aiohttp-security/docs/example_db_auth.rst

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.. _aiohttp-security-example-db-auth:
===========================================
Permissions with PostgreSQL-based storage
===========================================
Make sure that you have PostgreSQL and Redis servers up and running.
If you want the full source code in advance or for comparison, check out
the `demo source`_.
.. _demo source:
https://github.com/aio-libs/aiohttp_security/tree/master/demo
.. _passlib:
https://pythonhosted.org/passlib/
Database
--------
Launch these sql scripts to init database and fill it with sample data:
``psql template1 < demo/sql/init_db.sql``
and then
``psql template1 < demo/sql/sample_data.sql``
You will have two tables for storing users and their permissions
+--------------+
| users |
+==============+
| id |
+--------------+
| login |
+--------------+
| passwd |
+--------------+
| is_superuser |
+--------------+
| disabled |
+--------------+
and second table is permissions table:
+-----------------+
| permissions |
+=================+
| id |
+-----------------+
| user_id |
+-----------------+
| permission_name |
+-----------------+
Writing policies
----------------
You need to implement two entities: *IdentityPolicy* and *AuthorizationPolicy*.
First one should have these methods: *identify*, *remember* and *forget*.
For second one: *authorized_userid* and *permits*. We will use built-in
*SessionIdentityPolicy* and write our own database-based authorization policy.
In our example we will lookup database by user login and if present return
this identity::
@asyncio.coroutine
def authorized_userid(self, identity):
with (yield from self.dbengine) as conn:
where = sa.and_(db.users.c.login == identity,
sa.not_(db.users.c.disabled))
query = db.users.count().where(where)
ret = yield from conn.scalar(query)
if ret:
return identity
else:
return None
For permission check we will fetch the user first, check if he is superuser
(all permissions are allowed), otherwise check if permission is explicitly set
for that user::
@asyncio.coroutine
def permits(self, identity, permission, context=None):
if identity is None:
return False
with (yield from self.dbengine) as conn:
where = sa.and_(db.users.c.login == identity,
sa.not_(db.users.c.disabled))
query = db.users.select().where(where)
ret = yield from conn.execute(query)
user = yield from ret.fetchone()
if user is not None:
user_id = user[0]
is_superuser = user[4]
if is_superuser:
return True
where = db.permissions.c.user_id == user_id
query = db.permissions.select().where(where)
ret = yield from conn.execute(query)
result = yield from ret.fetchall()
if ret is not None:
for record in result:
if record.perm_name == permission:
return True
return False
Setup
-----
Once we have all the code in place we can install it for our application::
from aiohttp_session.redis_storage import RedisStorage
from aiohttp_security import setup as setup_security
from aiohttp_security import SessionIdentityPolicy
from aiopg.sa import create_engine
from aioredis import create_pool
from .db_auth import DBAuthorizationPolicy
@asyncio.coroutine
def init(loop):
redis_pool = yield from create_pool(('localhost', 6379))
dbengine = yield from create_engine(user='aiohttp_security',
password='aiohttp_security',
database='aiohttp_security',
host='127.0.0.1')
app = web.Application(loop=loop)
setup_session(app, RedisStorage(redis_pool))
setup_security(app,
SessionIdentityPolicy(),
DBAuthorizationPolicy(dbengine))
return app
Now we have authorization and can decorate every other view with access rights
based on permissions. This simple decorator (for class-based handlers) will
help to do that::
def require(permission):
def wrapper(f):
@asyncio.coroutine
@functools.wraps(f)
def wrapped(self, request):
has_perm = yield from permits(request, permission)
if not has_perm:
message = 'User has no permission {}'.format(permission)
raise web.HTTPForbidden(body=message.encode())
return (yield from f(self, request))
return wrapped
return wrapper
For each view you need to protect just apply the decorator on it::
class Web:
@require('protected')
@asyncio.coroutine
def protected_page(self, request):
response = web.Response(body=b'You are on protected page')
return response
If someone will try to access this protected page he will see::
403, User has no permission "protected"
The best part about it is that you can implement any logic you want until it
follows the API conventions.
Launch application
------------------
For working with passwords there is a good library passlib_. Once you've
created some users you want to check their credentials on login. Similar
function may do what you trying to accomplish::
from passlib.hash import sha256_crypt
@asyncio.coroutine
def check_credentials(db_engine, username, password):
with (yield from db_engine) as conn:
where = sa.and_(db.users.c.login == username,
sa.not_(db.users.c.disabled))
query = db.users.select().where(where)
ret = yield from conn.execute(query)
user = yield from ret.fetchone()
if user is not None:
hash = user[2]
return sha256_crypt.verify(password, hash)
return False
Final step is to launch your application::
python demo/main.py
Try to login with admin/moderator/user accounts (with *password* password)
and access **/public** or **/protected** endpoints.