# ------------------------------------
# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.
# ------------------------------------
from azure.core.exceptions import ClientAuthenticationError
try:
from typing import TYPE_CHECKING
except ImportError:
TYPE_CHECKING = False
if TYPE_CHECKING:
# pylint:disable=unused-import,ungrouped-imports
from typing import Any
from azure.core.credentials import AccessToken, TokenCredential
def _get_error_message(history):
attempts = []
for credential, error in history:
if error:
attempts.append("{}: {}".format(credential.__class__.__name__, error))
else:
attempts.append(credential.__class__.__name__)
return """No credential in this chain provided a token.
Attempted credentials:\n\t{}""".format(
"\n\t".join(attempts)
)
[docs]class ChainedTokenCredential(object):
"""A sequence of credentials that is itself a credential.
Its :func:`get_token` method calls ``get_token`` on each credential in the sequence, in order, returning the first
valid token received.
:param credentials: credential instances to form the chain
:type credentials: :class:`azure.core.credentials.TokenCredential`
"""
def __init__(self, *credentials):
# type: (*TokenCredential) -> None
if not credentials:
raise ValueError("at least one credential is required")
self.credentials = credentials
[docs] def get_token(self, *scopes, **kwargs): # pylint:disable=unused-argument
# type: (*str, **Any) -> AccessToken
"""Request a token from each chained credential, in order, returning the first token received.
.. note:: This method is called by Azure SDK clients. It isn't intended for use in application code.
:param str scopes: desired scopes for the token
:raises ~azure.core.exceptions.ClientAuthenticationError: when no credential in the chain provides a token
"""
history = []
for credential in self.credentials:
try:
return credential.get_token(*scopes, **kwargs)
except ClientAuthenticationError as ex:
history.append((credential, ex.message))
except Exception as ex: # pylint: disable=broad-except
history.append((credential, str(ex)))
error_message = _get_error_message(history)
raise ClientAuthenticationError(message=error_message)