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# Copyright 2015 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Google OAuth2 related functions."""
from __future__ import annotations
import collections
import datetime
import functools
import httplib2
import json
import logging
import os
from typing import Optional
import subprocess2
# TODO: Should fix these warnings.
# pylint: disable=line-too-long
# This is what most GAE apps require for authentication.
OAUTH_SCOPE_EMAIL = 'https://www.googleapis.com/auth/userinfo.email'
# Gerrit and Git on *.googlesource.com require this scope.
OAUTH_SCOPE_GERRIT = 'https://www.googleapis.com/auth/gerritcodereview'
# Deprecated. Use OAUTH_SCOPE_EMAIL instead.
OAUTH_SCOPES = OAUTH_SCOPE_EMAIL
# Mockable datetime.datetime.utcnow for testing.
def datetime_now():
return datetime.datetime.utcnow()
# OAuth access token or ID token with its expiration time (UTC datetime or None
# if unknown).
class Token(collections.namedtuple('Token', [
'token',
'expires_at',
])):
def needs_refresh(self):
"""True if this token should be refreshed."""
if self.expires_at is not None:
# Allow 30s of clock skew between client and backend.
return datetime_now() + datetime.timedelta(
seconds=30) >= self.expires_at
# Token without expiration time never expires.
return False
class LoginRequiredError(Exception):
"""Interaction with the user is required to authenticate."""
def __init__(self, scopes=OAUTH_SCOPE_EMAIL):
self.scopes = scopes
msg = ('You are not logged in. Please login first by running:\n'
' %s' % self.login_command)
super(LoginRequiredError, self).__init__(msg)
@property
def login_command(self) -> str:
return 'luci-auth login -scopes "%s"' % self.scopes
class GitLoginRequiredError(Exception):
"""Interaction with the user is required to authenticate.
This is for git-credential-luci, not luci-auth.
"""
def __init__(self):
msg = (
'You are not logged in to Gerrit. Please login first by running:\n'
' %s' % self.login_command)
super(GitLoginRequiredError, self).__init__(msg)
@property
def login_command(self) -> str:
return 'git-credential-luci login'
def has_luci_context_local_auth():
"""Returns whether LUCI_CONTEXT should be used for ambient authentication."""
ctx_path = os.environ.get('LUCI_CONTEXT')
if not ctx_path:
return False
try:
with open(ctx_path) as f:
loaded = json.load(f)
except (OSError, IOError, ValueError):
return False
return loaded.get('local_auth', {}).get('default_account_id') is not None
class Authenticator(object):
"""Object that knows how to refresh access tokens or id tokens when needed.
Args:
scopes: space separated oauth scopes. It's used to generate access tokens.
Defaults to OAUTH_SCOPE_EMAIL.
audience: An audience in ID tokens to claim which clients should accept it.
"""
def __init__(self, scopes=OAUTH_SCOPE_EMAIL, audience=None):
self._access_token = None
self._scopes = scopes
self._id_token = None
self._audience = audience
def has_cached_credentials(self):
"""Returns True if credentials can be obtained.
If returns False, get_access_token() or get_id_token() later will probably
ask for interactive login by raising LoginRequiredError.
If returns True, get_access_token() or get_id_token() won't ask for
interactive login.
"""
return bool(self._get_luci_auth_token())
def get_access_token(self):
"""Returns AccessToken, refreshing it if necessary.
Raises:
LoginRequiredError if user interaction is required.
"""
if self._access_token and not self._access_token.needs_refresh():
return self._access_token
# Token expired or missing. Maybe some other process already updated it,
# reload from the cache.
self._access_token = self._get_luci_auth_token()
if self._access_token and not self._access_token.needs_refresh():
return self._access_token
# Nope, still expired. Needs user interaction.
logging.debug('Failed to create access token')
raise LoginRequiredError(self._scopes)
def get_id_token(self):
"""Returns id token, refreshing it if necessary.
Returns:
A Token object.
Raises:
LoginRequiredError if user interaction is required.
"""
if self._id_token and not self._id_token.needs_refresh():
return self._id_token
self._id_token = self._get_luci_auth_token(use_id_token=True)
if self._id_token and not self._id_token.needs_refresh():
return self._id_token
# Nope, still expired. Needs user interaction.
logging.debug('Failed to create id token')
raise LoginRequiredError()
def authorize(self, http, use_id_token=False):
"""Monkey patches authentication logic of httplib2.Http instance.
The modified http.request method will add authentication headers to each
request.
Args:
http: An instance of httplib2.Http.
Returns:
A modified instance of http that was passed in.
"""
# Adapted from oauth2client.OAuth2Credentials.authorize.
request_orig = http.request
@functools.wraps(request_orig)
def new_request(uri,
method='GET',
body=None,
headers=None,
redirections=httplib2.DEFAULT_MAX_REDIRECTS,
connection_type=None):
headers = (headers or {}).copy()
auth_token = self.get_access_token(
) if not use_id_token else self.get_id_token()
headers['Authorization'] = 'Bearer %s' % auth_token.token
return request_orig(uri, method, body, headers, redirections,
connection_type)
http.request = new_request
return http
## Private methods.
def _get_luci_auth_token(self, use_id_token=False):
logging.debug('Running luci-auth token')
if use_id_token:
args = ['-use-id-token'] + ['-audience', self._audience
] if self._audience else []
else:
args = ['-scopes', self._scopes]
try:
out, err = subprocess2.check_call_out(['luci-auth', 'token'] +
args + ['-json-output', '-'],
stdout=subprocess2.PIPE,
stderr=subprocess2.PIPE)
logging.debug('luci-auth token stderr:\n%s', err)
token_info = json.loads(out)
return Token(
token_info['token'],
datetime.datetime.utcfromtimestamp(token_info['expiry']))
except subprocess2.CalledProcessError as e:
# subprocess2.CalledProcessError.__str__ nicely formats
# stdout/stderr.
logging.error('luci-auth token failed: %s', e)
return None
class GerritAuthenticator(object):
"""Object that knows how to refresh access tokens for Gerrit.
Unlike Authenticator, this is specifically for authenticating Gerrit
requests.
"""
def __init__(self):
self._access_token: Optional[str] = None
def get_access_token(self) -> str:
"""Returns AccessToken, refreshing it if necessary.
Raises:
GitLoginRequiredError if user interaction is required.
"""
access_token = self._get_luci_auth_token()
if access_token:
return access_token
logging.debug('Failed to create access token')
raise GitLoginRequiredError()
def _get_luci_auth_token(self, use_id_token=False) -> Optional[str]:
logging.debug('Running git-credential-luci')
try:
out, err = subprocess2.check_call_out(
['git-credential-luci', 'get'],
stdout=subprocess2.PIPE,
stderr=subprocess2.PIPE)
logging.debug('git-credential-luci stderr:\n%s', err)
for line in out.decode().splitlines():
if line.startswith('password='):
return line[len('password='):].rstrip()
logging.error('git-credential-luci did not return a token')
return None
except subprocess2.CalledProcessError as e:
# subprocess2.CalledProcessError.__str__ nicely formats
# stdout/stderr.
logging.error('git-credential-luci failed: %s', e)
return None
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