SAML PDP authorization

Overview

API Gateway can request an authorization decision from a Security Assertion Markup Language (SAML) Policy Decision Point (PDP) for an authenticated client using the SAML Protocol (SAMLP). In such cases, the API Gateway presents evidence to the PDP in the form of some user credentials, such as the Distinguished Name of a client's X.509 certificate.

The PDP decides whether the user is authorized to access the requested resource. It then creates an authorization assertion, signs it, and returns it to the API Gateway in a SAML Protocol response. The API Gateway can then perform a number of checks on the response, such as validating the PDP signature and certificate, and examining the assertion. It can also insert the SAML authorization assertion into the message for consumption by a downstream web service.

Request settings

The Request tab describes how the API Gateway packages the SAMLP request before sending to the SAML PDP.

You can configure the following fields on the Request tab:

SAML PDP URL Set:
You can configure a group of SAML PDPs to which the API Gateway connects in a round-robin fashion if one or more of the PDPs are unavailable. This is known as a SAML PDP URL set. Click the button on the right, and select a previously configured SAML PDP URL set in the tree. To add a URL set, right-click the SAML PDP URL Sets tree node, and select Add a URL Set. Alternatively, you can configure a SAML PDP URL set under the Environment Configuration > External Connections node in the Policy Studio tree.

SOAP Action:
Enter the SOAP action required to send SAMLP requests to the PDP. Click the Use Default button to use the following default SOAP action as specified by SAMLP:

http://www.oasis-open.org/committees/security

SAML Version:
Select the SAML version to use in the SAMLP request.

Signing Key:
If the SAMLP request is to be signed, click the Signing Key button, and select the appropriate signing key from the certificate store.

Resource:
Enter the resource to obtain the authorization assertion for. You should specify the resource as a URI (for example, http://www.axway.com/TestService). The name of the resource is then included in the assertion.

Evidence:
SAMLP stipulates that proof of identity in the form of a SAML authentication assertion must be presented to the SAML PDP as part of the SAMLP request. API Gateway can use an existing SAML authentication assertion that is already present in the message, or generate one based on the user that authenticated to it.

Select the Use SAML Assertion in message option to include an existing assertion in the SAMLP request. Specify the actor/role of the WS-Security block where the assertion is found in the SOAP Actor/Role field.

Alternatively, select the Create SAML Assertion from authenticated client radio button to generate a new authentication assertion for inclusion in the SAMLP request. To sign the newly generated assertion with a private key from the certificate store, click Signing Key. Alternatively, you can enter a selector expression for the signing certificate (for example, ${certificate}).

The specified Drift Time is subtracted from the time that API Gateway generates the authentication assertion. This accounts for any possible difference in the times of the machines hosting the SAML PDP and the API Gateway.

SAML subject settings

You can describe the subject of the SAML assertion on the SAML Subject tab. Complete the following fields:

Subject Selector Expression:
Enter a selector expression for the message attribute that contains the user name of an authenticated user. The default value is ${authentication.subject.id}.

Subject Format:
Select the format of the subject selected in the Subject Selector Expression field above.

Note   There is no need to select a format here if the Subject Attribute field is set to authentication.subject.id.

Subject confirmation settings

The settings on the Subject Confirmation tab determine how the SubjectConfirmation block of the SAML assertion is generated. When the assertion is consumed by a downstream web service, the information contained in the SubjectConfirmation block can be used to authenticate the end user that authenticated to the API Gateway, or the issuer of the assertion, depending on what is configured.

The following is a typical SubjectConfirmation block:

<saml:SubjectConfirmation>
  <saml:ConfirmationMethod>
    urn:oasis:names:tc:SAML:1.0:cm:holder-of-key
  </saml:ConfirmationMethod>
  <dsig:KeyInfo xmlns:dsig="http://www.w3.org/2000/09/xmldsig#">
    <dsig:X509Data>
      <dsig:X509SubjectName>CN=axway</dsig:X509SubjectName>
      <dsig:X509Certificate>
        MIICmzCCAY ...... mB9CJEw4Q=
      </dsig:X509Certificate>
    </dsig:X509Data>
  </dsig:KeyInfo>
</saml:SubjectConfirmation>

You must configure the following fields on the Subject Confirmation tab:

Method:
The selected value determines the value of the <ConfirmationMethod> element. The following table shows the available methods, their meanings, and their respective values in the <ConfirmationMethod> element:

Method Meaning Value
Holder Of Key A <SubjectConfirmation> is inserted into the SAMLP request. The <SubjectConfirmation> contains a <dsig:KeyInfo> section with the certificate of the user selected to sign the SAMLP request. The user selected to sign the SAMLP request must be the authenticated subject (authentication.subject.id).
Select the Include Certificate option if the signer's certificate is to be included in the SubjectConfirmation block. Alternatively, select the Include Key Name option if only the key name is to be included.
urn:oasis:names:tc:SAML:1.0:cm:
holder-of-key
Bearer A <SubjectConfirmation> is inserted into the SAMLP request. urn:oasis:names:tc:SAML:1.0:cm:
bearer
SAML Artifact A <SubjectConfirmation> is inserted into the SAMLP request. urn:oasis:names:tc:SAML:1.0:cm:
artifact
Sender Vouches A <SubjectConfirmation> is inserted into the SAMLP request. The SAMLP request must be signed by a user. urn:oasis:names:tc:SAML:1.0:cm:
bearer

If the Method field is left blank, no <ConfirmationMethod> block is inserted into the assertion.

Include Certificate:
Select this option to include the SAML subject's certificate in the <KeyInfo> section of the <SubjectConfirmation> block.

Include Key Name:
Alternatively, if you do not want to include the certificate, you can select this option to only include the key name in the <KeyInfo> section.

Response settings

The Response tab enables you to configure the API Gateway to perform a number of checks on the SAMLP response from the PDP by examining the contents of various key elements in the authorization assertion.

SOAP Actor/Role:
If the SAMLP response from the PDP contains a SAML authorization assertion, the API Gateway can extract it from the response and insert it into the downstream message. The SAML assertion is inserted into the WS-Security block identified by the specified SOAP actor/role.

Drift Time:
The SAMLP request to the PDP is time stamped by the API Gateway. To account for differences in the times on the machines running the API Gateway and the SAML PDP the specified time is subtracted from the time at which the API Gateway generates the SAMLP request.

Subject in the assertion (the NameIdentifier) must match:
The authorization assertion can be checked to ensure that the authorized subject matches a specified value, and that the resource specified in the assertion matches the one entered here. API Gateway can verify that the subject in the SAML assertion (the NameIdentifier ) matches one of the following options:

  • The subject of the authentication filter
  • The following value (for example, CN=sample, O=Company, C=ie)
  • Neither of the above

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