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gns3-server
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Merge a91740dae0 into 7a229e33f9

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Kieran Carmichael 1 month ago committed by GitHub
parent 7a229e33f9 a91740dae0
commit 62b3b7c42b
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2 changed files with 85 additions and 105 deletions
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189
gns3server/utils/asyncio/telnet_server.py
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@ -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
@ -320,44 +286,53 @@ 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]:
@ -398,17 +373,21 @@ 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))
@ -424,7 +403,7 @@ 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()

1
requirements.txt
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@ -13,3 +13,4 @@ platformdirs>=2.4.0
importlib-resources>=1.3; python_version < '3.9'
truststore>=0.8.0; python_version >= '3.10'
setuptools>=60.8.1
telnetlib3==2.0.4; # Used for new implementation of telnet_server.py

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