An authentication policy for Pyramid that proxies to a stack of other authentication policies.

MultiAuthenticationPolicy is a Pyramid authentication policy that proxies to a stack of other IAuthenticationPolicy objects, to provide a combined auth solution from individual pieces. Simply pass it a list of policies that should be tried in order:

policies = [
    IPAuthenticationPolicy("127.0.*.*", principals=["local"])
    IPAuthenticationPolicy("192.168.*.*", principals=["trusted"])
]
authn_policy = MultiAuthenticationPolicy(policies)
config.set_authentication_policy(authn_policy)

This example uses the pyramid_ipauth module to assign effective principals based on originating IP address of the request. It combines two such policies so that requests originating from "127.0.." will have principal "local" while requests originating from "192.168.." will have principal "trusted".

In general, the results from the stacked authentication policies are combined as follows:

• authenticated_userid: return userid from first successful policy
• unauthenticated_userid: return userid from first successful policy
• effective_principals: return union of principals from all policies
• remember: return headers from all policies
• forget: return headers from all policies

It is also possible to specify the authentication policies as part of your paste deployment settings. Consider the following example:

[app:pyramidapp]
use = egg:mypyramidapp

multiauth.policies = ipauth1 ipauth2 pyramid_browserid

multiauth.policy.ipauth1.use = pyramid_ipauth.IPAuthentictionPolicy
multiauth.policy.ipauth1.ipaddrs = 127.0.*.*
multiauth.policy.ipauth1.principals = local

multiauth.policy.ipauth2.use = pyramid_ipauth.IPAuthentictionPolicy
multiauth.policy.ipauth2.ipaddrs = 192.168.*.*
multiauth.policy.ipauth2.principals = trusted

To configure authentication from these settings, simply include the multiauth module into your configurator:

config.include("pyramid_multiauth")

In this example you would get a MultiAuthenticationPolicy with three stacked auth policies. The first two, ipauth1 and ipauth2, are defined as the name of of a callable along with a set of keyword arguments. The third is defined as the name of a module, pyramid_browserid, which will be processed via the standard config.include() mechanism.

The end result would be a system that authenticates users via BrowserID, and assigns additional principal identifiers based on the originating IP address of the request.

If necessary, the group finder function and the authorization policy can also be specified from configuration:

[app:pyramidapp]
use = egg:mypyramidapp

multiauth.authorization_policy = mypyramidapp.acl.Custom
multiauth.groupfinder  = mypyramidapp.acl.groupfinder

...

An event is triggered when one of the multiple policies configured is selected.

from pyramid_multiauth import MultiAuthPolicySelected


# Track policy used, for prefixing user_id and for logging.
def on_policy_selected(event):
    print("%s (%s) authenticated %s for request %s" % (event.policy_name,
                                                       event.policy,
                                                       event.userid,
                                                       event.request))

config.add_subscriber(on_policy_selected, MultiAuthPolicySelected)