@ -15,50 +15,19 @@
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import sys
import socket
import asyncio
import asyncio . subprocess
import struct
from telnetlib3 import TelnetServer
from telnetlib3 . telopt import (
ECHO , WILL , WONT , DO , DONT , IAC , NAWS , BINARY , SGA , SE , SB , NOP , AYT
)
import logging
log = logging . getLogger ( __name__ )
# Mostly from https://code.google.com/p/miniboa/source/browse/trunk/miniboa/telnet.py
# Telnet Commands
SE = 240 # End of sub-negotiation parameters
NOP = 241 # No operation
DATMK = 242 # Data stream portion of a sync.
BREAK = 243 # NVT Character BRK
IP = 244 # Interrupt Process
AO = 245 # Abort Output
AYT = 246 # Are you there
EC = 247 # Erase Character
EL = 248 # Erase Line
GA = 249 # The Go Ahead Signal
SB = 250 # Sub-option to follow
WILL = 251 # Will; request or confirm option begin
WONT = 252 # Wont; deny option request
DO = 253 # Do = Request or confirm remote option
DONT = 254 # Don't = Demand or confirm option halt
IAC = 255 # Interpret as Command
SEND = 1 # Sub-process negotiation SEND command
IS = 0 # Sub-process negotiation IS command
# Telnet Options
BINARY = 0 # Transmit Binary
ECHO = 1 # Echo characters back to sender
RECON = 2 # Reconnection
SGA = 3 # Suppress Go-Ahead
TMARK = 6 # Timing Mark
TTYPE = 24 # Terminal Type
NAWS = 31 # Negotiate About Window Size
LINEMO = 34 # Line Mode
READ_SIZE = 1024
class TelnetConnection ( object ) :
""" Default implementation of telnet connection which may but may not be used. """
def __init__ ( self , reader , writer , window_size_changed_callback = None ) :
@ -101,29 +70,41 @@ class TelnetConnection(object):
Sending data back to client
: return :
"""
data = data . decode ( ) . replace ( " \n " , " \r \n " )
self . writer . write ( data . encode ( ) )
try :
data = data . decode ( ) . replace ( " \n " , " \r \n " )
self . writer . write ( data . encode ( ) )
except Exception as e :
log . error ( f " Failed to send data to client: { e } " )
def close ( self ) :
"""
Closes current connection
: return :
"""
self . is_closing = True
try :
self . is_closing = True
except Exception as e :
log . error ( f " Failed to close connection: { e } " )
class AsyncioTelnetServer :
class AsyncioTelnetServer (TelnetServer ) :
MAX_NEGOTIATION_READ = 10
def __init__ ( self , reader = None , writer = None , binary = True , echo = False , naws = False , window_size_changed_callback = None , connection_factory = None ) :
"""
Refactored using telnetlib3 for robust Telnet session management .
Background : telnetlib3 enhances and provides abstraction for telnet session and command processing .
Its use is also aimed at addressing a bug in the telnet bridge impacting console connectivity ,
particularly prevalent in complex network simulations with high - demand appliances .
"""
def __init__ (
self , reader = None , writer = None , binary = True , echo = False , naws = False ,
window_size_changed_callback = None , connection_factory = None ) :
"""
Initializes telnet server
: param naws when True make a window size negotiation
: param connection_factory : when set it ' s possible to inject own implementation of connection
: param connection_factory : when set it ' s possible to inject own implementation of connection
"""
assert connection_factory is None or ( connection_factory is not None and reader is None and writer is None ) , \
" Please use either reader and writer either connection_factory, otherwise duplicate data may be produced. "
self . _reader = reader
self . _writer = writer
self . _connections = dict ( )
@ -151,52 +132,40 @@ class AsyncioTelnetServer:
async def write_client_intro ( writer , echo = False ) :
# Send initial telnet session opening
if echo :
writer . write ( bytes ( [ IAC , WILL , ECHO ] ) )
writer . write ( IAC + WILL + ECHO )
else :
writer . write ( bytes ( [
IAC , WONT , ECHO ,
IAC , DONT , ECHO ] ) )
writer . write ( IAC + WONT + ECHO + IAC + DONT + ECHO )
await writer . drain ( )
async def _write_intro ( self , writer , binary = False , echo = False , naws = False ) :
# Send initial telnet session opening
if echo :
writer . write ( bytes ( [ IAC , WILL , ECHO ] ) )
writer . write ( IAC + WILL + ECHO )
else :
writer . write ( bytes ( [
IAC , WONT , ECHO ,
IAC , DONT , ECHO ] ) )
writer . write (
IAC + WONT + ECHO
+ IAC + DONT + ECHO
)
if binary :
writer . write ( bytes ( [
IAC , WILL , SGA ,
IAC , WILL , BINARY ,
IAC , DO , BINARY ] ) )
writer . write (
IAC + WILL + SGA
+ IAC + WILL + BINARY
+ IAC + DO + BINARY
)
else :
writer . write ( bytes ( [
IAC , WONT , SGA ,
IAC , DONT , SGA ,
IAC , WONT , BINARY ,
IAC , DONT , BINARY ] ) )
writer . write (
IAC + WONT + SGA
+ IAC + DONT + SGA
+ IAC + WONT + BINARY
+ IAC + DONT + BINARY
)
if naws :
writer . write ( bytes ( [
IAC , DO , NAWS
] ) )
writer . write (
IAC + DO + NAWS
)
await writer . drain ( )
async def run ( self , network_reader , network_writer ) :
sock = network_writer . get_extra_info ( " socket " )
sock . setsockopt ( socket . SOL_SOCKET , socket . SO_KEEPALIVE , 1 )
sock . setsockopt ( socket . IPPROTO_TCP , socket . TCP_NODELAY , 1 )
# 60 sec keep alives, close tcp session after 4 missed
# Will keep a firewall from aging out telnet console.
sock . setsockopt ( socket . IPPROTO_TCP , socket . TCP_KEEPIDLE , 60 )
sock . setsockopt ( socket . IPPROTO_TCP , socket . TCP_KEEPINTVL , 10 )
sock . setsockopt ( socket . IPPROTO_TCP , socket . TCP_KEEPCNT , 4 )
#log.debug("New connection from {}".format(sock.getpeername()))
# Keep track of connected clients
connection = self . _connection_factory ( network_reader , network_writer , self . _window_size_changed_callback )
self . _connections [ network_writer ] = connection
@ -208,10 +177,8 @@ class AsyncioTelnetServer:
except ConnectionError :
async with self . _lock :
network_writer . close ( )
# await network_writer.wait_closed() # this doesn't work in Python 3.6
if self . _reader_process == network_reader :
self . _reader_process = None
# Cancel current read from this reader
if self . _current_read is not None :
self . _current_read . cancel ( )
@ -224,7 +191,6 @@ class AsyncioTelnetServer:
writer . write_eof ( )
await writer . drain ( )
writer . close ( )
# await writer.wait_closed() # this doesn't work in Python 3.6
except ( AttributeError , ConnectionError ) :
continue
@ -312,44 +278,53 @@ class AsyncioTelnetServer:
buffer . extend ( op )
cmd . append ( buffer [ location ] )
return op
async def _negotiate ( self , data , connection ) :
""" Performs negotiation commands """
""" Performs negotiation commands """
command , payload = data [ 0 ] , data [ 1 : ]
log . info ( f " _negotiate called! - command: { command } , payload: { payload } " )
if command == NAWS :
if len ( payload ) == 4 :
columns , rows = struct . unpack ( str ( ' !HH ' ) , bytes ( payload ) )
columns , rows = struct . unpack ( ' !HH ' , bytes ( payload ) )
await connection . window_size_changed ( columns , rows )
else :
log . warning ( ' Wrong number of NAWS bytes ' )
else :
log . debug ( " Not supported negotiation sequence, received {} bytes " , len ( data ) )
log . info ( " Not supported negotiation sequence, received {} bytes " , len ( data ) )
async def _IAC_parser ( self , buf , network_reader , network_writer , connection ) :
"""
Processes and removes any Telnet commands from the buffer .
# Changes in _IAC_parser:
- Removed bytearray for building IAC commands ; now directly appending to a byte string .
- Eliminated ' skip_to ' index , streamlining buffer parsing .
- Condensed and simplified command identification logic for improved readability .
- Modified buffer manipulation approach for removing processed commands .
# Additions in _IAC_parser:
+ Enhanced handling of DO command with specific cases for ECHO , SGA , and BINARY .
+ Added specific handling for agreeing to SGA and Binary Transmission upon request .
+ Implemented more concise logging for unhandled telnet commands .
: param buf : buffer
: returns : buffer minus Telnet commands
"""
skip_to = 0
while True :
# Locate an IAC to process
iac_loc = buf . find ( IAC , skip_to )
iac_loc = buf . find ( IAC )
if iac_loc < 0 :
break
# Get the TELNET command
iac_cmd = bytearray ( [ IAC ] )
# Initialise IAC command
iac_cmd = IAC
#Try and get the next byte after IAC
try :
iac_cmd . append ( buf [ iac_loc + 1 ] )
iac_cmd + = bytes ( [ buf [ iac_loc + 1 ] ] )
except IndexError :
# If can't get the next byte, read it from the network
d = await network_reader . read ( 1 )
buf . extend ( d )
iac_cmd . append ( buf [ iac_loc + 1 ] )
iac_cmd + = d
# Is this just a 2-byte TELNET command?
if iac_cmd [ 1 ] not in [ WILL , WONT , DO , DONT , SB ] :
@ -390,17 +365,21 @@ class AsyncioTelnetServer:
iac_cmd . append ( buf [ iac_loc + 2 ] )
# We do ECHO, SGA, and BINARY. Period.
if iac_cmd [ 1 ] == DO :
if iac_cmd [ 2 ] not in [ ECHO , SGA , BINARY ] :
network_writer . write ( bytes ( [ IAC , WONT , iac_cmd [ 2 ] ] ) )
log . debug ( " Telnet WON ' T {:#x} " . format ( iac_cmd [ 2 ] ) )
if iac_cmd [ 2 ] == ECHO :
if self . _echo :
network_writer . write ( bytes ( [ IAC , WILL , ECHO ] ) )
log . debug ( " Telnet WILL ECHO " )
else :
network_writer . write ( bytes ( [ IAC , WONT , ECHO ] ) )
log . debug ( " Telnet WONT ECHO " )
elif iac_cmd [ 2 ] in [ SGA , BINARY ] :
# Agree to SGA and Binary Transmission if requested
network_writer . write ( bytes ( [ IAC , WILL , iac_cmd [ 2 ] ] ) )
log . debug ( " Telnet WILL {:#x} " . format ( iac_cmd [ 2 ] ) )
else :
if iac_cmd [ 2 ] == SGA :
if self . _binary :
network_writer . write ( bytes ( [ IAC , WILL , iac_cmd [ 2 ] ] ) )
else :
network_writer . write ( bytes ( [ IAC , WONT , iac_cmd [ 2 ] ] ) )
log . debug ( " Telnet WON ' T {:#x} " . format ( iac_cmd [ 2 ] ) )
# Refuse other options
network_writer . write ( bytes ( [ IAC , WONT , iac_cmd [ 2 ] ] ) )
log . debug ( " Telnet WONT {:#x} " . format ( iac_cmd [ 2 ] ) )
elif iac_cmd [ 1 ] == DONT :
log . debug ( " Unhandled DONT telnet command: "
" {0:#x} {1:#x} {2:#x} " . format ( * iac_cmd ) )
@ -416,7 +395,7 @@ class AsyncioTelnetServer:
" {0:#x} {1:#x} {2:#x} " . format ( * iac_cmd ) )
# Remove the entire TELNET command from the buffer
buf = buf . replace ( iac_cmd , b ' ' , 1 )
buf = buf [ : iac_loc ] + buf [ iac_loc + len ( iac_cmd ) : ]
await network_writer . drain ( )