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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
40
41 name = 'diffie-hellman-group1-sha1'
42
48
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
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
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 x_bytes = self.transport.rng.read(128)
83 x_bytes = chr(ord(x_bytes[0]) & 0x7f) + x_bytes[1:]
84 if (x_bytes[:8] != '\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF') and \
85 (x_bytes[:8] != '\x00\x00\x00\x00\x00\x00\x00\x00'):
86 break
87 self.x = util.inflate_long(x_bytes)
88
90 # client mode
91 host_key = m.get_string()
92 self.f = m.get_mpint()
93 if (self.f < 1) or (self.f > P - 1):
94 raise SSHException('Server kex "f" is out of range')
95 sig = m.get_string()
96 K = pow(self.f, self.x, P)
97 # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K)
98 hm = Message()
99 hm.add(self.transport.local_version, self.transport.remote_version,
100 self.transport.local_kex_init, self.transport.remote_kex_init)
101 hm.add_string(host_key)
102 hm.add_mpint(self.e)
103 hm.add_mpint(self.f)
104 hm.add_mpint(K)
105 self.transport._set_K_H(K, SHA.new(str(hm)).digest())
106 self.transport._verify_key(host_key, sig)
107 self.transport._activate_outbound()
108
110 # server mode
111 self.e = m.get_mpint()
112 if (self.e < 1) or (self.e > P - 1):
113 raise SSHException('Client kex "e" is out of range')
114 K = pow(self.e, self.x, P)
115 key = str(self.transport.get_server_key())
116 # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K)
117 hm = Message()
118 hm.add(self.transport.remote_version, self.transport.local_version,
119 self.transport.remote_kex_init, self.transport.local_kex_init)
120 hm.add_string(key)
121 hm.add_mpint(self.e)
122 hm.add_mpint(self.f)
123 hm.add_mpint(K)
124 H = SHA.new(str(hm)).digest()
125 self.transport._set_K_H(K, H)
126 # sign it
127 sig = self.transport.get_server_key().sign_ssh_data(self.transport.rng, H)
128 # send reply
129 m = Message()
130 m.add_byte(chr(_MSG_KEXDH_REPLY))
131 m.add_string(key)
132 m.add_mpint(self.f)
133 m.add_string(str(sig))
134 self.transport._send_message(m)
135 self.transport._activate_outbound()
136
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