[project @ Arch-1:robey@lag.net--2003-public%secsh--dev--1.0--patch-5]

big chunk of work which makes server code 95% done
fixed auth check methods to return just a result (failed, succeeded,
partially succeeded) and always use get_allowed_auths to determine the
list of allowed auth methods to return.

channel's internal API changed a bit to allow for client-side vs.
server-side channels.  we now honor the "want-reply" bit from channel
requests.  in server mode (for now), we automatically allow pty-req
and shell requests without doing anything.

ChannelFile was fixed up a bit to support universal newlines.  readline
got rewritten: the old way used the "greedy" read call from ChannelFile,
which won't work if the socket doesn't have that much data buffered and
ready.  now it uses recv directly, and tracks the different newlines.

demo-server.py now answers to a single shell request (like a CLI ssh
tool will make) and does a very simple demo pretending to be a BBS.

transport: fixed a bug with parsing the remote side's banner.  channel
requests are passed to another method in server mode, to determine if
we should allow it.  new allowed channels are added to an accept queue,
and a new method 'accept' (with timeout) will block until the next
incoming channel is ready.

auth_transport.py

@@ -10,11 +10,13 @@ from logging import DEBUG, INFO, WARNING, ERROR, CRITICAL
 DISCONNECT_SERVICE_NOT_AVAILABLE, DISCONNECT_AUTH_CANCELLED_BY_USER, \
     DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE = 7, 13, 14
 
-AUTH_SUCCESSFUL, AUTH_PARTIALLY_SUCCESSFUL, AUTH_FAILED = range(3)
 
 
 class Transport(BaseTransport):
     "BaseTransport with the auth framework hooked up"
+    
+    AUTH_SUCCESSFUL, AUTH_PARTIALLY_SUCCESSFUL, AUTH_FAILED = range(3)
+
     def __init__(self, sock):
         BaseTransport.__init__(self, sock)
         self.auth_event = None
@@ -111,21 +113,21 @@ class Transport(BaseTransport):
         else:
             self.log(DEBUG, 'Service request "%s" accepted (?)' % service)
 
-    def get_allowed_auths(self):
+    def get_allowed_auths(self, username):
         "override me!"
         return 'password'
 
     def check_auth_none(self, username):
-        "override me!  return tuple of (int, string) ==> (auth status, list of acceptable auth methods)"
+        "override me!  return int ==> auth status"
-        return (AUTH_FAILED, self.get_allowed_auths())
+        return self.AUTH_FAILED
 
     def check_auth_password(self, username, password):
-        "override me!  return tuple of (int, string) ==> (auth status, list of acceptable auth methods)"
+        "override me!  return int ==> auth status"
-        return (AUTH_FAILED, self.get_allowed_auths())
+        return self.AUTH_FAILED
 
     def check_auth_publickey(self, username, key):
-        "override me!  return tuple of (int, string) ==> (auth status, list of acceptable auth methods)"
+        "override me!  return int ==> auth status"
-        return (AUTH_FAILED, self.get_allowed_auths())
+        return self.AUTH_FAILED
 
     def parse_userauth_request(self, m):
         if not self.server_mode:
@@ -142,11 +144,12 @@ class Transport(BaseTransport):
         username = m.get_string()
         service = m.get_string()
         method = m.get_string()
+        self.log(DEBUG, 'Auth request (type=%s) service=%s, username=%s' % (method, service, username))
         if service != 'ssh-connection':
             self.disconnect_service_not_available()
             return
         if (self.auth_username is not None) and (self.auth_username != username):
-            # trying to change username in mid-flight!
+            self.log(DEBUG, 'Auth rejected because the client attempted to change username in mid-flight')
             self.disconnect_no_more_auth()
             return
         if method == 'none':
@@ -157,27 +160,27 @@ class Transport(BaseTransport):
             if changereq:
                 # always treated as failure, since we don't support changing passwords, but collect
                 # the list of valid auth types from the callback anyway
+                self.log(DEBUG, 'Auth request to change passwords (rejected)')
                 newpassword = m.get_string().decode('UTF-8')
-                result = self.check_auth_password(username, password)
+                result = self.AUTH_FAILED
-                result = (AUTH_FAILED, result[1])
             else:
                 result = self.check_auth_password(username, password)
         elif method == 'publickey':
             # FIXME
             result = self.check_auth_none(username)
-            result = (AUTH_FAILED, result[1])
         else:
             result = self.check_auth_none(username)
-            result = (AUTH_FAILED, result[1])
         # okay, send result
         m = Message()
-        if result[0] == AUTH_SUCCESSFUL:
+        if result == self.AUTH_SUCCESSFUL:
-            m.add_byte(chr(MSG_USERAUTH_SUCCESSFUL))
+            self.log(DEBUG, 'Auth granted.')
+            m.add_byte(chr(MSG_USERAUTH_SUCCESS))
             self.auth_complete = 1
         else:
+            self.log(DEBUG, 'Auth rejected.')
             m.add_byte(chr(MSG_USERAUTH_FAILURE))
-            m.add_string(result[1])
+            m.add_string(self.get_allowed_auths(username))
-            if result[0] == AUTH_PARTIALLY_SUCCESSFUL:
+            if result == self.AUTH_PARTIALLY_SUCCESSFUL:
                 m.add_boolean(1)
             else:
                 m.add_boolean(0)

channel.py

@@ -1,7 +1,7 @@
 from message import Message
 from secsh import SSHException
 from transport import MSG_CHANNEL_REQUEST, MSG_CHANNEL_CLOSE, MSG_CHANNEL_WINDOW_ADJUST, MSG_CHANNEL_DATA, \
-	MSG_CHANNEL_EOF
+	MSG_CHANNEL_EOF, MSG_CHANNEL_SUCCESS, MSG_CHANNEL_FAILURE
 
 import time, threading, logging, socket, os
 from logging import DEBUG
@@ -18,9 +18,9 @@ class Channel(object):
     Abstraction for a secsh channel.
     """
     
-    def __init__(self, chanid, transport):
+    def __init__(self, chanid):
         self.chanid = chanid
-        self.transport = transport
+        self.transport = None
         self.active = 0
         self.eof_received = 0
         self.eof_sent = 0
@@ -50,6 +50,9 @@ class Channel(object):
         out += '>'
         return out
 
+    def set_transport(self, transport):
+        self.transport = transport
+
     def log(self, level, msg):
         self.logger.log(level, msg)
 
@@ -60,8 +63,8 @@ class Channel(object):
         self.in_window_threshold = window_size // 10
         self.in_window_sofar = 0
         
-    def set_server_channel(self, chanid, window_size, max_packet_size):
+    def set_remote_channel(self, chanid, window_size, max_packet_size):
-        self.server_chanid = chanid
+        self.remote_chanid = chanid
         self.out_window_size = window_size
         self.out_max_packet_size = max_packet_size
         self.active = 1
@@ -99,14 +102,29 @@ class Channel(object):
 
     def handle_request(self, m):
         key = m.get_string()
+        want_reply = m.get_boolean()
+        ok = False
         if key == 'exit-status':
             self.exit_status = m.get_int()
-            return
+            ok = True
         elif key == 'xon-xoff':
             # ignore
-            return
+            ok = True
+        elif (key == 'pty-req') or (key == 'shell'):
+            if self.transport.server_mode:
+                # humor them
+                ok = True
         else:
             self.log(DEBUG, 'Unhandled channel request "%s"' % key)
+            ok = False
+        if want_reply:
+            m = Message()
+            if ok:
+                m.add_byte(chr(MSG_CHANNEL_SUCCESS))
+            else:
+                m.add_byte(chr(MSG_CHANNEL_FAILURE))
+            m.add_int(self.remote_chanid)
+            self.transport.send_message(m)
 
     def handle_eof(self, m):
         self.eof_received = 1
@@ -140,7 +158,7 @@ class Channel(object):
             raise SSHException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         m.add_string('pty-req')
         m.add_boolean(0)
         m.add_string(term)
@@ -156,7 +174,7 @@ class Channel(object):
             raise SSHException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         m.add_string('shell')
         m.add_boolean(1)
         self.transport.send_message(m)
@@ -166,7 +184,7 @@ class Channel(object):
             raise SSHException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         m.add_string('exec')
         m.add_boolean(1)
         m.add_string(command)
@@ -177,7 +195,7 @@ class Channel(object):
             raise SSHException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         m.add_string('subsystem')
         m.add_boolean(1)
         m.add_string(subsystem)
@@ -188,7 +206,7 @@ class Channel(object):
             raise SSHException('Channel is not open')
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_REQUEST))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         m.add_string('window-change')
         m.add_boolean(0)
         m.add_int(width)
@@ -211,7 +229,7 @@ class Channel(object):
             return
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_EOF))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         self.transport.send_message(m)
         self.eof_sent = 1
         self.log(DEBUG, 'EOF sent')
@@ -238,7 +256,7 @@ class Channel(object):
         self.send_eof()
         m = Message()
         m.add_byte(chr(MSG_CHANNEL_CLOSE))
-        m.add_int(self.server_chanid)
+        m.add_int(self.remote_chanid)
         self.transport.send_message(m)
         self.closed = 1
         self.transport.unlink_channel(self.chanid)
@@ -316,7 +334,7 @@ class Channel(object):
                 size = self.out_max_packet_size
             m = Message()
             m.add_byte(chr(MSG_CHANNEL_DATA))
-            m.add_int(self.server_chanid)
+            m.add_int(self.remote_chanid)
             m.add_string(s[:size])
             self.transport.send_message(m)
             self.out_window_size -= size
@@ -469,7 +487,7 @@ class Channel(object):
             self.log(DEBUG, 'addwindow send %d' % self.in_window_sofar)
             m = Message()
             m.add_byte(chr(MSG_CHANNEL_WINDOW_ADJUST))
-            m.add_int(self.server_chanid)
+            m.add_int(self.remote_chanid)
             m.add_int(self.in_window_sofar)
             self.transport.send_message(m)
             self.in_window_sofar = 0
@@ -490,7 +508,7 @@ class ChannelFile(object):
     def __init__(self, channel, mode = "r", buf_size = -1):
         self.channel = channel
         self.mode = mode
-        if buf_size < 0:
+        if buf_size <= 0:
             self.buf_size = 1024
             self.line_buffered = 0
         elif buf_size == 1:
@@ -503,10 +521,12 @@ class ChannelFile(object):
         self.rbuffer = ""
         self.readable = ("r" in mode)
         self.writable = ("w" in mode) or ("+" in mode) or ("a" in mode)
+        self.universal_newlines = ('U' in mode)
         self.binary = ("b" in mode)
-        if not self.binary:
+        self.at_trailing_cr = False
-            raise NotImplementedError("text mode not supported")
+        self.name = '<file from ' + repr(self.channel) + '>'
-        self.softspace = 0
+        self.newlines = None
+        self.softspace = False
 
     def __iter__(self):
         return self
@@ -570,23 +590,56 @@ class ChannelFile(object):
         self.rbuffer[size:]
         return result
 
-    def readline(self, size = None):
+    def readline(self, size=None):
-        line = ""
+        line = self.rbuffer
-        while "\n" not in line:
+        while 1:
-            if size >= 0:
+            if self.at_trailing_cr and (len(line) > 0):
-                new_data = self.read(size - len(line))
+                if line[0] == '\n':
+                    line = line[1:]
+                self.at_trailing_cr = False
+            if self.universal_newlines:
+                if ('\n' in line) or ('\r' in line):
+                    break
             else:
-                new_data = self.read(64)
+                if '\n' in line:
+                    break
+            if size >= 0:
+                if len(line) >= size:
+                    # truncate line and return
+                    self.rbuffer = line[size:]
+                    line = line[:size]
+                    return line
+                n = size - len(line)
+            else:
+                n = 64
+            new_data = self.channel.recv(n)
             if not new_data:
-                break
+                self.rbuffer = ''
+                return line
             line += new_data
-        newline_pos = line.find("\n")
+        # find the newline
-        if newline_pos >= 0:
+        pos = line.find('\n')
-            self.rbuffer = line[newline_pos+1:] + self.rbuffer
+        if self.universal_newlines:
-            return line[:newline_pos+1]
+            rpos = line.find('\r')
-        elif len(line) > size:
+            if (rpos >= 0) and ((rpos < pos) or (pos < 0)):
-            self.rbuffer = line[size:] + self.rbuffer
+                pos = rpos
-            return line[:size]
+        xpos = pos + 1
+        if (line[pos] == '\r') and (xpos < len(line)) and (line[xpos] == '\n'):
+            xpos += 1
+        self.rbuffer = line[xpos:]
+        lf = line[pos:xpos]
+        line = line[:xpos]
+        if (len(self.rbuffer) == 0) and (lf == '\r'):
+            # we could read the line up to a '\r' and there could still be a
+            # '\n' following that we read next time.  note that and eat it.
+            self.at_trailing_cr = True
+        # silliness about tracking what kinds of newlines we've seen
+        if self.newlines is None:
+            self.newlines = lf
+        elif (type(self.newlines) is str) and (self.newlines != lf):
+            self.newlines = (self.newlines, lf)
+        elif lf not in self.newlines:
+            self.newlines += (lf,)
         return line
 
     def readlines(self, sizehint = None):

demo-server.py

@@ -1,6 +1,6 @@
 #!/usr/bin/python
 
-import sys, os, socket, threading, logging, traceback
+import sys, os, socket, threading, logging, traceback, time
 import secsh
 
 # setup logging
@@ -15,6 +15,19 @@ if len(l.handlers) == 0:
 host_key = secsh.RSAKey()
 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 self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
+
+    def check_auth_password(self, username, password):
+        if (username == 'robey') and (password == 'foo'):
+            return self.AUTH_SUCCESSFUL
+        return self.AUTH_FAILED
+
+
 # now connect
 try:
     sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
@@ -35,7 +48,7 @@ except Exception, e:
 
 try:
     event = threading.Event()
-    t = secsh.Transport(client)
+    t = ServerTransport(client)
     t.add_server_key(host_key)
     t.ultra_debug = 1
     t.start_server(event)
@@ -45,6 +58,18 @@ try:
         print '*** SSH negotiation failed.'
         sys.exit(1)
     # print repr(t)
+
+    chan = t.accept()
+    time.sleep(2)
+    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')
+    chan.send('Username: ')
+    f = chan.makefile('rU')
+    username = f.readline().strip('\r\n')
+    chan.send('\r\nI don\'t like you, ' + username + '.\r\n')
+    chan.close()
+
 except Exception, e:
     print '*** Caught exception: ' + str(e.__class__) + ': ' + str(e)
     traceback.print_exc()

demo.py

@@ -76,7 +76,7 @@ try:
     # print repr(t)
 
     keys = load_host_keys()
-    keytype, hostkey = t.get_host_key()
+    keytype, hostkey = t.get_remote_server_key()
     if not keys.has_key(hostname):
         print '*** WARNING: Unknown host key!'
     elif not keys[hostname].has_key(keytype):

transport.py

@@ -11,12 +11,11 @@ MSG_CHANNEL_OPEN, MSG_CHANNEL_OPEN_SUCCESS, MSG_CHANNEL_OPEN_FAILURE, \
 	MSG_CHANNEL_EOF, MSG_CHANNEL_CLOSE, MSG_CHANNEL_REQUEST, \
 	MSG_CHANNEL_SUCCESS, MSG_CHANNEL_FAILURE = range(90, 101)
 
-
 import sys, os, string, threading, socket, logging, struct
 from message import Message
 from channel import Channel
 from secsh import SSHException
-from util import format_binary, safe_string, inflate_long, deflate_long
+from util import format_binary, safe_string, inflate_long, deflate_long, tb_strings
 from rsakey import RSAKey
 from dsskey import DSSKey
 from kex_group1 import KexGroup1
@@ -105,6 +104,9 @@ class BaseTransport(threading.Thread):
     REKEY_PACKETS = pow(2, 30)
     REKEY_BYTES = pow(2, 30)
 
+    OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED, OPEN_FAILED_CONNECT_FAILED, OPEN_FAILED_UNKNOWN_CHANNEL_TYPE, \
+	OPEN_FAILED_RESOURCE_SHORTAGE = range(1, 5)
+
     def __init__(self, sock):
         threading.Thread.__init__(self)
         self.randpool = randpool
@@ -143,6 +145,8 @@ class BaseTransport(threading.Thread):
         # server mode:
         self.server_mode = 0
         self.server_key_dict = { }
+        self.server_accepts = [ ]
+        self.server_accept_cv = threading.Condition(self.lock)
 
     def start_client(self, event=None):
         self.completion_event = event
@@ -196,7 +200,7 @@ class BaseTransport(threading.Thread):
         for chan in self.channels.values():
             chan.unlink()
 
-    def get_host_key(self):
+    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')
@@ -225,8 +229,9 @@ class BaseTransport(threading.Thread):
             m.add_int(chanid)
             m.add_int(self.window_size)
             m.add_int(self.max_packet_size)
-            self.channels[chanid] = chan = Channel(chanid, self)
+            self.channels[chanid] = chan = Channel(chanid)
             self.channel_events[chanid] = event = threading.Event()
+            chan.set_transport(self)
             chan.set_window(self.window_size, self.max_packet_size)
             self.send_message(m)
         finally:
@@ -445,10 +450,12 @@ class BaseTransport(threading.Thread):
                     self.send_message(msg)
         except SSHException, e:
             self.log(DEBUG, 'Exception: ' + str(e))
+            self.log(DEBUG, tb_strings())
         except EOFError, e:
             self.log(DEBUG, 'EOF')
         except Exception, e:
             self.log(DEBUG, 'Unknown exception: ' + str(e))
+            self.log(DEBUG, tb_strings())
         if self.active:
             self.active = 0
             if self.completion_event != None:
@@ -503,7 +510,11 @@ class BaseTransport(threading.Thread):
             comment = buffer[i+1:]
             buffer = buffer[:i]
         # parse out version string and make sure it matches
-        _unused, version, client = string.split(buffer, '-')
+        segs = buffer.split('-', 2)
+        if len(segs) < 3:
+            raise SSHException('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,))
         self.log(INFO, 'Connected (version %s, client %s)' % (version, client))
@@ -681,6 +692,7 @@ class BaseTransport(threading.Thread):
         code = m.get_int()
         desc = m.get_string()
         self.log(INFO, 'Disconnect (code %d): %s' % (code, desc))
+
     def parse_channel_open_success(self, m):
         chanid = m.get_int()
         server_chanid = m.get_int()
@@ -692,7 +704,7 @@ class BaseTransport(threading.Thread):
         try:
             self.lock.acquire()
             chan = self.channels[chanid]
-            chan.set_server_channel(server_chanid, server_window_size, server_max_packet_size)
+            chan.set_remote_channel(server_chanid, server_window_size, server_max_packet_size)
             self.log(INFO, 'Secsh channel %d opened.' % chanid)
             if self.channel_events.has_key(chanid):
                 self.channel_events[chanid].set()
@@ -719,20 +731,85 @@ class BaseTransport(threading.Thread):
                     self.channel_events[chanid].set()
                     del self.channel_events[chanid]
         finally:
-            self.lock_release()
+            self.lock.release()
         return
 
+    def check_channel_request(self, kind, chanid):
+        "override me!  return object descended from Channel to allow, or None to reject"
+        return None
+
     def parse_channel_open(self, m):
         kind = m.get_string()
-        self.log(DEBUG, 'Rejecting "%s" channel request from server.' % kind)
         chanid = m.get_int()
-        msg = Message()
+        initial_window_size = m.get_int()
-        msg.add_byte(chr(MSG_CHANNEL_OPEN_FAILURE))
+        max_packet_size = m.get_int()
-        msg.add_int(chanid)
+        reject = False
-        msg.add_int(1)
+        if not self.server_mode:
-        msg.add_string('Client connections are not allowed.')
+            self.log(DEBUG, 'Rejecting "%s" channel request from server.' % kind)
-        msg.add_string('en')
+            reject = True
-        self.send_message(msg)
+            reason = self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
+        else:
+            try:
+                self.lock.acquire()
+                my_chanid = self.channel_counter
+                self.channel_counter += 1
+            finally:
+                self.lock.release()
+            chan = self.check_channel_request(kind, my_chanid)
+            if (chan is None) or (type(chan) is int):
+                self.log(DEBUG, 'Rejecting "%s" channel request from client.' % kind)
+                reject = True
+                if type(chan) is int:
+                    reason = chan
+                else:
+                    reason = self.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
+        if reject:
+            msg = Message()
+            msg.add_byte(chr(MSG_CHANNEL_OPEN_FAILURE))
+            msg.add_int(chanid)
+            msg.add_int(reason)
+            msg.add_string('')
+            msg.add_string('en')
+            self.send_message(msg)
+            return
+        try:
+            self.lock.acquire()
+            self.channels[my_chanid] = chan
+            chan.set_transport(self)
+            chan.set_window(self.window_size, self.max_packet_size)
+            chan.set_remote_channel(chanid, initial_window_size, max_packet_size)
+        finally:
+            self.lock.release()
+        m = Message()
+        m.add_byte(chr(MSG_CHANNEL_OPEN_SUCCESS))
+        m.add_int(chanid)
+        m.add_int(my_chanid)
+        m.add_int(self.window_size)
+        m.add_int(self.max_packet_size)
+        self.send_message(m)
+        self.log(INFO, 'Secsh channel %d opened.' % my_chanid)
+        try:
+            self.lock.acquire()
+            self.server_accepts.append(chan)
+            self.server_accept_cv.notify()
+        finally:
+            self.lock.release()
+
+    def accept(self, timeout=None):
+        try:
+            self.lock.acquire()
+            if len(self.server_accepts) > 0:
+                chan = self.server_accepts.pop(0)
+            else:
+                self.server_accept_cv.wait(timeout)
+                if len(self.server_accepts) > 0:
+                    chan = self.server_accepts.pop(0)
+                else:
+                    # timeout
+                    chan = None
+        finally:
+            self.lock.release()
+        return chan
 
     def parse_debug(self, m):
         always_display = m.get_boolean()