Note

You are reading an old version of the Evennia documentation. The latest version is here

.

# Source code for evennia.server.portal.ssh

    """
    This module implements the ssh (Secure SHell) protocol for encrypted
    connections.

    This depends on a generic session module that implements the actual
    login procedure of the game, tracks sessions etc.

    Using standard ssh client,

    """

    import os
    import re

    from twisted.conch.interfaces import IConchUser
    from twisted.cred import checkers
    from twisted.cred.portal import Portal

    _SSH_IMPORT_ERROR = """
    ERROR: Missing crypto library for SSH. Install it with

           pip install cryptography pyasn1 bcrypt

    (On older Twisted versions you may have to do 'pip install pycrypto pyasn1' instead).

    If you get a compilation error you must install a C compiler and the
    SSL dev headers (On Debian-derived systems this is the gcc and libssl-dev
    packages).
    """

    try:
        from twisted.conch.ssh.keys import Key
    except ImportError:
        raise ImportError(_SSH_IMPORT_ERROR)

    from django.conf import settings
    from evennia.accounts.models import AccountDB
    from evennia.utils import ansi
    from evennia.utils.utils import class_from_module, to_str
    from twisted.conch import interfaces as iconch
    from twisted.conch.insults import insults
    from twisted.conch.manhole import Manhole, recvline
    from twisted.conch.manhole_ssh import ConchFactory, TerminalRealm, _Glue
    from twisted.conch.ssh import common
    from twisted.conch.ssh.userauth import SSHUserAuthServer
    from twisted.internet import defer, protocol
    from twisted.python import components

    _RE_N = re.compile(r"\|n$")
    _RE_SCREENREADER_REGEX = re.compile(
        r"%s" % settings.SCREENREADER_REGEX_STRIP, re.DOTALL + re.MULTILINE
    )
    _GAME_DIR = settings.GAME_DIR
    _PRIVATE_KEY_FILE = os.path.join(_GAME_DIR, "server", "ssh-private.key")
    _PUBLIC_KEY_FILE = os.path.join(_GAME_DIR, "server", "ssh-public.key")
    _KEY_LENGTH = 2048

    CTRL_C = "\x03"
    CTRL_D = "\x04"
    CTRL_BACKSLASH = "\x1c"
    CTRL_L = "\x0c"

    _NO_AUTOGEN = f"""
    Evennia could not generate SSH private- and public keys ({{err}})
    Using conch default keys instead.

    If this error persists, create the keys manually (using the tools for your OS)
    and put them here:
        {_PRIVATE_KEY_FILE}
        {_PUBLIC_KEY_FILE}
    """

    _BASE_SESSION_CLASS = class_from_module(settings.BASE_SESSION_CLASS)

    # not used atm
    class SSHServerFactory(protocol.ServerFactory):
        """
        This is only to name this better in logs

        """

        noisy = False

        def logPrefix(self):
            return "SSH"

    class SshProtocol(Manhole, _BASE_SESSION_CLASS):
        """
        Each account connecting over ssh gets this protocol assigned to
        them.  All communication between game and account goes through
        here.

        """

        noisy = False

        def __init__(self, starttuple):
            """
            For setting up the account.  If account is not None then we'll
            login automatically.

            Args:
                starttuple (tuple): A (account, factory) tuple.

            """
            self.protocol_key = "ssh"
            self.authenticated_account = starttuple[0]
            # obs must not be called self.factory, that gets overwritten!
            self.cfactory = starttuple[1]

        def terminalSize(self, width, height):
            """
            Initialize the terminal and connect to the new session.

            Args:
                width (int): Width of terminal.
                height (int): Height of terminal.

            """
            # Clear the previous input line, redraw it at the new
            # cursor position
            self.terminal.eraseDisplay()
            self.terminal.cursorHome()
            self.width = width
            self.height = height

            # Set color defaults
            for color in ("ANSI", "XTERM256", "TRUECOLOR"):
                self.protocol_flags[color] = True

            # initialize the session
            client_address = self.getClientAddress()
            client_address = client_address.host if client_address else None
            self.init_session("ssh", client_address, self.cfactory.sessionhandler)

            # since we might have authenticated already, we might set this here.
            if self.authenticated_account:
                self.logged_in = True
                self.uid = self.authenticated_account.id
            self.sessionhandler.connect(self)

        def connectionMade(self):
            """
            This is called when the connection is first established.

            """
            recvline.HistoricRecvLine.connectionMade(self)
            self.keyHandlers[CTRL_C] = self.handle_INT
            self.keyHandlers[CTRL_D] = self.handle_EOF
            self.keyHandlers[CTRL_L] = self.handle_FF
            self.keyHandlers[CTRL_BACKSLASH] = self.handle_QUIT

            # initalize

        def handle_INT(self):
            """
            Handle ^C as an interrupt keystroke by resetting the current
            input variables to their initial state.

            """
            self.lineBuffer = []
            self.lineBufferIndex = 0

            self.terminal.nextLine()
            self.terminal.write("KeyboardInterrupt")
            self.terminal.nextLine()

        def handle_EOF(self):
            """
            Handles EOF generally used to exit.

            """
            if self.lineBuffer:
                self.terminal.write("\a")
            else:
                self.handle_QUIT()

        def handle_FF(self):
            """
            Handle a 'form feed' byte - generally used to request a screen
            refresh/redraw.

            """
            self.terminal.eraseDisplay()
            self.terminal.cursorHome()

        def handle_QUIT(self):
            """
            Quit, end, and lose the connection.

            """
            self.terminal.loseConnection()

        def connectionLost(self, reason=None):
            """
            This is executed when the connection is lost for whatever
            reason. It can also be called directly, from the disconnect
            method.

            Args:
                reason (str): Motivation for loosing connection.

            """
            insults.TerminalProtocol.connectionLost(self, reason)
            self.sessionhandler.disconnect(self)
            self.terminal.loseConnection()

        def getClientAddress(self):
            """
            Get client address.

            Returns:
                address_and_port (tuple): The client's address and port in
                    a tuple. For example `('127.0.0.1', 41917)`.

            """
            return self.terminal.transport.getPeer()

        def lineReceived(self, string):
            """
            Communication User -> Evennia. Any line return indicates a
            command for the purpose of the MUD.  So we take the user input
            and pass it on to the game engine.

            Args:
                string (str): Input text.

            """
            self.sessionhandler.data_in(self, text=string)

        def sendLine(self, string):
            """
            Communication Evennia -> User.  Any string sent should
            already have been properly formatted and processed before
            reaching this point.

            Args:
                string (str): Output text.

            """
            for line in string.split("\n"):
                # the telnet-specific method for sending
                self.terminal.write(line)
                self.terminal.nextLine()

        # session-general method hooks

        def at_login(self):
            """
            Called when this session gets authenticated by the server.
            """
            pass

        def disconnect(self, reason="Connection closed. Goodbye for now."):
            """
            Disconnect from server.

            Args:
                reason (str): Motivation for disconnect.

            """
            if reason:
                self.data_out(text=((reason,), {}))
            self.connectionLost(reason)

        def data_out(self, **kwargs):
            """
            Data Evennia -> User

            Keyword Args:
                kwargs (any): Options to the protocol.

            """
            self.sessionhandler.data_out(self, **kwargs)

        def send_text(self, *args, **kwargs):
            """
            Send text data. This is an in-band telnet operation.

            Args:
                text (str): The first argument is always the text string to send. No other arguments
                    are considered.
            Keyword Args:
                options (dict): Send-option flags (booleans)

                    - mxp: enforce mxp link support.
                    - ansi: enforce no ansi colors.
                    - xterm256: enforce xterm256 colors, regardless of ttype setting.
                    - nocolor: strip all colors.
                    - raw: pass string through without any ansi processing
                      (i.e. include evennia ansi markers but do not
                      convert them into ansi tokens)
                    - echo: turn on/off line echo on the client. turn
                      off line echo for client, for example for password.
                      note that it must be actively turned back on again!

            """
            # print "telnet.send_text", args,kwargs  # DEBUG
            text = args[0] if args else ""
            if text is None:
                return
            text = to_str(text)

            # handle arguments
            options = kwargs.get("options", {})
            flags = self.protocol_flags
            xterm256 = options.get("xterm256", flags.get("XTERM256", True))
            useansi = options.get("ansi", flags.get("ANSI", True))
            raw = options.get("raw", flags.get("RAW", False))
            nocolor = options.get("nocolor", flags.get("NOCOLOR") or not (xterm256 or useansi))
            # echo = options.get("echo", None)  # DEBUG
            screenreader = options.get("screenreader", flags.get("SCREENREADER", False))

            if screenreader:
                # screenreader mode cleans up output
                text = ansi.parse_ansi(text, strip_ansi=True, xterm256=False, mxp=False)
                text = _RE_SCREENREADER_REGEX.sub("", text)

            if raw:
                # no processing
                self.sendLine(text)
                return
            else:
                # we need to make sure to kill the color at the end in order
                # to match the webclient output.
                linetosend = ansi.parse_ansi(
                    _RE_N.sub("", text) + ("||n" if text.endswith("|") else "|n"),
                    strip_ansi=nocolor,
                    xterm256=xterm256,
                    mxp=False,
                )
                self.sendLine(linetosend)

        def send_prompt(self, *args, **kwargs):
            self.send_text(*args, **kwargs)

        def send_default(self, *args, **kwargs):
            pass

    class ExtraInfoAuthServer(SSHUserAuthServer):
        noisy = False

        def auth_password(self, packet):
            """
            Password authentication.

            Used mostly for setting up the transport so we can query
            username and password later.

            Args:
                packet (Packet): Auth packet.

            """
            password = common.getNS(packet[1:])[0]
            c = checkers.UsernamePassword(self.user, password)
            c.transport = self.transport
            return self.portal.login(c, None, IConchUser).addErrback(self._ebPassword)

    class AccountDBPasswordChecker(object):
        """
        Checks the django db for the correct credentials for
        username/password otherwise it returns the account or None which is
        useful for the Realm.

        """

        noisy = False
        credentialInterfaces = (checkers.IUsernamePassword,)

        def __init__(self, factory):
            """
            Initialize the factory.

            Args:
                factory (SSHFactory): Checker factory.

            """
            self.factory = factory
            super().__init__()

        def requestAvatarId(self, c):
            """
            Generic credentials.

            """
            up = checkers.IUsernamePassword(c, None)
            username = up.username
            password = up.password
            account = AccountDB.objects.get_account_from_name(username)
            res = (None, self.factory)
            if account and account.check_password(password):
                res = (account, self.factory)
            return defer.succeed(res)

    class PassAvatarIdTerminalRealm(TerminalRealm):
        """
        Returns an avatar that passes the avatarId through to the
        protocol.  This is probably not the best way to do it.

        """

        noisy = False

        def _getAvatar(self, avatarId):
            comp = components.Componentized()
            user = self.userFactory(comp, avatarId)
            sess = self.sessionFactory(comp)

            sess.transportFactory = self.transportFactory
            sess.chainedProtocolFactory = lambda: self.chainedProtocolFactory(avatarId)

            comp.setComponent(iconch.IConchUser, user)
            comp.setComponent(iconch.ISession, sess)

            return user

    class TerminalSessionTransport_getPeer(object):
        """
        Taken from twisted's TerminalSessionTransport which doesn't
        provide getPeer to the transport.  This one does.

        """

        noisy = False

        def __init__(self, proto, chainedProtocol, avatar, width, height):
            self.proto = proto
            self.avatar = avatar
            self.chainedProtocol = chainedProtocol

            session = self.proto.session

            self.proto.makeConnection(
                _Glue(
                    write=self.chainedProtocol.dataReceived,
                    loseConnection=lambda: avatar.conn.sendClose(session),
                    name="SSH Proto Transport",
                )
            )

            def loseConnection():
                self.proto.loseConnection()

            def getPeer():
                return session.conn.transport.transport.getPeer()

            self.chainedProtocol.makeConnection(
                _Glue(
                    getPeer=getPeer,
                    write=self.proto.write,
                    loseConnection=loseConnection,
                    name="Chained Proto Transport",
                )
            )

            self.chainedProtocol.terminalProtocol.terminalSize(width, height)

    def getKeyPair(pubkeyfile, privkeyfile):
        """
        This function looks for RSA keypair files in the current directory. If they
        do not exist, the keypair is created.
        """

        if not (os.path.exists(pubkeyfile) and os.path.exists(privkeyfile)):
            # No keypair exists. Generate a new RSA keypair
            from cryptography.hazmat.backends import default_backend
            from cryptography.hazmat.primitives.asymmetric import rsa

            rsa_key = Key(
                rsa.generate_private_key(
                    public_exponent=65537, key_size=_KEY_LENGTH, backend=default_backend()
                )
            )
            public_key_string = rsa_key.public().toString(type="OPENSSH").decode()
            private_key_string = rsa_key.toString(type="OPENSSH").decode()

            # save keys for the future.
            with open(privkeyfile, "wt") as pfile:
                pfile.write(private_key_string)
                print("Created SSH private key in '{}'".format(_PRIVATE_KEY_FILE))
            with open(pubkeyfile, "wt") as pfile:
                pfile.write(public_key_string)
                print("Created SSH public key in '{}'".format(_PUBLIC_KEY_FILE))
        else:
            with open(pubkeyfile) as pfile:
                public_key_string = pfile.read()
            with open(privkeyfile) as pfile:
                private_key_string = pfile.read()

        return Key.fromString(public_key_string), Key.fromString(private_key_string)

    def makeFactory(configdict):
        """
        Creates the ssh server factory.
        """

        def chainProtocolFactory(username=None):
            return insults.ServerProtocol(
                configdict["protocolFactory"],
                *configdict.get("protocolConfigdict", (username,)),
                **configdict.get("protocolKwArgs", {}),
            )

        rlm = PassAvatarIdTerminalRealm()
        rlm.transportFactory = TerminalSessionTransport_getPeer
        rlm.chainedProtocolFactory = chainProtocolFactory
        factory = ConchFactory(Portal(rlm))
        factory.sessionhandler = configdict["sessions"]

        try:
            # create/get RSA keypair
            publicKey, privateKey = getKeyPair(_PUBLIC_KEY_FILE, _PRIVATE_KEY_FILE)
            factory.publicKeys = {b"ssh-rsa": publicKey}
            factory.privateKeys = {b"ssh-rsa": privateKey}
        except Exception as err:
            print(_NO_AUTOGEN.format(err=err))

        factory.services = factory.services.copy()
        factory.services["ssh-userauth"] = ExtraInfoAuthServer

        factory.portal.registerChecker(AccountDBPasswordChecker(factory))

        return factory

Note

You are reading an old version of the Evennia documentation. The latest version is here

.