m): 
114          # server mode 
115          self.e = m.get_mpint() 
116          if (self.e < 1) or (self.e > P - 1): 
117              raise SSHException('Client kex "e" is out of range') 
118          K = pow(self.e, self.x, P) 
119          key = self.transport.get_server_key().asbytes() 
120          # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) 
121          hm = Message() 
122          hm.add(self.transport.remote_version, self.transport.local_version, 
123                 self.transport.remote_kex_init, self.transport.local_kex_init) 
124          hm.add_string(key) 
125          hm.add_mpint(self.e) 
126          hm.add_mpint(self.f) 
127          hm.add_mpint(K) 
128          H = sha1(hm.asbytes()).digest() 
129          self.transport._set_K_H(K, H) 
130          # sign it 
131          sig = self.transport.get_server_key().sign_ssh_data(H) 
132          # send reply 
133          m = Message() 
134          m.add_byte(c_MSG_KEXDH_REPLY) 
135          m.add_string(key) 
136          m.add_mpint(self.f) 
137          m.add_string(sig) 
138          self.transport._send_message(m) 
139          self.transport._activate_outbound() 
140