remote.py
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remote.py
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	# Copyright 2021 VyOS maintainers and contributors <maintainers@vyos.io>
	#
	# This library is free software; you can redistribute it and/or
	# modify it under the terms of the GNU Lesser General Public
	# License as published by the Free Software Foundation; either
	# version 2.1 of the License, or (at your option) any later version.
	#
	# This library 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
	# Lesser General Public License for more details.
	#
	# You should have received a copy of the GNU Lesser General Public
	# License along with this library. If not, see <http://www.gnu.org/licenses/>.

	import os
	import pwd
	import shutil
	import socket
	import ssl
	import stat
	import sys
	import tempfile
	import urllib.parse

	from contextlib import contextmanager
	from pathlib import Path

	from ftplib import FTP
	from ftplib import FTP_TLS

	from paramiko import SSHClient, SSHException
	from paramiko import MissingHostKeyPolicy

	from requests import Session
	from requests.adapters import HTTPAdapter
	from requests.packages.urllib3 import PoolManager

	from vyos.progressbar import Progressbar
	from vyos.utils.io import ask_yes_no
	from vyos.utils.io import is_interactive
	from vyos.utils.io import print_error
	from vyos.utils.misc import begin
	from vyos.utils.process import cmd, rc_cmd
	from vyos.version import get_version
	from vyos.base import Warning

	CHUNK_SIZE = 8192

	class InteractivePolicy(MissingHostKeyPolicy):
	"""
	Paramiko policy for interactively querying the user on whether to proceed
	with SSH connections to unknown hosts.
	"""
	def missing_host_key(self, client, hostname, key):
	print_error(f"Host '{hostname}' not found in known hosts.")
	print_error('Fingerprint: ' + key.get_fingerprint().hex())
	if not sys.stdin.isatty():
	return
	if not ask_yes_no('Do you wish to continue?'):
	raise SSHException(f"Cannot connect to unknown host '{hostname}'.")
	if client._host_keys_filename is None:
	Warning('no \'known_hosts\' file; create to store keys permanently')
	return
	if ask_yes_no('Do you wish to permanently add this host/key pair to known_hosts file?'):
	client._host_keys.add(hostname, key.get_name(), key)
	client.save_host_keys(client._host_keys_filename)

	class SourceAdapter(HTTPAdapter):
	"""
	urllib3 transport adapter for setting source addresses per session.
	"""
	def __init__(self, source_pair, args, *kwargs):
	# A source pair is a tuple of a source host string and source port respectively.
	# Supply '' and 0 respectively for default values.
	self._source_pair = source_pair
	super(SourceAdapter, self).__init__(args, *kwargs)

	def init_poolmanager(self, connections, maxsize, block=False):
	self.poolmanager = PoolManager(
	num_pools=connections, maxsize=maxsize,
	block=block, source_address=self._source_pair)

	@contextmanager
	def umask(mask: int):
	"""
	Context manager that temporarily sets the process umask.
	"""
	import os
	oldmask = os.umask(mask)
	try:
	yield
	finally:
	os.umask(oldmask)

	def check_storage(path, size):
	"""
	Check whether `path` has enough storage space for a transfer of `size` bytes.
	"""
	path = os.path.abspath(os.path.expanduser(path))
	directory = path if os.path.isdir(path) else (os.path.dirname(os.path.expanduser(path)) or os.getcwd())
	# `size` can be None or 0 to indicate unknown size.
	if not size:
	print_error('Warning: Cannot determine size of remote file. Bravely continuing regardless.')
	return

	if size < 1024 * 1024:
	print_error(f'The file is {size / 1024.0:.3f} KiB.')
	else:
	print_error(f'The file is {size / (1024.0 * 1024.0):.3f} MiB.')

	# Will throw `FileNotFoundError' if `directory' is absent.
	if size > shutil.disk_usage(directory).free:
	raise OSError(f'Not enough disk space available in "{directory}".')


	class FtpC:
	def __init__(self,
	url,
	progressbar=False,
	check_space=False,
	source_host='',
	source_port=0,
	timeout=10):
	self.secure = url.scheme == 'ftps'
	self.hostname = url.hostname
	self.path = url.path
	self.username = url.username or os.getenv('REMOTE_USERNAME', 'anonymous')
	self.password = url.password or os.getenv('REMOTE_PASSWORD', '')
	self.port = url.port or 21
	self.source = (source_host, source_port)
	self.progressbar = progressbar
	self.check_space = check_space
	self.timeout = timeout

	def _establish(self):
	if self.secure:
	return FTP_TLS(source_address=self.source,
	context=ssl.create_default_context(),
	timeout=self.timeout)
	else:
	return FTP(source_address=self.source, timeout=self.timeout)

	def download(self, location: str):
	# Open the file upfront before establishing connection.
	with open(location, 'wb') as f, self._establish() as conn:
	conn.connect(self.hostname, self.port)
	conn.login(self.username, self.password)
	# Set secure connection over TLS.
	if self.secure:
	conn.prot_p()
	# Almost all FTP servers support the `SIZE' command.
	size = conn.size(self.path)
	if self.check_space:
	check_storage(location, size)
	# No progressbar if we can't determine the size or if the file is too small.
	if self.progressbar and size and size > CHUNK_SIZE:
	with Progressbar(CHUNK_SIZE / size) as p:
	callback = lambda block: begin(f.write(block), p.increment())
	conn.retrbinary('RETR ' + self.path, callback, CHUNK_SIZE)
	else:
	conn.retrbinary('RETR ' + self.path, f.write, CHUNK_SIZE)

	def upload(self, location: str):
	size = os.path.getsize(location)
	with open(location, 'rb') as f, self._establish() as conn:
	conn.connect(self.hostname, self.port)
	conn.login(self.username, self.password)
	if self.secure:
	conn.prot_p()
	if self.progressbar and size and size > CHUNK_SIZE:
	with Progressbar(CHUNK_SIZE / size) as p:
	conn.storbinary('STOR ' + self.path, f, CHUNK_SIZE, lambda block: p.increment())
	else:
	conn.storbinary('STOR ' + self.path, f, CHUNK_SIZE)

	class SshC:
	known_hosts = os.path.expanduser('~/.ssh/known_hosts')
	def __init__(self,
	url,
	progressbar=False,
	check_space=False,
	source_host='',
	source_port=0,
	timeout=10.0):
	self.hostname = url.hostname
	self.path = url.path
	self.username = url.username or os.getenv('REMOTE_USERNAME')
	self.password = url.password or os.getenv('REMOTE_PASSWORD')
	self.port = url.port or 22
	self.source = (source_host, source_port)
	self.progressbar = progressbar
	self.check_space = check_space
	self.timeout = timeout

	def _establish(self):
	ssh = SSHClient()
	ssh.load_system_host_keys()
	# Try to load from a user-local known hosts file if one exists.
	if os.path.exists(self.known_hosts):
	ssh.load_host_keys(self.known_hosts)
	ssh.set_missing_host_key_policy(InteractivePolicy())
	# `socket.create_connection()` automatically picks a NIC and an IPv4/IPv6 address family
	# for us on dual-stack systems.
	sock = socket.create_connection((self.hostname, self.port), self.timeout, self.source)
	ssh.connect(self.hostname, self.port, self.username, self.password, sock=sock)
	return ssh

	def download(self, location: str):
	with self._establish() as ssh, ssh.open_sftp() as sftp:
	if self.check_space:
	check_storage(location, sftp.stat(self.path).st_size)
	if self.progressbar:
	with Progressbar() as p:
	sftp.get(self.path, location, callback=p.progress)
	else:
	sftp.get(self.path, location)

	def upload(self, location: str):
	with self._establish() as ssh, ssh.open_sftp() as sftp:
	try:
	# If the remote path is a directory, use the original filename.
	if stat.S_ISDIR(sftp.stat(self.path).st_mode):
	path = os.path.join(self.path, os.path.basename(location))
	# A file exists at this destination. We're simply going to clobber it.
	else:
	path = self.path
	# This path doesn't point at any existing file. We can freely use this filename.
	except IOError:
	path = self.path
	finally:
	if self.progressbar:
	with Progressbar() as p:
	sftp.put(location, path, callback=p.progress)
	else:
	sftp.put(location, path)


	class HttpC:
	def __init__(self,
	url,
	progressbar=False,
	check_space=False,
	source_host='',
	source_port=0,
	timeout=10.0):
	self.urlstring = urllib.parse.urlunsplit(url)
	self.progressbar = progressbar
	self.check_space = check_space
	self.source_pair = (source_host, source_port)
	self.username = url.username or os.getenv('REMOTE_USERNAME')
	self.password = url.password or os.getenv('REMOTE_PASSWORD')
	self.timeout = timeout

	def _establish(self):
	session = Session()
	session.mount(self.urlstring, SourceAdapter(self.source_pair))
	session.headers.update({'User-Agent': 'VyOS/' + get_version()})
	if self.username:
	session.auth = self.username, self.password
	return session

	def download(self, location: str):
	with self._establish() as s:
	# We ask for uncompressed downloads so that we don't have to deal with decoding.
	# Not only would it potentially mess up with the progress bar but
	# `shutil.copyfileobj(request.raw, file)` does not handle automatic decoding.
	s.headers.update({'Accept-Encoding': 'identity'})
	with s.head(self.urlstring,
	allow_redirects=True,
	timeout=self.timeout) as r:
	# Abort early if the destination is inaccessible.
	r.raise_for_status()
	# If the request got redirected, keep the last URL we ended up with.
	final_urlstring = r.url
	if r.history and self.progressbar:
	print_error('Redirecting to ' + final_urlstring)
	# Check for the prospective file size.
	try:
	size = int(r.headers['Content-Length'])
	# In case the server does not supply the header.
	except KeyError:
	size = None
	if self.check_space:
	check_storage(location, size)
	with s.get(final_urlstring, stream=True,
	timeout=self.timeout) as r, open(location, 'wb') as f:
	if self.progressbar and size:
	with Progressbar(CHUNK_SIZE / size) as p:
	for chunk in iter(lambda: begin(p.increment(), r.raw.read(CHUNK_SIZE)), b''):
	f.write(chunk)
	else:
	# We'll try to stream the download directly with `copyfileobj()` so that large
	# files (like entire VyOS images) don't occupy much memory.
	shutil.copyfileobj(r.raw, f)

	def upload(self, location: str):
	# Does not yet support progressbars.
	with self._establish() as s, open(location, 'rb') as f:
	s.post(self.urlstring,
	data=f,
	allow_redirects=True,
	timeout=self.timeout)


	class TftpC:
	# We simply allow `curl` to take over because
	# 1. TFTP is rather simple.
	# 2. Since there's no concept authentication, we don't need to deal with keys/passwords.
	# 3. It would be a waste to import, audit and maintain a third-party library for TFTP.
	# 4. I'd rather not implement the entire protocol here, no matter how simple it is.
	def __init__(self,
	url,
	progressbar=False,
	check_space=False,
	source_host=None,
	source_port=0,
	timeout=10):
	source_option = f'--interface {source_host} --local-port {source_port}' if source_host else ''
	progress_flag = '--progress-bar' if progressbar else '-s'
	self.command = f'curl {source_option} {progress_flag} --connect-timeout {timeout}'
	self.urlstring = urllib.parse.urlunsplit(url)

	def download(self, location: str):
	with open(location, 'wb') as f:
	f.write(cmd(f'{self.command} "{self.urlstring}"').encode())

	def upload(self, location: str):
	with open(location, 'rb') as f:
	cmd(f'{self.command} -T - "{self.urlstring}"', input=f.read())

	class GitC:
	def __init__(self,
	url,
	progressbar=False,
	check_space=False,
	source_host=None,
	source_port=0,
	timeout=10,
	):
	self.command = 'git'
	self.url = url
	self.urlstring = urllib.parse.urlunsplit(url)
	if self.urlstring.startswith("git+"):
	self.urlstring = self.urlstring.replace("git+", "", 1)

	def download(self, location: str):
	raise NotImplementedError("not supported")

	@umask(0o077)
	def upload(self, location: str):
	scheme = self.url.scheme
	_, _, scheme = scheme.partition("+")
	netloc = self.url.netloc
	url = Path(self.url.path).parent
	with tempfile.TemporaryDirectory(prefix="git-commit-archive-") as directory:
	# Determine username, fullname, email for Git commit
	pwd_entry = pwd.getpwuid(os.getuid())
	user = pwd_entry.pw_name
	name = pwd_entry.pw_gecos.split(",")[0] or user
	fqdn = socket.getfqdn()
	email = f"{user}@{fqdn}"

	# environment vars for our git commands
	env = {
	"GIT_TERMINAL_PROMPT": "0",
	"GIT_AUTHOR_NAME": name,
	"GIT_AUTHOR_EMAIL": email,
	"GIT_COMMITTER_NAME": name,
	"GIT_COMMITTER_EMAIL": email,
	}

	# build ssh command for git
	ssh_command = ["ssh"]

	# if we are not interactive, we use StrictHostKeyChecking=yes to avoid any prompts
	if not sys.stdout.isatty():
	ssh_command += ["-o", "StrictHostKeyChecking=yes"]

	env["GIT_SSH_COMMAND"] = " ".join(ssh_command)

	# git clone
	path_repository = Path(directory) / "repository"
	scheme = f"{scheme}://" if scheme else ""
	rc, out = rc_cmd(
	[self.command, "clone", f"{scheme}{netloc}{url}", str(path_repository), "--depth=1"],
	env=env,
	shell=False,
	)
	if rc:
	raise Exception(out)

	# git add
	filename = Path(Path(self.url.path).name).stem
	dst = path_repository / filename
	shutil.copy2(location, dst)
	rc, out = rc_cmd(
	[self.command, "-C", str(path_repository), "add", filename],
	env=env,
	shell=False,
	)

	# git commit -m
	commit_message = os.environ.get("COMMIT_COMMENT", "commit")
	rc, out = rc_cmd(
	[self.command, "-C", str(path_repository), "commit", "-m", commit_message],
	env=env,
	shell=False,
	)

	# git push
	rc, out = rc_cmd(
	[self.command, "-C", str(path_repository), "push"],
	env=env,
	shell=False,
	)
	if rc:
	raise Exception(out)


	def urlc(urlstring, args, *kwargs):
	"""
	Dynamically dispatch the appropriate protocol class.
	"""
	url_classes = {
	"http": HttpC,
	"https": HttpC,
	"ftp": FtpC,
	"ftps": FtpC,
	"sftp": SshC,
	"ssh": SshC,
	"scp": SshC,
	"tftp": TftpC,
	"git": GitC,
	}
	url = urllib.parse.urlsplit(urlstring)
	scheme, _, _ = url.scheme.partition("+")
	try:
	return url_classes[scheme](url, args, *kwargs)
	except KeyError:
	raise ValueError(f'Unsupported URL scheme: "{scheme}"')

	def download(local_path, urlstring, progressbar=False, check_space=False,
	source_host='', source_port=0, timeout=10.0, raise_error=False):
	try:
	progressbar = progressbar and is_interactive()
	urlc(urlstring, progressbar, check_space, source_host, source_port, timeout).download(local_path)
	except Exception as err:
	if raise_error:
	raise
	print_error(f'Unable to download "{urlstring}": {err}')
	sys.exit(1)
	except KeyboardInterrupt:
	print_error('\nDownload aborted by user.')
	sys.exit(1)

	def upload(local_path, urlstring, progressbar=False,
	source_host='', source_port=0, timeout=10.0):
	try:
	progressbar = progressbar and is_interactive()
	urlc(urlstring, progressbar, False, source_host, source_port, timeout).upload(local_path)
	except Exception as err:
	print_error(f'Unable to upload "{urlstring}": {err}')
	sys.exit(1)
	except KeyboardInterrupt:
	print_error('\nUpload aborted by user.')
	sys.exit(1)

	def get_remote_config(urlstring, source_host='', source_port=0):
	"""
	Quietly download a file and return it as a string.
	"""
	temp = tempfile.NamedTemporaryFile(delete=False).name
	try:
	download(temp, urlstring, False, False, source_host, source_port)
	with open(temp, 'r') as f:
	return f.read()
	finally:
	os.remove(temp)

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