[project @ Arch-1:robey@lag.net--2003-public%secsh--dev--1.0--patch-7]

cleaned up server code, renamed some files & classes
renamed demo-server.py and demo-host-key to demo_server.py and
demo_host_key, just to be consistent.

renamed SSHException -> SecshException.

generalized the mechanism where Channel decides whether to allow
different channel requests: 4 of the main ones (pty, window-change,
shell, and subsystem) go through easily override-able methods now.
you could probably make an actual ssh shell server.

gave ChannelFile a repr().

turned off ultra debugging in the demos.  demo_server creates a
subclass of Channel to allow pty/shell and sets an event when the
shell request is made, so that it knows when it can start sending
the fake bbs.

renamed to charmander and updated some of the distutils files.

12 files changed, 127 insertions, 78 deletions

diff --git a/MANIFEST b/MANIFEST
index 68d7bdee..e53d8e7b 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -1,4 +1,5 @@
 README
+auth_transport.py
 ber.py
 channel.py
 dsskey.py
@@ -11,3 +12,5 @@ setup.py
 transport.py
 util.py
 demo.py
+demo_server.py
+demo_host_key
diff --git a/NOTES b/NOTES
index e722b140..de3d2fc9 100644
--- a/NOTES
+++ b/NOTES
@@ -58,6 +58,9 @@ from Channel:
     exec_command
     invoke_subsystem
     resize_pty
+  [server:]
+    check_pty_request
+    check_shell_request
 
 from ChannelFile:
     next
diff --git a/auth_transport.py b/auth_transport.py
index 78ce8d70..13b4a23c 100644
--- a/auth_transport.py
+++ b/auth_transport.py
@@ -4,7 +4,7 @@ from transport import BaseTransport
 from transport import MSG_SERVICE_REQUEST, MSG_SERVICE_ACCEPT, MSG_USERAUTH_REQUEST, MSG_USERAUTH_FAILURE, \
      MSG_USERAUTH_SUCCESS, MSG_USERAUTH_BANNER
 from message import Message
-from secsh import SSHException
+from secsh import SecshException
 from logging import DEBUG, INFO, WARNING, ERROR, CRITICAL
 
 DISCONNECT_SERVICE_NOT_AVAILABLE, DISCONNECT_AUTH_CANCELLED_BY_USER, \
@@ -34,7 +34,7 @@ class Transport(BaseTransport):
     def auth_key(self, username, key, event):
         if (not self.active) or (not self.initial_kex_done):
             # we should never try to send the password unless we're on a secure link
-            raise SSHException('No existing session')
+            raise SecshException('No existing session')
         try:
             self.lock.acquire()
             self.auth_event = event
@@ -49,7 +49,7 @@ class Transport(BaseTransport):
         'authenticate using a password; event is triggered on success or fail'
         if (not self.active) or (not self.initial_kex_done):
             # we should never try to send the password unless we're on a secure link
-            raise SSHException('No existing session')
+            raise SecshException('No existing session')
         try:
             self.lock.acquire()
             self.auth_event = event
@@ -108,7 +108,7 @@ class Transport(BaseTransport):
                 m.add_string(str(self.private_key))
                 m.add_string(self.private_key.sign_ssh_session(self.randpool, self.H, self.username))
             else:
-                raise SSHException('Unknown auth method "%s"' % self.auth_method)
+                raise SecshException('Unknown auth method "%s"' % self.auth_method)
             self.send_message(m)
         else:
             self.log(DEBUG, 'Service request "%s" accepted (?)' % service)
diff --git a/channel.py b/channel.py
index 8f53d379..8bbe22a5 100644
--- a/channel.py
+++ b/channel.py
@@ -1,5 +1,5 @@
 from message import Message
-from secsh import SSHException
+from secsh import SecshException
 from transport import MSG_CHANNEL_REQUEST, MSG_CHANNEL_CLOSE, MSG_CHANNEL_WINDOW_ADJUST, MSG_CHANNEL_DATA, \
 	MSG_CHANNEL_EOF, MSG_CHANNEL_SUCCESS, MSG_CHANNEL_FAILURE
 
@@ -100,6 +100,22 @@ class Channel(object):
         finally:
             self.lock.release()
 
+    def check_pty_request(self, term, width, height, pixelwidth, pixelheight, modes):
+        "override me!  return True if a pty of the given dimensions (for shell access, usually) can be provided"
+        return False
+
+    def check_shell_request(self):
+        "override me!  return True if shell access will be provided"
+        return False
+
+    def check_subsystem_request(self, name):
+        "override me!  return True if the given subsystem can be provided"
+        return False
+
+    def check_window_change_request(self, width, height, pixelwidth, pixelheight):
+        "override me!  return True if the pty was resized"
+        return False
+
     def handle_request(self, m):
         key = m.get_string()
         want_reply = m.get_boolean()
@@ -110,10 +126,25 @@ class Channel(object):
         elif key == 'xon-xoff':
             # ignore
             ok = True
-        elif (key == 'pty-req') or (key == 'shell'):
-            if self.transport.server_mode:
-                # humor them
-                ok = True
+        elif key == 'pty-req':
+            term = m.get_string()
+            width = m.get_int()
+            height = m.get_int()
+            pixelwidth = m.get_int()
+            pixelheight = m.get_int()
+            modes = m.get_string()
+            ok = self.check_pty_request(term, width, height, pixelwidth, pixelheight, modes)
+        elif key == 'shell':
+            ok = self.check_shell_request()
+        elif key == 'subsystem':
+            name = m.get_string()
+            ok = self.check_subsystem_request(name)
+        elif key == 'window-change':
+            width = m.get_int()
+            height = m.get_int()
+            pixelwidth = m.get_int()
+            pixelheight = m.get_int()
+            ok = self.check_window_change_request(width, height, pixelwidth, pixelheight)
         else:
             self.log(DEBUG, 'Unhandled channel request "%s"' % key)
             ok = False
@@ -155,7 +186,7 @@ class Channel(object):
 
     def get_pty(self, term='vt100', width=80, height=24):
         if self.closed or self.eof_received or self.eof_sent or not self.active:
-            raise SSHException('Channel is not open')
+            raise SecshException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
         m.add_int(self.remote_chanid)
@@ -171,7 +202,7 @@ class Channel(object):
 
     def invoke_shell(self):
         if self.closed or self.eof_received or self.eof_sent or not self.active:
-            raise SSHException('Channel is not open')
+            raise SecshException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
         m.add_int(self.remote_chanid)
@@ -181,7 +212,7 @@ class Channel(object):
 
     def exec_command(self, command):
         if self.closed or self.eof_received or self.eof_sent or not self.active:
-            raise SSHException('Channel is not open')
+            raise SecshException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
         m.add_int(self.remote_chanid)
@@ -192,7 +223,7 @@ class Channel(object):
 
     def invoke_subsystem(self, subsystem):
         if self.closed or self.eof_received or self.eof_sent or not self.active:
-            raise SSHException('Channel is not open')
+            raise SecshException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
         m.add_int(self.remote_chanid)
@@ -203,7 +234,7 @@ class Channel(object):
 
     def resize_pty(self, width=80, height=24):
         if self.closed or self.eof_received or self.eof_sent or not self.active:
-            raise SSHException('Channel is not open')
+            raise SecshException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
         m.add_int(self.remote_chanid)
@@ -500,9 +531,6 @@ class ChannelFile(object):
     XXX Todo: the channel and its file-wrappers should be able to be closed or
     garbage-collected independently, for compatibility with real sockets and
     their file-wrappers. Currently, closing does nothing but flush the buffer.
-    XXX Todo: translation of the various forms of newline is not implemented,
-    let alone the universal newline. Line buffering (for writing) is
-    implemented, though, which makes little sense without text mode support.
     """
 
     def __init__(self, channel, mode = "r", buf_size = -1):
@@ -528,6 +556,9 @@ class ChannelFile(object):
         self.newlines = None
         self.softspace = False
 
+    def __repr__(self):
+        return '<secsh.ChannelFile from ' + repr(self.channel) + '>'
+
     def __iter__(self):
         return self
 
diff --git a/demo.py b/demo.py
index 069077d7..50ae3f92 100755
--- a/demo.py
+++ b/demo.py
@@ -66,7 +66,7 @@ except Exception, e:
 try:
     event = threading.Event()
     t = secsh.Transport(sock)
-    t.ultra_debug = 1
+    t.ultra_debug = 0
     t.start_client(event)
     # print repr(t)
     event.wait(10)
diff --git a/demo-host-key b/demo_host_key
index f50e9c53..f50e9c53 100644
--- a/demo-host-key
+++ b/demo_host_key
diff --git a/demo-server.py b/demo_server.py
index b0f8326a..a4cf01c8 100755
--- a/demo-server.py
+++ b/demo_server.py
@@ -1,25 +1,25 @@
 #!/usr/bin/python
 
-import sys, os, socket, threading, logging, traceback, time
+import sys, os, socket, threading, logging, traceback
 import secsh
 
 # setup logging
 l = logging.getLogger("secsh")
 l.setLevel(logging.DEBUG)
 if len(l.handlers) == 0:
-    f = open('demo-server.log', 'w')
+    f = open('demo_server.log', 'w')
     lh = logging.StreamHandler(f)
     lh.setFormatter(logging.Formatter('%(levelname)-.3s [%(asctime)s] %(name)s: %(message)s', '%Y%m%d:%H%M%S'))
     l.addHandler(lh)
 
 host_key = secsh.RSAKey()
-host_key.read_private_key_file('demo-host-key')
+host_key.read_private_key_file('demo_host_key')
 
 
 class ServerTransport(secsh.Transport):
     def check_channel_request(self, kind, chanid):
         if kind == 'session':
-            return secsh.Channel(chanid)
+            return ServerChannel(chanid)
         return self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
 
     def check_auth_password(self, username, password):
@@ -27,6 +27,20 @@ class ServerTransport(secsh.Transport):
             return self.AUTH_SUCCESSFUL
         return self.AUTH_FAILED
 
+class ServerChannel(secsh.Channel):
+    "Channel descendant that pretends to understand pty and shell requests"
+
+    def __init__(self, chanid):
+        secsh.Channel.__init__(self, chanid)
+        self.event = threading.Event()
+
+    def check_pty_request(self, term, width, height, pixelwidth, pixelheight, modes):
+        return True
+
+    def check_shell_request(self):
+        self.event.set()
+        return True
+
 
 # now connect
 try:
@@ -50,7 +64,7 @@ try:
     event = threading.Event()
     t = ServerTransport(client)
     t.add_server_key(host_key)
-    t.ultra_debug = 1
+    t.ultra_debug = 0
     t.start_server(event)
     # print repr(t)
     event.wait(10)
@@ -60,7 +74,11 @@ try:
     # print repr(t)
 
     chan = t.accept()
-    time.sleep(2)
+    chan.event.wait(10)
+    if not chan.event.isSet():
+        print '*** Client never asked for a shell.'
+        sys.exit(1)
+
     chan.send('\r\n\r\nWelcome to my dorky little BBS!\r\n\r\n')
     chan.send('We are on fire all the time!  Hooray!  Candy corn for everyone!\r\n')
     chan.send('Happy birthday to Robot Dave!\r\n\r\n')
diff --git a/kex_gex.py b/kex_gex.py
index 2b6e11cd..ef1bd9fc 100644
--- a/kex_gex.py
+++ b/kex_gex.py
@@ -5,8 +5,8 @@
 # LOT more on the server side).
 
 from message import Message
-from util import inflate_long, deflate_long, generate_prime
-from secsh import SSHException
+from util import inflate_long, deflate_long, generate_prime, bit_length
+from secsh import SecshException
 from transport import MSG_NEWKEYS
 from Crypto.Hash import SHA
 from Crypto.Util import number
@@ -49,17 +49,7 @@ class KexGex(object):
             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)
-
-    def bit_length(n):
-        norm = deflate_long(n, 0)
-        hbyte = ord(norm[0])
-        bitlen = len(norm) * 8
-        while not (hbyte & 0x80):
-            hbyte <<= 1
-            bitlen -= 1
-        return bitlen
-    bit_length = staticmethod(bit_length)
+        raise SecshException('KexGex asked to handle packet type %d' % ptype)
 
     def generate_x(self):
         # generate an "x" (1 < x < (p-1)/2).
@@ -116,9 +106,9 @@ class KexGex(object):
         self.p = m.get_mpint()
         self.g = m.get_mpint()
         # reject if p's bit length < 1024 or > 8192
-        bitlen = self.bit_length(self.p)
+        bitlen = 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)
+            raise SecshException('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
@@ -132,7 +122,7 @@ class KexGex(object):
     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')
+            raise SecshException('Client kex "e" is out of range')
         self.generate_x()
         K = pow(self.e, self.x, P)
         key = str(self.transport.get_server_key())
@@ -164,7 +154,7 @@ class KexGex(object):
         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')
+            raise SecshException('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().add(self.transport.local_version).add(self.transport.remote_version)
diff --git a/kex_group1.py b/kex_group1.py
index 7d65c388..ab16ee4e 100644
--- a/kex_group1.py
+++ b/kex_group1.py
@@ -5,7 +5,7 @@
 # "g" generator.
 
 from message import Message, inflate_long
-from secsh import SSHException
+from secsh import SecshException
 from transport import MSG_NEWKEYS
 from Crypto.Hash import SHA
 from logging import DEBUG, INFO, WARNING, ERROR, CRITICAL
@@ -59,14 +59,14 @@ class KexGroup1(object):
             return self.parse_kexdh_init(m)
         elif not self.transport.server_mode and (ptype == MSG_KEXDH_REPLY):
             return self.parse_kexdh_reply(m)
-        raise SSHException('KexGroup1 asked to handle packet type %d' % ptype)
+        raise SecshException('KexGroup1 asked to handle packet type %d' % ptype)
 
     def parse_kexdh_reply(self, m):
         # client mode
         host_key = m.get_string()
         self.f = m.get_mpint()
         if (self.f < 1) or (self.f > P - 1):
-            raise SSHException('Server kex "f" is out of range')
+            raise SecshException('Server kex "f" is out of range')
         sig = m.get_string()
         K = pow(self.f, self.x, P)
         # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K)
@@ -82,7 +82,7 @@ class KexGroup1(object):
         # server mode
         self.e = m.get_mpint()
         if (self.e < 1) or (self.e > P - 1):
-            raise SSHException('Client kex "e" is out of range')
+            raise SecshException('Client kex "e" is out of range')
         K = pow(self.e, self.x, 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 || e || f || K)
diff --git a/secsh.py b/secsh.py
index 6f124947..526a9660 100644
--- a/secsh.py
+++ b/secsh.py
@@ -5,8 +5,7 @@ import sys
 if (sys.version_info[0] < 2) or ((sys.version_info[0] == 2) and (sys.version_info[1] < 3)):
     raise RuntimeError('You need python 2.3 for this module.')
 
-# FIXME rename
-class SSHException(Exception):
+class SecshException(Exception):
     pass
 
 
@@ -17,7 +16,7 @@ from dsskey import DSSKey
 
 
 __author__ = "Robey Pointer <robey@lag.net>"
-__date__ = "18 Sep 2003"
-__version__ = "0.1-bulbasaur"
+__date__ = "9 Nov 2003"
+__version__ = "0.1-charmander"
 __credits__ = "Huzzah!"
 
diff --git a/setup.py b/setup.py
index 64b3401f..9eb1c9d0 100644
--- a/setup.py
+++ b/setup.py
@@ -1,23 +1,25 @@
 from distutils.core import setup
 
 longdesc = '''
-This is a library for making client-side SSH2 connections (server-side is
-coming soon).  All major ciphers and hash methods are supported.
+This is a library for making SSH2 connections (client or server).
+Emphasis is on using SSH2 as an alternative to SSL for making secure
+connections between pyton scripts.  All major ciphers and hash methods
+are supported.
 
 Required packages:
     pyCrypto
 '''
 
 setup(name = "secsh",
-      version = "0.1-bulbasaur",
+      version = "0.1-charmander",
       description = "SSH2 protocol library",
       author = "Robey Pointer",
       author_email = "robey@lag.net",
       url = "http://www.lag.net/~robey/secsh/",
-      py_modules = [ 'secsh', 'transport', 'channel', 'message', 'util', 'ber',
-                     'kex_group1', 'kex_gex', 'rsakey', 'dsskey' ],
-      scripts = [ 'demo.py' ],
-      download_url = 'http://www.lag.net/~robey/secsh/secsh-0.1-bulbasaur.zip',
+      py_modules = [ 'secsh', 'transport', 'auth_transport', 'channel',
+                     'message', 'util', 'ber', 'kex_group1', 'kex_gex',
+                     'rsakey', 'dsskey' ],
+      download_url = 'http://www.lag.net/~robey/secsh/secsh-0.1-charmander.zip',
       license = 'LGPL',
       platforms = 'Posix; MacOS X; Windows',
       classifiers = [ 'Development Status :: 3 - Alpha',
diff --git a/transport.py b/transport.py
index c5ff252b..611e5771 100644
--- a/transport.py
+++ b/transport.py
@@ -14,7 +14,7 @@ MSG_CHANNEL_OPEN, MSG_CHANNEL_OPEN_SUCCESS, MSG_CHANNEL_OPEN_FAILURE, \
 import sys, os, string, threading, socket, logging, struct
 from message import Message
 from channel import Channel
-from secsh import SSHException
+from secsh import SecshException
 from util import format_binary, safe_string, inflate_long, deflate_long, tb_strings
 from rsakey import RSAKey
 from dsskey import DSSKey
@@ -79,8 +79,7 @@ class BaseTransport(threading.Thread):
     preferred_ciphers = [ 'aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc' ]
     preferred_macs = [ 'hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96' ]
     preferred_keys = [ 'ssh-rsa', 'ssh-dss' ]
-    preferred_kex = [ 'diffie-hellman-group1-sha1' ]
-#    preferred_kex = [ 'diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1' ]
+    preferred_kex = [ 'diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1' ]
 
     cipher_info = {
         'blowfish-cbc': { 'class': Blowfish, 'mode': Blowfish.MODE_CBC, 'block-size': 8, 'key-size': 16 },
@@ -203,7 +202,7 @@ class BaseTransport(threading.Thread):
     def get_remote_server_key(self):
         'returns (type, key) where type is like "ssh-rsa" and key is an opaque string'
         if (not self.active) or (not self.initial_kex_done):
-            raise SSHException('No existing session')
+            raise SecshException('No existing session')
         key_msg = Message(self.host_key)
         key_type = key_msg.get_string()
         return key_type, self.host_key
@@ -324,7 +323,7 @@ class BaseTransport(threading.Thread):
         # leftover contains decrypted bytes from the first block (after the length field)
         leftover = header[4:]
         if (packet_size - len(leftover)) % self.block_size_in != 0:
-            raise SSHException('Invalid packet blocking')
+            raise SecshException('Invalid packet blocking')
         buffer = self.read_all(packet_size + self.remote_mac_len - len(leftover))
         packet = buffer[:packet_size - len(leftover)]
         post_packet = buffer[packet_size - len(leftover):]
@@ -338,7 +337,7 @@ class BaseTransport(threading.Thread):
             mac_payload = struct.pack('>II', self.sequence_number_in, packet_size) + packet
             my_mac = HMAC.HMAC(self.mac_key_in, mac_payload, self.remote_mac_engine).digest()[:self.remote_mac_len]
             if my_mac != mac:
-                raise SSHException('Mismatched MAC')
+                raise SecshException('Mismatched MAC')
         padding = ord(packet[0])
         payload = packet[1:packet_size - padding + 1]
         randpool.add_event(packet[packet_size - padding + 1])
@@ -361,7 +360,7 @@ class BaseTransport(threading.Thread):
                 # comply, then just drop the connection
                 self.received_packets_overflow += 1
                 if self.received_packets_overflow >= 20:
-                    raise SSHException('Remote transport is ignoring rekey requests')
+                    raise SecshException('Remote transport is ignoring rekey requests')
                 
         return ord(payload[0]), msg
 
@@ -380,9 +379,9 @@ class BaseTransport(threading.Thread):
         else:
             key = None
         if (key == None) or not key.valid:
-            raise SSHException('Unknown host key type')
+            raise SecshException('Unknown host key type')
         if not key.verify_ssh_sig(self.H, Message(sig)):
-            raise SSHException('Signature verification (%s) failed.  Boo.  Robey should debug this.' % self.host_key_type)
+            raise SecshException('Signature verification (%s) failed.  Boo.  Robey should debug this.' % self.host_key_type)
         self.host_key = host_key
 
     def compute_key(self, id, nbytes):
@@ -405,7 +404,7 @@ class BaseTransport(threading.Thread):
 
     def get_cipher(self, name, key, iv):
         if not self.cipher_info.has_key(name):
-            raise SSHException('Unknown client cipher ' + name)
+            raise SecshException('Unknown client cipher ' + name)
         return self.cipher_info[name]['class'].new(key, self.cipher_info[name]['mode'], iv)
 
     def run(self):
@@ -430,7 +429,7 @@ class BaseTransport(threading.Thread):
                     continue
                 if self.expected_packet != 0:
                     if ptype != self.expected_packet:
-                        raise SSHException('Expecting packet %d, got %d' % (self.expected_packet, ptype))
+                        raise SecshException('Expecting packet %d, got %d' % (self.expected_packet, ptype))
                     self.expected_packet = 0
                     if (ptype >= 30) and (ptype <= 39):
                         self.kex_engine.parse_next(ptype, m)
@@ -448,7 +447,7 @@ class BaseTransport(threading.Thread):
                     msg.add_byte(chr(MSG_UNIMPLEMENTED))
                     msg.add_int(m.seqno)
                     self.send_message(msg)
-        except SSHException, e:
+        except SecshException, e:
             self.log(DEBUG, 'Exception: ' + str(e))
             self.log(DEBUG, tb_strings())
         except EOFError, e:
@@ -480,7 +479,7 @@ class BaseTransport(threading.Thread):
         return 1
 
     def negotiate_keys(self, m):
-        # throws SSHException on anything unusual
+        # throws SecshException on anything unusual
         if self.local_kex_init == None:
             # remote side wants to renegotiate
             self.send_kex_init()
@@ -500,7 +499,7 @@ class BaseTransport(threading.Thread):
                 break
             self.log(DEBUG, 'Banner: ' + buffer)
         if buffer[:4] != 'SSH-':
-            raise SSHException('Indecipherable protocol version "' + buffer + '"')
+            raise SecshException('Indecipherable protocol version "' + buffer + '"')
         # save this server version string for later
         self.remote_version = buffer
         # pull off any attached comment
@@ -512,15 +511,19 @@ class BaseTransport(threading.Thread):
         # parse out version string and make sure it matches
         segs = buffer.split('-', 2)
         if len(segs) < 3:
-            raise SSHException('Invalid SSH banner')
+            raise SecshException('Invalid SSH banner')
         version = segs[1]
         client = segs[2]
         if version != '1.99' and version != '2.0':
-            raise SSHException('Incompatible version (%s instead of 2.0)' % (version,))
+            raise SecshException('Incompatible version (%s instead of 2.0)' % (version,))
         self.log(INFO, 'Connected (version %s, client %s)' % (version, client))
 
     def send_kex_init(self):
         # send a really wimpy kex-init packet that says we're a bare-bones ssh client
+        if self.server_mode:
+            # FIXME: can't do group-exchange (gex) yet -- too slow
+            if 'diffie-hellman-group-exchange-sha1' in self.preferred_kex:
+                self.preferred_kex.remove('diffie-hellman-group-exchange-sha1')
         m = Message()
         m.add_byte(chr(MSG_KEXINIT))
         m.add_bytes(randpool.get_bytes(16))
@@ -563,7 +566,7 @@ class BaseTransport(threading.Thread):
         # no compression support (yet?)
         if (not('none' in client_compress_algo_list) or
             not('none' in server_compress_algo_list)):
-            raise SSHException('Incompatible ssh peer.')
+            raise SecshException('Incompatible ssh peer.')
 
         # as a server, we pick the first item in the client's list that we support.
         # as a client, we pick the first item in our list that the server supports.
@@ -572,7 +575,7 @@ class BaseTransport(threading.Thread):
         else:
             agreed_kex = filter(kex_algo_list.__contains__, self.preferred_kex)
         if len(agreed_kex) == 0:
-            raise SSHException('Incompatible ssh peer (no acceptable kex algorithm)')
+            raise SecshException('Incompatible ssh peer (no acceptable kex algorithm)')
         self.kex_engine = self.kex_info[agreed_kex[0]](self)
 
         if self.server_mode:
@@ -580,10 +583,10 @@ class BaseTransport(threading.Thread):
         else:
             agreed_keys = filter(server_key_algo_list.__contains__, self.preferred_keys)
         if len(agreed_keys) == 0:
-            raise SSHException('Incompatible ssh peer (no acceptable host key)')
+            raise SecshException('Incompatible ssh peer (no acceptable host key)')
         self.host_key_type = agreed_keys[0]
         if self.server_mode and (self.get_server_key() is None):
-            raise SSHException('Incompatible ssh peer (can\'t match requested host key type)')
+            raise SecshException('Incompatible ssh peer (can\'t match requested host key type)')
 
         if self.server_mode:
             agreed_local_ciphers = filter(self.preferred_ciphers.__contains__,
@@ -596,7 +599,7 @@ class BaseTransport(threading.Thread):
             agreed_remote_ciphers = filter(server_encrypt_algo_list.__contains__,
                                            self.preferred_ciphers)
         if (len(agreed_local_ciphers) == 0) or (len(agreed_remote_ciphers) == 0):
-            raise SSHException('Incompatible ssh server (no acceptable ciphers)')
+            raise SecshException('Incompatible ssh server (no acceptable ciphers)')
         self.local_cipher = agreed_local_ciphers[0]
         self.remote_cipher = agreed_remote_ciphers[0]
         self.log(DEBUG, 'Ciphers agreed: local=%s, remote=%s' % (self.local_cipher, self.remote_cipher))
@@ -608,7 +611,7 @@ class BaseTransport(threading.Thread):
             agreed_local_macs = filter(client_mac_algo_list.__contains__, self.preferred_macs)
             agreed_remote_macs = filter(server_mac_algo_list.__contains__, self.preferred_macs)
         if (len(agreed_local_macs) == 0) or (len(agreed_remote_macs) == 0):
-            raise SSHException('Incompatible ssh server (no acceptable macs)')
+            raise SecshException('Incompatible ssh server (no acceptable macs)')
         self.local_mac = agreed_local_macs[0]
         self.remote_mac = agreed_remote_macs[0]