✨ Implement OAuth2ClientCredentials class

docs/de/docs/reference/security/index.md

@@ -21,6 +21,7 @@ from fastapi.security import (
     OAuth2,
     OAuth2AuthorizationCodeBearer,
     OAuth2PasswordBearer,
+    OAuth2ClientCredentials,
     OAuth2PasswordRequestForm,
     OAuth2PasswordRequestFormStrict,
     OpenIdConnect,
@@ -58,6 +59,8 @@ from fastapi.security import (
 
 ::: fastapi.security.OAuth2PasswordBearer
 
+::: fastapi.security.OAuth2ClientCredentials
+
 ## OAuth2-Passwortformulare
 
 ::: fastapi.security.OAuth2PasswordRequestForm

docs/en/docs/reference/security/index.md

@@ -21,6 +21,7 @@ from fastapi.security import (
     OAuth2,
     OAuth2AuthorizationCodeBearer,
     OAuth2PasswordBearer,
+    OAuth2ClientCredentials,
     OAuth2PasswordRequestForm,
     OAuth2PasswordRequestFormStrict,
     OpenIdConnect,
@@ -58,6 +59,8 @@ from fastapi.security import (
 
 ::: fastapi.security.OAuth2PasswordBearer
 
+::: fastapi.security.OAuth2ClientCredentials
+
 ## OAuth2 Password Form
 
 ::: fastapi.security.OAuth2PasswordRequestForm

docs/en/docs/release-notes.md

@@ -5,6 +5,8 @@ hide:
 
 # Release Notes
 
+* Implement `OAuth2ClientCredentials` class. PR [#11560](https://github.com/tiangolo/fastapi/pull/11560) by [@rhysrevans3](https://github.com/rhysrevans3).
+
 ## Latest Changes
 
 * 🌐 Add Turkish translation for `docs/tr/docs/tutorial/request-forms.md`. PR [#11553](https://github.com/tiangolo/fastapi/pull/11553) by [@hasansezertasan](https://github.com/hasansezertasan).

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 +595,105 @@ 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

tests/test_security_oauth2_authorization_client_credentials.py

@@ -0,0 +1,72 @@
+from typing import Optional
+
+from fastapi import FastAPI, Security
+from fastapi.security import OAuth2ClientCredentials
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+oauth2_scheme = OAuth2ClientCredentials(tokenUrl="token", auto_error=True)
+
+
+@app.get("/items/")
+async def read_items(token: Optional[str] = Security(oauth2_scheme)):
+    return {"token": token}
+
+
+client = TestClient(app)
+
+
+def test_no_token():
+    response = client.get("/items")
+    assert response.status_code == 401, response.text
+    assert response.json() == {"detail": "Not authenticated"}
+
+
+def test_incorrect_token():
+    response = client.get("/items", headers={"Authorization": "Non-existent testtoken"})
+    assert response.status_code == 401, response.text
+    assert response.json() == {"detail": "Not authenticated"}
+
+
+def test_token():
+    response = client.get("/items", headers={"Authorization": "Bearer testtoken"})
+    assert response.status_code == 200, response.text
+    assert response.json() == {"token": "testtoken"}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "openapi": "3.1.0",
+        "info": {"title": "FastAPI", "version": "0.1.0"},
+        "paths": {
+            "/items/": {
+                "get": {
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        }
+                    },
+                    "summary": "Read Items",
+                    "operationId": "read_items_items__get",
+                    "security": [{"OAuth2ClientCredentials": []}],
+                }
+            }
+        },
+        "components": {
+            "securitySchemes": {
+                "OAuth2ClientCredentials": {
+                    "type": "oauth2",
+                    "flows": {
+                        "clientCredentials": {
+                            "tokenUrl": "token",
+                            "scopes": {},
+                        }
+                    },
+                }
+            }
+        },
+    }

tests/test_security_oauth2_authorization_client_credentials_description.py

@@ -0,0 +1,77 @@
+from typing import Optional
+
+from fastapi import FastAPI, Security
+from fastapi.security import OAuth2ClientCredentials
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+oauth2_scheme = OAuth2ClientCredentials(
+    tokenUrl="token",
+    description="OAuth2 Client Credentials Flow",
+    auto_error=True,
+)
+
+
+@app.get("/items/")
+async def read_items(token: Optional[str] = Security(oauth2_scheme)):
+    return {"token": token}
+
+
+client = TestClient(app)
+
+
+def test_no_token():
+    response = client.get("/items")
+    assert response.status_code == 401, response.text
+    assert response.json() == {"detail": "Not authenticated"}
+
+
+def test_incorrect_token():
+    response = client.get("/items", headers={"Authorization": "Non-existent testtoken"})
+    assert response.status_code == 401, response.text
+    assert response.json() == {"detail": "Not authenticated"}
+
+
+def test_token():
+    response = client.get("/items", headers={"Authorization": "Bearer testtoken"})
+    assert response.status_code == 200, response.text
+    assert response.json() == {"token": "testtoken"}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "openapi": "3.1.0",
+        "info": {"title": "FastAPI", "version": "0.1.0"},
+        "paths": {
+            "/items/": {
+                "get": {
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        }
+                    },
+                    "summary": "Read Items",
+                    "operationId": "read_items_items__get",
+                    "security": [{"OAuth2ClientCredentials": []}],
+                }
+            }
+        },
+        "components": {
+            "securitySchemes": {
+                "OAuth2ClientCredentials": {
+                    "type": "oauth2",
+                    "flows": {
+                        "clientCredentials": {
+                            "tokenUrl": "token",
+                            "scopes": {},
+                        }
+                    },
+                    "description": "OAuth2 Client Credentials Flow",
+                }
+            }
+        },
+    }