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Filename : DataSourceGCE.py
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# Author: Vaidas Jablonskis <jablonskis@gmail.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import datetime
import json

from base64 import b64decode

from cloudinit import dmi
from cloudinit.distros import ug_util
from cloudinit import log as logging
from cloudinit import sources
from cloudinit import url_helper
from cloudinit import util

LOG = logging.getLogger(__name__)

MD_V1_URL = 'http://metadata.google.internal/computeMetadata/v1/'
BUILTIN_DS_CONFIG = {'metadata_url': MD_V1_URL}
REQUIRED_FIELDS = ('instance-id', 'availability-zone', 'local-hostname')
GUEST_ATTRIBUTES_URL = ('http://metadata.google.internal/computeMetadata/'
                        'v1/instance/guest-attributes')
HOSTKEY_NAMESPACE = 'hostkeys'
HEADERS = {'Metadata-Flavor': 'Google'}


class GoogleMetadataFetcher(object):

    def __init__(self, metadata_address):
        self.metadata_address = metadata_address

    def get_value(self, path, is_text, is_recursive=False):
        value = None
        try:
            url = self.metadata_address + path
            if is_recursive:
                url += '/?recursive=True'
            resp = url_helper.readurl(url=url, headers=HEADERS)
        except url_helper.UrlError as exc:
            msg = "url %s raised exception %s"
            LOG.debug(msg, path, exc)
        else:
            if resp.code == 200:
                if is_text:
                    value = util.decode_binary(resp.contents)
                else:
                    value = resp.contents.decode('utf-8')
            else:
                LOG.debug("url %s returned code %s", path, resp.code)
        return value


class DataSourceGCE(sources.DataSource):

    dsname = 'GCE'

    def __init__(self, sys_cfg, distro, paths):
        sources.DataSource.__init__(self, sys_cfg, distro, paths)
        self.default_user = None
        if distro:
            (users, _groups) = ug_util.normalize_users_groups(sys_cfg, distro)
            (self.default_user, _user_config) = ug_util.extract_default(users)
        self.metadata = dict()
        self.ds_cfg = util.mergemanydict([
            util.get_cfg_by_path(sys_cfg, ["datasource", "GCE"], {}),
            BUILTIN_DS_CONFIG])
        self.metadata_address = self.ds_cfg['metadata_url']

    def _get_data(self):
        ret = util.log_time(
            LOG.debug, 'Crawl of GCE metadata service',
            read_md, kwargs={'address': self.metadata_address})

        if not ret['success']:
            if ret['platform_reports_gce']:
                LOG.warning(ret['reason'])
            else:
                LOG.debug(ret['reason'])
            return False
        self.metadata = ret['meta-data']
        self.userdata_raw = ret['user-data']
        return True

    @property
    def launch_index(self):
        # GCE does not provide lauch_index property.
        return None

    def get_instance_id(self):
        return self.metadata['instance-id']

    def get_public_ssh_keys(self):
        public_keys_data = self.metadata['public-keys-data']
        return _parse_public_keys(public_keys_data, self.default_user)

    def publish_host_keys(self, hostkeys):
        for key in hostkeys:
            _write_host_key_to_guest_attributes(*key)

    def get_hostname(self, fqdn=False, resolve_ip=False, metadata_only=False):
        # GCE has long FDQN's and has asked for short hostnames.
        return self.metadata['local-hostname'].split('.')[0]

    @property
    def availability_zone(self):
        return self.metadata['availability-zone']

    @property
    def region(self):
        return self.availability_zone.rsplit('-', 1)[0]


def _write_host_key_to_guest_attributes(key_type, key_value):
    url = '%s/%s/%s' % (GUEST_ATTRIBUTES_URL, HOSTKEY_NAMESPACE, key_type)
    key_value = key_value.encode('utf-8')
    resp = url_helper.readurl(url=url, data=key_value, headers=HEADERS,
                              request_method='PUT', check_status=False)
    if resp.ok():
        LOG.debug('Wrote %s host key to guest attributes.', key_type)
    else:
        LOG.debug('Unable to write %s host key to guest attributes.', key_type)


def _has_expired(public_key):
    # Check whether an SSH key is expired. Public key input is a single SSH
    # public key in the GCE specific key format documented here:
    # https://cloud.google.com/compute/docs/instances/adding-removing-ssh-keys#sshkeyformat
    try:
        # Check for the Google-specific schema identifier.
        schema, json_str = public_key.split(None, 3)[2:]
    except (ValueError, AttributeError):
        return False

    # Do not expire keys if they do not have the expected schema identifier.
    if schema != 'google-ssh':
        return False

    try:
        json_obj = json.loads(json_str)
    except ValueError:
        return False

    # Do not expire keys if there is no expriation timestamp.
    if 'expireOn' not in json_obj:
        return False

    expire_str = json_obj['expireOn']
    format_str = '%Y-%m-%dT%H:%M:%S+0000'
    try:
        expire_time = datetime.datetime.strptime(expire_str, format_str)
    except ValueError:
        return False

    # Expire the key if and only if we have exceeded the expiration timestamp.
    return datetime.datetime.utcnow() > expire_time


def _parse_public_keys(public_keys_data, default_user=None):
    # Parse the SSH key data for the default user account. Public keys input is
    # a list containing SSH public keys in the GCE specific key format
    # documented here:
    # https://cloud.google.com/compute/docs/instances/adding-removing-ssh-keys#sshkeyformat
    public_keys = []
    if not public_keys_data:
        return public_keys
    for public_key in public_keys_data:
        if not public_key or not all(ord(c) < 128 for c in public_key):
            continue
        split_public_key = public_key.split(':', 1)
        if len(split_public_key) != 2:
            continue
        user, key = split_public_key
        if user in ('cloudinit', default_user) and not _has_expired(key):
            public_keys.append(key)
    return public_keys


def read_md(address=None, platform_check=True):

    if address is None:
        address = MD_V1_URL

    ret = {'meta-data': None, 'user-data': None,
           'success': False, 'reason': None}
    ret['platform_reports_gce'] = platform_reports_gce()

    if platform_check and not ret['platform_reports_gce']:
        ret['reason'] = "Not running on GCE."
        return ret

    # If we cannot resolve the metadata server, then no point in trying.
    if not util.is_resolvable_url(address):
        LOG.debug("%s is not resolvable", address)
        ret['reason'] = 'address "%s" is not resolvable' % address
        return ret

    # url_map: (our-key, path, required, is_text, is_recursive)
    url_map = [
        ('instance-id', ('instance/id',), True, True, False),
        ('availability-zone', ('instance/zone',), True, True, False),
        ('local-hostname', ('instance/hostname',), True, True, False),
        ('instance-data', ('instance/attributes',), False, False, True),
        ('project-data', ('project/attributes',), False, False, True),
    ]

    metadata_fetcher = GoogleMetadataFetcher(address)
    md = {}
    # Iterate over url_map keys to get metadata items.
    for (mkey, paths, required, is_text, is_recursive) in url_map:
        value = None
        for path in paths:
            new_value = metadata_fetcher.get_value(path, is_text, is_recursive)
            if new_value is not None:
                value = new_value
        if required and value is None:
            msg = "required key %s returned nothing. not GCE"
            ret['reason'] = msg % mkey
            return ret
        md[mkey] = value

    instance_data = json.loads(md['instance-data'] or '{}')
    project_data = json.loads(md['project-data'] or '{}')
    valid_keys = [instance_data.get('sshKeys'), instance_data.get('ssh-keys')]
    block_project = instance_data.get('block-project-ssh-keys', '').lower()
    if block_project != 'true' and not instance_data.get('sshKeys'):
        valid_keys.append(project_data.get('ssh-keys'))
        valid_keys.append(project_data.get('sshKeys'))
    public_keys_data = '\n'.join([key for key in valid_keys if key])
    md['public-keys-data'] = public_keys_data.splitlines()

    if md['availability-zone']:
        md['availability-zone'] = md['availability-zone'].split('/')[-1]

    if 'user-data' in instance_data:
        # instance_data was json, so values are all utf-8 strings.
        ud = instance_data['user-data'].encode("utf-8")
        encoding = instance_data.get('user-data-encoding')
        if encoding == 'base64':
            ud = b64decode(ud)
        elif encoding:
            LOG.warning('unknown user-data-encoding: %s, ignoring', encoding)
        ret['user-data'] = ud

    ret['meta-data'] = md
    ret['success'] = True

    return ret


def platform_reports_gce():
    pname = dmi.read_dmi_data('system-product-name') or "N/A"
    if pname == "Google Compute Engine":
        return True

    # system-product-name is not always guaranteed (LP: #1674861)
    serial = dmi.read_dmi_data('system-serial-number') or "N/A"
    if serial.startswith("GoogleCloud-"):
        return True

    LOG.debug("Not running on google cloud. product-name=%s serial=%s",
              pname, serial)
    return False


# Used to match classes to dependencies.
datasources = [
    (DataSourceGCE, (sources.DEP_FILESYSTEM, sources.DEP_NETWORK)),
]


# Return a list of data sources that match this set of dependencies.
def get_datasource_list(depends):
    return sources.list_from_depends(depends, datasources)


if __name__ == "__main__":
    import argparse
    import sys

    from base64 import b64encode

    parser = argparse.ArgumentParser(description='Query GCE Metadata Service')
    parser.add_argument("--endpoint", metavar="URL",
                        help="The url of the metadata service.",
                        default=MD_V1_URL)
    parser.add_argument("--no-platform-check", dest="platform_check",
                        help="Ignore smbios platform check",
                        action='store_false', default=True)
    args = parser.parse_args()
    data = read_md(address=args.endpoint, platform_check=args.platform_check)
    if 'user-data' in data:
        # user-data is bytes not string like other things. Handle it specially.
        # If it can be represented as utf-8 then do so. Otherwise print base64
        # encoded value in the key user-data-b64.
        try:
            data['user-data'] = data['user-data'].decode()
        except UnicodeDecodeError:
            sys.stderr.write("User-data cannot be decoded. "
                             "Writing as base64\n")
            del data['user-data']
            # b64encode returns a bytes value. Decode to get the string.
            data['user-data-b64'] = b64encode(data['user-data']).decode()

    print(json.dumps(data, indent=1, sort_keys=True, separators=(',', ': ')))

# vi: ts=4 expandtab