Pyramid authentication stack

The pyramid_authstack package makes it possible to stack multiple authentication policies in a pyramid project. This can be useful in several scenarios:

• You need to be able to identify a user for a long period of time, while requiting a recent login to access personal information. Amazon is an example of a site doing this.

• You want to send a newsletter to users and log the user in automatically when they follow a link in the newsletter, but not give automatically give them access to sensitive information.

Confusing a multi-authentication policy is simple: create an instance of the AuthenticationStackPolicy object, add the authentication policies you want to it and then tell Pyramid to use it.

from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid_authstack import AuthenticationStackPolicy

auth_policy = AuthenticationStackPolicy()
# Add an authentication policy with a one-hour timeout to control
# access to sensitive information.
auth_policy.add_policy(
    'sensitive',
    AuthTktAuthenticationPolicy('secret', timeout=60 * 60))
# Add a second authentication policy with a one-year timeout so
# we can identify the user.
auth_policy.add_policy(
    'identity',
    AuthTktAuthenticationPolicy('secret', timeout=60 * 60 * 24 * 365))
config.set_authentication_policy(auth_policy)

The name used for the sub-policy (sensitive and identity in the example above) will be added to the principals if the sub-policy can authenticate the user. This makes it very easy to check which authentication policies matched in an ACL:

class MyModel(object):
    # Only allow access if user authenticated recently.
    __acl__ = [(Allow, 'auth:sensitive', 'view')]

When you call remember() or forget() all sub-policies will be trigged. You can filter the list of policies used by adding a policies parameter. A use case where this is important is a user coming to the site via a link in a newsletter: in that scenario you can identify the user, but do not want to give access to sensitive information without asking for extra credentials.

from pyramid.security import remember

# Only set identity-authentication.
headers = remember(request, 'chrism', policies=['identity'])

Comparison to pyramid_multiauth

Mozilla has a similar project: pyramid_multiauth. There are a few difference between that package and this one:

• pyramid_multiauth has no way to indicate which authentication policy matched, which makes it unusable for my uses causes unless you always use custom authentication sub-policies which add custom an extra principal. This could be fixed, but it would require changing the API in a non-backward compatible way.

• pyramid_multiauth duplicates some of the callback-handling code instead of reusing pyramid’s CallbackAuthenticationPolicy.

• pyramid_multiauth allows configuration via the PasteDeploy .ini file, which pyramid_authstack does not support.

Changelog