[feature] new authentification mode

fastapi/security/__init__.py

@@ -8,6 +8,7 @@
 from .http import HTTPDigest as HTTPDigest
 from .oauth2 import OAuth2 as OAuth2
 from .oauth2 import OAuth2AuthorizationCodeBearer as OAuth2AuthorizationCodeBearer
+from .oauth2 import OAuth2ClientCredentials as OAuth2ClientCredentials
 from .oauth2 import OAuth2PasswordBearer as OAuth2PasswordBearer
 from .oauth2 import OAuth2PasswordRequestForm as OAuth2PasswordRequestForm
 from .oauth2 import OAuth2PasswordRequestFormStrict as OAuth2PasswordRequestFormStrict

fastapi/security/oauth2.py

@@ -595,6 +595,100 @@ async def __call__(self, request: Request) -> Optional[str]:
         return param
 
 
+class OAuth2ClientCredentials(OAuth2):
+    """
+    OAuth2 flow for authentication using a bearer token obtained with an OAuth2 client
+    credentials flow. An instance of it would be used as a dependency.
+    """
+
+    def __init__(
+        self,
+        tokenUrl: Annotated[
+            str,
+            Doc(
+                """
+                    The URL to obtain the OAuth2 token.
+                    """
+            ),
+        ],
+        scheme_name: Annotated[
+            Optional[str],
+            Doc(
+                """
+                    Security scheme name.
+                    It will be included in the generated OpenAPI (e.g. visible at `/docs`).
+                    """
+            ),
+        ] = None,
+        scopes: Annotated[
+            Optional[Dict[str, str]],
+            Doc(
+                """
+                    The OAuth2 scopes that would be required by the *"path" operations* that
+                    use this dependency.
+                    """
+            ),
+        ] = None,
+        description: Annotated[
+            Optional[str],
+            Doc(
+                """
+                    Security scheme description.
+                    It will be included in the generated OpenAPI (e.g. visible at `/docs`).
+                    """
+            ),
+        ] = None,
+        auto_error: Annotated[
+            bool,
+            Doc(
+                """
+                    By default, if no HTTP Auhtorization header is provided, required for
+                    OAuth2 authentication, it will automatically cancel the request and
+                    send the client an error.
+                    If `auto_error` is set to `False`, when the HTTP Authorization header
+                    is not available, instead of erroring out, the dependency result will
+                    be `None`.
+                    This is useful when you want to have optional authentication.
+                    It is also useful when you want to have authentication that can be
+                    provided in one of multiple optional ways (for example, with OAuth2
+                    or in a cookie).
+                    """
+            ),
+        ] = True,
+    ):
+        if not scopes:
+            scopes = {}
+        flows = OAuthFlowsModel(
+            clientCredentials=cast(
+                Any,
+                {
+                    "tokenUrl": tokenUrl,
+                    "scopes": scopes,
+                },
+            )
+        )
+        super().__init__(
+            flows=flows,
+            scheme_name=scheme_name,
+            description=description,
+            auto_error=auto_error,
+        )
+
+    async def __call__(self, request: Request) -> Optional[str]:
+        authorization = request.headers.get("Authorization")
+        scheme, param = get_authorization_scheme_param(authorization)
+        if not authorization or scheme.lower() != "bearer":
+            if self.auto_error:
+                raise HTTPException(
+                    status_code=HTTP_401_UNAUTHORIZED,
+                    detail="Not authenticated",
+                    headers={"WWW-Authenticate": "Bearer"},
+                )
+            else:
+                return None  # pragma: nocover
+        return param
+
+
 class SecurityScopes:
     """
     This is a special class that you can define in a parameter in a dependency to