Synnefo » snf-ganeti

#

#

# 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

def GetUserFiles(user, mkdir=False):

  """Return the paths of a user's ssh files.

  The function will return a triplet (priv_key_path, pub_key_path,

  auth_key_path) that are used for ssh authentication. Currently, the

  keys used are DSA keys, so this function will return:

  (~user/.ssh/id_dsa, ~user/.ssh/id_dsa.pub,

  ~user/.ssh/authorized_keys).

  If the optional parameter mkdir is True, the ssh directory will be

  created if it doesn't exist.

  Regardless of the mkdir parameters, the script will raise an error

  if ~user/.ssh is not a directory.

  """

  user_dir = utils.GetHomeDir(user)

  if not user_dir:

    raise errors.OpExecError("Cannot resolve home of user %s" % user)

  ssh_dir = os.path.join(user_dir, ".ssh")

  if not os.path.lexists(ssh_dir):

    if mkdir:

      try:

        os.mkdir(ssh_dir, 0700)

      except EnvironmentError, err:

        raise errors.OpExecError("Can't create .ssh dir for user %s: %s" %

                                 (user, str(err)))

  elif not os.path.isdir(ssh_dir):

    raise errors.OpExecError("path ~%s/.ssh is not a directory" % user)

  return [os.path.join(ssh_dir, base)

          for base in ["id_dsa", "id_dsa.pub", "authorized_keys"]]

class SshRunner:

  """Wrapper for SSH commands.

  """

  def __init__(self, cluster_name):

    self.cluster_name = cluster_name

  def _BuildSshOptions(self, batch, ask_key, use_cluster_key,

                       strict_host_check):

    options = [

      "-oEscapeChar=none",

      "-oHashKnownHosts=no",

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

      "-oUserKnownHostsFile=/dev/null",

      ]

    if use_cluster_key:

      options.append("-oHostKeyAlias=%s" % self.cluster_name)

    # TODO: Too many boolean options, maybe convert them to more descriptive

    # constants.

    # Note: ask_key conflicts with batch mode

    if batch:

      if ask_key:

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

      options.append("-oBatchMode=yes")

      if strict_host_check:

        options.append("-oStrictHostKeyChecking=yes")

      else:

        options.append("-oStrictHostKeyChecking=no")

    elif ask_key:

      options.extend([

        "-oStrictHostKeyChecking=ask",

        ])

    return options

  def BuildCmd(self, hostname, user, command, batch=True, ask_key=False,

               tty=False, use_cluster_key=True, strict_host_check=True):

    """Build an ssh command 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)

      use_cluster_key: Whether to expect and use the cluster-global SSH key

      strict_host_check: Whether to check the host's SSH key at all

    Returns:

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

    """

    argv = [constants.SSH, "-q"]

    argv.extend(self._BuildSshOptions(batch, ask_key, use_cluster_key,

                                      strict_host_check))

    if tty:

      argv.append("-t")

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

    return argv

  def Run(self, *args, **kwargs):

    """Runs a command on a remote node.

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

    uses to launch ssh.

    Args:

      See SshRunner.BuildCmd.

    Returns:

      `utils.RunResult` like `utils.RunCmd()`

    """

    return utils.RunCmd(self.BuildCmd(*args, **kwargs))

  def CopyFileToNode(self, 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.isabs(filename):

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

      return False

    if not os.path.isfile(filename):

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

      return False

    command = [constants.SCP, "-q", "-p"]

    command.extend(self._BuildSshOptions(True, False, True, True))

    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(self, 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 = self.Run(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"

def WriteKnownHostsFile(cfg, file_name):

  """Writes the cluster-wide equally known_hosts file.

  """

  utils.WriteFile(file_name, mode=0700,

                  data="%s ssh-rsa %s\n" % (cfg.GetClusterName(),

                                            cfg.GetHostKey()))