[project @ robey@lag.net-20060723235649-5f757e44908ffb31]

attempt to implement support for kex-gex 'old' packet type, which is apparently used by putty (this would only affect paramiko in server mode)

1 files changed, 42 insertions, 9 deletions

diff --git a/paramiko/kex_gex.py b/paramiko/kex_gex.py
index e945c1f5..9f8848c8 100644
--- a/paramiko/kex_gex.py
+++ b/paramiko/kex_gex.py
@@ -31,7 +31,8 @@ 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)
+_MSG_KEXDH_GEX_REQUEST_OLD, _MSG_KEXDH_GEX_GROUP, _MSG_KEXDH_GEX_INIT, \
+    _MSG_KEXDH_GEX_REPLY, _MSG_KEXDH_GEX_REQUEST = range(30, 35)
 
 
 class KexGex (object):
@@ -49,19 +50,25 @@ class KexGex (object):
         self.x = None
         self.e = None
         self.f = None
+        self.old_style = False
 
-    def start_kex(self):
+    def start_kex(self, _test_old_style=False):
         if self.transport.server_mode:
-            self.transport._expect_packet(_MSG_KEXDH_GEX_REQUEST)
+            self.transport._expect_packet(_MSG_KEXDH_GEX_REQUEST, _MSG_KEXDH_GEX_REQUEST_OLD)
             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)
+        if _test_old_style:
+            # only used for unit tests: we shouldn't ever send this
+            m.add_byte(chr(_MSG_KEXDH_GEX_REQUEST_OLD))
+            m.add_int(self.preferred_bits)
+        else:
+            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)
 
@@ -74,6 +81,8 @@ class KexGex (object):
             return self._parse_kexdh_gex_init(m)
         elif ptype == _MSG_KEXDH_GEX_REPLY:
             return self._parse_kexdh_gex_reply(m)
+        elif ptype == _MSG_KEXDH_GEX_REQUEST_OLD:
+            return self._parse_kexdh_gex_request_old(m)
         raise SSHException('KexGex asked to handle packet type %d' % ptype)
 
 
@@ -132,6 +141,28 @@ class KexGex (object):
         self.transport._send_message(m)
         self.transport._expect_packet(_MSG_KEXDH_GEX_INIT)
 
+    def _parse_kexdh_gex_request_old(self, m):
+        # same as above, but without min_bits or max_bits (used by older clients like putty)
+        self.preferred_bits = m.get_int()
+        # smoosh the user's preferred size into our own limits
+        if self.preferred_bits > self.max_bits:
+            self.preferred_bits = self.max_bits
+        if self.preferred_bits < self.min_bits:
+            self.preferred_bits = self.min_bits
+        # 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 bits)' % (self.preferred_bits,))
+        self.g, self.p = pack.get_modulus(self.min_bits, self.preferred_bits, self.max_bits)
+        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)
+        self.old_style = True
+
     def _parse_kexdh_gex_group(self, m):
         self.p = m.get_mpint()
         self.g = m.get_mpint()
@@ -162,9 +193,11 @@ class KexGex (object):
         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)
+        if not self.old_style:
+            hm.add_int(self.min_bits)
         hm.add_int(self.preferred_bits)
-        hm.add_int(self.max_bits)
+        if not self.old_style:
+            hm.add_int(self.max_bits)
         hm.add_mpint(self.p)
         hm.add_mpint(self.g)
         hm.add_mpint(self.e)