# ------------------------------------
# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.
# ------------------------------------
import os
from typing import TYPE_CHECKING
from azure.core.exceptions import ClientAuthenticationError
from ..._constants import EnvironmentVariables
from .client_credential import CertificateCredential, ClientSecretCredential
if TYPE_CHECKING:
from typing import Any, Optional, Union
from azure.core.credentials import AccessToken
[docs]class EnvironmentCredential:
"""A credential configured by environment variables.
This credential is capable of authenticating as a service principal using a client secret or a certificate, or as
a user with a username and password. Configuration is attempted in this order, using these environment variables:
Service principal with secret:
- **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
- **AZURE_CLIENT_ID**: the service principal's client ID
- **AZURE_CLIENT_SECRET**: one of the service principal's client secrets
Service principal with certificate:
- **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
- **AZURE_CLIENT_ID**: the service principal's client ID
- **AZURE_CLIENT_CERTIFICATE_PATH**: path to a PEM-encoded certificate file including the private key The
certificate must not be password-protected.
"""
def __init__(self, **kwargs: "Any") -> None:
self._credential = None # type: Optional[Union[CertificateCredential, ClientSecretCredential]]
if all(os.environ.get(v) is not None for v in EnvironmentVariables.CLIENT_SECRET_VARS):
self._credential = ClientSecretCredential(
client_id=os.environ[EnvironmentVariables.AZURE_CLIENT_ID],
client_secret=os.environ[EnvironmentVariables.AZURE_CLIENT_SECRET],
tenant_id=os.environ[EnvironmentVariables.AZURE_TENANT_ID],
**kwargs
)
elif all(os.environ.get(v) is not None for v in EnvironmentVariables.CERT_VARS):
self._credential = CertificateCredential(
client_id=os.environ[EnvironmentVariables.AZURE_CLIENT_ID],
tenant_id=os.environ[EnvironmentVariables.AZURE_TENANT_ID],
certificate_path=os.environ[EnvironmentVariables.AZURE_CLIENT_CERTIFICATE_PATH],
**kwargs
)
[docs] async def get_token(self, *scopes: str, **kwargs: "Any") -> "AccessToken":
"""Asynchronously request an access token for `scopes`.
.. 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
:rtype: :class:`azure.core.credentials.AccessToken`
:raises ~azure.core.exceptions.ClientAuthenticationError:
"""
if not self._credential:
raise ClientAuthenticationError(message="Incomplete environment configuration.")
return await self._credential.get_token(*scopes, **kwargs)