This example is based on the based on How to configure Shibboleth SP attribute checker. Please see that wiki page for further description on how to use Shibboleth SP attribute checker.
Shibboleth Service Provider (SP) provides a hook for performing attribute checks for required attributes and a attribute extractor for fetching Identity Provider (IdP) metadata attributes where the login was performed. Without require any changes to the service the end user'will get an error message. THe example contains an a possiblity for the end user to send a detailed error report to their Identity Provider support contact.
In this example the Identity Provider is tested for
- metadata declaration for support of REFEDS SIRTFI; and
- attribute release based on REFEDS R&S.
Attribute Checker Handler
The AttributeChecker validates the user session against attributes specified as a required. If requirements are fulfilled, the login completes otherwise an error page is displayed instead. Note that the required attributes have to be "hard coded" here and kept in sync with the required attributes expressed in the Metadata.
Configuration
Add a sessionHook for attribute checker: sessionHook="/Shibboleth.sso/AttrChecker" to ApplicationDefaults. Add also the metadataAttributePrefix="Meta-" (This will be explained later).
In context: /etc/shibboleth/shibboleth2.xml -> ApplicationDefault element
<ApplicationDefaults entityID="https://<HOST>/shibboleth" REMOTE_USER="eppn persistent-id targeted-id" signing="front" encryption="false" sessionHook="/Shibboleth.sso/AttrChecker" metadataAttributePrefix="Meta-" >
Add the attribute checker handler with the list of required attributes to Sessions.
/etc/shibboleth/shibboleth2.xml -> Sessions element
If you want to describe more complex scenarios with required attributes, operators such as "AND" and "OR" are available.
<Handler type="AttributeChecker" Location="/AttrChecker" template="attrChecker.html" flushSession="true">
<AND>
<!-- Check for REFEDS SIRTFI Assurance Declaration in metadata -->
<Rule require="Meta-AssuranceCertification">https://refeds.org/sirtfi</Rule>
<!-- Check for REFEDS R&S compliant attribute release -->
<Rule require="eppn"/>
<Rule require="mail"/>
<OR>
<Rule require="displayName"/>
<AND>
<Rule require="givenName"/>
<Rule require="surname"/>
</AND>
</OR>
</AND>
</Handler>
Now we have an session hook for the attribute checker to check specified attributes before a user login is completed.
Add the AttributeExtractor element of the type metadata next to the already existing type XML: (<AttributeExtractor type="XML" validate="true" path="attribute-map.xml"/>)
For customization and error checks on the error page (attrChecker.html) we want to enable the "Attribute Extractor" with the type "metadata" to be able to fetch IdP attributes from the metadata feed. The attributes we need is the email addresses of the IdP support and security contacts. We've already added metadataAttributePrefix to the ApplicationDefaults element.
/etc/shibboleth/shibboleth2.xml -> ApplicationDefault element
<!-- Extracts support information for IdP from its metadata. -->
<AttributeExtractor type="Metadata" errorURL="errorURL" DisplayName="displayName"
InformationURL="informationURL" PrivacyStatementURL="privacyStatementURL"
OrganizationURL="organizationURL">
<ContactPerson id="Support-Contact" contactType="support" formatter="$EmailAddress" />
<ContactPerson id="Other-Contact" contactType="other" formatter="$EmailAddress" />
<Logo id="Small-Logo" height="16" width="16" formatter="$_string"/>
</AttributeExtractor>
When you modify shibboleth2.xml you can test validity of the configuration file with command "shibd -t". If configuration file is still valid XML you can now restart your shibboleth with "sudo service shibd restart". Shibboleth should anyways reload configuration file if it detects any change on it.
Add attribute definition for the metadata Assurance Certification attribute
To be able to check for REFEDS SIRTFI you need to add a definition for the metadata based attribute Assurance Certification. We've already added metadataAttributePrefix to the ApplicationDefaults element in shibboleth2.xml.
/etc/shibboleth/attribute-map.xml -> Attributes element
<!-- Metadata based attribute for Assurance Certification --> <Attribute name="urn:oasis:names:tc:SAML:attribute:assurance-certification" id="AssuranceCertification"/>
Logging
Shibboleth SP doesn't track nor log failed logins due to missing attributes. The Shibboleth SP web server can be used for "pixel tracking". This means that you load an image (eg: containing only one transparent pixel) from the web server from where you can monitor logs and observe access for you image. In the url of your image you can also insert details you want to see, eg: Authentication source (IdP) and missing attributes.
Replace the image with your existing one from the following code or comment it out if you dont need it. Example below loads track.png from document root and adds variables like "idp" containing the entityID of the authentication source and "miss" denoting missing attributes.
Pixel tracking
<img title="track" src="/track.png?idp=<shibmlp entityID/>&miss=<shibmlpifnot displayName>-displayName</shibmlpifnot><shibmlpifnot givenName>-givenName</shibmlpifnot><shibmlpifnot cn>-cn</shibmlpifnot><shibmlpifnot sn>-sn</shibmlpifnot><shibmlpifnot eduPersonPrinpalName>-eduPersonPrinpalName</shibmlpifnot><shibmlpifnot schacHomeOrganization>-schacHomeOrganization</shibmlpifnot><shibmlpifnot schacHomeOrganizationType>-schacHomeOrganizationType</shibmlpifnot>" alt="" width="1" height="1" />
Template customization
The attrChecker.html is located in the "/etc/shibboleth" directory. If you don't want to edit it by yourself, you can use the ready made template. The template has links to external components such as jquery and bootstrap. They are fetched on the fly from third party sources. Basically there are three locations needing modifications:
- The pixel tracking link after the comment "PixelTracking". The Image tag and all required attributes after the variable must be configured here. After "miss=" define all required attributes you updated in shibboleth2.xml using shibboleth tagging. Eg <shibmlpifnot $attribute>-$attribute</shibmlpifnot> (this echoes $attribute if it's not received by shibboleth). This example uses "-" as a delimiter.
- The table showing missing attributes between the tags "TableStart" and "TableEnd". You have to insert again all the same attributes as above.
Define row for each required attribute (eg: displayName below)
<tr <shibmlpifnot displayName> class='warning text-danger'</shibmlpifnot>> <td>displayName</td> <td><shibmlp displayName /></td> </tr>
- The email template between the tags "<textarea>" and "</textarea>". After "The attributes that were not released to the service are:". Again define all required attributes using shibboleth tagging like in section 1 ( eg: <shibmlpifnot $attribute> * $attribute</shibmlpifnot>). Note that for SP identifier target URL is used instead of entityID. There arent yet any tag for SP entityID so you can replace this target URL manually.
You can also update attrChecker.html with a Perl-script (attrChecker.pl). The script extracts the required attributes from the Attribute Checker handler element in shibboleth2.xml and modifies attrChecker.html accordingly (Note that script doesnt work with complex scenarios using AND and OR operators, it uses only "attributes" attribute from the handler). If you customize attrChecker.html and execute the Perl-script, make a backup of attrChecker.html before executing attrChecker.pl. If the script doesn't find the tags it needs for replacing content, it might break the template. The script updates the PixelTracking link by replacing shibboleth tags between miss= and following ", attribute table rows between "TableStart" and "TableEnd" and after line "The attributes that were not released to the service are:" until the next empty line.
- attrChecker.html and attrChecker.pl script can be downloaded from the GitHub