Add Windows native SSH support

libagent/device/ui.py

@@ -78,7 +78,8 @@ class UI:
 def create_default_options_getter():
     """Return current TTY and DISPLAY settings for GnuPG pinentry."""
     options = []
-    if sys.stdin.isatty():  # short-circuit calling `tty`
+    # Windows reports that it has a TTY but throws FileNotFoundError
+    if sys.platform != 'win32' and sys.stdin.isatty():  # short-circuit calling `tty`
         try:
             ttyname = subprocess.check_output(args=['tty']).strip()
             options.append(b'ttyname=' + ttyname)
@@ -88,7 +89,8 @@ def create_default_options_getter():
     display = os.environ.get('DISPLAY')
     if display is not None:
         options.append('display={}'.format(display).encode('ascii'))
-    else:
+    # Windows likely doesn't support this anyway
+    elif sys.platform != 'win32':
         log.warning('DISPLAY not defined')
 
     log.info('using %s for pinentry options', options)

libagent/ssh/__init__.py

@@ -4,24 +4,32 @@ import functools
 import io
 import logging
 import os
+import random
 import re
 import signal
+import string
 import subprocess
 import sys
 import tempfile
 import threading
 
 import configargparse
+try:
+    # TODO: Not supported on Windows. Use daemoniker instead?
     import daemon
+except ImportError:
+    daemon = None
 import pkg_resources
 
-from .. import device, formats, server, util
+from .. import device, formats, server, util, win_server
 from . import client, protocol
 
 log = logging.getLogger(__name__)
 
 UNIX_SOCKET_TIMEOUT = 0.1
-
+WIN_PIPE_TIMEOUT = 0.1
+DEFAULT_TIMEOUT = WIN_PIPE_TIMEOUT if sys.platform == 'win32' else UNIX_SOCKET_TIMEOUT
+SOCK_TYPE = 'Windows named pipe' if sys.platform == 'win32' else 'UNIX domain socket'
 
 def ssh_args(conn):
     """Create SSH command for connecting specified server."""
@@ -35,7 +43,7 @@ def ssh_args(conn):
     if 'user' in identity:
         args += ['-l', identity['user']]
 
-    args += ['-o', 'IdentityFile={}'.format(pubkey_tempfile.name)]
+    args += ['-o', 'IdentityFile={}'.format(pubkey_tempfile)]
     args += ['-o', 'IdentitiesOnly=true']
     return args + [identity['host']]
 
@@ -83,14 +91,14 @@ def create_agent_parser(device_type):
                    default=formats.CURVE_NIST256,
                    help='specify ECDSA curve name: ' + curve_names)
     p.add_argument('--timeout',
-                   default=UNIX_SOCKET_TIMEOUT, type=float,
+                   default=DEFAULT_TIMEOUT, type=float,
                    help='timeout for accepting SSH client connections')
     p.add_argument('--debug', default=False, action='store_true',
                    help='log SSH protocol messages for debugging.')
     p.add_argument('--log-file', type=str,
                    help='Path to the log file (to be written by the agent).')
     p.add_argument('--sock-path', type=str,
-                   help='Path to the UNIX domain socket of the agent.')
+                   help='Path to the ' + SOCK_TYPE + ' of the agent.')
 
     p.add_argument('--pin-entry-binary', type=str, default='pinentry',
                    help='Path to PIN entry UI helper.')
@@ -100,15 +108,18 @@ def create_agent_parser(device_type):
                    help='Expire passphrase from cache after this duration.')
 
     g = p.add_mutually_exclusive_group()
+    if daemon:
         g.add_argument('-d', '--daemonize', default=False, action='store_true',
-                   help='Daemonize the agent and print its UNIX socket path')
+                       help='Daemonize the agent and print its ' + SOCK_TYPE)
     g.add_argument('-f', '--foreground', default=False, action='store_true',
-                   help='Run agent in foreground with specified UNIX socket path')
+                   help='Run agent in foreground with specified ' + SOCK_TYPE)
     g.add_argument('-s', '--shell', default=False, action='store_true',
                    help=('run ${SHELL} as subprocess under SSH agent, allowing '
                          'regular SSH-based tools to be used in the shell'))
     g.add_argument('-c', '--connect', default=False, action='store_true',
                    help='connect to specified host via SSH')
+    # Windows doesn't have native mosh
+    if sys.platform != 'win32':
         g.add_argument('--mosh', default=False, action='store_true',
                        help='connect to specified host via using Mosh')
 
@@ -119,18 +130,48 @@ def create_agent_parser(device_type):
     return p
 
 
+def get_ssh_env(sock_path):
+    ssh_version = subprocess.check_output(['ssh', '-V'],
+                                          stderr=subprocess.STDOUT)
+    log.debug('local SSH version: %r', ssh_version)
+    return {'SSH_AUTH_SOCK': sock_path, 'SSH_AGENT_PID': str(os.getpid())}
+
+
+# Windows doesn't support AF_UNIX yet
+# https://bugs.python.org/issue33408
 @contextlib.contextmanager
-def serve(handler, sock_path, timeout=UNIX_SOCKET_TIMEOUT):
+def serve_win(handler, sock_path, timeout=WIN_PIPE_TIMEOUT):
+    """
+    Start the ssh-agent server on a Windows named pipe.
+    """
+    environ = get_ssh_env(sock_path)
+    device_mutex = threading.Lock()
+    quit_event = threading.Event()
+    handle_conn = functools.partial(win_server.handle_connection,
+                                    handler=handler,
+                                    mutex=device_mutex,
+                                    quit_event=quit_event)
+    kwargs = dict(pipe_name=sock_path,
+                  handle_conn=handle_conn,
+                  quit_event=quit_event,
+                  timeout=timeout)
+    with server.spawn(win_server.server_thread, kwargs):
+        try:
+            yield environ
+        finally:
+            log.debug('closing server')
+            quit_event.set()
+
+
+@contextlib.contextmanager
+def serve_unix(handler, sock_path, timeout=UNIX_SOCKET_TIMEOUT):
     """
     Start the ssh-agent server on a UNIX-domain socket.
 
     If no connection is made during the specified timeout,
     retry until the context is over.
     """
-    ssh_version = subprocess.check_output(['ssh', '-V'],
+    environ = get_ssh_env(sock_path)
-                                          stderr=subprocess.STDOUT)
-    log.debug('local SSH version: %r', ssh_version)
-    environ = {'SSH_AUTH_SOCK': sock_path, 'SSH_AGENT_PID': str(os.getpid())}
     device_mutex = threading.Lock()
     with server.unix_domain_socket_server(sock_path) as sock:
         sock.settimeout(timeout)
@@ -154,12 +195,15 @@ def run_server(conn, command, sock_path, debug, timeout):
     ret = 0
     try:
         handler = protocol.Handler(conn=conn, debug=debug)
-        with serve(handler=handler, sock_path=sock_path,
+        serve_platform = serve_win if sys.platform == 'win32' else serve_unix
-                   timeout=timeout) as env:
+        with serve_platform(handler=handler, sock_path=sock_path, timeout=timeout) as env:
             if command:
                 ret = server.run_process(command=command, environ=env)
             else:
+                try:
                     signal.pause() # wait for signal (e.g. SIGINT)
+                except AttributeError:
+                    sys.stdin.read() # Windows doesn't support signal.pause
     except KeyboardInterrupt:
         log.info('server stopped')
     return ret
@@ -221,10 +265,9 @@ class JustInTimeConnection:
         """Store public keys as temporary SSH identity files."""
         if not self.public_keys_tempfiles:
             for pk in self.public_keys():
-                f = tempfile.NamedTemporaryFile(prefix='trezor-ssh-pubkey-', mode='w')
+                with tempfile.NamedTemporaryFile(prefix='trezor-ssh-pubkey-', mode='w', delete=False, newline='') as f:
                     f.write(pk)
-                f.flush()
+                    self.public_keys_tempfiles.append(f.name)
-                self.public_keys_tempfiles.append(f)
 
         return self.public_keys_tempfiles
 
@@ -241,13 +284,16 @@ def _dummy_context():
 
 def _get_sock_path(args):
     sock_path = args.sock_path
-    if not sock_path:
+    if sock_path:
-        if args.foreground:
-            log.error('running in foreground mode requires specifying UNIX socket path')
-            sys.exit(1)
-        else:
-            sock_path = tempfile.mktemp(prefix='trezor-ssh-agent-')
         return sock_path
+    elif args.foreground:
+        log.error('running in foreground mode requires specifying ' + SOCK_TYPE)
+        sys.exit(1)
+    elif sys.platform == 'win32':
+        suffix = random.choices(string.ascii_letters, k=10)
+        return '\\\\.\pipe\\trezor-ssh-agent-' + ''.join(suffix)
+    else:
+        return tempfile.mktemp(prefix='trezor-ssh-agent-')
 
 
 @handle_connection_error
@@ -286,7 +332,7 @@ def main(device_type):
         command = ['ssh'] + ssh_args(conn) + args.command
     elif args.mosh:
         command = ['mosh'] + mosh_args(conn) + args.command
-    elif args.daemonize:
+    elif daemon and args.daemonize:
         out = 'SSH_AUTH_SOCK={0}; export SSH_AUTH_SOCK;\n'.format(sock_path)
         sys.stdout.write(out)
         sys.stdout.flush()
@@ -300,7 +346,7 @@ def main(device_type):
         command = os.environ['SHELL']
         sys.stdin.close()
 
-    if command or args.daemonize or args.foreground:
+    if command or (daemon and args.daemonize) or args.foreground:
         with context:
             return run_server(conn=conn, command=command, sock_path=sock_path,
                               debug=args.debug, timeout=args.timeout)

libagent/win_server.py

@@ -0,0 +1,191 @@
+"""Windows named pipe server for ssh-agent implementation."""
+import logging
+import pywintypes
+import struct
+import threading
+import win32api
+import win32event
+import win32pipe
+import win32file
+import winerror
+
+from . import util
+
+log = logging.getLogger(__name__)
+
+PIPE_BUFFER_SIZE = 64 * 1024
+
+# Make MemoryView look like a buffer to reuse util.recv
+class MvBuffer:
+    def __init__(self, mv):
+        self.mv = mv
+    def read(self, n):
+        return self.mv[0:n]
+
+# Based loosely on https://docs.microsoft.com/en-us/windows/win32/ipc/multithreaded-pipe-server
+class NamedPipe:
+    __frame_size_size = struct.calcsize('>L')
+
+    def __close(handle):
+        """Closes a named pipe handle."""
+        if handle == win32file.INVALID_HANDLE_VALUE:
+            return
+        win32file.FlushFileBuffers(handle)
+        win32pipe.DisconnectNamedPipe(handle)
+        win32api.CloseHandle(handle)
+
+    def open(name):
+        """Opens a named pipe server for receiving connections."""
+        handle = win32pipe.CreateNamedPipe(
+            name,
+            win32pipe.PIPE_ACCESS_DUPLEX | win32file.FILE_FLAG_OVERLAPPED,
+            win32pipe.PIPE_TYPE_MESSAGE | win32pipe.PIPE_READMODE_MESSAGE | win32pipe.PIPE_WAIT,
+            win32pipe.PIPE_UNLIMITED_INSTANCES,
+            PIPE_BUFFER_SIZE,
+            PIPE_BUFFER_SIZE,
+            0,
+            None) # Default security attributes
+
+        if handle == win32file.INVALID_HANDLE_VALUE:
+            log.error("CreateNamedPipe failed (%d)", win32api.GetLastError())
+            return None
+        
+        try:
+            pending_io = False
+            overlapped = win32file.OVERLAPPED()
+            overlapped.hEvent = win32event.CreateEvent(None, True, True, None)
+            error_code = win32pipe.ConnectNamedPipe(handle, overlapped)
+            if error_code == winerror.ERROR_IO_PENDING:
+                pending_io = True
+            elif error_code != winerror.ERROR_PIPE_CONNECTED or not win32event.SetEvent(overlapped.hEvent):
+                log.error('ConnectNamedPipe failed (%d)', error_code)
+                return None
+            log.debug('waiting for connection on %s', name)
+            return NamedPipe(name, handle, overlapped, pending_io)
+        except:
+            NamedPipe.__close(handle)
+            raise
+
+    def __init__(self, name, handle, overlapped, pending_io):
+        self.name = name
+        self.handle = handle
+        self.overlapped = overlapped
+        self.pending_io = pending_io
+
+    def close(self):
+        """Close the named pipe."""
+        NamedPipe.__close(self.handle)
+
+    def connect(self, timeout):
+        """Connect to an SSH client with the specified timeout."""
+        waitHandle = win32event.WaitForSingleObject(
+            self.overlapped.hEvent,
+            timeout)
+        if waitHandle == win32event.WAIT_TIMEOUT:
+            return False
+        if not self.pending_io:
+            return True
+        win32pipe.GetOverlappedResult(
+            self.handle,
+            self.overlapped,
+            False)
+        error_code = win32api.GetLastError()
+        if error_code == winerror.NO_ERROR:
+            return True
+        log.error('GetOverlappedResult failed (%d)', error_code)
+        return False
+
+    def read_frame(self, quit_event):
+        """Read the request frame from the SSH client."""
+        request_size = None
+        remaining = None
+        buf = MvBuffer(win32file.AllocateReadBuffer(PIPE_BUFFER_SIZE))
+        while True:
+            if quit_event.is_set():
+                return None
+            error_code, _ = win32file.ReadFile(self.handle, buf.mv, self.overlapped)
+            if error_code not in (winerror.NO_ERROR, winerror.ERROR_IO_PENDING, winerror.ERROR_MORE_DATA):
+                log.error('ReadFile failed (%d)', error_code)
+                return None
+            win32event.WaitForSingleObject(self.overlapped.hEvent, win32event.INFINITE)
+            chunk_size = win32pipe.GetOverlappedResult(self.handle, self.overlapped, False)
+            error_code = win32api.GetLastError()
+            if error_code != winerror.NO_ERROR:
+                log.error('GetOverlappedResult failed (%d)', error_code)
+                return None
+            if request_size:
+                remaining -= chunk_size
+            else:
+                request_size, = util.recv(buf, '>L')
+                remaining = request_size - (chunk_size - NamedPipe.__frame_size_size)
+            if remaining <= 0:
+                break
+        return util.recv(buf, request_size)
+
+    def send(self, reply):
+        """Send the specified reply to the SSH client."""
+        error_code, _ = win32file.WriteFile(self.handle, reply)
+        if error_code == winerror.NO_ERROR:
+            return True
+        log.error('WriteFile failed (%d)', error_code)
+        return False
+
+
+def handle_connection(pipe, handler, mutex, quit_event):
+    """
+    Handle a single connection using the specified protocol handler in a loop.
+
+    Since this function may be called concurrently from server_thread,
+    the specified mutex is used to synchronize the device handling.
+    """
+    log.debug('welcome agent')
+
+    try:
+        while True:
+            if quit_event.is_set():
+                return
+            msg = pipe.read_frame(quit_event)
+            if not msg:
+                return
+            with mutex:
+                reply = handler.handle(msg=msg)
+            if not pipe.send(reply):
+                return
+    except pywintypes.error as e:
+        # Surface errors that aren't related to the client disconnecting
+        if e.args[0] == winerror.ERROR_BROKEN_PIPE:
+            log.debug('goodbye agent')
+        else:
+            raise
+    except Exception as e:  # pylint: disable=broad-except
+        log.warning('error: %s', e, exc_info=True)
+    finally:
+        pipe.close()
+
+
+def server_thread(pipe_name, handle_conn, quit_event, timeout):
+    """Run a Windows server on the specified pipe."""
+    log.debug('server thread started')
+
+    while True:
+        if quit_event.is_set():
+            break
+        # A new pipe instance is necessary for each client
+        pipe = NamedPipe.open(pipe_name)
+        if not pipe:
+            break
+        try:
+            # Poll for a new client connection
+            while True:
+                if quit_event.is_set():
+                    break
+                if pipe.connect(timeout * 1000):
+                    # Handle connections from SSH concurrently.
+                    threading.Thread(target=handle_conn,
+                                     kwargs=dict(pipe=pipe)).start()
+                    break
+        except:
+            pipe.close()
+            raise
+
+    log.debug('server thread stopped')

setup.py

@@ -27,6 +27,7 @@ setup(
         'pymsgbox>=1.0.6',
         'semver>=2.2',
         'unidecode>=0.4.20',
+        'pypiwin32'
     ],
     platforms=['POSIX'],
     classifiers=[

tox.ini

@@ -14,6 +14,7 @@ deps=
     semver
     pydocstyle
     isort<5
+    pypiwin32
 commands=
     pycodestyle libagent
     isort --skip-glob .tox -c -rc libagent