ssh.py - git-repo - Git at Google

 # Copyright (C) 2008 The Android Open Source Project
 #
 # 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.

 """Common SSH management logic."""

 import functools
 import multiprocessing
 import os
 import re
 import signal
 import subprocess
 import sys
 import tempfile
 import time

 import platform_utils
 from repo_trace import Trace


 PROXY_PATH = os.path.join(os.path.dirname(__file__), 'git_ssh')


 def _run_ssh_version():
   """run ssh -V to display the version number"""
   return subprocess.check_output(['ssh', '-V'], stderr=subprocess.STDOUT).decode()


 def _parse_ssh_version(ver_str=None):
   """parse a ssh version string into a tuple"""
   if ver_str is None:
     ver_str = _run_ssh_version()
   m = re.match(r'^OpenSSH_([0-9.]+)(p[0-9]+)?\s', ver_str)
   if m:
     return tuple(int(x) for x in m.group(1).split('.'))
   else:
     return ()


 @functools.lru_cache(maxsize=None)
 def version():
   """return ssh version as a tuple"""
   try:
     return _parse_ssh_version()
   except FileNotFoundError:
     print('fatal: ssh not installed', file=sys.stderr)
     sys.exit(1)
   except subprocess.CalledProcessError:
     print('fatal: unable to detect ssh version', file=sys.stderr)
     sys.exit(1)


 URI_SCP = re.compile(r'^([^@:]*@?[^:/]{1,}):')
 URI_ALL = re.compile(r'^([a-z][a-z+-]*)://([^@/]*@?[^/]*)/')


 class ProxyManager:
   """Manage various ssh clients & masters that we spawn.

   This will take care of sharing state between multiprocessing children, and
   make sure that if we crash, we don't leak any of the ssh sessions.

   The code should work with a single-process scenario too, and not add too much
   overhead due to the manager.
   """

   # Path to the ssh program to run which will pass our master settings along.
   # Set here more as a convenience API.
   proxy = PROXY_PATH

   def __init__(self, manager):
     # Protect access to the list of active masters.
     self._lock = multiprocessing.Lock()
     # List of active masters (pid).  These will be spawned on demand, and we are
     # responsible for shutting them all down at the end.
     self._masters = manager.list()
     # Set of active masters indexed by "host:port" information.
     # The value isn't used, but multiprocessing doesn't provide a set class.
     self._master_keys = manager.dict()
     # Whether ssh masters are known to be broken, so we give up entirely.
     self._master_broken = manager.Value('b', False)
     # List of active ssh sesssions.  Clients will be added & removed as
     # connections finish, so this list is just for safety & cleanup if we crash.
     self._clients = manager.list()
     # Path to directory for holding master sockets.
     self._sock_path = None

   def __enter__(self):
     """Enter a new context."""
     return self

   def __exit__(self, exc_type, exc_value, traceback):
     """Exit a context & clean up all resources."""
     self.close()

   def add_client(self, proc):
     """Track a new ssh session."""
     self._clients.append(proc.pid)

   def remove_client(self, proc):
     """Remove a completed ssh session."""
     try:
       self._clients.remove(proc.pid)
     except ValueError:
       pass

   def add_master(self, proc):
     """Track a new master connection."""
     self._masters.append(proc.pid)

   def _terminate(self, procs):
     """Kill all |procs|."""
     for pid in procs:
       try:
         os.kill(pid, signal.SIGTERM)
         os.waitpid(pid, 0)
       except OSError:
         pass

     # The multiprocessing.list() API doesn't provide many standard list()
     # methods, so we have to manually clear the list.
     while True:
       try:
         procs.pop(0)
       except:
         break

   def close(self):
     """Close this active ssh session.

     Kill all ssh clients & masters we created, and nuke the socket dir.
     """
     self._terminate(self._clients)
     self._terminate(self._masters)

     d = self.sock(create=False)
     if d:
       try:
         platform_utils.rmdir(os.path.dirname(d))
       except OSError:
         pass

   def _open_unlocked(self, host, port=None):
     """Make sure a ssh master session exists for |host| & |port|.

     If one doesn't exist already, we'll create it.

     We won't grab any locks, so the caller has to do that.  This helps keep the
     business logic of actually creating the master separate from grabbing locks.
     """
     # Check to see whether we already think that the master is running; if we
     # think it's already running, return right away.
     if port is not None:
       key = '%s:%s' % (host, port)
     else:
       key = host

     if key in self._master_keys:
       return True

     if self._master_broken.value or 'GIT_SSH' in os.environ:
       # Failed earlier, so don't retry.
       return False

     # We will make two calls to ssh; this is the common part of both calls.
     command_base = ['ssh', '-o', 'ControlPath %s' % self.sock(), host]
     if port is not None:
       command_base[1:1] = ['-p', str(port)]

     # Since the key wasn't in _master_keys, we think that master isn't running.
     # ...but before actually starting a master, we'll double-check.  This can
     # be important because we can't tell that that 'git@myhost.com' is the same
     # as 'myhost.com' where "User git" is setup in the user's ~/.ssh/config file.
     check_command = command_base + ['-O', 'check']
     with Trace('Call to ssh (check call): %s', ' '.join(check_command)):
       try:
         check_process = subprocess.Popen(check_command,
                                         stdout=subprocess.PIPE,
                                         stderr=subprocess.PIPE)
         check_process.communicate()  # read output, but ignore it...
         isnt_running = check_process.wait()

         if not isnt_running:
           # Our double-check found that the master _was_ infact running.  Add to
           # the list of keys.
           self._master_keys[key] = True
           return True
       except Exception:
         # Ignore excpetions.  We we will fall back to the normal command and
         # print to the log there.
         pass

     command = command_base[:1] + ['-M', '-N'] + command_base[1:]
     p = None
     try:
       with Trace('Call to ssh: %s', ' '.join(command)):
         p = subprocess.Popen(command)
     except Exception as e:
       self._master_broken.value = True
       print('\nwarn: cannot enable ssh control master for %s:%s\n%s'
             % (host, port, str(e)), file=sys.stderr)
       return False

     time.sleep(1)
     ssh_died = (p.poll() is not None)
     if ssh_died:
       return False

     self.add_master(p)
     self._master_keys[key] = True
     return True

   def _open(self, host, port=None):
     """Make sure a ssh master session exists for |host| & |port|.

     If one doesn't exist already, we'll create it.

     This will obtain any necessary locks to avoid inter-process races.
     """
     # Bail before grabbing the lock if we already know that we aren't going to
     # try creating new masters below.
     if sys.platform in ('win32', 'cygwin'):
       return False

     # Acquire the lock.  This is needed to prevent opening multiple masters for
     # the same host when we're running "repo sync -jN" (for N > 1) _and_ the
     # manifest <remote fetch="ssh://xyz"> specifies a different host from the
     # one that was passed to repo init.
     with self._lock:
       return self._open_unlocked(host, port)

   def preconnect(self, url):
     """If |uri| will create a ssh connection, setup the ssh master for it."""
     m = URI_ALL.match(url)
     if m:
       scheme = m.group(1)
       host = m.group(2)
       if ':' in host:
         host, port = host.split(':')
       else:
         port = None
       if scheme in ('ssh', 'git+ssh', 'ssh+git'):
         return self._open(host, port)
       return False

     m = URI_SCP.match(url)
     if m:
       host = m.group(1)
       return self._open(host)

     return False

   def sock(self, create=True):
     """Return the path to the ssh socket dir.

     This has all the master sockets so clients can talk to them.
     """
     if self._sock_path is None:
       if not create:
         return None
       tmp_dir = '/tmp'
       if not os.path.exists(tmp_dir):
         tmp_dir = tempfile.gettempdir()
       if version() < (6, 7):
         tokens = '%r@%h:%p'
       else:
         tokens = '%C'  # hash of %l%h%p%r
       self._sock_path = os.path.join(
           tempfile.mkdtemp('', 'ssh-', tmp_dir),
           'master-' + tokens)
     return self._sock_path
	# Copyright (C) 2008 The Android Open Source Project
	#
	# 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.

	"""Common SSH management logic."""

	import functools
	import multiprocessing
	import os
	import re
	import signal
	import subprocess
	import sys
	import tempfile
	import time

	import platform_utils
	from repo_trace import Trace


	PROXY_PATH = os.path.join(os.path.dirname(__file__), 'git_ssh')


	def _run_ssh_version():
	"""run ssh -V to display the version number"""
	return subprocess.check_output(['ssh', '-V'], stderr=subprocess.STDOUT).decode()


	def _parse_ssh_version(ver_str=None):
	"""parse a ssh version string into a tuple"""
	if ver_str is None:
	ver_str = _run_ssh_version()
	m = re.match(r'^OpenSSH_([0-9.]+)(p[0-9]+)?\s', ver_str)
	if m:
	return tuple(int(x) for x in m.group(1).split('.'))
	else:
	return ()


	@functools.lru_cache(maxsize=None)
	def version():
	"""return ssh version as a tuple"""
	try:
	return _parse_ssh_version()
	except FileNotFoundError:
	print('fatal: ssh not installed', file=sys.stderr)
	sys.exit(1)
	except subprocess.CalledProcessError:
	print('fatal: unable to detect ssh version', file=sys.stderr)
	sys.exit(1)


	URI_SCP = re.compile(r'^([^@:]*@?[^:/]{1,}):')
	URI_ALL = re.compile(r'^([a-z][a-z+-])://([^@/]@?[^/]*)/')


	class ProxyManager:
	"""Manage various ssh clients & masters that we spawn.

	This will take care of sharing state between multiprocessing children, and
	make sure that if we crash, we don't leak any of the ssh sessions.

	The code should work with a single-process scenario too, and not add too much
	overhead due to the manager.
	"""

	# Path to the ssh program to run which will pass our master settings along.
	# Set here more as a convenience API.
	proxy = PROXY_PATH

	def __init__(self, manager):
	# Protect access to the list of active masters.
	self._lock = multiprocessing.Lock()
	# List of active masters (pid). These will be spawned on demand, and we are
	# responsible for shutting them all down at the end.
	self._masters = manager.list()
	# Set of active masters indexed by "host:port" information.
	# The value isn't used, but multiprocessing doesn't provide a set class.
	self._master_keys = manager.dict()
	# Whether ssh masters are known to be broken, so we give up entirely.
	self._master_broken = manager.Value('b', False)
	# List of active ssh sesssions. Clients will be added & removed as
	# connections finish, so this list is just for safety & cleanup if we crash.
	self._clients = manager.list()
	# Path to directory for holding master sockets.
	self._sock_path = None

	def __enter__(self):
	"""Enter a new context."""
	return self

	def __exit__(self, exc_type, exc_value, traceback):
	"""Exit a context & clean up all resources."""
	self.close()

	def add_client(self, proc):
	"""Track a new ssh session."""
	self._clients.append(proc.pid)

	def remove_client(self, proc):
	"""Remove a completed ssh session."""
	try:
	self._clients.remove(proc.pid)
	except ValueError:
	pass

	def add_master(self, proc):
	"""Track a new master connection."""
	self._masters.append(proc.pid)

	def _terminate(self, procs):
	"""Kill all \|procs\|."""
	for pid in procs:
	try:
	os.kill(pid, signal.SIGTERM)
	os.waitpid(pid, 0)
	except OSError:
	pass

	# The multiprocessing.list() API doesn't provide many standard list()
	# methods, so we have to manually clear the list.
	while True:
	try:
	procs.pop(0)
	except:
	break

	def close(self):
	"""Close this active ssh session.

	Kill all ssh clients & masters we created, and nuke the socket dir.
	"""
	self._terminate(self._clients)
	self._terminate(self._masters)

	d = self.sock(create=False)
	if d:
	try:
	platform_utils.rmdir(os.path.dirname(d))
	except OSError:
	pass

	def _open_unlocked(self, host, port=None):
	"""Make sure a ssh master session exists for \|host\| & \|port\|.

	If one doesn't exist already, we'll create it.

	We won't grab any locks, so the caller has to do that. This helps keep the
	business logic of actually creating the master separate from grabbing locks.
	"""
	# Check to see whether we already think that the master is running; if we
	# think it's already running, return right away.
	if port is not None:
	key = '%s:%s' % (host, port)
	else:
	key = host

	if key in self._master_keys:
	return True

	if self._master_broken.value or 'GIT_SSH' in os.environ:
	# Failed earlier, so don't retry.
	return False

	# We will make two calls to ssh; this is the common part of both calls.
	command_base = ['ssh', '-o', 'ControlPath %s' % self.sock(), host]
	if port is not None:
	command_base[1:1] = ['-p', str(port)]

	# Since the key wasn't in _master_keys, we think that master isn't running.
	# ...but before actually starting a master, we'll double-check. This can
	# be important because we can't tell that that 'git@myhost.com' is the same
	# as 'myhost.com' where "User git" is setup in the user's ~/.ssh/config file.
	check_command = command_base + ['-O', 'check']
	with Trace('Call to ssh (check call): %s', ' '.join(check_command)):
	try:
	check_process = subprocess.Popen(check_command,
	stdout=subprocess.PIPE,
	stderr=subprocess.PIPE)
	check_process.communicate() # read output, but ignore it...
	isnt_running = check_process.wait()

	if not isnt_running:
	# Our double-check found that the master _was_ infact running. Add to
	# the list of keys.
	self._master_keys[key] = True
	return True
	except Exception:
	# Ignore excpetions. We we will fall back to the normal command and
	# print to the log there.
	pass

	command = command_base[:1] + ['-M', '-N'] + command_base[1:]
	p = None
	try:
	with Trace('Call to ssh: %s', ' '.join(command)):
	p = subprocess.Popen(command)
	except Exception as e:
	self._master_broken.value = True
	print('\nwarn: cannot enable ssh control master for %s:%s\n%s'
	% (host, port, str(e)), file=sys.stderr)
	return False

	time.sleep(1)
	ssh_died = (p.poll() is not None)
	if ssh_died:
	return False

	self.add_master(p)
	self._master_keys[key] = True
	return True

	def _open(self, host, port=None):
	"""Make sure a ssh master session exists for \|host\| & \|port\|.

	If one doesn't exist already, we'll create it.

	This will obtain any necessary locks to avoid inter-process races.
	"""
	# Bail before grabbing the lock if we already know that we aren't going to
	# try creating new masters below.
	if sys.platform in ('win32', 'cygwin'):
	return False

	# Acquire the lock. This is needed to prevent opening multiple masters for
	# the same host when we're running "repo sync -jN" (for N > 1) _and_ the
	# manifest <remote fetch="ssh://xyz"> specifies a different host from the
	# one that was passed to repo init.
	with self._lock:
	return self._open_unlocked(host, port)

	def preconnect(self, url):
	"""If \|uri\| will create a ssh connection, setup the ssh master for it."""
	m = URI_ALL.match(url)
	if m:
	scheme = m.group(1)
	host = m.group(2)
	if ':' in host:
	host, port = host.split(':')
	else:
	port = None
	if scheme in ('ssh', 'git+ssh', 'ssh+git'):
	return self._open(host, port)
	return False

	m = URI_SCP.match(url)
	if m:
	host = m.group(1)
	return self._open(host)

	return False

	def sock(self, create=True):
	"""Return the path to the ssh socket dir.

	This has all the master sockets so clients can talk to them.
	"""
	if self._sock_path is None:
	if not create:
	return None
	tmp_dir = '/tmp'
	if not os.path.exists(tmp_dir):
	tmp_dir = tempfile.gettempdir()
	if version() < (6, 7):
	tokens = '%r@%h:%p'
	else:
	tokens = '%C' # hash of %l%h%p%r
	self._sock_path = os.path.join(
	tempfile.mkdtemp('', 'ssh-', tmp_dir),
	'master-' + tokens)
	return self._sock_path