317 lines
12 KiB
Python
317 lines
12 KiB
Python
# Copyright 2019, David Wilson
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# 3. Neither the name of the copyright holder nor the names of its contributors
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# may be used to endorse or promote products derived from this software without
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# specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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# !mitogen: minify_safe
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"""
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Functionality to allow establishing new slave contexts over an SSH connection.
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"""
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import logging
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import re
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try:
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from shlex import quote as shlex_quote
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except ImportError:
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from pipes import quote as shlex_quote
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import mitogen.parent
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from mitogen.core import b
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from mitogen.core import bytes_partition
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try:
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any
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except NameError:
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from mitogen.core import any
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LOG = logging.getLogger('mitogen')
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# sshpass uses 'assword' because it doesn't lowercase the input.
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PASSWORD_PROMPT = b('password')
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HOSTKEY_REQ_PROMPT = b('are you sure you want to continue connecting (yes/no)?')
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HOSTKEY_FAIL = b('host key verification failed.')
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# [user@host: ] permission denied
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PERMDENIED_RE = re.compile(
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('(?:[^@]+@[^:]+: )?' # Absent in OpenSSH <7.5
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'Permission denied').encode(),
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re.I
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)
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DEBUG_PREFIXES = (b('debug1:'), b('debug2:'), b('debug3:'))
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def filter_debug(stream, it):
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"""
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Read line chunks from it, either yielding them directly, or building up and
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logging individual lines if they look like SSH debug output.
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This contains the mess of dealing with both line-oriented input, and partial
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lines such as the password prompt.
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Yields `(line, partial)` tuples, where `line` is the line, `partial` is
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:data:`True` if no terminating newline character was present and no more
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data exists in the read buffer. Consuming code can use this to unreliably
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detect the presence of an interactive prompt.
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"""
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# The `partial` test is unreliable, but is only problematic when verbosity
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# is enabled: it's possible for a combination of SSH banner, password
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# prompt, verbose output, timing and OS buffering specifics to create a
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# situation where an otherwise newline-terminated line appears to not be
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# terminated, due to a partial read(). If something is broken when
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# ssh_debug_level>0, this is the first place to look.
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state = 'start_of_line'
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buf = b('')
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for chunk in it:
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buf += chunk
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while buf:
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if state == 'start_of_line':
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if len(buf) < 8:
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# short read near buffer limit, block awaiting at least 8
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# bytes so we can discern a debug line, or the minimum
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# interesting token from above or the bootstrap
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# ('password', 'MITO000\n').
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break
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elif any(buf.startswith(p) for p in DEBUG_PREFIXES):
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state = 'in_debug'
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else:
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state = 'in_plain'
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elif state == 'in_debug':
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if b('\n') not in buf:
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break
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line, _, buf = bytes_partition(buf, b('\n'))
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LOG.debug('%s: %s', stream.name,
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mitogen.core.to_text(line.rstrip()))
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state = 'start_of_line'
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elif state == 'in_plain':
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line, nl, buf = bytes_partition(buf, b('\n'))
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yield line + nl, not (nl or buf)
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if nl:
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state = 'start_of_line'
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class PasswordError(mitogen.core.StreamError):
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pass
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class HostKeyError(mitogen.core.StreamError):
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pass
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class Stream(mitogen.parent.Stream):
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child_is_immediate_subprocess = False
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#: Default to whatever is available as 'python' on the remote machine,
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#: overriding sys.executable use.
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python_path = 'python'
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#: Number of -v invocations to pass on command line.
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ssh_debug_level = 0
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#: The path to the SSH binary.
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ssh_path = 'ssh'
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hostname = None
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username = None
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port = None
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identity_file = None
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password = None
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ssh_args = None
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check_host_keys_msg = 'check_host_keys= must be set to accept, enforce or ignore'
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def construct(self, hostname, username=None, ssh_path=None, port=None,
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check_host_keys='enforce', password=None, identity_file=None,
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compression=True, ssh_args=None, keepalive_enabled=True,
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keepalive_count=3, keepalive_interval=15,
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identities_only=True, ssh_debug_level=None, **kwargs):
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super(Stream, self).construct(**kwargs)
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if check_host_keys not in ('accept', 'enforce', 'ignore'):
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raise ValueError(self.check_host_keys_msg)
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self.hostname = hostname
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self.username = username
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self.port = port
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self.check_host_keys = check_host_keys
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self.password = password
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self.identity_file = identity_file
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self.identities_only = identities_only
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self.compression = compression
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self.keepalive_enabled = keepalive_enabled
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self.keepalive_count = keepalive_count
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self.keepalive_interval = keepalive_interval
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if ssh_path:
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self.ssh_path = ssh_path
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if ssh_args:
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self.ssh_args = ssh_args
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if ssh_debug_level:
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self.ssh_debug_level = ssh_debug_level
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self._init_create_child()
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def _requires_pty(self):
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"""
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Return :data:`True` if the configuration requires a PTY to be
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allocated. This is only true if we must interactively accept host keys,
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or type a password.
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"""
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return (self.check_host_keys == 'accept' or
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self.password is not None)
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def _init_create_child(self):
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"""
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Initialize the base class :attr:`create_child` and
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:attr:`create_child_args` according to whether we need a PTY or not.
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"""
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if self._requires_pty():
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self.create_child = mitogen.parent.hybrid_tty_create_child
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else:
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self.create_child = mitogen.parent.create_child
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self.create_child_args = {
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'stderr_pipe': True,
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}
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def get_boot_command(self):
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bits = [self.ssh_path]
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if self.ssh_debug_level:
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bits += ['-' + ('v' * min(3, self.ssh_debug_level))]
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else:
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# issue #307: suppress any login banner, as it may contain the
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# password prompt, and there is no robust way to tell the
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# difference.
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bits += ['-o', 'LogLevel ERROR']
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if self.username:
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bits += ['-l', self.username]
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if self.port is not None:
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bits += ['-p', str(self.port)]
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if self.identities_only and (self.identity_file or self.password):
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bits += ['-o', 'IdentitiesOnly yes']
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if self.identity_file:
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bits += ['-i', self.identity_file]
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if self.compression:
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bits += ['-o', 'Compression yes']
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if self.keepalive_enabled:
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bits += [
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'-o', 'ServerAliveInterval %s' % (self.keepalive_interval,),
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'-o', 'ServerAliveCountMax %s' % (self.keepalive_count,),
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]
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if not self._requires_pty():
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bits += ['-o', 'BatchMode yes']
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if self.check_host_keys == 'enforce':
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bits += ['-o', 'StrictHostKeyChecking yes']
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if self.check_host_keys == 'accept':
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bits += ['-o', 'StrictHostKeyChecking ask']
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elif self.check_host_keys == 'ignore':
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bits += [
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'-o', 'StrictHostKeyChecking no',
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'-o', 'UserKnownHostsFile /dev/null',
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'-o', 'GlobalKnownHostsFile /dev/null',
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]
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if self.ssh_args:
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bits += self.ssh_args
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bits.append(self.hostname)
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base = super(Stream, self).get_boot_command()
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return bits + [shlex_quote(s).strip() for s in base]
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def _get_name(self):
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s = u'ssh.' + mitogen.core.to_text(self.hostname)
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if self.port:
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s += u':%s' % (self.port,)
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return s
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auth_incorrect_msg = 'SSH authentication is incorrect'
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password_incorrect_msg = 'SSH password is incorrect'
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password_required_msg = 'SSH password was requested, but none specified'
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hostkey_config_msg = (
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'SSH requested permission to accept unknown host key, but '
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'check_host_keys=ignore. This is likely due to ssh_args= '
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'conflicting with check_host_keys=. Please correct your '
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'configuration.'
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)
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hostkey_failed_msg = (
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'Host key checking is enabled, and SSH reported an unrecognized or '
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'mismatching host key.'
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)
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def _host_key_prompt(self):
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if self.check_host_keys == 'accept':
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LOG.debug('%s: accepting host key', self.name)
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self.diag_stream.transmit_side.write(b('yes\n'))
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return
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# _host_key_prompt() should never be reached with ignore or enforce
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# mode, SSH should have handled that. User's ssh_args= is conflicting
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# with ours.
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raise HostKeyError(self.hostkey_config_msg)
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def _connect_input_loop(self, it):
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password_sent = False
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for buf, partial in filter_debug(self, it):
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LOG.debug('%s: stdout: %s', self.name, buf.rstrip())
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if buf.endswith(self.EC0_MARKER):
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self._ec0_received()
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return
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elif HOSTKEY_REQ_PROMPT in buf.lower():
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self._host_key_prompt()
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elif HOSTKEY_FAIL in buf.lower():
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raise HostKeyError(self.hostkey_failed_msg)
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elif PERMDENIED_RE.match(buf):
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# issue #271: work around conflict with user shell reporting
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# 'permission denied' e.g. during chdir($HOME) by only matching
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# it at the start of the line.
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if self.password is not None and password_sent:
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raise PasswordError(self.password_incorrect_msg)
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elif PASSWORD_PROMPT in buf and self.password is None:
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# Permission denied (password,pubkey)
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raise PasswordError(self.password_required_msg)
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else:
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raise PasswordError(self.auth_incorrect_msg)
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elif partial and PASSWORD_PROMPT in buf.lower():
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if self.password is None:
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raise PasswordError(self.password_required_msg)
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LOG.debug('%s: sending password', self.name)
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self.diag_stream.transmit_side.write(
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(self.password + '\n').encode()
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)
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password_sent = True
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raise mitogen.core.StreamError('bootstrap failed')
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def _connect_bootstrap(self):
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fds = [self.receive_side.fd]
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if self.diag_stream is not None:
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fds.append(self.diag_stream.receive_side.fd)
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it = mitogen.parent.iter_read(fds=fds, deadline=self.connect_deadline)
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try:
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self._connect_input_loop(it)
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finally:
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it.close()
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