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Filename : ssh.py
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# Copyright 2020 Canonical, Ltd.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import logging
import os
import pwd

from subiquitycore.utils import run_command


log = logging.getLogger("subiquitycore.ssh")


def host_key_fingerprints():
    """Query sshd to find the host keys and then fingerprint them.

    Returns a sequence of (key-type, fingerprint) pairs.
    """
    config = run_command(['sshd', '-T'])
    if config.returncode != 0:
        log.debug("sshd -T failed %r", config.stderr)
        return []
    keyfiles = []
    for line in config.stdout.splitlines():
        if line.startswith('hostkey '):
            keyfiles.append(line.split(None, 1)[1])
    info = []
    for keyfile in keyfiles:
        info.extend(fingerprints(keyfile))
    return info


def fingerprints(keyfile):
    info = []
    cp = run_command(['ssh-keygen', '-lf', keyfile])
    if cp.returncode != 0:
        log.debug("ssh-keygen -lf %s failed %r", keyfile, cp.stderr)
        return info
    for line in cp.stdout.splitlines():
        parts = line.strip().replace('\r', '').split()
        fingerprint = parts[1]
        keytype = parts[-1].strip('()')
        info.append((keytype, fingerprint))
    return info


host_keys_intro = _("""\
The host key fingerprints are:
""")

host_key_tmpl = """
    {keytype:{width}} {fingerprint}"""

single_host_key_tmpl = _("""\
The {keytype} host key fingerprint is:
    {fingerprint}
""")


def host_key_info():
    return summarize_host_keys(host_key_fingerprints())


def summarize_host_keys(fingerprints):
    if len(fingerprints) == 0:
        return ''
    if len(fingerprints) == 1:
        [(keytype, fingerprint)] = fingerprints
        return _(single_host_key_tmpl).format(keytype=keytype,
                                              fingerprint=fingerprint)
    lines = [_(host_keys_intro)]
    longest_type = max([len(keytype) for keytype, _ in fingerprints])
    for keytype, fingerprint in fingerprints:
        lines.append(host_key_tmpl.format(keytype=keytype,
                                          fingerprint=fingerprint,
                                          width=longest_type))
    return "".join(lines)


def user_key_fingerprints(username):
    try:
        user_info = pwd.getpwnam(username)
    except KeyError:
        log.exception("getpwnam(%s) failed", username)
        return []
    user_key_file = '{}/.ssh/authorized_keys'.format(user_info.pw_dir)
    if os.path.exists(user_key_file):
        return fingerprints(user_key_file)
    else:
        return []


def get_ips_standalone():
    from probert.prober import Prober
    from subiquitycore.models.network import NETDEV_IGNORED_IFACE_TYPES
    prober = Prober()
    prober.probe_network()
    links = prober.get_results()['network']['links']
    ips = []
    for link in sorted(links, key=lambda link: link['netlink_data']['name']):
        if link['type'] in NETDEV_IGNORED_IFACE_TYPES:
            continue
        for addr in link['addresses']:
            if addr['scope'] == "global":
                ips.append(addr['address'].split('/')[0])
    return ips