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Commit 3d2b8cf7 authored by Andreas Åkre Solberg's avatar Andreas Åkre Solberg
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New documentation: Authentication Processing Filters in SimpleSAMLphp 

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Authentication Processing Filters in SimpleSAMLphp
==================================================
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In SimpleSAMLphp, there is an API where you can *do stuff* at the IdP after authentication is complete, and just before you are sent back to the SP. The same API is available on the SP, after you have received a successfull Authentication Response from the IdP and before you are sent back to the SP application.
Examples of neat things to do using Authentication Processing Filters:
* Filter out a subset of available attributes that are sent to a SP.
* Mofify the name of attributes
* Generate new attributes that are composed of others. In example eduPersonTargetedID.
* Ask the user for consent, before the user is sent back to a service
* Implement basic Access Control on the IdP (not neccessarily a good idea), limiting access for some users to some SPs.
Be aware that Authentication Proccessing Filters do replace some of the preivous features in simpleSAMLphp, named:
* `attributemap`
* `attributealter`
* attribute filter
Later in this document, we will desribe in detail the alternative Authentication Proccessing Filters that will replicate these functionalities.
How to configure Auth Proc Filters
----------------------------------
*Auth Proc Filters* can be set globally, or to be specific for only one SP or one IdP. That means there is three locations where you can configure *Auth Proc Filters*:
* Globally in `config.php`
* On the SP: Specific for only one hosted SP in `saml20-sp-hosted` or `shib13-sp-hosted`
* On the SP: Specific for only one remote IdP in `saml20-idp-remote` or `shib13-idp-remote`
* On the IdP: Specific for only one hosted IdP in `saml20-idp-hosted` or `shib13-idp-hosted`
* On the IdP: Specific for only one remote SP in `saml20-sp-remote` or `shib13-sp-remote`
The configuration of *Auth Proc Filters* is a list of filters with priority as *index*. Here is an example of *Auth Proc Filters* configured in `config.php`:
'authproc.idp' => array(
10 => array(
'class' => 'core:AttributeMap',
'addurnprefix'
),
20 => 'core:TargetedID',
40 => 'core:AttributeRealm',
50 => 'core:AttributeLimit',
90 => array(
'class' => 'consent:Consent',
'store' => 'consent:Cookie',
'focus' => 'yes',
'checked' => TRUE
),
),
This configuration will execute *Auth Proc Filters* one by one, with the priority value in increasing order. When *Auth Proc Filters* is configured in multiple places, in example both globally, in the hosted IdP and remote SP metadata, then the list is interleaved sorted by priority.
The most important parameter of each item on the list is the *class* of the *Auth Proc Filter*. The syntax of the class is `modulename:classname`. As an example the class definition `core:AttributeLimit` will be expanded to look for the class `sspmod_core_Auth_Process_AttributeLimit`. The location of this class file *must* then be: `modules/core/lib/Auth/Process/AttributeLimit.php`.
You will see that a bunch of useful filters is included in the `core` module. In addition the `consent` module that is included in the simpleSAMLphp distribution implements a filter. Beyond that, you are encourage to create your own filters and share with the community. If you have created a cool *Auth Proc Filter* that do something useful, let us know, and we may share it from the [simpleSAMLphp web site][].
[simpleSAMLphp web site]: http://rnd.feide.no/simplesamlphp
When you know the class definition of a filter, and the priority, the simple way to configure the filter is:
20 => 'core:TargetedID',
This is analogue to:
20 => array(
'class' => 'core:TargetedID'
),
Some *Auth Proc Filters* have optional or required *parameters*. To send parameters to *Auth Proc Filters*, you need to choose the second of the two alernatives above. Here is an example of provided parameters to the consent module:
90 => array(
'class' => 'consent:Consent',
'store' => 'consent:Cookie',
'focus' => 'yes',
'checked' => TRUE
),
### Filters in `config.php`
Global *Auth Proc Filters* is configured in the `config.php` file. You will see that the config template already includes an example configuration.
There is two config parameters:
* `authproc.idp` and
* `authproc.sp`
The filters in `authproc.idp` will be executed at the IdP side regardless of which IdP and SP entity that is involved.
The filters in `authproc.sp` will be executed at the SP side regardless of which SP and IdP entity that is involved.
### Filters in metadata
Filters can be added both in `hosted` and `remote` metadata. Here is an example of a filter added in a metadata file:
'__DYNAMIC:1__' => array(
'host' => '__DEFAULT_',
'privatekey' => 'server.pem',
'certificate' => 'server.crt',
'auth' => 'feide',
'authproc' => array(
40 => 'core:AttributeRealm',
),
)
The example above is in `saml20-idp-hosted`.
Auth Proc Filters included in the simpleSAMLphp distribution
------------------------------------------------------------
Here is documentation on the *Auth Proc Filters* that is included in the simpleSAMLphp distribution.
### Adding attributes (`core:AttributeAdd`)
This filter allows you to add attributes to the attribute set being processed.
If the attribute already exists, the values added will be merged into a multi valued attribute. If you want to replace instead of merge attributes, you may add the `'%merge'` parameter.
Add a single valued attributes:
'authproc' => array(
50 => array(
'class' => 'core:AttributeAdd',
'source' => array('myidp')
),
),
Add a multi valued attribute:
'authproc' => array(
50 => array(
'class' => 'core:AttributeAdd',
'groups' => array('users', 'members')
),
),
Replace an existing attributes
'authproc' => array(
50 => array(
'class' => 'core:AttributeAdd',
'%replace',
'uid' => array('guest')
),
),
### Filtering attributes (`core:AttributeFilter`)
This *Auth Proc Filter* is backward compatible with the old way of filtering attributes. It operates in two modes:
1. List of attributes added as configuration to the filter
2. List of attributes specified in metadata (both SP and IdP) in the `attribute` parameter (as always)
#### Attribute list added as a parameter
Example configuration
'authproc' => array(
50 => array(
'class' => 'core:AttributeLimit',
'cn', 'mail'
),
),
#### Attribute list in metadata
If you do not add attributes as parameters to the filter, the filter will look up attributes in metadata.
'authproc' => array(
50 => 'core:AttributeLimit',
),
Here is an example of how attribute liste is defined in metadata:
'__DYNAMIC:1__' => array(
'host' => 'dev11.andreas.feide.no',
'privatekey' => 'server.pem',
'certificate' => 'server.crt',
'auth' => 'example-static',
'logouttype' => 'iframe',
'attributes' => array('cn', 'mail', 'sn', 'eduPersonTargetedID'),
),
Attribute filtering can be done both on the IdP and the SP side. On the SP side, attribute lists is read from *sp-hosted* and *idp-remote*. On IdP side, attribute lists is read from *idp-hosted* and *sp-remote*.
### Modifying attribute names (`core:AttributeMap`)
This *Auth Proc Filter* is backward compatible with the old way of modifying attribute names. It operates in two modes:
1. Attribute mapping table included as parameters to the filter.
2. The filter gets a name of an attributemap file as a parameter
#### Attribute maps embedded as parameters
Here is an example:
'authproc' => array(
50 => array(
'class' => 'core:AttributeMap',
'mail' => 'email',
'uid' => 'user'),
),
#### Attribute maps in separate files
Here is an example:
'authproc' => array(
50 => array(
'class' => 'core:AttributeMap',
'addurnprefix'
),
),
The example above will look for this file: `simpesamlphp/attributemap/addurnprefix.php`. As you see this file is already included as an example. Copy `addurnprefix.php` and add the new file in the same directory to add new attributemaps.
### Adding realm as an attribute (`core:AttributeRealm`)
No parameters required:
40 => 'core:AttributeRealm',
Alternatively, you can specify the attribute name that should be used instead of the default `realm`:
40 => array(
'class' => 'core:AttributeRealm',
'attributename' => 'homedomain',
)
This filter will look for the user ID on a format like `andreas@uninett.no`, and extract the part after the '`@`'-sign.
*What is the User ID?*
The User ID can be any attribute. The name of the User ID can be specified in the metadata as a `userid.attribute` parameter. Default value is `eduPersonPrincipalName`.
**Important**: You have to make sure that the User ID attribute is available at the time this filter is executed. You can do that by setting a lower priority number on this filter, than the filter that filters attributes.
### Automatically generated eduPersonTargetedID (`core:TargetedID`)
*eduPersonTargetedID* is an anonymous user attribute that is unique for each combination IdP and SP.
Example configuration:
'authproc' => array(
50 => 'core:TargetedID',
)
If you want to inject this new attribute with another name than the default `eduPersonTargetedID`:
'authproc' => array(
50 => array(
'class' => 'core:TargetedID',
'attributename' => 'anonymousID',
),
)
The automatic generation of `eduPersonTargetedID` requires that the User ID attribute is available.
*What is the User ID?*
The User ID can be any attribute. The name of the User ID can be specified in the metadata as a `userid.attribute` parameter. Default value is `eduPersonPrincipalName`.
**Important**: You have to make sure that the User ID attribute is available at the time this filter is executed. You can do that by setting a lower priority number on this filter, than the filter that filters attributes.
The formula used for automatically calculating this value is (pseudo code):
sha1(
'uidhashbase' + $secretSalt +
strlen($idpEntityid) + ':' + $idpEntityid +
strlen($spEntityid) + ':' + $spEntityid +
strlen($userID) + ':' + $userID +
$secretSalt
)
In example that could mean:
sha1( 'uidhashbaseq8d76f8ds75f68d7s24:https://idp.example.org
23:https://sp.example.org19:andreas@uninett.noq8d76f8ds75f68d7s' )
### Adding a group attribute (`core:GenerateGroups`)
By default this filter will generate groups from the following set of attributes:
- `eduPersonAffiliation`
- `eduPersonOrgUnitDN`
- `eduPersonEntitlement`
This can be overridden by specifying the names of the attributes in the configuration.
It will attempt to determine a realm the user belongs to based on the User ID attribute, if it is present.
The groups this filter generates are on the form: `<attribute name>-<attributevalue>` and `<attributename>-<realm>-<attributevalue>`.
Note that this filter isn't a drop-in replacement for the groups attributealter function. The difference is that it uses the full attribute name, instead of shortening them to for example affiliation, and it escapes illegal characters in a style similar to urlencoding. It also generates groups both with and without a realm part. If no realm is determined, it will only generate attributes without a realm-part.
Example - generate from default set of attributes:
'authproc' => array(
50 => 'core:GenerateGroups',
),
Example - generate from only the `eduPersonAffilitation` attribute:
'authproc' => array(
50 => array(
'class' => 'core:GenerateGroups',
'eduPersonAffiliation'
),
),
Writing your own Auth Proc Filter
---------------------------------
For now look at the included *Auth Proc Filters* as examples. Copy the classes into your own module and start playing around.
Don't hestitate to ask on the simpleSAMLphp mailinglist if you have problems or questions, or want to share your *Auth Proc Filter* with others.
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