1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
Starlette offers a simple but powerful interface for handling authentication
and permissions. Once you've installed `AuthenticationMiddleware` with an
appropriate authentication backend the `request.user` and `request.auth`
interfaces will be available in your endpoints.
```python
from starlette.applications import Starlette
from starlette.authentication import (
AuthCredentials, AuthenticationBackend, AuthenticationError, SimpleUser
)
from starlette.middleware import Middleware
from starlette.middleware.authentication import AuthenticationMiddleware
from starlette.responses import PlainTextResponse
from starlette.routing import Route
import base64
import binascii
class BasicAuthBackend(AuthenticationBackend):
async def authenticate(self, conn):
if "Authorization" not in conn.headers:
return
auth = conn.headers["Authorization"]
try:
scheme, credentials = auth.split()
if scheme.lower() != 'basic':
return
decoded = base64.b64decode(credentials).decode("ascii")
except (ValueError, UnicodeDecodeError, binascii.Error) as exc:
raise AuthenticationError('Invalid basic auth credentials')
username, _, password = decoded.partition(":")
# TODO: You'd want to verify the username and password here.
return AuthCredentials(["authenticated"]), SimpleUser(username)
async def homepage(request):
if request.user.is_authenticated:
return PlainTextResponse('Hello, ' + request.user.display_name)
return PlainTextResponse('Hello, you')
routes = [
Route("/", endpoint=homepage)
]
middleware = [
Middleware(AuthenticationMiddleware, backend=BasicAuthBackend())
]
app = Starlette(routes=routes, middleware=middleware)
```
## Users
Once `AuthenticationMiddleware` is installed the `request.user` interface
will be available to endpoints or other middleware.
This interface should subclass `BaseUser`, which provides two properties,
as well as whatever other information your user model includes.
* `.is_authenticated`
* `.display_name`
Starlette provides two built-in user implementations: `UnauthenticatedUser()`,
and `SimpleUser(username)`.
## AuthCredentials
It is important that authentication credentials are treated as separate concept
from users. An authentication scheme should be able to restrict or grant
particular privileges independently of the user identity.
The `AuthCredentials` class provides the basic interface that `request.auth`
exposes:
* `.scopes`
## Permissions
Permissions are implemented as an endpoint decorator, that enforces that the
incoming request includes the required authentication scopes.
```python
from starlette.authentication import requires
@requires('authenticated')
async def dashboard(request):
...
```
You can include either one or multiple required scopes:
```python
from starlette.authentication import requires
@requires(['authenticated', 'admin'])
async def dashboard(request):
...
```
By default 403 responses will be returned when permissions are not granted.
In some cases you might want to customize this, for example to hide information
about the URL layout from unauthenticated users.
```python
from starlette.authentication import requires
@requires(['authenticated', 'admin'], status_code=404)
async def dashboard(request):
...
```
!!! note
The `status_code` parameter is not supported with WebSockets. The 403 (Forbidden)
status code will always be used for those.
Alternatively you might want to redirect unauthenticated users to a different
page.
```python
from starlette.authentication import requires
async def homepage(request):
...
@requires('authenticated', redirect='homepage')
async def dashboard(request):
...
```
When redirecting users, the page you redirect them to will include URL they originally requested at the `next` query param:
```python
from starlette.authentication import requires
from starlette.responses import RedirectResponse
@requires('authenticated', redirect='login')
async def admin(request):
...
async def login(request):
if request.method == "POST":
# Now that the user is authenticated,
# we can send them to their original request destination
if request.user.is_authenticated:
next_url = request.query_params.get("next")
if next_url:
return RedirectResponse(next_url)
return RedirectResponse("/")
```
For class-based endpoints, you should wrap the decorator
around a method on the class.
```python
from starlette.authentication import requires
from starlette.endpoints import HTTPEndpoint
class Dashboard(HTTPEndpoint):
@requires("authenticated")
async def get(self, request):
...
```
## Custom authentication error responses
You can customise the error response sent when a `AuthenticationError` is
raised by an auth backend:
```python
from starlette.applications import Starlette
from starlette.middleware import Middleware
from starlette.middleware.authentication import AuthenticationMiddleware
from starlette.requests import Request
from starlette.responses import JSONResponse
def on_auth_error(request: Request, exc: Exception):
return JSONResponse({"error": str(exc)}, status_code=401)
app = Starlette(
middleware=[
Middleware(AuthenticationMiddleware, backend=BasicAuthBackend(), on_error=on_auth_error),
],
)
```
|
