Imported Upstream version 1.5.2upstream/1.5.2

1 files changed, 202 insertions, 0 deletions

diff --git a/paramiko/kex_gex.py b/paramiko/kex_gex.py
new file mode 100644
index 0000000..994d76c
--- /dev/null
+++ b/paramiko/kex_gex.py
@@ -0,0 +1,202 @@
+# 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.
+
+"""
+Variant on L{KexGroup1 <paramiko.kex_group1.KexGroup1>} where the prime "p" and
+generator "g" are provided by the server.  A bit more work is required on the
+client side, and a B{lot} more on the server side.
+"""
+
+from Crypto.Hash import SHA
+from Crypto.Util import number
+
+from paramiko.common import *
+from paramiko import util
+from paramiko.message import Message
+from paramiko.ssh_exception import SSHException
+
+
+_MSG_KEXDH_GEX_GROUP, _MSG_KEXDH_GEX_INIT, _MSG_KEXDH_GEX_REPLY, _MSG_KEXDH_GEX_REQUEST = range(31, 35)
+
+
+class KexGex (object):
+
+    name = 'diffie-hellman-group-exchange-sha1'
+    min_bits = 1024
+    max_bits = 8192
+    preferred_bits = 2048
+
+    def __init__(self, transport):
+        self.transport = transport
+
+    def start_kex(self):
+        if self.transport.server_mode:
+            self.transport._expect_packet(_MSG_KEXDH_GEX_REQUEST)
+            return
+        # request a bit range: we accept (min_bits) to (max_bits), but prefer
+        # (preferred_bits).  according to the spec, we shouldn't pull the
+        # minimum up above 1024.
+        m = Message()
+        m.add_byte(chr(_MSG_KEXDH_GEX_REQUEST))
+        m.add_int(self.min_bits)
+        m.add_int(self.preferred_bits)
+        m.add_int(self.max_bits)
+        self.transport._send_message(m)
+        self.transport._expect_packet(_MSG_KEXDH_GEX_GROUP)
+
+    def parse_next(self, ptype, m):
+        if ptype == _MSG_KEXDH_GEX_REQUEST:
+            return self._parse_kexdh_gex_request(m)
+        elif ptype == _MSG_KEXDH_GEX_GROUP:
+            return self._parse_kexdh_gex_group(m)
+        elif ptype == _MSG_KEXDH_GEX_INIT:
+            return self._parse_kexdh_gex_init(m)
+        elif ptype == _MSG_KEXDH_GEX_REPLY:
+            return self._parse_kexdh_gex_reply(m)
+        raise SSHException('KexGex asked to handle packet type %d' % ptype)
+
+
+    ###  internals...
+
+    
+    def _generate_x(self):
+        # generate an "x" (1 < x < (p-1)/2).
+        q = (self.p - 1) // 2
+        qnorm = util.deflate_long(q, 0)
+        qhbyte = ord(qnorm[0])
+        bytes = len(qnorm)
+        qmask = 0xff
+        while not (qhbyte & 0x80):
+            qhbyte <<= 1
+            qmask >>= 1
+        while True:
+            self.transport.randpool.stir()
+            x_bytes = self.transport.randpool.get_bytes(bytes)
+            x_bytes = chr(ord(x_bytes[0]) & qmask) + x_bytes[1:]
+            x = util.inflate_long(x_bytes, 1)
+            if (x > 1) and (x < q):
+                break
+        self.x = x
+
+    def _parse_kexdh_gex_request(self, m):
+        minbits = m.get_int()
+        preferredbits = m.get_int()
+        maxbits = m.get_int()
+        # smoosh the user's preferred size into our own limits
+        if preferredbits > self.max_bits:
+            preferredbits = self.max_bits
+        if preferredbits < self.min_bits:
+            preferredbits = self.min_bits
+        # fix min/max if they're inconsistent.  technically, we could just pout
+        # and hang up, but there's no harm in giving them the benefit of the
+        # doubt and just picking a bitsize for them.
+        if minbits > preferredbits:
+            minbits = preferredbits
+        if maxbits < preferredbits:
+            maxbits = preferredbits
+        # now save a copy
+        self.min_bits = minbits
+        self.preferred_bits = preferredbits
+        self.max_bits = maxbits
+        # generate prime
+        pack = self.transport._get_modulus_pack()
+        if pack is None:
+            raise SSHException('Can\'t do server-side gex with no modulus pack')
+        self.transport._log(DEBUG, 'Picking p (%d <= %d <= %d bits)' % (minbits, preferredbits, maxbits))
+        self.g, self.p = pack.get_modulus(minbits, preferredbits, maxbits)
+        m = Message()
+        m.add_byte(chr(_MSG_KEXDH_GEX_GROUP))
+        m.add_mpint(self.p)
+        m.add_mpint(self.g)
+        self.transport._send_message(m)
+        self.transport._expect_packet(_MSG_KEXDH_GEX_INIT)
+
+    def _parse_kexdh_gex_group(self, m):
+        self.p = m.get_mpint()
+        self.g = m.get_mpint()
+        # reject if p's bit length < 1024 or > 8192
+        bitlen = util.bit_length(self.p)
+        if (bitlen < 1024) or (bitlen > 8192):
+            raise SSHException('Server-generated gex p (don\'t ask) is out of range (%d bits)' % bitlen)
+        self.transport._log(DEBUG, 'Got server p (%d bits)' % bitlen)
+        self._generate_x()
+        # now compute e = g^x mod p
+        self.e = pow(self.g, self.x, self.p)
+        m = Message()
+        m.add_byte(chr(_MSG_KEXDH_GEX_INIT))
+        m.add_mpint(self.e)
+        self.transport._send_message(m)
+        self.transport._expect_packet(_MSG_KEXDH_GEX_REPLY)
+
+    def _parse_kexdh_gex_init(self, m):
+        self.e = m.get_mpint()
+        if (self.e < 1) or (self.e > self.p - 1):
+            raise SSHException('Client kex "e" is out of range')
+        self._generate_x()
+        self.f = pow(self.g, self.x, self.p)
+        K = pow(self.e, self.x, self.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 || min || n || max || p || g || 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,
+               key)
+        hm.add_int(self.min_bits)
+        hm.add_int(self.preferred_bits)
+        hm.add_int(self.max_bits)
+        hm.add_mpint(self.p)
+        hm.add_mpint(self.g)
+        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_GEX_REPLY))
+        m.add_string(key)
+        m.add_mpint(self.f)
+        m.add_string(str(sig))
+        self.transport._send_message(m)
+        self.transport._activate_outbound()
+        
+    def _parse_kexdh_gex_reply(self, m):
+        host_key = m.get_string()
+        self.f = m.get_mpint()
+        sig = m.get_string()
+        if (self.f < 1) or (self.f > self.p - 1):
+            raise SSHException('Server kex "f" is out of range')
+        K = pow(self.f, self.x, self.p)
+        # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || min || n || max || p || g || 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,
+               host_key)
+        hm.add_int(self.min_bits)
+        hm.add_int(self.preferred_bits)
+        hm.add_int(self.max_bits)
+        hm.add_mpint(self.p)
+        hm.add_mpint(self.g)
+        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()