# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible 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 3 of the License, or
# (at your option) any later version.
#
# Ansible 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 Ansible.  If not, see <http://www.gnu.org/licenses/>.
#
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import gettext
import fcntl
import hmac
import os
import pipes
import pty
import pwd
import random
import re
import select
import shlex
import subprocess
import time

from hashlib import sha1

from ansible import constants as C
from ansible.errors import AnsibleError, AnsibleConnectionFailure, AnsibleFileNotFound
from ansible.plugins.connections import ConnectionBase

class Connection(ConnectionBase):
    ''' ssh based connections '''

    has_pipelining = True
    become_methods = frozenset(C.BECOME_METHODS).difference(['runas'])

    def __init__(self, *args, **kwargs):
        # SSH connection specific init stuff
        self._common_args = []
        self.HASHED_KEY_MAGIC = "|1|"

        # FIXME: move the lockfile locations to ActionBase?
        #fcntl.lockf(self.runner.process_lockfile, fcntl.LOCK_EX)
        #self.cp_dir = utils.prepare_writeable_dir('$HOME/.ansible/cp',mode=0700)
        self._cp_dir = '/tmp'
        #fcntl.lockf(self.runner.process_lockfile, fcntl.LOCK_UN)

        super(Connection, self).__init__(*args, **kwargs)

        # FIXME: make this work, should be set from connection info
        self._ipv6 = False
        self.host = self._play_context.remote_addr
        if self._ipv6:
            self.host = '[%s]' % self.host

    @property
    def transport(self):
        ''' used to identify this connection object from other classes '''
        return 'ssh'

    def _connect(self):
        ''' connect to the remote host '''

        self._display.vvv("ESTABLISH SSH CONNECTION FOR USER: {0}".format(self._play_context.remote_user), host=self._play_context.remote_addr)

        if self._connected:
            return self

        extra_args = C.ANSIBLE_SSH_ARGS
        if extra_args is not None:
            # make sure there is no empty string added as this can produce weird errors
            self._common_args += [x.strip() for x in shlex.split(extra_args) if x.strip()]
        else:
            self._common_args += (
                "-o", "ControlMaster=auto",
                "-o", "ControlPersist=60s",
                "-o", "ControlPath=\"{0}\"".format(C.ANSIBLE_SSH_CONTROL_PATH % dict(directory=self._cp_dir)),
            )

        cp_in_use = False
        cp_path_set = False
        for arg in self._common_args:
            if "ControlPersist" in arg:
                cp_in_use = True
            if "ControlPath" in arg:
                cp_path_set = True

        if cp_in_use and not cp_path_set:
            self._common_args += ("-o", "ControlPath=\"{0}\"".format(
                C.ANSIBLE_SSH_CONTROL_PATH % dict(directory=self._cp_dir))
            )

        if not C.HOST_KEY_CHECKING:
            self._common_args += ("-o", "StrictHostKeyChecking=no")

        if self._play_context.port is not None:
            self._common_args += ("-o", "Port={0}".format(self._play_context.port))
        if self._play_context.private_key_file is not None:
            self._common_args += ("-o", "IdentityFile=\"{0}\"".format(os.path.expanduser(self._play_context.private_key_file)))
        if self._play_context.password:
            self._common_args += ("-o", "GSSAPIAuthentication=no",
                                 "-o", "PubkeyAuthentication=no")
        else:
            self._common_args += ("-o", "KbdInteractiveAuthentication=no",
                                 "-o", "PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey",
                                 "-o", "PasswordAuthentication=no")
        if self._play_context.remote_user is not None and self._play_context.remote_user != pwd.getpwuid(os.geteuid())[0]:
            self._common_args += ("-o", "User={0}".format(self._play_context.remote_user))
        self._common_args += ("-o", "ConnectTimeout={0}".format(self._play_context.timeout))

        self._connected = True

        return self

    def _run(self, cmd, indata):
        if indata:
            # do not use pseudo-pty
            p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
            stdin = p.stdin
        else:
            # try to use upseudo-pty
            try:
                # Make sure stdin is a proper (pseudo) pty to avoid: tcgetattr errors
                master, slave = pty.openpty()
                p = subprocess.Popen(cmd, stdin=slave, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                stdin = os.fdopen(master, 'w', 0)
                os.close(slave)
            except:
                p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                stdin = p.stdin

        return (p, stdin)

    def _password_cmd(self):
        if self._play_context.password:
            try:
                p = subprocess.Popen(["sshpass"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                p.communicate()
            except OSError:
                raise AnsibleError("to use the 'ssh' connection type with passwords, you must install the sshpass program")
            (self.rfd, self.wfd) = os.pipe()
            return ["sshpass", "-d{0}".format(self.rfd)]
        return []

    def _send_password(self):
        if self._play_context.password:
            os.close(self.rfd)
            os.write(self.wfd, "{0}\n".format(self._play_context.password))
            os.close(self.wfd)

    def _communicate(self, p, stdin, indata, sudoable=True):
        fcntl.fcntl(p.stdout, fcntl.F_SETFL, fcntl.fcntl(p.stdout, fcntl.F_GETFL) & ~os.O_NONBLOCK)
        fcntl.fcntl(p.stderr, fcntl.F_SETFL, fcntl.fcntl(p.stderr, fcntl.F_GETFL) & ~os.O_NONBLOCK)
        # We can't use p.communicate here because the ControlMaster may have stdout open as well
        stdout = ''
        stderr = ''
        rpipes = [p.stdout, p.stderr]
        if indata:
            try:
                stdin.write(indata)
                stdin.close()
            except:
                raise AnsibleConnectionFailure('SSH Error: data could not be sent to the remote host. Make sure this host can be reached over ssh')
        # Read stdout/stderr from process
        while True:
            rfd, wfd, efd = select.select(rpipes, [], rpipes, 1)

            # fail early if the become password is wrong
            if self._play_context.become and sudoable:
                if self._play_context.become_pass:
                    self.check_incorrect_password(stdout)
                elif self.check_password_prompt(stdout):
                    raise AnsibleError('Missing %s password' % self._play_context.become_method)

            if p.stderr in rfd:
                dat = os.read(p.stderr.fileno(), 9000)
                stderr += dat
                if dat == '':
                    rpipes.remove(p.stderr)
            elif p.stdout in rfd:
                dat = os.read(p.stdout.fileno(), 9000)
                stdout += dat
                if dat == '':
                    rpipes.remove(p.stdout)

            # only break out if no pipes are left to read or
            # the pipes are completely read and
            # the process is terminated
            if (not rpipes or not rfd) and p.poll() is not None:
                break
            # No pipes are left to read but process is not yet terminated
            # Only then it is safe to wait for the process to be finished
            # NOTE: Actually p.poll() is always None here if rpipes is empty
            elif not rpipes and p.poll() == None:
                p.wait()
                # The process is terminated. Since no pipes to read from are
                # left, there is no need to call select() again.
                break
        # close stdin after process is terminated and stdout/stderr are read
        # completely (see also issue #848)
        stdin.close()
        return (p.returncode, stdout, stderr)

    def not_in_host_file(self, host):
        if 'USER' in os.environ:
            user_host_file = os.path.expandvars("~${USER}/.ssh/known_hosts")
        else:
            user_host_file = "~/.ssh/known_hosts"
        user_host_file = os.path.expanduser(user_host_file)

        host_file_list = []
        host_file_list.append(user_host_file)
        host_file_list.append("/etc/ssh/ssh_known_hosts")
        host_file_list.append("/etc/ssh/ssh_known_hosts2")

        hfiles_not_found = 0
        for hf in host_file_list:
            if not os.path.exists(hf):
                hfiles_not_found += 1
                continue
            try:
                host_fh = open(hf)
            except IOError as e:
                hfiles_not_found += 1
                continue
            else:
                data = host_fh.read()
                host_fh.close()

            for line in data.split("\n"):
                if line is None or " " not in line:
                    continue
                tokens = line.split()
                if not tokens:
                    continue

                if isinstance(tokens, list) and tokens: # skip invalid hostlines
                    if tokens[0].find(self.HASHED_KEY_MAGIC) == 0:
                        # this is a hashed known host entry
                        try:
                            (kn_salt,kn_host) = tokens[0][len(self.HASHED_KEY_MAGIC):].split("|",2)
                            hash = hmac.new(kn_salt.decode('base64'), digestmod=sha1)
                            hash.update(host)
                            if hash.digest() == kn_host.decode('base64'):
                                return False
                        except:
                            # invalid hashed host key, skip it
                            continue
                    else:
                        # standard host file entry
                        if host in tokens[0]:
                            return False

        if (hfiles_not_found == len(host_file_list)):
            self._display.vvv("EXEC previous known host file not found for {0}".format(host))
        return True

    def lock_host_keys(self, lock):

        if C.HOST_KEY_CHECKING and  self.not_in_host_file(self.host):
            if lock:
               action = fcntl.LOCK_EX
            else:
               action = fcntl.LOCK_UN

            # lock around the initial SSH connectivity so the user prompt about whether to add
            # the host to known hosts is not intermingled with multiprocess output.
        # FIXME: move the locations of these lock files, same as init above, these came from runner, probably need to be in task_executor
        #    fcntl.lockf(self.process_lockfile, action)
        #    fcntl.lockf(self.output_lockfile, action)

    def exec_command(self, *args, **kwargs):
        """
        Wrapper around _exec_command to retry in the case of an ssh failure

        Will retry if:
        * an exception is caught
        * ssh returns 255
        Will not retry if
        * remaining_tries is <2
        * retries limit reached
        """

        remaining_tries = int(C.ANSIBLE_SSH_RETRIES) + 1
        cmd_summary = "%s..." % args[0]
        for attempt in xrange(remaining_tries):
            try:
                return_tuple = self._exec_command(*args, **kwargs)
                # 0 = success
                # 1-254 = remote command return code
                # 255 = failure from the ssh command itself
                if return_tuple[0] != 255 or attempt == (remaining_tries - 1):
                    break
                else:
                    raise AnsibleConnectionFailure("Failed to connect to the host via ssh.")
            except (AnsibleConnectionFailure, Exception) as e:
                if attempt == remaining_tries - 1:
                    raise e
                else:
                    pause = 2 ** attempt - 1
                    if pause > 30:
                        pause = 30

                    if isinstance(e, AnsibleConnectionFailure):
                        msg = "ssh_retry: attempt: %d, ssh return code is 255. cmd (%s), pausing for %d seconds" % (attempt, cmd_summary, pause)
                    else:
                        msg = "ssh_retry: attempt: %d, caught exception(%s) from cmd (%s), pausing for %d seconds" % (attempt, e, cmd_summary, pause)

                    self._display.vv(msg)

                    time.sleep(pause)
                    continue


        return return_tuple

    def _exec_command(self, cmd, tmp_path, in_data=None, sudoable=True):
        ''' run a command on the remote host '''

        super(Connection, self).exec_command(cmd, tmp_path, in_data=in_data, sudoable=sudoable)

        ssh_cmd = self._password_cmd()
        ssh_cmd += ("ssh", "-C")
        if not in_data:
            # we can only use tty when we are not pipelining the modules. piping data into /usr/bin/python
            # inside a tty automatically invokes the python interactive-mode but the modules are not
            # compatible with the interactive-mode ("unexpected indent" mainly because of empty lines)
            ssh_cmd.append("-tt")
        if self._play_context.verbosity > 3:
            ssh_cmd.append("-vvv")
        else:
            ssh_cmd.append("-q")
        ssh_cmd += self._common_args

        if self._ipv6:
            ssh_cmd += ['-6']
        ssh_cmd.append(self.host)

        ssh_cmd.append(cmd)
        self._display.vvv("EXEC {0}".format(' '.join(ssh_cmd)), host=self.host)

        self.lock_host_keys(True)

        # create process
        (p, stdin) = self._run(ssh_cmd, in_data)

        self._send_password()

        no_prompt_out = ''
        no_prompt_err = ''

        if self._play_context.prompt:
            '''
                Several cases are handled for privileges with password
                * NOPASSWD (tty & no-tty): detect success_key on stdout
                * without NOPASSWD:
                  * detect prompt on stdout (tty)
                  * detect prompt on stderr (no-tty)
            '''

            self._display.debug("Handling privilege escalation password prompt.")

            if self._play_context.become and self._play_context.become_pass:

                fcntl.fcntl(p.stdout, fcntl.F_SETFL, fcntl.fcntl(p.stdout, fcntl.F_GETFL) | os.O_NONBLOCK)
                fcntl.fcntl(p.stderr, fcntl.F_SETFL, fcntl.fcntl(p.stderr, fcntl.F_GETFL) | os.O_NONBLOCK)

                become_output = ''
                become_errput = ''
                while True:
                    self._display.debug('Waiting for Privilege Escalation input')
                    if self.check_become_success(become_output + become_errput) or self.check_password_prompt(become_output + become_errput):
                        break

                    rfd, wfd, efd = select.select([p.stdout, p.stderr], [], [p.stdout], self._play_context.timeout)
                    if not rfd:
                        # timeout. wrap up process communication
                        stdout, stderr = p.communicate()
                        raise AnsibleError('Connection error waiting for privilege escalation password prompt: %s' % become_output)

                    elif p.stderr in rfd:
                        chunk = p.stderr.read()
                        become_errput += chunk
                        self.check_incorrect_password(become_errput)

                    elif p.stdout in rfd:
                        chunk = p.stdout.read()
                        become_output += chunk

                    if not chunk:
                        raise AnsibleError('Connection closed waiting for privilege escalation password prompt: %s ' % become_output)

                if not self.check_become_success(become_output + become_errput):
                    self._display.debug("Sending privilege escalation password.")
                    stdin.write(self._play_context.become_pass + '\n')
                else:
                    no_prompt_out = become_output
                    no_prompt_err = become_errput


        (returncode, stdout, stderr) = self._communicate(p, stdin, in_data, sudoable=sudoable)

        self.lock_host_keys(False)

        controlpersisterror = 'Bad configuration option: ControlPersist' in stderr or 'unknown configuration option: ControlPersist' in stderr

        if C.HOST_KEY_CHECKING:
            if ssh_cmd[0] == "sshpass" and p.returncode == 6:
                raise AnsibleError('Using a SSH password instead of a key is not possible because Host Key checking is enabled and sshpass does not support this.  Please add this host\'s fingerprint to your known_hosts file to manage this host.')

        if p.returncode != 0 and controlpersisterror:
            raise AnsibleError('using -c ssh on certain older ssh versions may not support ControlPersist, set ANSIBLE_SSH_ARGS="" (or ssh_args in [ssh_connection] section of the config file) before running again')
        # FIXME: module name isn't in runner
        #if p.returncode == 255 and (in_data or self.runner.module_name == 'raw'):
        if p.returncode == 255 and in_data:
            raise AnsibleConnectionFailure('SSH Error: data could not be sent to the remote host. Make sure this host can be reached over ssh')

        return (p.returncode, '', no_prompt_out + stdout, no_prompt_err + stderr)

    def put_file(self, in_path, out_path):
        ''' transfer a file from local to remote '''

        super(Connection, self).put_file(in_path, out_path)

        self._display.vvv("PUT {0} TO {1}".format(in_path, out_path), host=self.host)
        if not os.path.exists(in_path):
            raise AnsibleFileNotFound("file or module does not exist: {0}".format(in_path))
        cmd = self._password_cmd()

        if C.DEFAULT_SCP_IF_SSH:
            cmd.append('scp')
            cmd.extend(self._common_args)
            cmd.extend([in_path, '{0}:{1}'.format(self.host, pipes.quote(out_path))])
            indata = None
        else:
            cmd.append('sftp')
            cmd.extend(self._common_args)
            cmd.append(self.host)
            indata = "put {0} {1}\n".format(pipes.quote(in_path), pipes.quote(out_path))

        (p, stdin) = self._run(cmd, indata)

        self._send_password()

        (returncode, stdout, stderr) = self._communicate(p, stdin, indata)

        if returncode != 0:
            raise AnsibleError("failed to transfer file to {0}:\n{1}\n{2}".format(out_path, stdout, stderr))

    def fetch_file(self, in_path, out_path):
        ''' fetch a file from remote to local '''

        super(Connection, self).fetch_file(in_path, out_path)

        self._display.vvv("FETCH {0} TO {1}".format(in_path, out_path), host=self.host)
        cmd = self._password_cmd()


        if C.DEFAULT_SCP_IF_SSH:
            cmd.append('scp')
            cmd.extend(self._common_args)
            cmd.extend(['{0}:{1}'.format(self.host, in_path), out_path])
            indata = None
        else:
            cmd.append('sftp')
            # sftp batch mode allows us to correctly catch failed transfers,
            # but can be disabled if for some reason the client side doesn't
            # support the option
            if C.DEFAULT_SFTP_BATCH_MODE:
                cmd.append('-b')
                cmd.append('-')
            cmd.extend(self._common_args)
            cmd.append(self.host)
            indata = "get {0} {1}\n".format(in_path, out_path)

        p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        self._send_password()
        stdout, stderr = p.communicate(indata)

        if p.returncode != 0:
            raise AnsibleError("failed to transfer file from {0}:\n{1}\n{2}".format(in_path, stdout, stderr))

    def close(self):
        ''' not applicable since we're executing openssh binaries '''

        if self._connected:

            if 'ControlMaster' in self._common_args:
                cmd = ['ssh','-O','stop']
                cmd.extend(self._common_args)
                cmd.append(self._play_context.remote_addr)

                p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                stdout, stderr = p.communicate()

            self._connected = False