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# ssh.py - Interact with remote SSH servers
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#
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# Copyright 2019 Gregory Szorc <gregory.szorc@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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# no-check-code because Python 3 native.
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import socket
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import time
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import warnings
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from cryptography.utils import (
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CryptographyDeprecationWarning,
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)
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import paramiko
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def wait_for_ssh(hostname, port, timeout=60, username=None, key_filename=None):
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"""Wait for an SSH server to start on the specified host and port."""
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class IgnoreHostKeyPolicy(paramiko.MissingHostKeyPolicy):
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def missing_host_key(self, client, hostname, key):
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return
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end_time = time.time() + timeout
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# paramiko triggers a CryptographyDeprecationWarning in the cryptography
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# package. Let's suppress
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with warnings.catch_warnings():
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warnings.filterwarnings('ignore',
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category=CryptographyDeprecationWarning)
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while True:
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client = paramiko.SSHClient()
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client.set_missing_host_key_policy(IgnoreHostKeyPolicy())
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try:
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client.connect(hostname, port=port, username=username,
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key_filename=key_filename,
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timeout=5.0, allow_agent=False,
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look_for_keys=False)
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return client
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except socket.error:
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pass
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except paramiko.AuthenticationException:
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raise
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except paramiko.SSHException:
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pass
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if time.time() >= end_time:
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raise Exception('Timeout reached waiting for SSH')
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time.sleep(1.0)
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def exec_command(client, command):
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"""exec_command wrapper that combines stderr/stdout and returns channel"""
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chan = client.get_transport().open_session()
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chan.exec_command(command)
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chan.set_combine_stderr(True)
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stdin = chan.makefile('wb', -1)
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stdout = chan.makefile('r', -1)
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return chan, stdin, stdout
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