153 lines
4.1 KiB
Python
153 lines
4.1 KiB
Python
"""UNIX-domain socket server for ssh-agent implementation."""
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import contextlib
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import logging
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import os
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import socket
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import subprocess
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import tempfile
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import threading
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from . import util
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log = logging.getLogger(__name__)
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UNIX_SOCKET_TIMEOUT = 0.1
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def remove_file(path, remove=os.remove, exists=os.path.exists):
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"""Remove file, and raise OSError if still exists."""
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try:
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remove(path)
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except OSError:
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if exists(path):
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raise
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@contextlib.contextmanager
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def unix_domain_socket_server(sock_path):
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"""
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Create UNIX-domain socket on specified path.
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Listen on it, and delete it after the generated context is over.
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"""
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log.debug('serving on SSH_AUTH_SOCK=%s', sock_path)
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remove_file(sock_path)
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server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
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server.bind(sock_path)
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server.listen(1)
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try:
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yield server
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finally:
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remove_file(sock_path)
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def handle_connection(conn, handler):
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"""
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Handle a single connection using the specified protocol handler in a loop.
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Exit when EOFError is raised.
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All other exceptions are logged as warnings.
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"""
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try:
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log.debug('welcome agent')
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while True:
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msg = util.read_frame(conn)
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reply = handler.handle(msg=msg)
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util.send(conn, reply)
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except IOError as e:
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log.error('I/O error: %s', e)
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except EOFError:
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log.debug('goodbye agent')
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except Exception as e: # pylint: disable=broad-except
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log.warning('error: %s', e, exc_info=True)
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def retry(func, exception_type, quit_event):
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"""
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Run the function, retrying when the specified exception_type occurs.
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Poll quit_event on each iteration, to be responsive to an external
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exit request.
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"""
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while True:
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if quit_event.is_set():
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raise StopIteration
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try:
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return func()
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except exception_type:
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pass
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def server_thread(sock, handler, quit_event):
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"""Run a server on the specified socket."""
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log.debug('server thread started')
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def accept_connection():
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conn, _ = sock.accept()
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conn.settimeout(None)
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return conn
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while True:
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log.debug('waiting for connection on %s', sock.getsockname())
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try:
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conn = retry(accept_connection, socket.timeout, quit_event)
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except StopIteration:
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log.debug('server stopped')
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break
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with contextlib.closing(conn):
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handle_connection(conn, handler)
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log.debug('server thread stopped')
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@contextlib.contextmanager
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def spawn(func, kwargs):
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"""Spawn a thread, and join it after the context is over."""
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t = threading.Thread(target=func, kwargs=kwargs)
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t.start()
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yield
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t.join()
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@contextlib.contextmanager
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def serve(handler, sock_path=None, timeout=UNIX_SOCKET_TIMEOUT):
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"""
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Start the ssh-agent server on a UNIX-domain socket.
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If no connection is made during the specified timeout,
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retry until the context is over.
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"""
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if sock_path is None:
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sock_path = tempfile.mktemp(prefix='ssh-agent-')
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environ = {'SSH_AUTH_SOCK': sock_path, 'SSH_AGENT_PID': str(os.getpid())}
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with unix_domain_socket_server(sock_path) as sock:
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sock.settimeout(timeout)
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quit_event = threading.Event()
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kwargs = dict(sock=sock, handler=handler, quit_event=quit_event)
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with spawn(server_thread, kwargs):
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try:
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yield environ
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finally:
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log.debug('closing server')
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quit_event.set()
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def run_process(command, environ):
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"""
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Run the specified process and wait until it finishes.
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Use environ dict for environment variables.
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"""
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log.info('running %r with %r', command, environ)
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env = dict(os.environ)
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env.update(environ)
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try:
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p = subprocess.Popen(args=command, env=env)
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except OSError as e:
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raise OSError('cannot run %r: %s' % (command, e))
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log.debug('subprocess %d is running', p.pid)
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ret = p.wait()
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log.debug('subprocess %d exited: %d', p.pid, ret)
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return ret
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