pas.plugins.headers

April 1, 2025 ยท View on GitHub

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=================== pas.plugins.headers

This PAS plugin reads request headers and uses them for authentication. Think SAML headers that are set by a front web server like Apache or nginx.

Features

On install in Plone, the plugin is added to the PluggableAuthService. It is registered for several plugin types:

  • Challenge plugin
  • Extraction plugin
  • Authentication plugin
  • Properties plugin
  • Roles plugin

You can configure them in the ZMI (Zope Management Interface) by editing properties in the plugin.

Installation

Install pas.plugins.headers by adding it to your setup.

Add a line pas.plugins.headers to the requirements.txt or to the pyproject.toml file (under dependencies) of your setup.

Then re-apply the installation, i.e. using your Makefile or running pip install -e . in your project.

With buildout, you can do this by adding it to the eggs line for your instance::

[buildout]
...
eggs =
    pas.plugins.headers

and then running bin/buildout.

In either case, start Plone and install the plugin in the Add-ons control panel.

Compatibility

This has been tested to work on Plone 6.0, 6.1, and 6.2. For older version of Plone use the 1.x release series.

Plain Zope?

No, this does not work in plain Zope. Theoretically it might work if you first install Products.PluggableAuthService, Products.GenericSetup and plone.base. But then you already almost have a CMF site with bits of Plone.

Manual configuration

You can configure the plugin by going to the ZMI (Zope Management Interface). Go to the acl_users (PluggableAuthService) folder in the Plone ZMI. Click on the request_headers plugin. Go to the Properties tab.

These are the properties that you can edit:

userid_header: Header to use as user id.

roles_header: Header to use as roles for the current user. This can give multiple roles: it is split on white space.

allowed_roles: Allowed roles. Roles that we allow in the roles_header. Any other roles that are in the header are ignored. Ignored when empty: all roles are taken over, also when the role is not known in Plone. The roles from the header and the allowed_roles property are compared lowercase. The reported roles use the case fromallowed_roles. For example, if the header contains PUPIL root and allowed_roles contains Pupil Teacher, then the reported roles will be only Pupil.

required_headers: Required headers. Without these, the extraction plugin does not extract headers, so the user is not authenticated. These headers may have an empty value in the request, as long as they are all there.

deny_unauthorized: Deny unauthorized access. Default: false. When this is true and the user is unauthorized, the Challenge plugin stops and presents an ugly error. When false, the Challenge plugin will check the redirect_url.

redirect_url: URL to redirect to when unauthorized. When empty, it has no effect. When set, the Challenge plugin redirects unauthorized users to this url. Usually you would configure your frontend server to force SAML or CAS login on this url. The headerlogin page defined by this plugin may be a good url. We treat the redirect_url as relative to the Plone site root, unless it is a full url. If deny_unauthorized is true, this option is ignored.

memberdata_to_header: Mapping from memberdata property to request header, one per row. Format: propname|header. Or: propname|header|parser. See the Parsers_ section for information about parsers You can also combine several headers: propname|header_with_firstname header_with_lastname.

create_ticket: Create an authentication ticket (__ac cookie) with plone.session. Default: false. When reading headers, this checks if Plone knows this user. If so, we create an authentication ticket. Then you could let your frontend server (nginx, Apache) only set the headers for some urls, instead of for all. Note that this does not work for root Zope users, and it does not take over properties and roles. See also issue 6 <https://github.com/collective/pas.plugins.headers/issues/6>_.

default_roles: Default roles to add when a user is successfully authenticated by this plugin. You always automatically get the Authenticated role. But you may want to give everyone the Member role. This is not checked against the allowed roles.

Configuration via GenericSetup

The package has a GS (GenericSetup) import step with id pas.plugins.headers. In the GS profile of your add-on, it looks for a file with name pas.plugins.headers.json. This file must contain a json string. Full example:

::

{
    "purge": true,
    "allowed_roles": [
        "Member",
        "Zebra"
    ],
    "create_ticket": true,
    "default_roles": [
        "Member"
    ],
    "deny_unauthorized": true,
    "memberdata_to_header": [
        "uid|HEADER_uid|lower",
        "fullname|HEADER_firstname HEADER_lastname"
    ],
    "redirect_url": "https://maurits.vanrees.org",
    "required_headers": [
        "uid",
        "test"
    ],
    "roles_header": "roles",
    "userid_header": "uid"
}

Some remarks:

  • When the contents cannot be parsed as json, or when the result is not a dictionary, a ValueError is raised.

  • purge is optional. When it is true, the default settings are restored before handling the rest of the file.

  • purge is only valid for the entire file. It does not work in individual lists. So you cannot add one required header and keep the current ones. You need to specify them all.

  • The keys are the properties that you see in the ZMI.

  • When an unknown key is used, it is silently ignored.

  • In memberdata_to_header, the importer does not check if the parsers are registered.

Parsers

In the memberdata_to_header property, you can use parsers. For example::

age|HEADER_age|int

When getting the properties for the current user, the properties plugin will calculate the age property. It reads the HEADER_age header, which may give a string like '42'. It then calls the int parser to turn this into integer 42.

Note: the properties plugin is currently the only part where the parsers are used. So it is not used when getting for example the user id from a header.

If you specify a parser that does not exist, the parser is ignored and you get the unmodified header value.

A few basic parsers are available:

bool: Returns either True or False. When the first character of the lowercase header value is y/j/t/1, the parser return True, else False.

int: Returns an integer. When parsing as integer fails, it returns zero.

lower: Returns the value in lowercase.

upper: Returns the value in uppercase.

split: Splits the value on whitespace, so you get a list.

You can register an own parser::

def extra_parser(value):
    return value + ' extra'

from pas.plugins.headers.parsers import register_parser
register_parser('extra', extra_parser)

Note: you get a warning when you override an existing parser.

Contribute

Support

If you are having issues, please let us know by adding an issue to the tracker: https://github.com/collective/pas.plugins.headers/issues

License

The project is licensed under the GPLv2.