Pecan provides no out-of-the-box support for authentication, but it does give you the necessary tools to handle authentication and authorization as you see fit.
You can wrap entire controller subtrees or individual method calls with access controls using the secure() decorator.
To decorate a method, use one argument:
secure('<check_permissions_method_name>')
To secure a class, invoke with two arguments:
secure(object_instance, '<check_permissions_method_name>')
from pecan import expose
from pecan.secure import secure
class HighlyClassifiedController(object):
pass
class UnclassifiedController(object):
pass
class RootController(object):
@classmethod
def check_permissions(cls):
if user_is_admin():
return True
return False
@expose()
def index(self):
#
# This controller is unlocked to everyone,
# and will not run any security checks.
#
return dict()
@secure('check_permissions')
@expose()
def topsecret(self):
#
# This controller is top-secret, and should
# only be reachable by administrators.
#
return dict()
highly_classified = secure(HighlyClassifiedController(), 'check_permissions')
unclassified = UnclassifiedController()
Alternatively, the same functionality can also be accomplished by subclassing Pecan’s SecureController. Implementations of SecureController should extend the check_permissions() class method to return True if the user has permissions to the controller branch and False if they do not.
from pecan import expose
from pecan.secure import SecureController, unlocked
class HighlyClassifiedController(object):
pass
class UnclassifiedController(object):
pass
class RootController(SecureController):
@classmethod
def check_permissions(cls):
if user_is_admin():
return True
return False
@expose()
@unlocked
def index(self):
#
# This controller is unlocked to everyone,
# and will not run any security checks.
#
return dict()
@expose()
def topsecret(self):
#
# This controller is top-secret, and should
# only be reachable by administrators.
#
return dict()
highly_classified = HighlyClassifiedController()
unclassified = unlocked(UnclassifiedController())
Also note the use of the unlocked() decorator in the above example, which can be used similarly to explicitly unlock a controller for public access without any security checks.
The check_permissions() method should be used to determine user authentication and authorization. The code you implement here could range from simple session assertions (the existing user is authenticated as an administrator) to connecting to an LDAP service.
The secure() method has several advanced uses that allow you to create robust security policies for your application.
First, you can pass via a string the name of either a class method or an instance method of the controller to use as the check_permissions() method. Instance methods are particularly useful if you wish to authorize access to attributes of a model instance. Consider the following example of a basic virtual filesystem.
from pecan import expose
from pecan.secure import secure
from myapp.session import get_current_user
from myapp.model import FileObject
class FileController(object):
def __init__(self, name):
self.file_object = FileObject(name)
def read_access(self):
self.file_object.read_access(get_current_user())
def write_access(self):
self.file_object.write_access(get_current_user())
@secure('write_access')
@expose()
def upload_file(self):
pass
@secure('read_access')
@expose()
def download_file(self):
pass
class RootController(object):
@expose()
def _lookup(self, name, *remainder):
return FileController(name), remainder
The secure() method also accepts a function argument. When passing a function, make sure that the function is imported from another file or defined in the same file before the class definition, otherwise you will likely get error during module import.
from pecan import expose
from pecan.secure import secure
from myapp.auth import user_authenitcated
class RootController(object):
@secure(user_authenticated)
@expose()
def index(self):
return 'Logged in'
You can also use the secure() method to change the behavior of a SecureController. Decorating a method or wrapping a subcontroller tells Pecan to use another security function other than the default controller method. This is useful for situations where you want a different level or type of security.
from pecan import expose
from pecan.secure import SecureController, secure
from myapp.auth import user_authenticated, admin_user
class ApiController(object):
pass
class RootController(SecureController):
@classmethod
def check_permissions(cls):
return user_authenticated()
@classmethod
def check_api_permissions(cls):
return admin_user()
@expose()
def index(self):
return 'logged in user'
api = secure(ApiController(), 'check_api_permissions')
In the example above, pecan will only call admin_user() when a request is made for /api/.
Secure controllers can be nested to provide increasing levels of security on subcontrollers. In the example below, when a request is made for /admin/index/, Pecan first calls check_permissions() on the RootController and then calls check_permissions() on the AdminController.
from pecan import expose
from pecan.secure import SecureController
from myapp.auth import user_logged_in, is_admin
class AdminController(SecureController):
@classmethod
def check_permissions(cls):
return is_admin()
@expose()
def index(self):
return 'admin dashboard'
class RootController(SecureController):
@classmethod
def check_permissions(cls):
return user_logged_in
@expose()
def index(self):
return 'user dashboard'