Source code for labgrid.util.ssh

# pylint: disable=no-member
import tempfile
import logging
import subprocess
import os
from select import select
from functools import wraps

import attr
from ..driver.exception import ExecutionError

from .helper import get_free_port

__all__ = ['sshmanager', 'SSHConnection', 'ForwardError']


@attr.s
class SSHConnectionManager:
    """The SSHConnectionManager manages multiple SSH connections. This class
    should not be directly instantiated, use the exported sshmanager from this
    module instead.
    """
    _connections = attr.ib(
        default=attr.Factory(dict),
        init=False,
        validator=attr.validators.optional(attr.validators.instance_of(dict))
    )

    def __attrs_post_init__(self):
        self.logger = logging.getLogger("{}".format(self))

    def get(self, host: str):
        """Retrieve or create a new connection to a given host

        Arguments:
            host (str): host to retrieve the connection for

        Returns:
            :obj:`SSHConnection`: the SSHConnection for the host"""
        instance = self._connections.get(host)
        if instance is None:
            # pylint: disable=unsupported-assignment-operation
            self.logger.debug("Creating SSHConnection for %s", host)
            instance = SSHConnection(host)
            instance.connect()
            self._connections[host] = instance
        return instance

    def add_connection(self, connection):
        """Add an existing SSHConnection to the manager.
        This is useful for manually created connections which should also be
        available via the manager.

        Arguments:
            connection (:obj:`SSHConnection`): SSHconnection to add to the manager
        """
        # pylint: disable=unsupported-assignment-operation
        assert isinstance(connection, SSHConnection)
        if connection.host not in self._connections:
            self._connections[connection.host] = connection

    def remove_connection(self, connection):
        # pylint: disable=unsupported-assignment-operation
        assert isinstance(connection, SSHConnection)
        if connection.isconnected():
            raise ExecutionError("Can't remove connected connection")
        del self._connections[connection.host]

    def remove_by_name(self, name):
        # pylint: disable=unsupported-assignment-operation
        del self._connections[name]

    def open(self, host):
        return self.get(host)

    def close(self, host):
        con = self.get(host)
        con.disconnect()
        self.remove_connection(con)

    def request_forward(self, host, dest, port):
        con = self.get(host)
        return con.add_port_forward(dest, port)

    def remove_forward(self, host, dest, port):
        con = self.get(host)
        con.remove_port_forward(dest, port)

    def put_file(self, host, local_file, remote_file):
        con = self.get(host)
        con.put_file(local_file, remote_file)

    def get_file(self, host, remote_file, local_file):
        con = self.get(host)
        con.get_file(remote_file, local_file)

    def close_all(self):
        """Close all open connections and remove them from the manager """
        for name, connection in self._connections.items():
            if connection.isconnected():
                connection.disconnect()
        names = self._connections.copy().keys()
        for name in names:
            self.remove_by_name(name)


[docs]@attr.s class SSHConnection: """SSHConnections are individual connections to hosts managed by a control socket. In addition to command execution this class also provides an interface to manage port forwardings. These are used in the remote infrastructure to tunnel multiple connections over one SSH link. A public identity infrastructure is assumed, no extra username or passwords are supported.""" host = attr.ib(validator=attr.validators.instance_of(str)) _connected = attr.ib( default=False, init=False, validator=attr.validators.instance_of(bool) ) _tmpdir = attr.ib( default=attr.Factory(lambda: tempfile.mkdtemp(prefix="labgrid-connection-")), init=False, validator=attr.validators.instance_of(str) ) _forwards = attr.ib(init=False, default=attr.Factory(dict))
[docs] def __attrs_post_init__(self): self._logger = logging.getLogger("{}".format(self)) self._socket = None self._master = None self._keepalive = None
@staticmethod def _get_ssh_base_args(): return ["-x", "-o", "LogLevel=ERROR", "-o", "PasswordAuthentication=no"] def _get_ssh_control_args(self): if self._socket: return [ "-o", "ControlMaster=no", "-o", "ControlPath={}".format(self._socket), ] return [] def _get_ssh_args(self): args = SSHConnection._get_ssh_base_args() args += self._get_ssh_control_args() return args def _open_connection(self): """Internal function which appends the control socket and checks if the connection is already open""" if self._check_external_master(): self._logger.info("Using existing SSH connection to %s", self.host) else: self._start_own_master() self._logger.info("Created new SSH connection to %s", self.host) self._start_keepalive() self._connected = True def _run_socket_command(self, command, forward=None): "Internal function to send a command to the control socket" complete_cmd = ["ssh"] + self._get_ssh_args() complete_cmd += ["-O", command] if forward: for item in forward: complete_cmd.append(item) complete_cmd.append(self.host) res = subprocess.check_call( complete_cmd, stdin=subprocess.DEVNULL, timeout=2, ) return res def _check_connected(func): # pylint: disable=no-self-argument """Check if an SSHConnection is connected as a decorator""" @wraps(func) def wrapper(self, *_args, **_kwargs): if not self.isconnected(): raise ExecutionError( "{} can not be called ({} is not connected)".format( func.__qualname__, self ) ) return func(self, *_args, **_kwargs) # pylint: disable=not-callable return wrapper
[docs] @_check_connected def get_prefix(self): return ["ssh"] + self._get_ssh_args() + [self.host]
[docs] @_check_connected def run(self, command, *, codec="utf-8", decodeerrors="strict", force_tty=False, stderr_merge=False, stderr_loglevel=None, stdout_loglevel=None): """Run a command over the SSHConnection Args: command (string): The command to run codec (string, optional): output encoding. Defaults to "utf-8". decodeerrors (string, optional): behavior on decode errors. Defaults to "strict". Refer to stdtypes' bytes.decode for details. force_tty (bool, optional): force allocate a tty (ssh -tt). Defaults to False stderr_merge (bool, optional): merge ssh subprocess stderr into stdout. Defaults to False. stdout_loglevel (int, optional): log stdout with specific log level as well. Defaults to None, i.e. don't log. stderr_loglevel (int, optional): log stderr with specific log level as well. Defaults to None, i.e. don't log. returns: (stdout, stderr, returncode) """ complete_cmd = ["ssh"] + self._get_ssh_args() if force_tty: complete_cmd += ["-tt"] complete_cmd += [self.host, command] self._logger.debug("Sending command: %s", complete_cmd) if stderr_merge: stderr_pipe = subprocess.STDOUT else: stderr_pipe = subprocess.PIPE try: sub = subprocess.Popen( complete_cmd, stdout=subprocess.PIPE, stderr=stderr_pipe, stdin=subprocess.DEVNULL ) except: raise ExecutionError( "error executing command: {}".format(complete_cmd) ) stdout = [] stderr = [] readable = { sub.stdout.fileno(): (sub.stdout, stdout, stdout_loglevel), } if sub.stderr is not None: readable[sub.stderr.fileno()] = (sub.stderr, stderr, stderr_loglevel) while readable: for fd in select(readable, [], [])[0]: stream, output, loglevel = readable[fd] line = stream.readline().decode(codec, decodeerrors) if line == "": # EOF del readable[fd] else: line = line.rstrip('\n') output.append(line) if loglevel is not None: self._logger.log(loglevel, line) return stdout, stderr, sub.wait()
[docs] def run_check(self, command, *, codec="utf-8", decodeerrors="strict", force_tty=False, stderr_merge=False, stderr_loglevel=None, stdout_loglevel=None): """ Runs a command over the SSHConnection returns the output if successful, raises ExecutionError otherwise. Except for the means of returning the value, this is equivalent to run. Args: command (string): The command to run codec (string, optional): output encoding. Defaults to "utf-8". decodeerrors (string, optional): behavior on decode errors. Defaults to "strict". Refer to stdtypes' bytes.decode for details. force_tty (bool, optional): force allocate a tty (ssh -tt). Defaults to False stderr_merge (bool, optional): merge ssh subprocess stderr into stdout. Defaults to False. stdout_loglevel (int, optional): log stdout with specific log level as well. Defaults to None, i.e. don't log. stderr_loglevel (int, optional): log stderr with specific log level as well. Defaults to None, i.e. don't log. Returns: List[str]: stdout of the executed command if successful and otherwise an ExecutionError Exception """ stdout, stderr, exitcode = self.run( command, codec=codec, decodeerrors=decodeerrors, force_tty=force_tty, stderr_merge=stderr_merge, stdout_loglevel=stdout_loglevel, stderr_loglevel=stderr_loglevel ) if exitcode != 0: raise ExecutionError(command, stdout, stderr) return stdout
[docs] @_check_connected def get_file(self, remote_file, local_file): """Get a file from the remote host""" complete_cmd = ["scp"] + self._get_ssh_control_args() complete_cmd += [ "{}:{}".format(self.host, remote_file), "{}".format(local_file) ] self._logger.debug("Running command: %s", complete_cmd) subprocess.check_call( complete_cmd, stdin=subprocess.DEVNULL, )
[docs] @_check_connected def put_file(self, local_file, remote_path): """Put a file onto the remote host""" complete_cmd = ["rsync", "--compress=1", "--sparse", "--copy-links", "--verbose", "--progress", "--times", "-e", " ".join(['ssh'] + self._get_ssh_args())] complete_cmd += [ "{}".format(local_file), "{}:{}".format(self.host, remote_path) ] self._logger.debug("Running command: %s", complete_cmd) subprocess.check_call( complete_cmd, stdin=subprocess.DEVNULL, )
[docs] @_check_connected def add_port_forward(self, remote_host, remote_port): """forward command""" local_port = get_free_port() destination = "{}:{}".format(remote_host, remote_port) # pylint: disable=not-an-iterable if destination in self._forwards: return self._forwards[destination] self._run_socket_command( "forward", [ "-L" "{local}:{destination}". format(local=local_port, destination=destination) ] ) self._forwards[destination] = local_port return local_port
[docs] @_check_connected def remove_port_forward(self, remote_host, remote_port): """cancel command""" destination = "{}:{}".format(remote_host, remote_port) local_port = self._forwards.pop(destination, None) # pylint: disable=not-an-iterable if local_port is None: raise ForwardError("Forward does not exist") self._run_socket_command( "cancel", [ "-L" "{local}:localhost:{remote}". format(local=local_port, remote=remote_port) ] )
[docs] def connect(self): if not self._connected: self._open_connection()
[docs] @_check_connected def disconnect(self): self._disconnect()
[docs] def isconnected(self): return self._connected and self._check_keepalive()
def _check_external_master(self): args = ["ssh", "-O", "check", "{}".format(self.host)] # We don't want to confuse the use with SSHs output here, so we need to # capture and parse it. proc = subprocess.Popen( args, stdin=subprocess.DEVNULL, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, ) stdout, _ = proc.communicate(timeout=60) check = proc.wait() if check == 0: self._logger.debug("Found existing control socket") return True if b"No such file or directory" in stdout: self._logger.debug("No existing control socket found") return False self._logger.debug("Unexpected ssh check output '%s'", stdout) return False def _start_own_master(self): """Starts a controlmaster connection in a temporary directory.""" control = os.path.join(self._tmpdir, 'control-{}'.format(self.host)) args = ["ssh"] + SSHConnection._get_ssh_base_args() args += [ "-n", "-MN", "-o", "ConnectTimeout=30", "-o", "ControlPersist=300", "-o", "ControlMaster=yes", "-o", "ControlPath={}".format(control), # We don't want to ask the user to confirm host keys here. "-o", "StrictHostKeyChecking=yes", self.host, ] assert self._master is None self._master = subprocess.Popen( args, stdin=subprocess.DEVNULL, stdout=subprocess.PIPE, stderr=subprocess.PIPE, ) try: if self._master.wait(timeout=30) != 0: raise ExecutionError( "failed to connect to {} with args {}, returncode={} {},{} ".format( self.host, args, self._master.wait(), self._master.stdout.readlines(), self._master.stderr.readlines() ) ) except subprocess.TimeoutExpired: raise ExecutionError( "failed to connect (timeout) to {} with args {} {},{}".format( self.host, args, self._master.stdout.readlines(), self._master.stderr.readlines() ) ) if not os.path.exists(control): raise ExecutionError("no control socket to {}".format(self.host)) self._socket = control self._logger.debug('Connected to %s', self.host) def _stop_own_master(self): assert self._socket is not None assert self._master is not None try: self._run_socket_command("cancel") self._run_socket_command("exit") # if the master doesn't terminate in less than 60 seconds, # something is very wrong self._master.wait(timeout=60) finally: self._socket = None self._master = None def _start_keepalive(self): """Starts a keepalive connection via the own or external master.""" args = ["ssh"] + self._get_ssh_args() + [self.host, "cat"] assert self._keepalive is None self._keepalive = subprocess.Popen( args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, ) self._logger.debug('Started keepalive for %s', self.host) def _check_keepalive(self): return self._keepalive.poll() is None def _stop_keepalive(self): assert self._keepalive is not None self._logger.debug('Stopping keepalive for %s', self.host) try: self._keepalive.communicate(timeout=60) except subprocess.TimeoutExpired: self._keepalive.kill() try: self._keepalive.wait(timeout=60) finally: self._keepalive = None def _disconnect(self): assert self._connected try: if self._socket: self._logger.info("Closing SSH connection to %s", self.host) self._stop_keepalive() self._stop_own_master() finally: self._connected = False
sshmanager = SSHConnectionManager()
[docs]@attr.s class ForwardError(Exception): msg = attr.ib(validator=attr.validators.instance_of(str))