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:
Then we will add the login and logout feature:
The source code for this tutorial stage can be browsed at http://github.com/Pylons/pyramid/tree/1.3-branch/docs/tutorials/wiki/src/authorization/.
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, [])
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The groupfinder function accepts a userid and a request and returns one of these values:
For example, groupfinder('editor', request ) returns [‘group:editor’], 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.
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 lines to the Wiki class:
1 2 3 4 5 | class Wiki(PersistentMapping):
__name__ = None
__parent__ = None
__acl__ = [ (Allow, Everyone, 'view'),
(Allow, 'group:editors', 'edit') ]
|
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 Wiki class that contains the ACL is the resource constructor for the root resource, which is a Wiki instance. The ACL is provided to each view in the context of the request, as the context attribute.
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. See Assigning ACLs to your Resource Objects for more information about what an ACL represents.
Open tutorial/__init__.py and add these import statements:
1 2 3 | from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from .security import groupfinder
|
Now add those policies to the configuration:
1 2 3 4 5 6 | authn_policy = AuthTktAuthenticationPolicy(
'sosecret', callback=groupfinder, hashalg='sha512')
authz_policy = ACLAuthorizationPolicy()
config = Configurator(root_factory=root_factory, settings=settings)
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 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.
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 34 | @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)
|
login() is decorated with two decorators:
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.
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="/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>
The above template is referred to within the login view we just added to views.py.
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.
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.
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 | 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 Pyramid WSGI application.
"""
authn_policy = AuthTktAuthenticationPolicy(
'sosecret', callback=groupfinder, hashalg='sha512')
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()
|
(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 | from persistent import Persistent
from persistent.mapping import PersistentMapping
from pyramid.security import (
Allow,
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']
|
(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 | 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 (
remember,
forget,
authenticated_userid,
)
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')
return dict(page = context, content = content, edit_url = edit_url,
logged_in = authenticated_userid(request))
@view_config(name='add_page', context='.models.Wiki',
renderer='templates/edit.pt',
permission='edit')
def add_page(context, request):
pagename = request.subpath[0]
if 'form.submitted' in request.params:
body = request.params['body']
page = Page(body)
page.__name__ = pagename
page.__parent__ = context
context[pagename] = page
return HTTPFound(location = request.resource_url(page))
save_url = request.resource_url(context, 'add_page', pagename)
page = Page('')
page.__name__ = pagename
page.__parent__ = context
return dict(page=page, save_url=save_url,
logged_in=authenticated_userid(request))
@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))
return dict(page=context,
save_url=request.resource_url(context, 'edit_page'),
logged_in=authenticated_userid(request))
@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)
|
(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="/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="${save_url}" method="post">
<textarea name="body" tal:content="page.data" rows="10"
cols="60"/><br/>
<input type="submit" name="form.submitted" value="Save"/>
</form>
</div>
</div>
</div>
<div id="footer">
<div class="footer"
>© Copyright 2008-2011, Agendaless Consulting.</div>
</div>
</body>
</html>
|
(Only the highlighted lines need to be added.)
Our tutorial/tutorial/templates/view.pt template will look something like this when we’re done:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal">
<head>
<title>${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="/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>
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(Only the highlighted lines need to be added.)
We can finally examine our application in a browser (See Start the Application). Launch a browser and visit each of the following URLs, check that the result is as expected: