Adding Authorization¶
Pyramid provides facilities for authentication and
authorization. We’ll make use of both features to provide security
to our application. Our application currently allows anyone with access to
the server to view, edit, and add pages to our wiki. We’ll change that
to allow only people who are members of a group named group:editors
to add and edit wiki pages but we’ll continue allowing
anyone with access to the server to view pages.
We will also add a login page and a logout link on all the pages. The login page will be shown when a user is denied access to any of the views that require a permission, instead of a default “403 Forbidden” page.
We will implement the access control with the following steps:
- Add users and groups (
security.py
, a new module). - Add an ACL (
models.py
and__init__.py
). - Add an authentication policy and an authorization policy
(
__init__.py
). - Add permission declarations to the
edit_page
andadd_page
views (views.py
).
Then we will add the login and logout feature:
- Add routes for /login and /logout (
__init__.py
). - Add
login
andlogout
views (views.py
). - Add a login template (
login.pt
). - Make the existing views return a
logged_in
flag to the renderer (views.py
). - Add a “Logout” link to be shown when logged in and viewing or editing a page
(
view.pt
,edit.pt
).
The source code for this tutorial stage can be browsed at http://github.com/Pylons/pyramid/tree/1.3-branch/docs/tutorials/wiki2/src/authorization/.
Access Control¶
Add users and groups¶
Create a new tutorial/tutorial/security.py
module with the
following content:
1 2 3 4 5 6 7 | USERS = {'editor':'editor',
'viewer':'viewer'}
GROUPS = {'editor':['group:editors']}
def groupfinder(userid, request):
if userid in USERS:
return GROUPS.get(userid, [])
|
The groupfinder
function accepts a userid and a request and
returns one of these values:
- If the userid exists in the system, it will return a sequence of group identifiers (or an empty sequence if the user isn’t a member of any groups).
- If the userid does not exist in the system, it will
return
None
.
For example, groupfinder('editor', request )
returns [‘group:editors’],
groupfinder('viewer', request)
returns [], and groupfinder('admin', request)
returns None
. We will use groupfinder()
as an authentication policy
“callback” that will provide the principal or principals
for a user.
In a production system, user and group data will most often come from a database, but here we use “dummy” data to represent user and groups sources.
Add an ACL¶
Open tutorial/tutorial/models.py
and add the following import
statement at the head:
1 2 3 4 | from pyramid.security import (
Allow,
Everyone,
)
|
Add the following class definition:
1 2 3 4 5 | class RootFactory(object):
__acl__ = [ (Allow, Everyone, 'view'),
(Allow, 'group:editors', 'edit') ]
def __init__(self, request):
pass
|
We import Allow
, an action that
means that permission is allowed:, and
Everyone
, a special principal
that is associated to all requests. Both are used in the
ACE entries that make up the ACL.
The ACL is a list that needs to be named __acl__ and be an
attribute of a class. We define an ACL with two
ACE entries: the first entry allows any user the view
permission. The second entry allows the group:editors
principal the edit permission.
The RootFactory
class that contains the ACL is a root factory.
We need to associate it to our Pyramid application, so the ACL is
provided to each view in the context of the request, as
the context
attribute.
Open tutorial/tutorial/__init__.py
and add a root_factory
parameter to our Configurator constructor, that points to
the class we created above:
1 2 | config = Configurator(settings=settings,
root_factory='tutorial.models.RootFactory')
|
(Only the highlighted line needs to be added.)
We are now providing the ACL to the application. See Assigning ACLs to your Resource Objects for more information about what an ACL represents.
Note
Although we don’t use the functionality here, the factory
used
to create route contexts may differ per-route as opposed to globally. See
the factory
argument to
pyramid.config.Configurator.add_route()
for more info.
Add Authentication and Authorization Policies¶
Open tutorial/__init__.py
and
add these import statements:
1 2 3 | from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from tutorial.security import groupfinder
|
Now add those policies to the configuration:
1 2 3 4 5 6 7 | authn_policy = AuthTktAuthenticationPolicy(
'sosecret', callback=groupfinder, hashalg='sha512')
authz_policy = ACLAuthorizationPolicy()
config = Configurator(settings=settings,
root_factory='tutorial.models.RootFactory')
config.set_authentication_policy(authn_policy)
config.set_authorization_policy(authz_policy)
|
(Only the highlighted lines need to be added.)
We are enabling an AuthTktAuthenticationPolicy
, it is based in an
auth ticket that may be included in the request, and an
ACLAuthorizationPolicy
that uses an ACL to determine the allow or deny
outcome for a view.
Note that the pyramid.authentication.AuthTktAuthenticationPolicy
constructor accepts two arguments: secret
and callback
. secret
is
a string representing an encryption key used by the “authentication ticket”
machinery represented by this policy: it is required. The callback
is the
groupfinder()
function that we created before.
Add permission declarations¶
Add a permission='edit'
parameter to the @view_config
decorator for add_page()
and edit_page()
, for example:
1 2 | @view_config(route_name='add_page', renderer='templates/edit.pt',
permission='edit')
|
(Only the highlighted line needs to be added.)
The result is that only users who possess the edit
permission at the time of the request may invoke those two views.
Add a permission='view'
parameter to the @view_config
decorator for view_wiki()
and view_page()
, like this:
1 2 | @view_config(route_name='view_page', renderer='templates/view.pt',
permission='view')
|
(Only the highlighted line needs to be added.)
This allows anyone to invoke these two views.
We are done with the changes needed to control access. The changes that follow will add the login and logout feature.
Login, Logout¶
Add routes for /login and /logout¶
Go back to tutorial/tutorial/__init__.py
and add these two
routes:
1 2 | config.add_route('login', '/login')
config.add_route('logout', '/logout')
|
Add Login and Logout Views¶
We’ll add a login
view which renders a login form and processes
the post from the login form, checking credentials.
We’ll also add a logout
view callable to our application and
provide a link to it. This view will clear the credentials of the
logged in user and redirect back to the front page.
Add the following import statements to the
head of tutorial/tutorial/views.py
:
1 2 3 4 5 6 7 8 9 10 11 | from pyramid.view import (
view_config,
forbidden_view_config,
)
from pyramid.security import (
remember,
forget,
)
from .security import USERS
|
(Only the highlighted lines need to be added.)
forbidden_view_config()
will be used
to customize the default 403 Forbidden page.
remember()
and
forget()
help to create and
expire an auth ticket cookie.
Now add the login
and logout
views:
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 | @view_config(route_name='login', renderer='templates/login.pt')
@forbidden_view_config(renderer='templates/login.pt')
def login(request):
login_url = request.route_url('login')
referrer = request.url
if referrer == login_url:
referrer = '/' # never use the login form itself as came_from
came_from = request.params.get('came_from', referrer)
message = ''
login = ''
password = ''
if 'form.submitted' in request.params:
login = request.params['login']
password = request.params['password']
if USERS.get(login) == password:
headers = remember(request, login)
return HTTPFound(location = came_from,
headers = headers)
message = 'Failed login'
return dict(
message = message,
url = request.application_url + '/login',
came_from = came_from,
login = login,
password = password,
)
@view_config(route_name='logout')
def logout(request):
headers = forget(request)
return HTTPFound(location = request.route_url('view_wiki'),
headers = headers)
|
login()
is decorated with two decorators:
- a
@view_config
decorator which associates it with thelogin
route and makes it visible when we visit/login
, - a
@forbidden_view_config
decorator which turns it into an forbidden view.login()
will be invoked when a users tries to execute a view callable that they are not allowed to. For example, if a user has not logged in and tries to add or edit a Wiki page, he will be shown the login form before being allowed to continue on.
The order of these two view configuration decorators is unimportant.
logout()
is decorated with a @view_config
decorator
which associates it with the logout
route. It will be
invoked when we visit /logout
.
Add the login.pt
Template¶
Create tutorial/tutorial/templates/login.pt
with the following
content:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal">
<head>
<title>Login - Pyramid tutorial wiki (based on TurboGears
20-Minute Wiki)</title>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/>
<meta name="keywords" content="python web application" />
<meta name="description" content="pyramid web application" />
<link rel="shortcut icon"
href="${request.static_url('tutorial:static/favicon.ico')}" />
<link rel="stylesheet"
href="${request.static_url('tutorial:static/pylons.css')}"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="${request.static_url('tutorial:static/ie6.css')}"
type="text/css" media="screen" charset="utf-8" />
<![endif]-->
</head>
<body>
<div id="wrap">
<div id="top-small">
<div class="top-small align-center">
<div>
<img width="220" height="50" alt="pyramid"
src="${request.static_url('tutorial:static/pyramid-small.png')}" />
</div>
</div>
</div>
<div id="middle">
<div class="middle align-right">
<div id="left" class="app-welcome align-left">
<b>Login</b><br/>
<span tal:replace="message"/>
</div>
<div id="right" class="app-welcome align-right"></div>
</div>
</div>
<div id="bottom">
<div class="bottom">
<form action="${url}" method="post">
<input type="hidden" name="came_from" value="${came_from}"/>
<input type="text" name="login" value="${login}"/><br/>
<input type="password" name="password"
value="${password}"/><br/>
<input type="submit" name="form.submitted" value="Log In"/>
</form>
</div>
</div>
</div>
<div id="footer">
<div class="footer"
>© Copyright 2008-2011, Agendaless Consulting.</div>
</div>
</body>
</html>
The above template is referred to within the login view we just
added to views.py
.
Return a logged_in flag to the renderer¶
Add the following line to the import at the head of
tutorial/tutorial/views.py
:
1 2 3 4 5 | from pyramid.security import (
remember,
forget,
authenticated_userid,
)
|
(Only the highlighted line needs to be added.)
Add a logged_in
parameter to the return value of
view_page()
, edit_page()
and add_page()
,
like this:
1 2 3 4 | return dict(page = page,
content = content,
edit_url = edit_url,
logged_in = authenticated_userid(request))
|
(Only the highlighted line needs to be added.)
authenticated_userid()
will return None
if the user is not authenticated, or some user id it the user
is authenticated.
Add a “Logout” link when logged in¶
Open tutorial/tutorial/templates/edit.pt
and
tutorial/tutorial/templates/view.pt
and add this within the
<div id="right" class="app-welcome align-right">
div:
<span tal:condition="logged_in">
<a href="${request.application_url}/logout">Logout</a>
</span>
The attribute tal:condition="logged_in"
will make the element be
included when logged_in
is any user id. The link will invoke
the logout view. The above element will not be included if logged_in
is None
, such as when a user is not authenticated.
Seeing Our Changes¶
Our tutorial/tutorial/__init__.py
will look something like this
when we’re done:
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 | from pyramid.config import Configurator
from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from sqlalchemy import engine_from_config
from tutorial.security import groupfinder
from .models import (
DBSession,
Base,
)
def main(global_config, **settings):
""" This function returns a Pyramid WSGI application.
"""
engine = engine_from_config(settings, 'sqlalchemy.')
DBSession.configure(bind=engine)
Base.metadata.bind = engine
authn_policy = AuthTktAuthenticationPolicy(
'sosecret', callback=groupfinder, hashalg='sha512')
authz_policy = ACLAuthorizationPolicy()
config = Configurator(settings=settings,
root_factory='tutorial.models.RootFactory')
config.set_authentication_policy(authn_policy)
config.set_authorization_policy(authz_policy)
config.add_static_view('static', 'static', cache_max_age=3600)
config.add_route('view_wiki', '/')
config.add_route('login', '/login')
config.add_route('logout', '/logout')
config.add_route('view_page', '/{pagename}')
config.add_route('add_page', '/add_page/{pagename}')
config.add_route('edit_page', '/{pagename}/edit_page')
config.scan()
return config.make_wsgi_app()
|
(Only the highlighted lines need to be added.)
Our tutorial/tutorial/models.py
will look something like this
when we’re done:
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 | from pyramid.security import (
Allow,
Everyone,
)
from sqlalchemy import (
Column,
Integer,
Text,
)
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import (
scoped_session,
sessionmaker,
)
from zope.sqlalchemy import ZopeTransactionExtension
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
Base = declarative_base()
class Page(Base):
""" The SQLAlchemy declarative model class for a Page object. """
__tablename__ = 'pages'
id = Column(Integer, primary_key=True)
name = Column(Text, unique=True)
data = Column(Text)
def __init__(self, name, data):
self.name = name
self.data = data
class RootFactory(object):
__acl__ = [ (Allow, Everyone, 'view'),
(Allow, 'group:editors', 'edit') ]
def __init__(self, request):
pass
|
(Only the highlighted lines need to be added.)
Our tutorial/tutorial/views.py
will look something like this
when we’re done:
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 | import re
from docutils.core import publish_parts
from pyramid.httpexceptions import (
HTTPFound,
HTTPNotFound,
)
from pyramid.view import (
view_config,
forbidden_view_config,
)
from pyramid.security import (
remember,
forget,
authenticated_userid,
)
from .models import (
DBSession,
Page,
)
from .security import USERS
# regular expression used to find WikiWords
wikiwords = re.compile(r"\b([A-Z]\w+[A-Z]+\w+)")
@view_config(route_name='view_wiki',
permission='view')
def view_wiki(request):
return HTTPFound(location = request.route_url('view_page',
pagename='FrontPage'))
@view_config(route_name='view_page', renderer='templates/view.pt',
permission='view')
def view_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).first()
if page is None:
return HTTPNotFound('No such page')
def check(match):
word = match.group(1)
exists = DBSession.query(Page).filter_by(name=word).all()
if exists:
view_url = request.route_url('view_page', pagename=word)
return '<a href="%s">%s</a>' % (view_url, word)
else:
add_url = request.route_url('add_page', pagename=word)
return '<a href="%s">%s</a>' % (add_url, word)
content = publish_parts(page.data, writer_name='html')['html_body']
content = wikiwords.sub(check, content)
edit_url = request.route_url('edit_page', pagename=pagename)
return dict(page=page, content=content, edit_url=edit_url,
logged_in=authenticated_userid(request))
@view_config(route_name='add_page', renderer='templates/edit.pt',
permission='edit')
def add_page(request):
pagename = request.matchdict['pagename']
if 'form.submitted' in request.params:
body = request.params['body']
page = Page(pagename, body)
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
save_url = request.route_url('add_page', pagename=pagename)
page = Page('', '')
return dict(page=page, save_url=save_url,
logged_in=authenticated_userid(request))
@view_config(route_name='edit_page', renderer='templates/edit.pt',
permission='edit')
def edit_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).one()
if 'form.submitted' in request.params:
page.data = request.params['body']
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
return dict(
page=page,
save_url = request.route_url('edit_page', pagename=pagename),
logged_in=authenticated_userid(request),
)
@view_config(route_name='login', renderer='templates/login.pt')
@forbidden_view_config(renderer='templates/login.pt')
def login(request):
login_url = request.route_url('login')
referrer = request.url
if referrer == login_url:
referrer = '/' # never use the login form itself as came_from
came_from = request.params.get('came_from', referrer)
message = ''
login = ''
password = ''
if 'form.submitted' in request.params:
login = request.params['login']
password = request.params['password']
if USERS.get(login) == password:
headers = remember(request, login)
return HTTPFound(location = came_from,
headers = headers)
message = 'Failed login'
return dict(
message = message,
url = request.application_url + '/login',
came_from = came_from,
login = login,
password = password,
)
@view_config(route_name='logout')
def logout(request):
headers = forget(request)
return HTTPFound(location = request.route_url('view_wiki'),
headers = headers)
|
(Only the highlighted lines need to be added.)
Our tutorial/tutorial/templates/edit.pt
template will look
something like this when we’re done:
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 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal">
<head>
<title>${page.name} - Pyramid tutorial wiki (based on
TurboGears 20-Minute Wiki)</title>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/>
<meta name="keywords" content="python web application" />
<meta name="description" content="pyramid web application" />
<link rel="shortcut icon"
href="${request.static_url('tutorial:static/favicon.ico')}" />
<link rel="stylesheet"
href="${request.static_url('tutorial:static/pylons.css')}"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="${request.static_url('tutorial:static/ie6.css')}"
type="text/css" media="screen" charset="utf-8" />
<![endif]-->
</head>
<body>
<div id="wrap">
<div id="top-small">
<div class="top-small align-center">
<div>
<img width="220" height="50" alt="pyramid"
src="${request.static_url('tutorial:static/pyramid-small.png')}" />
</div>
</div>
</div>
<div id="middle">
<div class="middle align-right">
<div id="left" class="app-welcome align-left">
Editing <b><span tal:replace="page.name">Page Name
Goes Here</span></b><br/>
You can return to the
<a href="${request.application_url}">FrontPage</a>.<br/>
</div>
<div id="right" class="app-welcome align-right">
<span tal:condition="logged_in">
<a href="${request.application_url}/logout">Logout</a>
</span>
</div>
</div>
</div>
<div id="bottom">
<div class="bottom">
<form action="${save_url}" method="post">
<textarea name="body" tal:content="page.data" rows="10"
cols="60"/><br/>
<input type="submit" name="form.submitted" value="Save"/>
</form>
</div>
</div>
</div>
<div id="footer">
<div class="footer"
>© Copyright 2008-2011, Agendaless Consulting.</div>
</div>
</body>
</html>
|
(Only the highlighted lines need to be added.)
Our tutorial/tutorial/templates/view.pt
template will look
something like this when we’re done:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal">
<head>
<title>${page.name} - Pyramid tutorial wiki (based on
TurboGears 20-Minute Wiki)</title>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/>
<meta name="keywords" content="python web application" />
<meta name="description" content="pyramid web application" />
<link rel="shortcut icon"
href="${request.static_url('tutorial:static/favicon.ico')}" />
<link rel="stylesheet"
href="${request.static_url('tutorial:static/pylons.css')}"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="${request.static_url('tutorial:static/ie6.css')}"
type="text/css" media="screen" charset="utf-8" />
<![endif]-->
</head>
<body>
<div id="wrap">
<div id="top-small">
<div class="top-small align-center">
<div>
<img width="220" height="50" alt="pyramid"
src="${request.static_url('tutorial:static/pyramid-small.png')}" />
</div>
</div>
</div>
<div id="middle">
<div class="middle align-right">
<div id="left" class="app-welcome align-left">
Viewing <b><span tal:replace="page.name">Page Name
Goes Here</span></b><br/>
You can return to the
<a href="${request.application_url}">FrontPage</a>.<br/>
</div>
<div id="right" class="app-welcome align-right">
<span tal:condition="logged_in">
<a href="${request.application_url}/logout">Logout</a>
</span>
</div>
</div>
</div>
<div id="bottom">
<div class="bottom">
<div tal:replace="structure content">
Page text goes here.
</div>
<p>
<a tal:attributes="href edit_url" href="">
Edit this page
</a>
</p>
</div>
</div>
</div>
<div id="footer">
<div class="footer"
>© Copyright 2008-2011, Agendaless Consulting.</div>
</div>
</body>
</html>
|
(Only the highlighted lines need to be added.)
Viewing the Application in a Browser¶
We can finally examine our application in a browser (See Starting the Application). Launch a browser and visit each of the following URLs, check that the result is as expected:
http://localhost:6543/
invokes theview_wiki
view. This always redirects to theview_page
view of the FrontPage page object. It is executable by any user.http://localhost:6543/FrontPage
invokes theview_page
view of the FrontPage page object.http://localhost:6543/FrontPage/edit_page
invokes the edit view for the FrontPage object. It is executable by only theeditor
user. If a different user (or the anonymous user) invokes it, a login form will be displayed. Supplying the credentials with the usernameeditor
, passwordeditor
will display the edit page form.http://localhost:6543/add_page/SomePageName
invokes the add view for a page. It is executable by only theeditor
user. If a different user (or the anonymous user) invokes it, a login form will be displayed. Supplying the credentials with the usernameeditor
, passwordeditor
will display the edit page form.- After logging in (as a result of hitting an edit or add page
and submitting the login form with the
editor
credentials), we’ll see a Logout link in the upper right hand corner. When we click it, we’re logged out, and redirected back to the front page.