"""DNS Authenticator for Google Cloud DNS."""
import json
import logging
import httplib2
import zope.interface
from googleapiclient import discovery
from googleapiclient import errors as googleapiclient_errors
from oauth2client.service_account import ServiceAccountCredentials
from certbot import errors
from certbot import interfaces
from certbot.plugins import dns_common
logger = logging.getLogger(__name__)
ACCT_URL = 'https://developers.google.com/identity/protocols/OAuth2ServiceAccount#creatinganaccount'
PERMISSIONS_URL = 'https://cloud.google.com/dns/access-control#permissions_and_roles'
METADATA_URL = 'http://metadata.google.internal/computeMetadata/v1/'
METADATA_HEADERS = {'Metadata-Flavor': 'Google'}
[docs]@zope.interface.implementer(interfaces.IAuthenticator)
@zope.interface.provider(interfaces.IPluginFactory)
class Authenticator(dns_common.DNSAuthenticator):
"""DNS Authenticator for Google Cloud DNS
This Authenticator uses the Google Cloud DNS API to fulfill a dns-01 challenge.
"""
description = ('Obtain certificates using a DNS TXT record (if you are using Google Cloud DNS '
'for DNS).')
ttl = 60
def __init__(self, *args, **kwargs):
super(Authenticator, self).__init__(*args, **kwargs)
self.credentials = None
@classmethod
def add_parser_arguments(cls, add): # pylint: disable=arguments-differ
super(Authenticator, cls).add_parser_arguments(add, default_propagation_seconds=60)
add('credentials',
help=('Path to Google Cloud DNS service account JSON file. (See {0} for' +
'information about creating a service account and {1} for information about the' +
'required permissions.)').format(ACCT_URL, PERMISSIONS_URL),
default=None)
def more_info(self): # pylint: disable=missing-docstring,no-self-use
return 'This plugin configures a DNS TXT record to respond to a dns-01 challenge using ' + \
'the Google Cloud DNS API.'
def _setup_credentials(self):
if self.conf('credentials') is None:
try:
# use project_id query to check for availability of google metadata server
# we won't use the result but know we're not on GCP when an exception is thrown
_GoogleClient.get_project_id()
except (ValueError, httplib2.ServerNotFoundError):
raise errors.PluginError('Unable to get Google Cloud Metadata and no credentials'
' specified. Automatic credential lookup is only '
'available on Google Cloud Platform. Please configure'
' credentials using --dns-google-credentials <file>')
else:
self._configure_file('credentials',
'path to Google Cloud DNS service account JSON file')
dns_common.validate_file_permissions(self.conf('credentials'))
def _perform(self, domain, validation_name, validation):
self._get_google_client().add_txt_record(domain, validation_name, validation, self.ttl)
def _cleanup(self, domain, validation_name, validation):
self._get_google_client().del_txt_record(domain, validation_name, validation, self.ttl)
def _get_google_client(self):
return _GoogleClient(self.conf('credentials'))
[docs]class _GoogleClient(object):
"""
Encapsulates all communication with the Google Cloud DNS API.
"""
def __init__(self, account_json=None):
scopes = ['https://www.googleapis.com/auth/ndev.clouddns.readwrite']
if account_json is not None:
credentials = ServiceAccountCredentials.from_json_keyfile_name(account_json, scopes)
with open(account_json) as account:
self.project_id = json.load(account)['project_id']
else:
credentials = None
self.project_id = self.get_project_id()
self.dns = discovery.build('dns', 'v1', credentials=credentials, cache_discovery=False)
[docs] def add_txt_record(self, domain, record_name, record_content, record_ttl):
"""
Add a TXT record using the supplied information.
:param str domain: The domain to use to look up the managed zone.
:param str record_name: The record name (typically beginning with '_acme-challenge.').
:param str record_content: The record content (typically the challenge validation).
:param int record_ttl: The record TTL (number of seconds that the record may be cached).
:raises certbot.errors.PluginError: if an error occurs communicating with the Google API
"""
zone_id = self._find_managed_zone_id(domain)
record_contents = self.get_existing_txt_rrset(zone_id, record_name)
if record_contents is None:
record_contents = []
add_records = record_contents[:]
if "\""+record_content+"\"" in record_contents:
# The process was interrupted previously and validation token exists
return
add_records.append(record_content)
data = {
"kind": "dns#change",
"additions": [
{
"kind": "dns#resourceRecordSet",
"type": "TXT",
"name": record_name + ".",
"rrdatas": add_records,
"ttl": record_ttl,
},
],
}
if record_contents:
# We need to remove old records in the same request
data["deletions"] = [
{
"kind": "dns#resourceRecordSet",
"type": "TXT",
"name": record_name + ".",
"rrdatas": record_contents,
"ttl": record_ttl,
},
]
changes = self.dns.changes() # changes | pylint: disable=no-member
try:
request = changes.create(project=self.project_id, managedZone=zone_id, body=data)
response = request.execute()
status = response['status']
change = response['id']
while status == 'pending':
request = changes.get(project=self.project_id, managedZone=zone_id, changeId=change)
response = request.execute()
status = response['status']
except googleapiclient_errors.Error as e:
logger.error('Encountered error adding TXT record: %s', e)
raise errors.PluginError('Error communicating with the Google Cloud DNS API: {0}'
.format(e))
[docs] def del_txt_record(self, domain, record_name, record_content, record_ttl):
"""
Delete a TXT record using the supplied information.
:param str domain: The domain to use to look up the managed zone.
:param str record_name: The record name (typically beginning with '_acme-challenge.').
:param str record_content: The record content (typically the challenge validation).
:param int record_ttl: The record TTL (number of seconds that the record may be cached).
:raises certbot.errors.PluginError: if an error occurs communicating with the Google API
"""
try:
zone_id = self._find_managed_zone_id(domain)
except errors.PluginError as e:
logger.warn('Error finding zone. Skipping cleanup.')
return
record_contents = self.get_existing_txt_rrset(zone_id, record_name)
if record_contents is None:
record_contents = ["\"" + record_content + "\""]
data = {
"kind": "dns#change",
"deletions": [
{
"kind": "dns#resourceRecordSet",
"type": "TXT",
"name": record_name + ".",
"rrdatas": record_contents,
"ttl": record_ttl,
},
],
}
# Remove the record being deleted from the list
readd_contents = [r for r in record_contents if r != "\"" + record_content + "\""]
if readd_contents:
# We need to remove old records in the same request
data["additions"] = [
{
"kind": "dns#resourceRecordSet",
"type": "TXT",
"name": record_name + ".",
"rrdatas": readd_contents,
"ttl": record_ttl,
},
]
changes = self.dns.changes() # changes | pylint: disable=no-member
try:
request = changes.create(project=self.project_id, managedZone=zone_id, body=data)
request.execute()
except googleapiclient_errors.Error as e:
logger.warn('Encountered error deleting TXT record: %s', e)
[docs] def get_existing_txt_rrset(self, zone_id, record_name):
"""
Get existing TXT records from the RRset for the record name.
If an error occurs while requesting the record set, it is suppressed
and None is returned.
:param str zone_id: The ID of the managed zone.
:param str record_name: The record name (typically beginning with '_acme-challenge.').
:returns: List of TXT record values or None
:rtype: `list` of `string` or `None`
"""
rrs_request = self.dns.resourceRecordSets() # pylint: disable=no-member
request = rrs_request.list(managedZone=zone_id, project=self.project_id)
# Add dot as the API returns absolute domains
record_name += "."
try:
response = request.execute()
except googleapiclient_errors.Error:
logger.info("Unable to list existing records. If you're "
"requesting a wildcard certificate, this might not work.")
logger.debug("Error was:", exc_info=True)
else:
if response:
for rr in response["rrsets"]:
if rr["name"] == record_name and rr["type"] == "TXT":
return rr["rrdatas"]
return None
[docs] def _find_managed_zone_id(self, domain):
"""
Find the managed zone for a given domain.
:param str domain: The domain for which to find the managed zone.
:returns: The ID of the managed zone, if found.
:rtype: str
:raises certbot.errors.PluginError: if the managed zone cannot be found.
"""
zone_dns_name_guesses = dns_common.base_domain_name_guesses(domain)
mz = self.dns.managedZones() # managedZones | pylint: disable=no-member
for zone_name in zone_dns_name_guesses:
try:
request = mz.list(project=self.project_id, dnsName=zone_name + '.')
response = request.execute()
zones = response['managedZones']
except googleapiclient_errors.Error as e:
raise errors.PluginError('Encountered error finding managed zone: {0}'
.format(e))
if len(zones) > 0:
zone_id = zones[0]['id']
logger.debug('Found id of %s for %s using name %s', zone_id, domain, zone_name)
return zone_id
raise errors.PluginError('Unable to determine managed zone for {0} using zone names: {1}.'
.format(domain, zone_dns_name_guesses))
[docs] @staticmethod
def get_project_id():
"""
Query the google metadata service for the current project ID
This only works on Google Cloud Platform
:raises ServerNotFoundError: Not running on Google Compute or DNS not available
:raises ValueError: Server is found, but response code is not 200
:returns: project id
"""
url = '{0}project/project-id'.format(METADATA_URL)
# Request an access token from the metadata server.
http = httplib2.Http()
r, content = http.request(url, headers=METADATA_HEADERS)
if r.status != 200:
raise ValueError("Invalid status code: {0}".format(r))
if isinstance(content, bytes):
return content.decode()
else:
return content