path: root/cloudinit/sources/DataSourceGCE.py

# 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 contextlib import suppress as noop

from cloudinit import dmi
from cloudinit import log as logging
from cloudinit import sources, url_helper, util
from cloudinit.distros import ug_util
from cloudinit.net.ephemeral import EphemeralDHCPv4
from cloudinit.sources import DataSourceHostname

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

    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,
                retries=self.num_retries,
                sec_between=self.sec_between_retries,
            )
        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"
    perform_dhcp_setup = False

    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):
        url_params = self.get_url_params()
        network_context = noop()
        if self.perform_dhcp_setup:
            network_context = EphemeralDHCPv4(
                self.distro,
                self.fallback_interface,
            )
        with network_context:
            ret = util.log_time(
                LOG.debug,
                "Crawl of GCE metadata service",
                read_md,
                kwargs={
                    "address": self.metadata_address,
                    "url_params": url_params,
                },
            )

        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 DataSourceHostname(
            self.metadata["local-hostname"].split(".")[0], False
        )

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

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


class DataSourceGCELocal(DataSourceGCE):
    perform_dhcp_setup = True


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, url_params=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, url_params.num_retries, url_params.sec_between_retries
    )
    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" or pname == "Google":
        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 = [
    (DataSourceGCELocal, (sources.DEP_FILESYSTEM,)),
    (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=(",", ": ")))