Synnefo » snf-ganeti

#!/usr/bin/python

#

# Copyright (C) 2006, 2007 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Module encapsulating ssh functionality.

"""

import os

from ganeti import logger

from ganeti import utils

from ganeti import errors

from ganeti import constants

__all__ = ["SSHCall", "CopyFileToNode", "VerifyNodeHostname",

           "KNOWN_HOSTS_OPTS", "BATCH_MODE_OPTS", "ASK_KEY_OPTS"]

KNOWN_HOSTS_OPTS = [

  "-oGlobalKnownHostsFile=%s" % constants.SSH_KNOWN_HOSTS_FILE,

  "-oUserKnownHostsFile=/dev/null",

  ]

# Note: BATCH_MODE conflicts with ASK_KEY

BATCH_MODE_OPTS = [

  "-oEscapeChar=none",

  "-oBatchMode=yes",

  "-oStrictHostKeyChecking=yes",

  ]

ASK_KEY_OPTS = [

  "-oStrictHostKeyChecking=ask",

  "-oEscapeChar=none",

  "-oHashKnownHosts=no",

  ]

def BuildSSHCmd(hostname, user, command, batch=True, ask_key=False):

  """Build an ssh string to execute a command on a remote node.

  Args:

    hostname: the target host, string

    user: user to auth as

    command: the command

    batch: if true, ssh will run in batch mode with no prompting

    ask_key: if true, ssh will run with StrictHostKeyChecking=ask, so that

             we can connect to an unknown host (not valid in batch mode)

  Returns:

    The ssh call to run 'command' on the remote host.

  """

  argv = ["ssh", "-q"]

  argv.extend(KNOWN_HOSTS_OPTS)

  if batch:

    # if we are in batch mode, we can't ask the key

    if ask_key:

      raise errors.ProgrammerError("SSH call requested conflicting options")

    argv.extend(BATCH_MODE_OPTS)

  elif ask_key:

    argv.extend(ASK_KEY_OPTS)

  argv.extend(["%s@%s" % (user, hostname), command])

  return argv

def SSHCall(hostname, user, command, batch=True, ask_key=False):

  """Execute a command on a remote node.

  This method has the same return value as `utils.RunCmd()`, which it

  uses to launch ssh.

  Args:

    hostname: the target host, string

    user: user to auth as

    command: the command

    batch: if true, ssh will run in batch mode with no prompting

    ask_key: if true, ssh will run with StrictHostKeyChecking=ask, so that

             we can connect to an unknown host (not valid in batch mode)

  Returns:

    `utils.RunResult` as for `utils.RunCmd()`

  """

  return utils.RunCmd(BuildSSHCmd(hostname, user, command, batch=batch, ask_key=ask_key))

def CopyFileToNode(node, filename):

  """Copy a file to another node with scp.

  Args:

    node: node in the cluster

    filename: absolute pathname of a local file

  Returns:

    success: True/False

  """

  if not os.path.isfile(filename):

    logger.Error("file %s does not exist" % (filename))

    return False

  if not os.path.isabs(filename):

    logger.Error("file %s must be an absolute path" % (filename))

    return False

  command = ["scp", "-q", "-p"]

  command.extend(KNOWN_HOSTS_OPTS)

  command.extend(BATCH_MODE_OPTS)

  command.append(filename)

  command.append("%s:%s" % (node, filename))

  result = utils.RunCmd(command)

  if result.failed:

    logger.Error("copy to node %s failed (%s) error %s,"

                 " command was %s" %

                 (node, result.fail_reason, result.output, result.cmd))

  return not result.failed

def VerifyNodeHostname(node):

  """Verify hostname consistency via SSH.

  This functions connects via ssh to a node and compares the hostname

  reported by the node to the name with have (the one that we

  connected to).

  This is used to detect problems in ssh known_hosts files

  (conflicting known hosts) and incosistencies between dns/hosts

  entries and local machine names

  Args:

    node: nodename of a host to check. can be short or full qualified hostname

  Returns:

    (success, detail)

    where

      success: True/False

      detail: String with details

  """

  retval = SSHCall(node, 'root', 'hostname')

  if retval.failed:

    msg = "ssh problem"

    output = retval.output

    if output:

      msg += ": %s" % output

    return False, msg

  remotehostname = retval.stdout.strip()

  if not remotehostname or remotehostname != node:

    return False, "hostname mismatch, got %s" % remotehostname

  return True, "host matches"