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# python3
# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Tunnel handles setting up connections to remote machines.
Tunnel dispatcher is a wrapper around the connection from a local UNIX socket
and a remote UNIX socket via SSH with port forwarding. This is done to
initialize the pythonic dockerpy client to run containers on the remote host by
connecting to /var/run/docker.sock (where Docker is listening). Tunnel
dispatcher sets up the local UNIX socket and calls the `ssh` command as a
subprocess, and holds a reference to that subprocess. It manages clean-up on
exit as best it can by killing the ssh subprocess and deleting the local UNIX
socket,stored in /tmp for easy cleanup in most systems if this fails.
Typical usage example:
t = Tunnel(name, **kwargs)
t.connect()
client = t.get_docker_client() #
client.containers.run("ubuntu", "echo hello world")
"""
import os
import tempfile
import time
import docker
import pexpect
SSH_TUNNEL_COMMAND = """ssh
-o GlobalKnownHostsFile=/dev/null
-o UserKnownHostsFile=/dev/null
-o StrictHostKeyChecking=no
-o IdentitiesOnly=yes
-nNT -L {filename}:/var/run/docker.sock
-i {key_path}
{username}@{hostname}"""
class Tunnel(object):
"""The tunnel object represents the tunnel via ssh.
This connects a local unix domain socket with a remote socket.
Attributes:
_filename: a temporary name of the UNIX socket prefixed by the name
argument.
_hostname: the IP or resolvable hostname of the remote host.
_username: the username of the ssh_key used to run ssh.
_key_path: path to a valid key.
_key_password: optional password to the ssh key in _key_path
_process: holds reference to the ssh subprocess created.
Returns:
The new minimum port.
Raises:
ConnectionError: If no available port is found.
"""
def __init__(self,
name: str,
hostname: str,
username: str,
key_path: str,
key_password: str = "",
**kwargs):
self._filename = tempfile.NamedTemporaryFile(prefix=name).name
self._hostname = hostname
self._username = username
self._key_path = key_path
self._key_password = key_password
self._kwargs = kwargs
self._process = None
def connect(self):
"""Connects the SSH tunnel and stores the subprocess reference in _process."""
cmd = SSH_TUNNEL_COMMAND.format(
filename=self._filename,
key_path=self._key_path,
username=self._username,
hostname=self._hostname)
self._process = pexpect.spawn(cmd, timeout=10)
# If given a password, assume we'll be asked for it.
if self._key_password:
self._process.expect(["Enter passphrase for key .*: "])
self._process.sendline(self._key_password)
while True:
# Wait for the tunnel to appear.
if self._process.exitstatus is not None:
raise ConnectionError("Error in setting up ssh tunnel")
if os.path.exists(self._filename):
return
time.sleep(0.1)
def path(self):
"""Return the socket file."""
return self._filename
def get_docker_client(self):
"""Returns a docker client for this Tunnel."""
return docker.DockerClient(base_url="unix:/" + self._filename)
def __del__(self):
"""Closes the ssh connection process and deletes the socket file."""
if self._process:
self._process.close()
if os.path.exists(self._filename):
os.remove(self._filename)
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