Adding Authorization¶
Our application currently allows anyone with access to the server to view,
edit, and add pages to our wiki. For purposes of demonstration we’ll change
our application to allow 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. Pyramid provides
facilities for authorization and authentication. We’ll make
use of both features to provide security to our application.
We will add an authentication policy and an
authorization policy to our application
registry, add a security.py
module and give our root
resource an ACL.
Then we will add login
and logout
views, and modify the
existing views to make them return a logged_in
flag to the
renderer and add permission declarations to their view_config
decorators.
Finally, we will add a login.pt
template and change the existing
view.pt
and edit.pt
to show a “Logout” link when not logged in.
The source code for this tutorial stage can be browsed via http://github.com/Pylons/pyramid/tree/1.3-branch/docs/tutorials/wiki/src/authorization/.
Add Authentication and Authorization Policies¶
We’ll change our package’s __init__.py
file to enable an
AuthTktAuthenticationPolicy
and an ACLAuthorizationPolicy
to enable
declarative security checking. We need to import the new policies:
1 2 3 | from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from .security import groupfinder
|
Then, we’ll add those policies to the configuration:
1 2 3 4 5 6 | authn_policy = AuthTktAuthenticationPolicy(secret='sosecret',
callback=groupfinder)
authz_policy = ACLAuthorizationPolicy()
config = Configurator(root_factory=root_factory, settings=settings)
config.set_authentication_policy(authn_policy)
config.set_authorization_policy(authz_policy)
|
Note that the creation of an AuthTktAuthenticationPolicy
requires 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 a reference to a
groupfinder
function in the tutorial
package’s security.py
file.
We haven’t added that module yet, but we’re about to.
When you’re done, your __init__.py
will
look like so:
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 | from pyramid.config import Configurator
from pyramid_zodbconn import get_connection
from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from .models import appmaker
from .security import groupfinder
def root_factory(request):
conn = get_connection(request)
return appmaker(conn.root())
def main(global_config, **settings):
""" This function returns a WSGI application.
"""
authn_policy = AuthTktAuthenticationPolicy(secret='sosecret',
callback=groupfinder)
authz_policy = ACLAuthorizationPolicy()
config = Configurator(root_factory=root_factory, settings=settings)
config.set_authentication_policy(authn_policy)
config.set_authorization_policy(authz_policy)
config.add_static_view('static', 'static', cache_max_age=3600)
config.scan()
return config.make_wsgi_app()
|
Add security.py
¶
Add a security.py
module within your package (in the same
directory as __init__.py
, views.py
, etc.) 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 defined here is an authentication policy
“callback”; it is a callable that accepts a userid and a request. If the
userid exists in the system, the callback 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, the callback will return
None
. 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. Note that the editor
user is a member of the group:editors
group in our dummy group data (the GROUPS
data structure).
Give Our Root Resource an ACL¶
We need to give our root resource object an ACL. This ACL will be
sufficient to provide enough information to the Pyramid security
machinery to challenge a user who doesn’t have appropriate credentials when
he attempts to invoke the add_page
or edit_page
views.
We need to perform some imports at module scope in our models.py
file:
1 2 | from pyramid.security import Allow
from pyramid.security import Everyone
|
Our root resource object is a Wiki
instance. We’ll add the following
line at class scope to our Wiki
class:
1 2 | __acl__ = [ (Allow, Everyone, 'view'),
(Allow, 'group:editors', 'edit') ]
|
It’s only happenstance that we’re assigning this ACL at class scope. An ACL can be attached to an object instance too; this is how “row level security” can be achieved in Pyramid applications. We actually only need one ACL for the entire system, however, because our security requirements are simple, so this feature is not demonstrated.
Our resulting models.py
file will now look like so:
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 | from persistent import Persistent
from persistent.mapping import PersistentMapping
from pyramid.security import Allow
from pyramid.security import Everyone
class Wiki(PersistentMapping):
__name__ = None
__parent__ = None
__acl__ = [ (Allow, Everyone, 'view'),
(Allow, 'group:editors', 'edit') ]
class Page(Persistent):
def __init__(self, data):
self.data = data
def appmaker(zodb_root):
if not 'app_root' in zodb_root:
app_root = Wiki()
frontpage = Page('This is the front page')
app_root['FrontPage'] = frontpage
frontpage.__name__ = 'FrontPage'
frontpage.__parent__ = app_root
zodb_root['app_root'] = app_root
import transaction
transaction.commit()
return zodb_root['app_root']
|
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 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.
We’ll add these views to the existing views.py
file we have in our
project. Here’s what the login
view callable will look like:
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 | @view_config(context='.models.Wiki', name='login',
renderer='templates/login.pt')
@forbidden_view_config(renderer='templates/login.pt')
def login(request):
login_url = request.resource_url(request.context, '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,
)
|
Here’s what the logout
view callable will look like:
1 2 3 4 5 | @view_config(context='.models.Wiki', name='logout')
def logout(request):
headers = forget(request)
return HTTPFound(location = request.resource_url(request.context),
headers = headers)
|
Note that the login
view callable has two view configuration
decorators. The order of these decorators is unimportant. Each just adds a
different view configuration for the login
view callable.
The first view configuration decorator configures the login
view callable
so it will be invoked when someone visits /login
(when the context is a
Wiki and the view name is login
). The second decorator, named
forbidden_view_config
specifies a forbidden view. This
configures our login view to be presented to the user when Pyramid
detects that a view invocation can not be authorized. Because we’ve
configured a forbidden view, the login
view callable will be invoked
whenever one of our users tries to execute a view callable that they are not
allowed to invoke as determined by the authorization policy in use.
In our application, for example, this means that if a user has not logged in,
and he tries to add or edit a Wiki page, he will be shown the login form.
Before being allowed to continue on to the add or edit form, he will have to
provide credentials that give him permission to add or edit via this login
form.
Note that we’re relying on some additional imports within the bodies of these
views (e.g. remember
and forget
). We’ll see a rendering of the
entire views.py file a little later here to show you where those come from.
Change Existing Views¶
In order to indicate whether the current user is logged in, we need to change
each of our view_page
, edit_page
and add_page
views in
views.py
to pass a “logged in” parameter into its template. We’ll add
something like this to each view body:
1 2 | from pyramid.security import authenticated_userid
logged_in = authenticated_userid(request)
|
We’ll then change the return value of each view that has an associated
renderer
to pass the resulting logged_in
value to the
template. For example:
1 2 3 4 | return dict(page = context,
content = content,
logged_in = logged_in,
edit_url = edit_url)
|
Add permission
Declarations to our view_config
Decorators¶
To protect each of our views with a particular permission, we need to pass a
permission
argument to each of our pyramid.view.view_config
decorators. To do so, within views.py
:
- We add
permission='view'
to the decorator attached to theview_wiki
andview_page
view functions. This makes the assertion that only users who possess theview
permission against the context resource at the time of the request may invoke these views. We’ve grantedpyramid.security.Everyone
the view permission at the root model via its ACL, so everyone will be able to invoke theview_wiki
andview_page
views. - We add
permission='edit'
to the decorator attached to theadd_page
andedit_page
view functions. This makes the assertion that only users who possess the effectiveedit
permission against the context resource at the time of the request may invoke these views. We’ve granted thegroup:editors
principal theedit
permission at the root model via its ACL, so only a user whom is a member of the group namedgroup:editors
will able to invoke theadd_page
oredit_page
views. We’ve likewise given theeditor
user membership to this group via thesecurity.py
file by mapping him to thegroup:editors
group in theGROUPS
data structure (GROUPS = {'editor':['group:editors']}
); thegroupfinder
function consults theGROUPS
data structure. This means that theeditor
user can add and edit pages.
Add the login.pt
Template¶
Add a login.pt
template to your templates directory. It’s
referred to within the login view we just added to views.py
.
<!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="/static/favicon.ico" />
<link rel="stylesheet"
href="/static/pylons.css"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="/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="/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>
Change view.pt
and edit.pt
¶
We’ll also need to change our edit.pt
and view.pt
templates to
display a “Logout” link if someone is logged in. This link will
invoke the logout view.
To do so we’ll add this to both templates 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>
See Our Changes To views.py
and our Templates¶
Our views.py
module 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 | from docutils.core import publish_parts
import re
from pyramid.httpexceptions import HTTPFound
from pyramid.view import (
view_config,
forbidden_view_config,
)
from pyramid.security import (
authenticated_userid,
remember,
forget,
)
from .security import USERS
from .models import Page
# regular expression used to find WikiWords
wikiwords = re.compile(r"\b([A-Z]\w+[A-Z]+\w+)")
@view_config(context='.models.Wiki', permission='view')
def view_wiki(context, request):
return HTTPFound(location=request.resource_url(context, 'FrontPage'))
@view_config(context='.models.Page',
renderer='templates/view.pt', permission='view')
def view_page(context, request):
wiki = context.__parent__
def check(match):
word = match.group(1)
if word in wiki:
page = wiki[word]
view_url = request.resource_url(page)
return '<a href="%s">%s</a>' % (view_url, word)
else:
add_url = request.application_url + '/add_page/' + word
return '<a href="%s">%s</a>' % (add_url, word)
content = publish_parts(context.data, writer_name='html')['html_body']
content = wikiwords.sub(check, content)
edit_url = request.resource_url(context, 'edit_page')
logged_in = authenticated_userid(request)
return dict(page = context, content = content, edit_url = edit_url,
logged_in = logged_in)
@view_config(name='add_page', context='.models.Wiki',
renderer='templates/edit.pt',
permission='edit')
def add_page(context, request):
name = request.subpath[0]
if 'form.submitted' in request.params:
body = request.params['body']
page = Page(body)
page.__name__ = name
page.__parent__ = context
context[name] = page
return HTTPFound(location = request.resource_url(page))
save_url = request.resource_url(context, 'add_page', name)
page = Page('')
page.__name__ = name
page.__parent__ = context
logged_in = authenticated_userid(request)
return dict(page = page, save_url = save_url, logged_in = logged_in)
@view_config(name='edit_page', context='.models.Page',
renderer='templates/edit.pt',
permission='edit')
def edit_page(context, request):
if 'form.submitted' in request.params:
context.data = request.params['body']
return HTTPFound(location = request.resource_url(context))
logged_in = authenticated_userid(request)
return dict(page = context,
save_url = request.resource_url(context, 'edit_page'),
logged_in = logged_in)
@view_config(context='.models.Wiki', name='login',
renderer='templates/login.pt')
@forbidden_view_config(renderer='templates/login.pt')
def login(request):
login_url = request.resource_url(request.context, '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(context='.models.Wiki', name='logout')
def logout(request):
headers = forget(request)
return HTTPFound(location = request.resource_url(request.context),
headers = headers)
|
Our 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="/static/favicon.ico" />
<link rel="stylesheet"
href="/static/pylons.css"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="/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="/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="${save_url}" method="post">
<textarea name="body" tal:content="page.data" rows="10"
cols="60"/><br/>
<input type="submit" name="form.submitted" value="Save"/>
</form>
</div>
</div>
</div>
<div id="footer">
<div class="footer"
>© Copyright 2008-2011, Agendaless Consulting.</div>
</div>
</body>
</html>
|
Our view.pt
template will look something like this when we’re done:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal">
<head>
<title>${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="/static/favicon.ico" />
<link rel="stylesheet"
href="/static/pylons.css"
type="text/css" media="screen" charset="utf-8" />
<!--[if lte IE 6]>
<link rel="stylesheet"
href="/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="/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>
|
View the Application in a Browser¶
We can finally examine our application in a browser. The views we’ll try are as follows:
- Visiting
http://localhost:6543/
in a browser invokes theview_wiki
view. This always redirects to theview_page
view of theFrontPage
page resource. It is executable by any user. - Visiting
http://localhost:6543/FrontPage/
in a browser invokes theview_page
view of theFrontPage
Page resource. This is because it’s the default view (a view without aname
) forPage
resources. It is executable by any user. - Visiting
http://localhost:6543/FrontPage/edit_page
in a browser invokes the edit view for theFrontPage
Page resource. 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 show the edit page form being displayed. - Visiting
http://localhost:6543/add_page/SomePageName
in a browser 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 show the edit page form being displayed. - 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.