# Copyright (c) 2013-2021 by Ron Frederick <ronf@timeheart.net> and others.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v2.0 which accompanies this
# distribution and is available at:
#
# http://www.eclipse.org/legal/epl-2.0/
#
# This program may also be made available under the following secondary
# licenses when the conditions for such availability set forth in the
# Eclipse Public License v2.0 are satisfied:
#
# GNU General Public License, Version 2.0, or any later versions of
# that license
#
# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
#
# Contributors:
# Ron Frederick - initial implementation, API, and documentation
"""SSH stream handlers"""
import asyncio
import inspect
import re
from typing import TYPE_CHECKING, Any, AnyStr, AsyncIterator
from typing import Callable, Dict, Generic, Iterable, List
from typing import Optional, Pattern, Set, Tuple, Union, cast
from .constants import EXTENDED_DATA_STDERR
from .logging import SSHLogger
from .misc import MaybeAwait, BreakReceived, SignalReceived
from .misc import SoftEOFReceived, TerminalSizeChanged
from .session import DataType, SSHClientSession, SSHServerSession
from .session import SSHTCPSession, SSHUNIXSession
from .sftp import SFTPServer, run_sftp_server
from .scp import run_scp_server
if TYPE_CHECKING:
# pylint: disable=cyclic-import
from .channel import SSHChannel
from .connection import SSHConnection
if TYPE_CHECKING:
_WaiterFuture = asyncio.Future[None]
else:
_WaiterFuture = asyncio.Future
_RecvBuf = List[Union[AnyStr, Exception]]
_RecvBufMap = Dict[DataType, _RecvBuf[AnyStr]]
_ReadLocks = Dict[DataType, asyncio.Lock]
_ReadWaiters = Dict[DataType, Optional[_WaiterFuture]]
_DrainWaiters = Dict[DataType, Set[_WaiterFuture]]
SSHSocketSessionFactory = Callable[['SSHReader', 'SSHWriter'],
MaybeAwait[None]]
_OptSocketSessionFactory = Optional[SSHSocketSessionFactory]
SSHServerSessionFactory = Callable[['SSHReader', 'SSHWriter',
'SSHWriter'], MaybeAwait[None]]
_OptServerSessionFactory = Optional[SSHServerSessionFactory]
SFTPServerFactory = Callable[['SSHChannel[bytes]'], SFTPServer]
_OptSFTPServerFactory = Optional[SFTPServerFactory]
_NEWLINE = object()
[docs]
class SSHReader(Generic[AnyStr]):
"""SSH read stream handler"""
def __init__(self, session: 'SSHStreamSession[AnyStr]',
chan: 'SSHChannel[AnyStr]', datatype: DataType = None):
self._session: 'SSHStreamSession[AnyStr]' = session
self._chan: 'SSHChannel[AnyStr]' = chan
self._datatype = datatype
async def __aiter__(self) -> AsyncIterator[AnyStr]:
"""Allow SSHReader to be an async iterator"""
while not self.at_eof():
yield await self.readline()
@property
def channel(self) -> 'SSHChannel[AnyStr]':
"""The SSH channel associated with this stream"""
return self._chan
@property
def logger(self) -> SSHLogger:
"""The SSH logger associated with this stream"""
return self._chan.logger
[docs]
def feed_data(self, data: AnyStr) -> None:
"""Feed data to the associated session
This method feeds data to the SSH session associated with
this stream, providing compatibility with the
:meth:`feed_data() <asyncio.StreamReader.feed_data>` method
on :class:`asyncio.StreamReader`. This is mostly useful
for testing.
"""
self._session.data_received(data, self._datatype)
[docs]
def feed_eof(self) -> None:
"""Feed EOF to the associated session
This method feeds an end-of-file indication to the SSH session
associated with this stream, providing compatibility with the
:meth:`feed_eof() <asyncio.StreamReader.feed_data>` method
on :class:`asyncio.StreamReader`. This is mostly useful
for testing.
"""
self._session.eof_received()
[docs]
async def read(self, n: int = -1) -> AnyStr:
"""Read data from the stream
This method is a coroutine which reads up to `n` bytes
or characters from the stream. If `n` is not provided or
set to `-1`, it reads until EOF or a signal is received.
If EOF is received and the receive buffer is empty, an
empty `bytes` or `str` object is returned.
If the next data in the stream is a signal, the signal is
delivered as a raised exception.
.. note:: Unlike traditional `asyncio` stream readers,
the data will be delivered as either `bytes` or
a `str` depending on whether an encoding was
specified when the underlying channel was opened.
"""
return await self._session.read(n, self._datatype, exact=False)
[docs]
async def readline(self) -> AnyStr:
"""Read one line from the stream
This method is a coroutine which reads one line, ending in
`'\\n'`.
If EOF is received before `'\\n'` is found, the partial
line is returned. If EOF is received and the receive buffer
is empty, an empty `bytes` or `str` object is returned.
If the next data in the stream is a signal, the signal is
delivered as a raised exception.
.. note:: In Python 3.5 and later, :class:`SSHReader` objects
can also be used as async iterators, returning input
data one line at a time.
"""
try:
return await self.readuntil(_NEWLINE)
except asyncio.IncompleteReadError as exc:
return cast(AnyStr, exc.partial)
[docs]
async def readuntil(self, separator: object,
max_separator_len = 0) -> AnyStr:
"""Read data from the stream until `separator` is seen
This method is a coroutine which reads from the stream until
the requested separator is seen. If a match is found, the
returned data will include the separator at the end.
The `separator` argument can be a single `bytes` or `str`
value, a sequence of multiple `bytes` or `str` values,
or a compiled regex (`re.Pattern`) to match against,
returning data as soon as a matching separator is found
in the stream.
When passing a regex pattern as the separator, the
`max_separator_len` argument should be set to the
maximum length of an expected separator match. This
can greatly improve performance, by minimizing how far
back into the stream must be searched for a match.
When passing literal separators to match against, the
max separator length will be set automatically.
.. note:: For best results, a separator regex should
both begin and end with data which is as
unique as possible, and should not start or
end with optional or repeated elements.
Otherwise, you run the risk of failing to
match parts of a separator when it is split
across multiple reads.
If EOF or a signal is received before a match occurs, an
:exc:`IncompleteReadError <asyncio.IncompleteReadError>`
is raised and its `partial` attribute will contain the
data in the stream prior to the EOF or signal.
If the next data in the stream is a signal, the signal is
delivered as a raised exception.
"""
return await self._session.readuntil(separator, self._datatype,
max_separator_len)
[docs]
async def readexactly(self, n: int) -> AnyStr:
"""Read an exact amount of data from the stream
This method is a coroutine which reads exactly n bytes or
characters from the stream.
If EOF or a signal is received in the stream before `n`
bytes are read, an :exc:`IncompleteReadError
<asyncio.IncompleteReadError>` is raised and its `partial`
attribute will contain the data before the EOF or signal.
If the next data in the stream is a signal, the signal is
delivered as a raised exception.
"""
return await self._session.read(n, self._datatype, exact=True)
[docs]
def at_eof(self) -> bool:
"""Return whether the stream is at EOF
This method returns `True` when EOF has been received and
all data in the stream has been read.
"""
return self._session.at_eof(self._datatype)
def get_redirect_info(self) -> Tuple['SSHStreamSession[AnyStr]', DataType]:
"""Get information needed to redirect from this SSHReader"""
return self._session, self._datatype
[docs]
class SSHWriter(Generic[AnyStr]):
"""SSH write stream handler"""
def __init__(self, session: 'SSHStreamSession[AnyStr]',
chan: 'SSHChannel[AnyStr]', datatype: DataType = None):
self._session: 'SSHStreamSession[AnyStr]' = session
self._chan: 'SSHChannel[AnyStr]' = chan
self._datatype = datatype
@property
def channel(self) -> 'SSHChannel[AnyStr]':
"""The SSH channel associated with this stream"""
return self._chan
@property
def logger(self) -> SSHLogger:
"""The SSH logger associated with this stream"""
return self._chan.logger
[docs]
def can_write_eof(self) -> bool:
"""Return whether the stream supports :meth:`write_eof`"""
return self._chan.can_write_eof()
[docs]
def close(self) -> None:
"""Close the channel
.. note:: After this is called, no data can be read or written
from any of the streams associated with this channel.
"""
return self._chan.close()
[docs]
def is_closing(self) -> bool:
"""Return if the stream is closing or is closed"""
return self._chan.is_closing()
[docs]
async def wait_closed(self) -> None:
"""Wait until the stream is closed
This should be called after :meth:`close` to wait until
the underlying connection is closed.
"""
await self._chan.wait_closed()
[docs]
async def drain(self) -> None:
"""Wait until the write buffer on the channel is flushed
This method is a coroutine which blocks the caller if the
stream is currently paused for writing, returning when
enough data has been sent on the channel to allow writing
to resume. This can be used to avoid buffering an excessive
amount of data in the channel's send buffer.
"""
await self._session.drain(self._datatype)
[docs]
def write(self, data: AnyStr) -> None:
"""Write data to the stream
This method writes bytes or characters to the stream.
.. note:: Unlike traditional `asyncio` stream writers,
the data must be supplied as either `bytes` or
a `str` depending on whether an encoding was
specified when the underlying channel was opened.
"""
return self._chan.write(data, self._datatype)
[docs]
def writelines(self, list_of_data: Iterable[AnyStr]) -> None:
"""Write a collection of data to the stream"""
return self._chan.writelines(list_of_data, self._datatype)
[docs]
def write_eof(self) -> None:
"""Write EOF on the channel
This method sends an end-of-file indication on the channel,
after which no more data can be written.
.. note:: On an :class:`SSHServerChannel` where multiple
output streams are created, writing EOF on one
stream signals EOF for all of them, since it
applies to the channel as a whole.
"""
return self._chan.write_eof()
def get_redirect_info(self) -> Tuple['SSHStreamSession[AnyStr]', DataType]:
"""Get information needed to redirect to this SSHWriter"""
return self._session, self._datatype
class SSHStreamSession(Generic[AnyStr]):
"""SSH stream session handler"""
def __init__(self) -> None:
self._chan: Optional['SSHChannel[AnyStr]'] = None
self._conn: Optional['SSHConnection'] = None
self._encoding: Optional[str] = None
self._errors = 'strict'
self._loop: Optional[asyncio.AbstractEventLoop] = None
self._limit = 0
self._exception: Optional[Exception] = None
self._eof_received = False
self._connection_lost = False
self._read_paused = False
self._write_paused = False
self._recv_buf_len = 0
self._recv_buf: _RecvBufMap[AnyStr] = {None: []}
self._read_locks: _ReadLocks = {None: asyncio.Lock()}
self._read_waiters: _ReadWaiters = {None: None}
self._drain_waiters: _DrainWaiters = {None: set()}
async def _block_read(self, datatype: DataType) -> None:
"""Wait for more data to arrive on the stream"""
try:
assert self._loop is not None
waiter: _WaiterFuture = self._loop.create_future()
self._read_waiters[datatype] = waiter
await waiter
finally:
self._read_waiters[datatype] = None
def _unblock_read(self, datatype: DataType) -> None:
"""Signal that more data has arrived on the stream"""
waiter = self._read_waiters[datatype]
if waiter and not waiter.done():
waiter.set_result(None)
def _should_block_drain(self, datatype: DataType) -> bool:
"""Return whether output is still being written to the channel"""
# pylint: disable=unused-argument
return self._write_paused and not self._connection_lost
def _unblock_drain(self, datatype: DataType) -> None:
"""Signal that more data can be written on the stream"""
if not self._should_block_drain(datatype):
for waiter in self._drain_waiters[datatype]:
if not waiter.done(): # pragma: no branch
waiter.set_result(None)
def _should_pause_reading(self) -> bool:
"""Return whether to pause reading from the channel"""
return bool(self._limit) and self._recv_buf_len >= self._limit
def _maybe_pause_reading(self) -> bool:
"""Pause reading if necessary"""
if not self._read_paused and self._should_pause_reading():
assert self._chan is not None
self._read_paused = True
self._chan.pause_reading()
return True
else:
return False
def _maybe_resume_reading(self) -> bool:
"""Resume reading if necessary"""
if self._read_paused and not self._should_pause_reading():
assert self._chan is not None
self._read_paused = False
self._chan.resume_reading()
return True
else:
return False
def connection_made(self, chan: 'SSHChannel[AnyStr]') -> None:
"""Handle a newly opened channel"""
self._chan = chan
self._conn = chan.get_connection()
self._encoding, self._errors = chan.get_encoding()
self._loop = chan.get_loop()
self._limit = self._chan.get_recv_window()
for datatype in chan.get_read_datatypes():
self._recv_buf[datatype] = []
self._read_locks[datatype] = asyncio.Lock()
self._read_waiters[datatype] = None
for datatype in chan.get_write_datatypes():
self._drain_waiters[datatype] = set()
def connection_lost(self, exc: Optional[Exception]) -> None:
"""Handle an incoming channel close"""
self._connection_lost = True
self._exception = exc
if not self._eof_received:
if exc:
for datatype in self._read_waiters:
self._recv_buf[datatype].append(exc)
self.eof_received()
for datatype in self._drain_waiters:
self._unblock_drain(datatype)
def data_received(self, data: AnyStr, datatype: DataType) -> None:
"""Handle incoming data on the channel"""
self._recv_buf[datatype].append(data)
self._recv_buf_len += len(data)
self._unblock_read(datatype)
self._maybe_pause_reading()
def eof_received(self) -> bool:
"""Handle an incoming end of file on the channel"""
self._eof_received = True
for datatype in self._read_waiters:
self._unblock_read(datatype)
return True
def at_eof(self, datatype: DataType) -> bool:
"""Return whether end of file has been received on the channel"""
return self._eof_received and not self._recv_buf[datatype]
def pause_writing(self) -> None:
"""Handle a request to pause writing on the channel"""
self._write_paused = True
def resume_writing(self) -> None:
"""Handle a request to resume writing on the channel"""
self._write_paused = False
for datatype in self._drain_waiters:
self._unblock_drain(datatype)
async def read(self, n: int, datatype: DataType, exact: bool) -> AnyStr:
"""Read data from the channel"""
recv_buf = self._recv_buf[datatype]
data: List[AnyStr] = []
break_read = False
async with self._read_locks[datatype]:
while True:
while recv_buf and n != 0:
if isinstance(recv_buf[0], Exception):
if data:
break_read = True
break
else:
exc = cast(Exception, recv_buf.pop(0))
if isinstance(exc, SoftEOFReceived):
n = 0
break
else:
raise exc
l = len(recv_buf[0])
if l > n > 0:
data.append(recv_buf[0][:n])
recv_buf[0] = recv_buf[0][n:]
self._recv_buf_len -= n
n = 0
break
data.append(cast(AnyStr, recv_buf.pop(0)))
self._recv_buf_len -= l
n -= l
if self._maybe_resume_reading():
continue
if n == 0 or (n > 0 and data and not exact) or \
(n < 0 and recv_buf) or \
self._eof_received or break_read:
break
await self._block_read(datatype)
result = cast(AnyStr, '' if self._encoding else b'').join(data)
if n > 0 and exact:
raise asyncio.IncompleteReadError(cast(bytes, result),
len(result) + n)
return result
async def readuntil(self, separator: object, datatype: DataType,
max_separator_len: int) -> AnyStr:
"""Read data from the channel until a separator is seen"""
if not separator:
raise ValueError('Separator cannot be empty')
buf = cast(AnyStr, '' if self._encoding else b'')
recv_buf = self._recv_buf[datatype]
if separator is _NEWLINE:
seplen = 1
separators = cast(AnyStr, '\n' if self._encoding else b'\n')
pat = re.compile(separators)
elif isinstance(separator, (bytes, str)):
seplen = len(separator)
pat = re.compile(re.escape(cast(AnyStr, separator)))
elif isinstance(separator, Pattern):
seplen = max_separator_len
pat = cast(Pattern[AnyStr], separator)
else:
bar = cast(AnyStr, '|' if self._encoding else b'|')
seplist = list(cast(Iterable[AnyStr], separator))
seplen = max(len(sep) for sep in seplist)
separators = bar.join(re.escape(sep) for sep in seplist)
pat = re.compile(separators)
curbuf = 0
buflen = 0
async with self._read_locks[datatype]:
while True:
while curbuf < len(recv_buf):
if isinstance(recv_buf[curbuf], Exception):
if buf:
recv_buf[:curbuf] = []
self._recv_buf_len -= buflen
raise asyncio.IncompleteReadError(
cast(bytes, buf), None)
else:
exc = recv_buf.pop(0)
if isinstance(exc, SoftEOFReceived):
return buf
else:
raise cast(Exception, exc)
newbuf = cast(AnyStr, recv_buf[curbuf])
buf += newbuf
start = 0 if seplen == 0 else max(buflen + 1 - seplen, 0)
match = pat.search(buf, start)
if match:
idx = match.end()
recv_buf[:curbuf] = []
recv_buf[0] = buf[idx:]
buf = buf[:idx]
self._recv_buf_len -= idx
if not recv_buf[0]:
recv_buf.pop(0)
self._maybe_resume_reading()
return buf
buflen += len(newbuf)
curbuf += 1
if self._read_paused or self._eof_received:
recv_buf[:curbuf] = []
self._recv_buf_len -= buflen
self._maybe_resume_reading()
raise asyncio.IncompleteReadError(cast(bytes, buf), None)
await self._block_read(datatype)
async def drain(self, datatype: DataType) -> None:
"""Wait for data written to the channel to drain"""
while self._should_block_drain(datatype):
try:
assert self._loop is not None
waiter: _WaiterFuture = self._loop.create_future()
self._drain_waiters[datatype].add(waiter)
await waiter
finally:
self._drain_waiters[datatype].remove(waiter)
if self._connection_lost:
exc = self._exception
if not exc and self._write_paused:
exc = BrokenPipeError()
if exc:
raise exc
class SSHClientStreamSession(SSHStreamSession[AnyStr],
SSHClientSession[AnyStr]):
"""SSH client stream session handler"""
class SSHServerStreamSession(SSHStreamSession[AnyStr],
SSHServerSession[AnyStr]):
"""SSH server stream session handler"""
def __init__(self, session_factory: _OptServerSessionFactory,
sftp_factory: _OptSFTPServerFactory = None,
sftp_version = 0, allow_scp = False):
super().__init__()
self._session_factory = session_factory
self._sftp_factory = sftp_factory
self._sftp_version = sftp_version
self._allow_scp = allow_scp and bool(sftp_factory)
def _init_sftp_server(self) -> SFTPServer:
"""Initialize an SFTP server for this stream to use"""
assert self._chan is not None
self._chan.set_encoding(None)
self._encoding = None
assert self._sftp_factory is not None
return self._sftp_factory(cast('SSHChannel[bytes]', self._chan))
def shell_requested(self) -> bool:
"""Return whether a shell can be requested"""
return bool(self._session_factory)
def exec_requested(self, command: str) -> bool:
"""Return whether execution of a command can be requested"""
# Avoid incorrect pylint suggestion to use ternary
# pylint: disable=consider-using-ternary
return ((self._allow_scp and command.startswith('scp ')) or
bool(self._session_factory))
def subsystem_requested(self, subsystem: str) -> bool:
"""Return whether starting a subsystem can be requested"""
if subsystem == 'sftp':
return bool(self._sftp_factory)
else:
return bool(self._session_factory)
def session_started(self) -> None:
"""Start a session for this newly opened server channel"""
assert self._chan is not None
command = self._chan.get_command()
stdin = SSHReader[AnyStr](self, self._chan)
stdout = SSHWriter[AnyStr](self, self._chan)
stderr = SSHWriter[AnyStr](self, self._chan, EXTENDED_DATA_STDERR)
handler: MaybeAwait[None]
if self._chan.get_subsystem() == 'sftp':
stdin_bytes = cast(SSHReader[bytes], stdin)
stdout_bytes = cast(SSHWriter[bytes], stdout)
handler = run_sftp_server(self._init_sftp_server(),
stdin_bytes, stdout_bytes,
self._sftp_version)
elif self._allow_scp and command and command.startswith('scp '):
stdin_bytes = cast(SSHReader[bytes], stdin)
stdout_bytes = cast(SSHWriter[bytes], stdout)
stderr_bytes = cast(SSHWriter[bytes], stderr)
handler = run_scp_server(self._init_sftp_server(), command,
stdin_bytes, stdout_bytes, stderr_bytes)
else:
assert self._session_factory is not None
handler = self._session_factory(stdin, stdout, stderr)
if inspect.isawaitable(handler):
assert self._conn is not None
assert handler is not None
self._conn.create_task(handler, stdin.logger)
def exception_received(self, exc: Exception) -> None:
"""Handle an incoming exception on the channel"""
self._recv_buf[None].append(exc)
self._unblock_read(None)
def break_received(self, msec: int) -> bool:
"""Handle an incoming break on the channel"""
self.exception_received(BreakReceived(msec))
return True
def signal_received(self, signal: str) -> None:
"""Handle an incoming signal on the channel"""
self.exception_received(SignalReceived(signal))
def soft_eof_received(self) -> None:
"""Handle an incoming soft EOF on the channel"""
self.exception_received(SoftEOFReceived())
def terminal_size_changed(self, width: int, height: int,
pixwidth: int, pixheight: int) -> None:
"""Handle an incoming terminal size change on the channel"""
self.exception_received(TerminalSizeChanged(width, height,
pixwidth, pixheight))
class SSHSocketStreamSession(SSHStreamSession[AnyStr]):
"""Socket stream session handler"""
def __init__(self, session_factory: _OptSocketSessionFactory = None):
super().__init__()
self._session_factory = session_factory
def session_started(self) -> None:
"""Start a session for this newly opened socket channel"""
if self._session_factory:
assert self._chan is not None
reader = SSHReader[AnyStr](self, self._chan)
writer = SSHWriter[AnyStr](self, self._chan)
handler = self._session_factory(reader, writer)
if inspect.isawaitable(handler):
assert self._conn is not None
assert handler is not None
self._conn.create_task(handler, reader.logger)
class SSHTCPStreamSession(SSHSocketStreamSession[AnyStr],
SSHTCPSession[AnyStr]):
"""TCP stream session handler"""
class SSHUNIXStreamSession(SSHSocketStreamSession[AnyStr],
SSHUNIXSession[AnyStr]):
"""UNIX stream session handler"""