contrib/automation/hgautomation/ssh.py

admin-command: add verify command

Start using the 'admin' namespace by adding a 'verify' command.
Invocation is 'admin::verify'.
The idea is to progressively add more focused checks than the existing
verify command.
To do so we need an advanced way to express what we want to check.

The first check for admin::verify is 'working-copy.dirstate' which has
no options, because it was an easy first check to implement, which
verifies the integrity of the dirstate.

This changeset was created with the help of Franck Bret.

# ssh.py - Interact with remote SSH servers
#
# Copyright 2019 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# no-check-code because Python 3 native.

import socket
import time
import warnings

from cryptography.utils import CryptographyDeprecationWarning
import paramiko


def wait_for_ssh(hostname, port, timeout=60, username=None, key_filename=None):
    """Wait for an SSH server to start on the specified host and port."""

    class IgnoreHostKeyPolicy(paramiko.MissingHostKeyPolicy):
        def missing_host_key(self, client, hostname, key):
            return

    end_time = time.time() + timeout

    # paramiko triggers a CryptographyDeprecationWarning in the cryptography
    # package. Let's suppress
    with warnings.catch_warnings():
        warnings.filterwarnings(
            'ignore', category=CryptographyDeprecationWarning
        )

        while True:
            client = paramiko.SSHClient()
            client.set_missing_host_key_policy(IgnoreHostKeyPolicy())
            try:
                client.connect(
                    hostname,
                    port=port,
                    username=username,
                    key_filename=key_filename,
                    timeout=5.0,
                    allow_agent=False,
                    look_for_keys=False,
                )

                return client
            except socket.error:
                pass
            except paramiko.AuthenticationException:
                raise
            except paramiko.SSHException:
                pass

            if time.time() >= end_time:
                raise Exception('Timeout reached waiting for SSH')

            time.sleep(1.0)


def exec_command(client, command):
    """exec_command wrapper that combines stderr/stdout and returns channel"""
    chan = client.get_transport().open_session()

    chan.exec_command(command)
    chan.set_combine_stderr(True)

    stdin = chan.makefile('wb', -1)
    stdout = chan.makefile('r', -1)

    return chan, stdin, stdout