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control_persist.py
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# Copyright Red Hat 2021, Jake Hunsaker <jhunsake@redhat.com> # This file is part of the sos project: https://github.com/sosreport/sos # # This copyrighted material is made available to anyone wishing to use, # modify, copy, or redistribute it subject to the terms and conditions of # version 2 of the GNU General Public License. # # See the LICENSE file in the source distribution for further information. import os import subprocess import pexpect from sos.collector.transports import RemoteTransport from sos.collector.exceptions import (InvalidPasswordException, TimeoutPasswordAuthException, PasswordRequestException, AuthPermissionDeniedException, ConnectionException, ConnectionTimeoutException, ControlSocketMissingException, ControlPersistUnsupportedException) from sos.utilities import sos_get_command_output class SSHControlPersist(RemoteTransport): """ A transport for collect that leverages OpenSSH's ControlPersist functionality which uses control sockets to transparently keep a connection open to the remote host without needing to rebuild the SSH connection for each and every command executed on the node. This transport will by default assume the use of SSH keys, meaning keys have already been distributed to target nodes. If this is not the case, users will need to provide a password using the --password or --password-per-node option, depending on if the password to connect to all nodes is the same or not. Note that these options prevent the use of the --batch option, as they require user input. """ name = 'control_persist' def _check_for_control_persist(self): """Checks to see if the local system supported SSH ControlPersist. ControlPersist allows OpenSSH to keep a single open connection to a remote host rather than building a new session each time. This is the same feature that Ansible uses in place of paramiko, which we have a need to drop in sos collect. This check relies on feedback from the ssh binary. The command being run should always generate stderr output, but depending on what that output reads we can determine if ControlPersist is supported or not. For our purposes, a host that does not support ControlPersist is not able to run sos collect. Returns True if ControlPersist is supported, else raise Exception. """ ssh_cmd = ['ssh', '-o', 'ControlPersist'] with subprocess.Popen(ssh_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE) as cmd: _, err = cmd.communicate() err = err.decode('utf-8') if 'Bad configuration option' in err or 'Usage:' in err: raise ControlPersistUnsupportedException return True def _connect(self, password=''): # pylint: disable=too-many-branches """ Using ControlPersist, create the initial connection to the node. This will generate an OpenSSH ControlPersist socket within the tmp directory created or specified for sos collect to use. At most, we will wait 30 seconds for a connection. This involves a 15 second wait for the initial connection attempt, and a subsequent 15 second wait for a response when we supply a password. Since we connect to nodes in parallel (using the --threads value), this means that the time between 'Connecting to nodes...' and 'Beginning collection of sosreports' that users see can be up to an amount of time equal to 30*(num_nodes/threads) seconds. Returns True if session is successfully opened, else raise Exception """ try: self._check_for_control_persist() except ControlPersistUnsupportedException: self.log_error("OpenSSH ControlPersist is not locally supported. " "Please update your OpenSSH installation.") raise self.log_info('Opening SSH session to create control socket') self.control_path = f"{self.tmpdir}/.sos-collector-{self.address}" self.ssh_cmd = '' connected = False ssh_key = '' ssh_port = '' if self.opts.ssh_port != 22: ssh_port = f"-p{self.opts.ssh_port} " if self.opts.ssh_key: ssh_key = f"-i{self.opts.ssh_key}" cmd = (f"ssh {ssh_key} {ssh_port} -oControlPersist=600 " "-oControlMaster=auto -oStrictHostKeyChecking=no " f"-oControlPath={self.control_path} {self.opts.ssh_user}@" f"{self.address} \"echo Connected\"") res = pexpect.spawn(cmd, encoding='utf-8') connect_expects = [ 'Connected', 'password:', '.*Permission denied.*', '.* port .*: No route to host', '.*Could not resolve hostname.*', pexpect.TIMEOUT ] index = res.expect(connect_expects, timeout=15) if index == 0: connected = True elif index == 1: if password: pass_expects = [ 'Connected', 'Permission denied, please try again.', pexpect.TIMEOUT ] res.sendline(password) pass_index = res.expect(pass_expects, timeout=15) if pass_index == 0: connected = True elif pass_index == 1: # Note that we do not get an exitstatus here, so matching # this line means an invalid password will be reported for # both invalid passwords and invalid user names raise InvalidPasswordException elif pass_index == 2: raise TimeoutPasswordAuthException else: raise PasswordRequestException elif index == 2: raise AuthPermissionDeniedException elif index == 3: raise ConnectionException(self.address, self.opts.ssh_port) elif index == 4: raise ConnectionException(self.address) elif index == 5: raise ConnectionTimeoutException else: raise Exception(f"Unknown error, client returned {res.before}") if connected: if not os.path.exists(self.control_path): raise ControlSocketMissingException self.log_debug("Successfully created control socket at " f"{self.control_path}") return True return False def _disconnect(self): if os.path.exists(self.control_path): try: os.remove(self.control_path) return True except Exception as err: self.log_debug(f"Could not disconnect properly: {err}") return False self.log_debug("Control socket not present when attempting to " "terminate session") return False @property def connected(self): """Check if the SSH control socket exists The control socket is automatically removed by the SSH daemon in the event that the last connection to the node was greater than the timeout set by the ControlPersist option. This can happen for us if we are collecting from a large number of nodes, and the timeout expires before we start collection. """ return os.path.exists(self.control_path) @property def remote_exec(self): if not self.ssh_cmd: self.ssh_cmd = (f"ssh -oControlPath={self.control_path} " f"{self.opts.ssh_user}@{self.address}") return self.ssh_cmd def _copy_file_to_remote(self, fname, dest): cmd = (f"/usr/bin/scp -oControlPath={self.control_path} " f"{fname} {self.opts.ssh_user}@{self.address}:{dest}") res = sos_get_command_output(cmd, timeout=10) return res['status'] == 0 def _retrieve_file(self, fname, dest): cmd = (f"/usr/bin/scp -oControlPath={self.control_path} " f"{self.opts.ssh_user}@{self.address}:{fname} {dest}") res = sos_get_command_output(cmd) return res['status'] == 0 # vim: set et ts=4 sw=4 :