SAMLAssertion policies

What

  • Inbound authentication and authorization: Validate SAML Assertion policy
    The SAML policy type enables API proxies to validate SAML assertions that are attached to inbound SOAP requests. The SAML policy validates incoming messages that contain a digitally-signed SAML assertion, rejects them if they are invalid, and sets variables that allow additional policies, or the backend services itself, to further validate the information in the assertion.
  • Outbound token generation: Generate SAML Assertion policy
    The SAML policy type enables API proxies to attach SAML assertions to outbound XML requests. Those assertions are then available to enable backend services to apply further security processing for authentication and authorization.

Samples

Generate SAML assertion

<GenerateSAMLAssertion name="SAML" ignoreContentType="false">
  <CanonicalizationAlgorithm />
  <Issuer ref="reference">Issuer name</Issuer>
  <KeyStore>
    <Name ref="reference">keystorename</Name>
    <Alias ref="reference">alias</Alias>
  </KeyStore>
  <OutputVariable>
    <FlowVariable>assertion.content</FlowVariable>
    <Message name="request">
      <Namespaces>
        <Namespace prefix="test">http://www.example.com/test</Namespace>
      </Namespaces>
      <XPath>/envelope/header</XPath>
    </Message>
  </OutputVariable>
  <SignatureAlgorithm />
  <Subject ref="reference">Subject name</Subject>
  <Template ignoreUnresolvedVariables="false">
    <!-- A lot of XML goes here, in CDATA, with {} around
         each variable -->
  </Template>
</GenerateSAMLAssertion>

Generating a SAML assertion

Validate SAML assertion

<ValidateSAMLAssertion name="SAML" ignoreContentType="false">
  <Source name="request">
    <Namespaces>
      <Namespace prefix='soap'>http://schemas.xmlsoap.org/soap/envelope/</Namespace>
      <Namespace prefix='wsse'>http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd</Namespace>
      <Namespace prefix='saml'>urn:oasis:names:tc:SAML:2.0:assertion</Namespace>
    </Namespaces>
    <XPath>/soap:Envelope/soap:Header/wsse:Security/saml:Assertion</XPath>
  </Source>
  <TrustStore>TrustStoreName</TrustStore>
  <RemoveAssertion>false</RemoveAssertion>
</ValidateSAMLAssertion>

Validating a SAML assertion


Element reference

Generate SAML Assertion

Field Name Description
name attribute The name of the policy instance. The name must be unique in the organization. Characters you can use in the name are restricted to: A-Z0-9._\-$ %. However, the Management UI enforces additional restrictions, such as automatically removing characters that are not alphanumeric.
ignoreContentType attribute A boolean that can be set to true or false. By default, the assertion will not be generated if the content type of the message is not an XML Content-Type. If this is set to true, then the message will be treated as XML regardless of the Content-type.
Issuer
The unique identifier of the identity provider. If the optional ref attribute is present, then the value of Issuer will be assigned at runtime based on the specified variable. If the optional ref attribute is not present, then the value of Issuer will be used.
KeyStore
The name of the KeyStore that contains the private key and the alias of the private key used to digitally sign SAML assertions.
OutputVariable
FlowVariable
Message The target of the policy. Valid values are message, request, and response. When set to message, the policy conditionally retrieves the message object based on the attachment point of the policy. When attached to the request Flow, the policy resolves message to request, and when attached to the response Flow, the policy resolves message to response.
XPath An XPath expression that indicates the element on the outbound XML document to which the policy will attach the SAML assertion.
SignatureAlgorithm SHA1 or SHA256
Subject
The unique identifier of the subject of the SAML assertion. If the optional ref attribute is present, then the value of Subject will be assigned at runtime based on the specified variable. If the optional ref attribute is present, then the value of Subject will be used.
Template
If present, then the assertion will be generated by running this template, replacing everything denoted {} with the corresponding variable, and then digitally signing the result. The template is processed following the AssignMessage policy rules. See Assign Message policy.

Validate SAML Assertion

Field Name Description
name attribute
The name of the policy instance. The name must be unique in the organization. Characters you can use in the name are restricted to: A-Z0-9._\-$ %. However, the Management UI enforces additional restrictions, such as automatically removing characters that are not alphanumeric.
ignoreContentType attribute A boolean that can be set to true or false. By default, the assertion will not be generated if the content type of the message is not an XML Content-Type. If this is set to true then the message will be treated as XML regardless of the Content-type.
Source The target of the policy. Valid values are message, request, and response. When set to message, the policy conditionally retrieves the message object based on the attachment point of the policy. When attached to the request Flow, the policy resolves message to request, and when attached to the response Flow, the policy resolves message to response.
XPath
Child of Source. An XPath expression that indicates the element on the inbound XML document from which the policy can extract the SAML assertion.
TrustStore
The name of the TrustStore that contains trusted X.509 certificates used to validate digital signatures on SAML assertions.
RemoveAssertion
A boolean that can be set to true or false. When true, the SAML assertion will be stripped from the request message before the message is forwarded to the backend service.

Usage notes

The Security Assertion Markup Language (SAML) specification defines formats and protocols that enable applications to exchange XML-formatted information for authentication and authorization.

A "security assertion" is a trusted token that describes an attribute of an app, an app user, or some other participant in a transaction. Security assertions are managed and consumed by two types of entities:

  • Identity providers: Generate security assertions on behalf of participants
  • Service providers: Validate security assertions through trusted relationships with identity providers

The API platform can act as an identity provider and as a service provider. It acts as an identity provider by generating assertions and attaching them to request messages, making those assertions available for processing by backend services. It acts as a service provider by validating assertions on inbound request messages.

The SAML policy type supports SAML assertions that match version 2.0 of the SAML Core Specification and Version 1.0 of the WS-Security SAML Token Profile specification.

Generate SAML Assertion

Policy processing:

  1. If the message is not XML, and IgnoreContentType is not set to true, then raise a fault.
  2. If "Template" is set, then process the template as described for the AssignMessage policy. If any variables are missing and IgnoreUnresolvedVariables is not set, then raise a fault.
  3. If "Template" is not set, then construct an assertion that includes the values of the Subject and Issuer parameters or their references.
  4. Sign the assertion using the specified key.
  5. Add the assertion to the message at the specified XPath.

Validate SAML Assertion

Policy processing:

  1. The policy checks the inbound message to verify that the request's media type is XML, by checking if the content type matches the formats text/(.*+)?xml or application/(.*+)?xml. If the media type is not XML, or if "IgnoreContentType" is not set, then the policy will raise a fault.
  2. The policy will parse the XML. If parsing fails then it will raise a fault.
  3. The policy will validate the XML digital signature, using the values of TrustStore and ValidateSigner as described above. If validation fails then it will raise a fault.
  4. If present, the policy will check the current timestamp against the NotBefore and NotOnOrAfter elements in the assertion, as described in SAML Core section 2.5.1.
  5. Any additional rules for processing the "Conditions" as described in SAML Core section 2.5.1.1.

Once the policy has completed without raising a fault, the developer of the proxy can be sure of the following:

  • The digital signature on the assertion is valid and was signed by a trusted CA
  • The assertion is valid for the current time period
  • The subject and issuer of the assertion will be extracted and set in flow variables. It is the responsibility of other policies to use these values for additional authentication, such as checking that the subject name is valid, or passing it to a target system for validation.

Other policies, such as ExtractVariables, may be used to parse the raw XML of the assertion for more complex validation.


Flow variables

There are many pieces of information that may be specified in a SAML assertion. The SAML assertion itself is XML that can be parsed using the ExtractVariables policy and other mechanisms in order to implement more complex validations.

Variable Description
saml.id The SAML assertion ID
saml.issuer The "Issuer" of the assertion, converted from its native XML type to a string
saml.subject The "Subject" of the assertion, converted from its native XML type to a string
saml.valid Returns true or false based on the result of the validity check
saml.issueInstant IssueInstant
saml.subjectFormat Subject format
saml.scmethod Subject confirmation method
saml.scdaddress Subject confirmation data address
saml.scdinresponse Subject confirmation data in response
saml.scdrcpt Subject confirmation data recipient
saml.authnSnooa AuthnStatement SessionNotOnOrAfter
saml.authnContextClassRef AuthnStatement AuthnContextClassRef
saml.authnInstant AuthnStatement AuthInstant
saml.authnSessionIndex AuthnStatement Session Index

Error reference

This section describes the fault codes and error messages that are returned and fault variables that are set by Edge when this policy triggers an error. This information is important to know if you are developing fault rules to handle faults. To learn more, see What you need to know about policy errors and Handling faults.

Deployment errors

These errors can occur when you deploy a proxy containing this policy.

Error name Cause Fix
SourceNotConfigured One or more of the following elements of the Validate SAML Assertion policy is not defined or empty: <Source>, <XPath>, <Namespaces>, <Namespace>. build
TrustStoreNotConfigured If the <TrustStore> element is empty or not specified in the ValidateSAMLAssertion policy, then the deployment of the API proxy fails. A valid Trust Store is required. build
NullKeyStoreAlias If the child element <Alias> is empty or not specified in the <Keystore> element of Generate SAML Assertion policy, then the deployment of the API proxy fails. A valid Keystore alias is required. build
NullKeyStore If the child element <Name> is empty or not specified in the <Keystore> element of GenerateSAMLAssertion policy, then the deployment of the API proxy fails. A valid Keystore name is required. build
NullIssuer If the <Issuer> element is empty or not specified in the Generate SAML Assertion policy, then the deployment of the API proxy fails. A valid <Issuer> value is required. build

Fault variables

These variables are set when a runtime error occurs. For more information, see What you need to know about policy errors.

Variables Where Example
fault.name="fault_name" fault_name is the name of the fault, as listed in the Runtime errors table above. The fault name is the last part of the fault code. fault.name = "SourceUnavailable"
xmltojson.policy_name.failed policy_name is the user-specified name of the policy that threw the fault. xmltojson.XMLtoJSON-1.failed = true

Example error response

{
  "fault": {
    "faultstring": "XMLToJSON[XMLtoJSON-1]: Source xyz is not available",
    "detail": {
      "errorcode": "steps.xml2json.SourceUnavailable"
    }
  }
}

Example fault rule

<faultrule name="VariableOfNonMsgType"></faultrule><FaultRule name="XML to JSON Faults">
    <Step>
        <Name>AM-SourceUnavailableMessage</Name>
        <Condition>(fault.name Matches "SourceUnavailable") </Condition>
    </Step>
    <Step>
        <Name>AM-BadXML</Name>
        <Condition>(fault.name = "ExecutionFailed")</Condition>
    </Step>
    <Condition>(xmltojson.XMLtoJSON-1.failed = true) </Condition>
</FaultRule>

Related topics

Extracting variables: Extract Variables policy