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 distrubuted 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  from Crypto.Hash import SHA 
 25   
 26  from paramiko.common import * 
 27  from paramiko import util 
 28  from paramiko.message import Message 
 29  from paramiko.ssh_exception import SSHException 
 30   
 31   
 32  _MSG_KEXDH_INIT, _MSG_KEXDH_REPLY = range(30, 32) 
 33   
 34  # draft-ietf-secsh-transport-09.txt, page 17 
 35  P = 0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFFL 
 36  G = 2 
 37   
 38   
 39 -class KexGroup1(object): 
 40   
 41      name = 'diffie-hellman-group1-sha1' 
 42   
 43 -    def __init__(self, transport): 
 44          self.transport = transport 
 45          self.x = 0L 
 46          self.e = 0L 
 47          self.f = 0L 
 48   
 49 -    def start_kex(self): 
 50          self._generate_x() 
 51          if self.transport.server_mode: 
 52              # compute f = g^x mod p, but don't send it yet 
 53              self.f = pow(G, self.x, P) 
 54              self.transport._expect_packet(_MSG_KEXDH_INIT) 
 55              return 
 56          # compute e = g^x mod p (where g=2), and send it 
 57          self.e = pow(G, self.x, P) 
 58          m = Message() 
 59          m.add_byte(chr(_MSG_KEXDH_INIT)) 
 60          m.add_mpint(self.e) 
 61          self.transport._send_message(m) 
 62          self.transport._expect_packet(_MSG_KEXDH_REPLY) 
 63   
 64 -    def parse_next(self, ptype, m): 
 65          if self.transport.server_mode and (ptype == _MSG_KEXDH_INIT): 
 66              return self._parse_kexdh_init(m) 
 67          elif not self.transport.server_mode and (ptype == _MSG_KEXDH_REPLY): 
 68              return self._parse_kexdh_reply(m) 
 69          raise SSHException('KexGroup1 asked to handle packet type %d' % ptype) 
 70       
 71   
 72      ###  internals... 
 73   
 74   
 75 -    def _generate_x(self): 
 76          # generate an "x" (1 < x < q), where q is (p-1)/2. 
 77          # p is a 128-byte (1024-bit) number, where the first 64 bits are 1.  
 78          # therefore q can be approximated as a 2^1023.  we drop the subset of 
 79          # potential x where the first 63 bits are 1, because some of those will be 
 80          # larger than q (but this is a tiny tiny subset of potential x). 
 81          while 1: 
 82              self.transport.randpool.stir() 
 83              x_bytes = self.transport.randpool.get_bytes(128) 
 84              x_bytes = chr(ord(x_bytes[0]) & 0x7f) + x_bytes[1:] 
 85              if (x_bytes[:8] != '\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF') and \ 
 86                     (x_bytes[:8] != '\x00\x00\x00\x00\x00\x00\x00\x00'): 
 87                  break 
 88          self.x = util.inflate_long(x_bytes) 
 89   
 90 -    def _parse_kexdh_reply(self, m): 
 91          # client mode 
 92          host_key = m.get_string() 
 93          self.f = m.get_mpint() 
 94          if (self.f < 1) or (self.f > P - 1): 
 95              raise SSHException('Server kex "f" is out of range') 
 96          sig = m.get_string() 
 97          K = pow(self.f, self.x, P) 
 98          # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) 
 99          hm = Message() 
100          hm.add(self.transport.local_version, self.transport.remote_version, 
101                 self.transport.local_kex_init, self.transport.remote_kex_init) 
102          hm.add_string(host_key) 
103          hm.add_mpint(self.e) 
104          hm.add_mpint(self.f) 
105          hm.add_mpint(K) 
106          self.transport._set_K_H(K, SHA.new(str(hm)).digest()) 
107          self.transport._verify_key(host_key, sig) 
108          self.transport._activate_outbound() 
109   
110 -    def _parse_kexdh_init(self, m): 
111          # server mode 
112          self.e = m.get_mpint() 
113          if (self.e < 1) or (self.e > P - 1): 
114              raise SSHException('Client kex "e" is out of range') 
115          K = pow(self.e, self.x, P) 
116          key = str(self.transport.get_server_key()) 
117          # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K) 
118          hm = Message() 
119          hm.add(self.transport.remote_version, self.transport.local_version, 
120                 self.transport.remote_kex_init, self.transport.local_kex_init) 
121          hm.add_string(key) 
122          hm.add_mpint(self.e) 
123          hm.add_mpint(self.f) 
124          hm.add_mpint(K) 
125          H = SHA.new(str(hm)).digest() 
126          self.transport._set_K_H(K, H) 
127          # sign it 
128          sig = self.transport.get_server_key().sign_ssh_data(self.transport.randpool, H) 
129          # send reply 
130          m = Message() 
131          m.add_byte(chr(_MSG_KEXDH_REPLY)) 
132          m.add_string(key) 
133          m.add_mpint(self.f) 
134          m.add_string(str(sig)) 
135          self.transport._send_message(m) 
136          self.transport._activate_outbound() 
137