
[[servlet-saml2login]]
== SAML 2.0 Login
:figures: images/servlet/saml2
:icondir: images/icons

The SAML 2.0 Login feature provides an application with the capability to act as a SAML 2.0 Relying Party, having users https://wiki.shibboleth.net/confluence/display/CONCEPT/FlowsAndConfig[log in] to the application by using their existing account at a SAML 2.0 Asserting Party (Okta, ADFS, etc).

NOTE: SAML 2.0 Login is implemented by using the *Web Browser SSO Profile*, as specified in
https://www.oasis-open.org/committees/download.php/35389/sstc-saml-profiles-errata-2.0-wd-06-diff.pdf#page=15[SAML 2 Profiles].

[[servlet-saml2login-spring-security-history]]
Since 2009, support for relying parties has existed as an https://github.com/spring-projects/spring-security-saml/tree/1e013b07a7772defd6a26fcfae187c9bf661ee8f#spring-saml[extension project].
In 2019, the process began to port that into https://github.com/spring-projects/spring-security[Spring Security] proper.
This process is similar to the one started in 2017 for <<oauth2,Spring Security's OAuth 2.0 support>>.

[NOTE]
====
A working sample for {gh-samples-url}/servlet/spring-boot/java/saml2-login[SAML 2.0 Login] is available in the {gh-samples-url}[Spring Security Samples repository].
====

Let's take a look at how SAML 2.0 Relying Party Authentication works within Spring Security.
First, we see that, like <<oauth2login, OAuth 2.0 Login>>, Spring Security takes the user to a third-party for performing authentication.
It does this through a series of redirects.

.Redirecting to Asserting Party Authentication
image::{figures}/saml2webssoauthenticationrequestfilter.png[]

The figure above builds off our <<servlet-securityfilterchain,`SecurityFilterChain`>> and <<servlet-authentication-abstractprocessingfilter, `AbstractAuthenticationProcessingFilter`>> diagrams:

image:{icondir}/number_1.png[] First, a user makes an unauthenticated request to the resource `/private` for which it is not authorized.

image:{icondir}/number_2.png[] Spring Security's <<servlet-authorization-filtersecurityinterceptor,`FilterSecurityInterceptor`>> indicates that the unauthenticated request is __Denied__ by throwing an `AccessDeniedException`.

image:{icondir}/number_3.png[] Since the user lacks authorization, the <<servlet-exceptiontranslationfilter,`ExceptionTranslationFilter`>> initiates __Start Authentication__.
The configured <<servlet-authentication-authenticationentrypoint,`AuthenticationEntryPoint`>> is an instance of {security-api-url}org/springframework/security/web/authentication/LoginUrlAuthenticationEntryPoint.html[`LoginUrlAuthenticationEntryPoint`] which redirects to <<servlet-saml2login-sp-initiated-factory,the `<saml2:AuthnRequest>` generating endpoint>>, `Saml2WebSsoAuthenticationRequestFilter`.
Or, if you've <<servlet-saml2login-relyingpartyregistrationrepository,configured more than one asserting party>>, it will first redirect to a picker page.

image:{icondir}/number_4.png[] Next, the `Saml2WebSsoAuthenticationRequestFilter` creates, signs, serializes, and encodes a `<saml2:AuthnRequest>` using its configured <<servlet-saml2login-sp-initiated-factory,`Saml2AuthenticationRequestFactory`>>.

image:{icondir}/number_5.png[] Then, the browser takes this `<saml2:AuthnRequest>` and presents it to the asserting party.
The asserting party attempts to authentication the user.
If successful, it will return a `<saml2:Response>` back to the browser.

image:{icondir}/number_6.png[] The browser then POSTs the `<saml2:Response>` to the assertion consumer service endpoint.

[[servlet-saml2login-authentication-saml2webssoauthenticationfilter]]
.Authenticating a `<saml2:Response>`
image::{figures}/saml2webssoauthenticationfilter.png[]

The figure builds off our <<servlet-securityfilterchain,`SecurityFilterChain`>> diagram.

image:{icondir}/number_1.png[] When the browser submits a `<saml2:Response>` to the application, it <<servlet-saml2login-authenticate-responses, delegates to `Saml2WebSsoAuthenticationFilter`>>.
This filter calls its configured `AuthenticationConverter` to create a `Saml2AuthenticationToken` by extracting the response from the `HttpServletRequest`.
This converter additionally resolves the <<servlet-saml2login-relyingpartyregistration, `RelyingPartyRegistration`>> and supplies it to `Saml2AuthenticationToken`.

image:{icondir}/number_2.png[] Next, the filter passes the token to its configured <<servlet-authentication-providermanager,`AuthenticationManager`>>.
By default, it will use the <<servlet-saml2login-architecture,`OpenSamlAuthenticationProvider`>>.

image:{icondir}/number_3.png[] If authentication fails, then __Failure__

* The <<servlet-authentication-securitycontextholder, `SecurityContextHolder`>> is cleared out.
* The <<servlet-authentication-authenticationentrypoint,`AuthenticationEntryPoint`>> is invoked to restart the authentication process.

image:{icondir}/number_4.png[] If authentication is successful, then __Success__.

* The <<servlet-authentication-authentication, `Authentication`>> is set on the <<servlet-authentication-securitycontextholder, `SecurityContextHolder`>>.
* The `Saml2WebSsoAuthenticationFilter` invokes `FilterChain#doFilter(request,response)` to continue with the rest of the application logic.

[[servlet-saml2login-minimaldependencies]]
=== Minimal Dependencies

SAML 2.0 service provider support resides in `spring-security-saml2-service-provider`.
It builds off of the OpenSAML library.

[[servlet-saml2login-minimalconfiguration]]
=== Minimal Configuration

When using https://spring.io/projects/spring-boot[Spring Boot], configuring an application as a service provider consists of two basic steps.
First, include the needed dependencies and second, indicate the necessary asserting party metadata.

[NOTE]
Also, this presupposes that you've already <<servlet-saml2login-metadata, registered the relying party with your asserting party>>.

==== Specifying Identity Provider Metadata

In a Spring Boot application, to specify an identity provider's metadata, simply do:

[source,yml]
----
spring:
  security:
    saml2:
      relyingparty:
        registration:
          adfs:
            identityprovider:
              entity-id: https://idp.example.com/issuer
              verification.credentials:
                - certificate-location: "classpath:idp.crt"
              singlesignon.url: https://idp.example.com/issuer/sso
              singlesignon.sign-request: false
----

where

* `https://idp.example.com/issuer` is the value contained in the `Issuer` attribute of the SAML responses that the identity provider will issue
* `classpath:idp.crt` is the location on the classpath for the identity provider's certificate for verifying SAML responses, and
* `https://idp.example.com/issuer/sso` is the endpoint where the identity provider is expecting `AuthnRequest` s.

And that's it!

[NOTE]
Identity Provider and Asserting Party are synonymous, as are Service Provider and Relying Party.
These are frequently abbreviated as AP and RP, respectively.

==== Runtime Expectations

As configured above, the application processes any `+POST /login/saml2/sso/{registrationId}+` request containing a `SAMLResponse` parameter:

[source,html]
----
POST /login/saml2/sso/adfs HTTP/1.1

SAMLResponse=PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZ...
----

There are two ways to see induce your asserting party to generate a `SAMLResponse`:

* First, you can navigate to your asserting party.
It likely has some kind of link or button for each registered relying party that you can click to send the `SAMLResponse`.
* Second, you can navigate to a protected page in your app, for example, `http://localhost:8080`.
Your app then redirects to the configured asserting party which then sends the `SAMLResponse`.

From here, consider jumping to:

* <<servlet-saml2login-architecture,How SAML 2.0 Login Integrates with OpenSAML>>
* <<servlet-saml2login-authenticatedprincipal,How to Use the `Saml2AuthenticatedPrincipal`>>
* <<servlet-saml2login-sansboot,How to Override or Replace Spring Boot's Auto Configuration>>

[[servlet-saml2login-architecture]]
=== How SAML 2.0 Login Integrates with OpenSAML

Spring Security's SAML 2.0 support has a couple of design goals:

* First, rely on a library for SAML 2.0 operations and domain objects.
To achieve this, Spring Security uses OpenSAML.
* Second, ensure this library is not required when using Spring Security's SAML support.
To achieve this, any interfaces or classes where Spring Security uses OpenSAML in the contract remain encapsulated.
This makes it possible for you to switch out OpenSAML for some other library or even an unsupported version of OpenSAML.

As a natural outcome of the above two goals, Spring Security's SAML API is quite small relative to other modules.
Instead, classes like `OpenSamlAuthenticationRequestFactory` and `OpenSamlAuthenticationProvider` expose `Converter` s that customize various steps in the authentication process.

For example, once your application receives a `SAMLResponse` and delegates to `Saml2WebSsoAuthenticationFilter`, the filter will delegate to `OpenSamlAuthenticationProvider`.

.Authenticating an OpenSAML `Response`
image:{figures}/opensamlauthenticationprovider.png[]

This figure builds off of the <<servlet-saml2login-authentication-saml2webssoauthenticationfilter,`Saml2WebSsoAuthenticationFilter` diagram>>.

image:{icondir}/number_1.png[] The `Saml2WebSsoAuthenticationFilter` formulates the `Saml2AuthenticationToken` and invokes the <<servlet-authentication-providermanager,`AuthenticationManager`>>.

image:{icondir}/number_2.png[] The <<servlet-authentication-providermanager,`AuthenticationManager`>> invokes the `OpenSamlAuthenticationProvider`.

image:{icondir}/number_3.png[] The authentication provider deserializes the response into an OpenSAML `Response` and checks its signature.
If the signature is invalid, authentication fails.

image:{icondir}/number_4.png[] Then, the provider <<servlet-saml2login-opensamlauthenticationprovider-decryption,decrypts any `EncryptedAssertion` elements>>.
If any decryptions fail, authentication fails.

image:{icondir}/number_5.png[] Next, the provider validates the response's `Issuer` and `Destination` values.
If they don't match what's in the `RelyingPartyRegistration`, authentication fails.

image:{icondir}/number_6.png[] After that, the provider verifies the signature of each `Assertion`.
If any signature is invalid, authentication fails.
Also, if neither the response nor the assertions have signatures, authentication fails.
Either the response or all the assertions must have signatures.

image:{icondir}/number_7.png[] Then, the provider <<servlet-saml2login-opensamlauthenticationprovider-decryption,decrypts any `EncryptedID` or `EncryptedAttribute` elements>>.
If any decryptions fail, authentication fails.

image:{icondir}/number_8.png[] Next, the provider validates each assertion's `ExpiresAt` and `NotBefore` timestamps, the `<Subject>` and any `<AudienceRestriction>` conditions.
If any validations fail, authentication fails.

image:{icondir}/number_9.png[] Following that, the provider takes the first assertion's `AttributeStatement` and maps it to a `Map<String, List<Object>>`.
It also grants the `ROLE_USER` granted authority.

image:{icondir}/number_10.png[] And finally, it takes the `NameID` from the first assertion, the `Map` of attributes, and the `GrantedAuthority` and constructs a `Saml2AuthenticatedPrincipal`.
Then, it places that principal and the authorities into a `Saml2Authentication`.

The resulting `Authentication#getPrincipal` is a Spring Security `Saml2AuthenticatedPrincipal` object, and `Authentication#getName` maps to the first assertion's `NameID` element.

[[servlet-saml2login-opensaml-customization]]
==== Customizing OpenSAML Configuration

Any class that uses both Spring Security and OpenSAML should statically initialize `OpenSamlInitializationService` at the beginning of the class, like so:

[source,java]
----
static {
	OpenSamlInitializationService.initialize();
}
----

This replaces OpenSAML's `InitializationService#initialize`.

Occasionally, it can be valuable to customize how OpenSAML builds, marshalls, and unmarshalls SAML objects.
In these circumstances, you may instead want to call `OpenSamlInitializationService#requireInitialize(Consumer)` that gives you access to OpenSAML's `XMLObjectProviderFactory`.

For example, when sending an unsigned AuthNRequest, you may want to force reauthentication.
In that case, you can register your own `AuthnRequestMarshaller`, like so:

[source,java]
----
static {
	OpenSamlInitializationService.requireInitialize(factory -> {
		AuthnRequestMarshaller marshaller = new AuthnRequestMarshaller() {
			@Override
            public Element marshall(XMLObject object, Element element) throws MarshallingException {
				configureAuthnRequest((AuthnRequest) object);
				return super.marshall(object, element);
            }

            public Element marshall(XMLObject object, Document document) throws MarshallingException {
				configureAuthnRequest((AuthnRequest) object);
				return super.marshall(object, document);
            }

            private void configureAuthnRequest(AuthnRequest authnRequest) {
				authnRequest.setForceAuthN(true);
            }
		}

	    factory.getMarshallerFactory().registerMarshaller(AuthnRequest.DEFAULT_ELEMENT_NAME, marshaller);
	});
}
----

The `requireInitialize` method may only be called once per application instance.

[[servlet-saml2login-sansboot]]
=== Overriding or Replacing Boot Auto Configuration

There are two `@Bean` s that Spring Boot generates for a relying party.

The first is a `WebSecurityConfigurerAdapter` that configures the app as a relying party.
When including `spring-security-saml2-service-provider`, the `WebSecurityConfigurerAdapter` looks like:

.Default JWT Configuration
====
.Java
[source,java,role="primary"]
----
protected void configure(HttpSecurity http) {
    http
        .authorizeRequests(authorize -> authorize
            .anyRequest().authenticated()
        )
        .saml2Login(withDefaults());
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
fun configure(http: HttpSecurity) {
    http {
        authorizeRequests {
            authorize(anyRequest, authenticated)
        }
        saml2Login { }
    }
}
----
====

If the application doesn't expose a `WebSecurityConfigurerAdapter` bean, then Spring Boot will expose the above default one.

You can replace this by exposing the bean within the application:

.Custom SAML 2.0 Login Configuration
====
.Java
[source,java,role="primary"]
----
@EnableWebSecurity
public class MyCustomSecurityConfiguration extends WebSecurityConfigurerAdapter {
    protected void configure(HttpSecurity http) {
        http
            .authorizeRequests(authorize -> authorize
                .mvcMatchers("/messages/**").hasAuthority("ROLE_USER")
                .anyRequest().authenticated()
            )
            .saml2Login(withDefaults());
    }
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@EnableWebSecurity
class MyCustomSecurityConfiguration : WebSecurityConfigurerAdapter() {
    override fun configure(http: HttpSecurity) {
        http {
            authorizeRequests {
                authorize("/messages/**", hasAuthority("ROLE_USER"))
                authorize(anyRequest, authenticated)
            }
            saml2Login {
            }
        }
    }
}
----
====

The above requires the role of `USER` for any URL that starts with `/messages/`.

[[servlet-saml2login-relyingpartyregistrationrepository]]
The second `@Bean` Spring Boot creates is a {security-api-url}org/springframework/security/saml2/provider/service/registration/RelyingPartyRegistrationRepository.html[`RelyingPartyRegistrationRepository`], which represents the asserting party and relying party metadata.
This includes things like the location of the SSO endpoint the relying party should use when requesting authentication from the asserting party.

You can override the default by publishing your own `RelyingPartyRegistrationRepository` bean.
For example, you can look up the asserting party's configuration by hitting its metadata endpoint like so:

.Relying Party Registration Repository
====
[source,java]
----
@Value("${metadata.location}")
String assertingPartyMetadataLocation;

@Bean
public RelyingPartyRegistrationRepository relyingPartyRegistrations() {
	RelyingPartyRegistration registration = RelyingPartyRegistrations
            .fromMetadataLocation(assertingPartyMetadataLocation)
            .registrationId("example")
            .build();
    return new InMemoryRelyingPartyRegistrationRepository(registration);
}
----
====

Or you can provide each detail manually, as you can see below:

.Relying Party Registration Repository Manual Configuration
====
[source,java]
----
@Value("${verification.key}")
File verificationKey;

@Bean
public RelyingPartyRegistrationRepository relyingPartyRegistrations() throws Exception {
    X509Certificate certificate = X509Support.decodeCertificate(this.verificationKey);
    Saml2X509Credential credential = Saml2X509Credential.verification(certificate);
    RelyingPartyRegistration registration = RelyingPartyRegistration
            .withRegistrationId("example")
            .assertingPartyDetails(party -> party
                .entityId("https://idp.example.com/issuer")
                .singleSignOnServiceLocation("https://idp.example.com/SSO.saml2")
                .wantAuthnRequestsSigned(false)
                .verificationX509Credentials(c -> c.add(credential))
            )
            .build();
    return new InMemoryRelyingPartyRegistrationRepository(registration);
}
----
====

[NOTE]
Note that `X509Support` is an OpenSAML class, used here in the snippet for brevity

[[servlet-saml2login-relyingpartyregistrationrepository-dsl]]

Alternatively, you can directly wire up the repository using the DSL, which will also override the auto-configured `WebSecurityConfigurerAdapter`:

.Custom Relying Party Registration DSL
====
.Java
[source,java,role="primary"]
----
@EnableWebSecurity
public class MyCustomSecurityConfiguration extends WebSecurityConfigurerAdapter {
    protected void configure(HttpSecurity http) {
        http
            .authorizeRequests(authorize -> authorize
                .mvcMatchers("/messages/**").hasAuthority("ROLE_USER")
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .relyingPartyRegistrationRepository(relyingPartyRegistrations())
            );
    }
}
----

.Kotlin
[source,kotlin,role="secondary"]
----
@EnableWebSecurity
class MyCustomSecurityConfiguration : WebSecurityConfigurerAdapter() {
    override fun configure(http: HttpSecurity) {
        http {
            authorizeRequests {
                authorize("/messages/**", hasAuthority("ROLE_USER"))
                authorize(anyRequest, authenticated)
            }
            saml2Login {
                relyingPartyRegistrationRepository = relyingPartyRegistrations()
            }
        }
    }
}
----
====

[NOTE]
A relying party can be multi-tenant by registering more than one relying party in the `RelyingPartyRegistrationRepository`.

[[servlet-saml2login-relyingpartyregistration]]
=== RelyingPartyRegistration
A {security-api-url}org/springframework/security/saml2/provider/service/registration/RelyingPartyRegistration.html[`RelyingPartyRegistration`]
instance represents a link between an relying party and assering party's metadata.

In a `RelyingPartyRegistration`, you can provide relying party metadata like its `Issuer` value, where it expects SAML Responses to be sent to, and any credentials that it owns for the purposes of signing or decrypting payloads.

Also, you can provide asserting party metadata like its `Issuer` value, where it expects AuthnRequests to be sent to, and any public credentials that it owns for the purposes of the relying party verifying or encrypting payloads.

The following `RelyingPartyRegistration` is the minimum required for most setups:

[source,java]
----
RelyingPartyRegistration relyingPartyRegistration = RelyingPartyRegistrations
        .fromMetadataLocation("https://ap.example.org/metadata")
        .registrationId("my-id")
        .build();
----

Though a more sophisticated setup is also possible, like so:

[source,java]
----
RelyingPartyRegistration relyingPartyRegistration = RelyingPartyRegistration.withRegistrationId("my-id")
        .entityId("{baseUrl}/{registrationId}")
        .decryptionX509Credentials(c -> c.add(relyingPartyDecryptingCredential()))
        .assertionConsumerServiceLocation("/my-login-endpoint/{registrationId}")
        .assertingParty(party -> party
                .entityId("https://ap.example.org")
                .verificationX509Credentials(c -> c.add(assertingPartyVerifyingCredential()))
                .singleSignOnServiceLocation("https://ap.example.org/SSO.saml2")
        );
----

[TIP]
The top-level metadata methods are details about the relying party.
The methods inside `assertingPartyDetails` are details about the asserting party.

[NOTE]
The location where a relying party is expecting SAML Responses is the Assertion Consumer Service Location.

The default for the relying party's `entityId` is `+{baseUrl}/saml2/service-provider-metadata/{registrationId}+`.
This is this value needed when configuring the asserting party to know about your relying party.

The default for the `assertionConsumerServiceLocation` is `+/login/saml2/sso/{registrationId}+`.
It's mapped by default to <<servlet-saml2login-authentication-saml2webssoauthenticationfilter,`Saml2WebSsoAuthenticationFilter`>> in the filter chain.

[[servlet-saml2login-rpr-uripatterns]]
==== URI Patterns

You probably noticed in the above examples the `+{baseUrl}+` and `+{registrationId}+` placeholders.

These are useful for generating URIs. As such, the relying party's `entityId` and `assertionConsumerServiceLocation` support the following placeholders:

* `baseUrl` - the scheme, host, and port of a deployed application
* `registrationId` - the registration id for this relying party
* `baseScheme` - the scheme of a deployed application
* `baseHost` - the host of a deployed application
* `basePort` - the port of a deployed application

For example, the `assertionConsumerServiceLocation` defined above was:

`+/my-login-endpoint/{registrationId}+`

which in a deployed application would translate to

`+/my-login-endpoint/adfs+`

The `entityId` above was defined as:

`+{baseUrl}/{registrationId}+`

which in a deployed application would translate to

`+https://rp.example.com/adfs+`

[[servlet-saml2login-rpr-credentials]]
==== Credentials

You also likely noticed the credential that was used.

Oftentimes, a relying party will use the same key to sign payloads as well as decrypt them.
Or it will use the same key to verify payloads as well as encrypt them.

Because of this, Spring Security ships with `Saml2X509Credential`, a SAML-specific credential that simplifies configuring the same key for different use cases.

At a minimum, it's necessary to have a certificate from the asserting party so that the asserting party's signed responses can be verified.

To construct a `Saml2X509Credential` that you'll use to verify assertions from the asserting party, you can load the file and use
the `CertificateFactory` like so:

[source,java]
----
Resource resource = new ClassPathResource("ap.crt");
try (InputStream is = resource.getInputStream()) {
	X509Certificate certificate = (X509Certificate)
            CertificateFactory.getInstance("X.509").generateCertificate(is);
	return Saml2X509Credential.verification(certificate);
}
----

Let's say that the asserting party is going to also encrypt the assertion.
In that case, the relying party will need a private key to be able to decrypt the encrypted value.

In that case, you'll need an `RSAPrivateKey` as well as its corresponding `X509Certificate`.
You can load the first using Spring Security's `RsaKeyConverters` utility class and the second as you did before:

[source,java]
----
X509Certificate certificate = relyingPartyDecryptionCertificate();
Resource resource = new ClassPathResource("rp.crt");
try (InputStream is = resource.getInputStream()) {
	RSAPrivateKey rsa = RsaKeyConverters.pkcs8().convert(is);
	return Saml2X509Credential.decryption(rsa, certificate);
}
----

[TIP]
When you specify the locations of these files as the appropriate Spring Boot properties, then Spring Boot will perform these conversions for you.

[[servlet-saml2login-rpr-relyingpartyregistrationresolver]]
==== Resolving the Relying Party from the Request

As seen so far, Spring Security resolves the `RelyingPartyRegistration` by looking for the registration id in the URI path.

There are a number of reasons you may want to customize. Among them:

* You may know that you will never be a multi-tenant application and so want to have a simpler URL scheme
* You may identify tenants in a way other than by the URI path

To customize the way that a `RelyingPartyRegistration` is resolved, you can configure a custom `Converter<HttpServletRequest, RelyingPartyRegistration>`.
The default looks up the registration id from the URI's last path element and looks it up in your `RelyingPartyRegistrationRepository`.

You can provide a simpler resolver that, for example, always returns the same relying party:

[source,java]
----
public class SingleRelyingPartyRegistrationResolver
        implements Converter<HttpServletRequest, RelyingPartyRegistration> {

	@Override
    public RelyingPartyRegistration convert(HttpServletRequest request) {
		return this.relyingParty;
    }
}
----

Then, you can provide this resolver to the appropriate filters that <<servlet-saml2login-sp-initiated-factory, produce `<saml2:AuthnRequest>` s>>, <<servlet-saml2login-authenticate-responses, authenticate `<saml2:Response>` s>>, and <<servlet-saml2login-metadata, produce `<saml2:SPSSODescriptor>` metadata>>.

[NOTE]
Remember that if you have any placeholders in your `RelyingPartyRegistration`, your resolver implementation should resolve them.

[[servlet-saml2login-rpr-duplicated]]
==== Duplicated Relying Party Configurations

When an application uses multiple asserting parties, some configuration is duplicated between `RelyingPartyRegistration` instances:

* The relying party's `entityId`
* Its `assertionConsumerServiceLocation`, and
* Its credentials, for example its signing or decryption credentials

What's nice about this setup is credentials may be more easily rotated for some identity providers vs others.

The duplication can be alleviated in a few different ways.

First, in YAML this can be alleviated with references, like so:

[source,yaml]
----
spring:
  security:
    saml2:
      relyingparty:
        okta:
          signing.credentials: &relying-party-credentials
            - private-key-location: classpath:rp.key
            - certificate-location: classpath:rp.crt
          identityprovider:
            entity-id: ...
        azure:
          signing.credentials: *relying-party-credentials
          identityprovider:
            entity-id: ...
----

Second, in a database, it's not necessary to replicate `RelyingPartyRegistration` 's model.

Third, in Java, you can create a custom configuration method, like so:

[source,java]
----
private RelyingPartyRegistration.Builder
        addRelyingPartyDetails(RelyingPartyRegistration.Builder builder) {

	Saml2X509Credential signingCredential = ...
	builder.signingX509Credentials(c -> c.addAll(signingCredential));
	// ... other relying party configurations
}

@Bean
public RelyingPartyRegistrationRepository relyingPartyRegistrations() {
    RelyingPartyRegistration okta = addRelyingPartyDetails(
            RelyingPartyRegistration
                .fromMetadataLocation(oktaMetadataUrl)
                .registrationId("okta")).build();

    RelyingPartyRegistration azure = addRelyingPartyDetails(
            RelyingPartyRegistration
                .fromMetadataLocation(oktaMetadataUrl)
                .registrationId("azure")).build();

    return new InMemoryRelyingPartyRegistrationRepository(okta, azure);
}
----

[[servlet-saml2login-sp-initiated-factory]]
=== Producing `<saml2:AuthnRequest>` s

As stated earlier, Spring Security's SAML 2.0 support produces a `<saml2:AuthnRequest>` to commence authentication with the asserting party.

Spring Security achieves this in part by registering the `Saml2WebSsoAuthenticationRequestFilter` in the filter chain.
This filter by default responds to endpoint `+/saml2/authenticate/{registrationId}+`.

For example, if you were deployed to `https://rp.example.com` and you gave your registration an ID of `okta`, you could navigate to:

`https://rp.example.org/saml2/authenticate/ping`

and the result would be a redirect that included a `SAMLRequest` parameter containing the signed, deflated, and encoded `<saml2:AuthnRequest>`.

[[servlet-saml2login-sp-initiated-factory-signing]]
==== Changing How the `<saml2:AuthnRequest>` Gets Sent

By default, Spring Security signs each `<saml2:AuthnRequest>` and send it as a GET to the asserting party.

Many asserting parties don't require a signed `<saml2:AuthnRequest>`.
This can be configured automatically via `RelyingPartyRegistrations`, or you can supply it manually, like so:


.Not Requiring Signed AuthnRequests
====
.Boot
[source,yaml,role="primary"]
----
spring:
  security:
    saml2:
      relyingparty:
        okta:
          identityprovider:
            entity-id: ...
            singlesignon.sign-request: false
----

.Java
[source,java,role="secondary"]
----
RelyingPartyRegistration relyingPartyRegistration = RelyingPartyRegistration.withRegistrationId("okta")
        // ...
        .assertingPartyDetails(party -> party
            // ...
            .wantAuthnRequestsSigned(false)
        );
----
====

Otherwise, you will need to specify a private key to `RelyingPartyRegistration#signingX509Credentials` so that Spring Security can sign the `<saml2:AuthnRequest>` before sending.

[[servlet-saml2login-sp-initiated-factory-algorithm]]
By default, Spring Security will sign the `<saml2:AuthnRequest>` using `rsa-sha256`, though some asserting parties will require a different algorithm, as indicated in their metadata.

You can configure the algorithm based on the asserting party's <<servlet-saml2login-relyingpartyregistrationrepository,metadata using `RelyingPartyRegistrations`>>.

Or, you can provide it manually:

[source,java]
----
String metadataLocation = "classpath:asserting-party-metadata.xml";
RelyingPartyRegistration relyingPartyRegistration = RelyingPartyRegistrations.fromMetadataLocation(metadataLocation)
        // ...
        .assertingPartyDetails((party) -> party
            // ...
            .signingAlgorithms((sign) -> sign.add(SignatureConstants.ALGO_ID_SIGNATURE_RSA_SHA512))
        );
----

NOTE: The snippet above uses the OpenSAML `SignatureConstants` class to supply the algorithm name.
But, that's just for convenience.
Since the datatype is `String`, you can supply the name of the algorithm directly.

[[servlet-saml2login-sp-initiated-factory-binding]]
Some asserting parties require that the `<saml2:AuthnRequest>` be POSTed.
This can be configured automatically via `RelyingPartyRegistrations`, or you can supply it manually, like so:

[source,java]
----
RelyingPartyRegistration relyingPartyRegistration = RelyingPartyRegistration.withRegistrationId("okta")
        // ...
        .assertingPartyDetails(party -> party
            // ...
            .singleSignOnServiceBinding(Saml2MessageType.POST)
        );
----


[[servlet-saml2login-sp-initiated-factory-custom-authnrequest]]
==== Customizing OpenSAML's `AuthnRequest` Instance

There are a number of reasons that you may want to adjust an `AuthnRequest`.
For example, you may want `ForceAuthN` to be set to `true`, which Spring Security sets to `false` by default.

If you don't need information from the `HttpServletRequest` to make your decision, then the easiest way is to <<servlet-saml2login-opensaml-customization,register a custom `AuthnRequestMarshaller` with OpenSAML>>.
This will give you access to post-process the `AuthnRequest` instance before it's serialized.

But, if you do need something from the request, then you can use create a custom `Saml2AuthenticationRequestContext` implementation and then a `Converter<Saml2AuthenticationRequestContext, AuthnRequest>` to build an `AuthnRequest` yourself, like so:

[source,java]
----
@Component
public class AuthnRequestConverter implements
        Converter<Saml2AuthenticationRequestContext, AuthnRequest> {

	private final AuthnRequestBuilder authnRequestBuilder;
	private final IssuerBuilder issuerBuilder;

	// ... constructor

	public AuthnRequest convert(Saml2AuthenticationRequestContext context) {
		MySaml2AuthenticationRequestContext myContext = (MySaml2AuthenticationRequestContext) context;
		Issuer issuer = issuerBuilder.buildObject();
		issuer.setValue(myContext.getIssuer());

		AuthnRequest authnRequest = authnRequestBuilder.buildObject();
		authnRequest.setIssuer(iss);
        authnRequest.setDestination(myContext.getDestination());
		authnRequest.setAssertionConsumerServiceURL(myContext.getAssertionConsumerServiceUrl());

		// ... additional settings

		authRequest.setForceAuthn(myContext.getForceAuthn());
		return authnRequest;
	}
}
----

Then, you can construct your own `Saml2AuthenticationRequestContextResolver` and `Saml2AuthenticationRequestFactory` and publish them as `@Bean` s:

[source,java]
----
@Bean
Saml2AuthenticationRequestContextResolver authenticationRequestContextResolver() {
	Saml2AuthenticationRequestContextResolver resolver =
            new DefaultSaml2AuthenticationRequestContextResolver();
	return request -> {
        Saml2AuthenticationRequestContext context = resolver.resolve(request);
        return new MySaml2AuthenticationRequestContext(context, request.getParameter("force") != null);
	};
}

@Bean
Saml2AuthenticationRequestFactory authenticationRequestFactory(
		AuthnRequestConverter authnRequestConverter) {

	OpenSamlAuthenticationRequestFactory authenticationRequestFactory =
            new OpenSamlAuthenticationRequestFactory();
	authenticationRequestFactory.setAuthenticationRequestContextConverter(authnRequestConverter);
	return authenticationRequestFactory;
}
----

[[servlet-saml2login-authenticate-responses]]
=== Authenticating `<saml2:Response>` s

To verify SAML 2.0 Responses, Spring Security uses <<servlet-saml2login-architecture,`OpenSamlAuthenticationProvider`>> by default.

You can configure this in a number of ways including:

1. Setting a clock skew to timestamp validation
2. Mapping the response to a list of `GrantedAuthority` instances
3. Customizing the strategy for validating assertions
4. Customizing the strategy for decrypting response and assertion elements

To configure these, you'll use the `saml2Login#authenticationManager` method in the DSL.

[[servlet-saml2login-opensamlauthenticationprovider-clockskew]]
==== Setting a Clock Skew

It's not uncommon for the asserting and relying parties to have system clocks that aren't perfectly synchronized.
For that reason, you can configure `OpenSamlAuthenticationProvider` 's default assertion validator with some tolerance:

[source,java]
----
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        OpenSamlAuthenticationProvider authenticationProvider = new OpenSamlAuthenticationProvider();
        authenticationProvider.setAssertionValidator(OpenSamlAuthenticationProvider
                .createDefaultAssertionValidator(assertionToken -> {
        			Map<String, Object> params = new HashMap<>();
        			params.put(CLOCK_SKEW, Duration.ofMinutes(10).toMillis());
        			// ... other validation parameters
        			return new ValidationContext(params);
        		})
        );

        http
            .authorizeRequests(authz -> authz
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(new ProviderManager(authenticationProvider))
            );
    }
}
----

[[servlet-saml2login-opensamlauthenticationprovider-userdetailsservice]]
==== Coordinating with a `UserDetailsService`

Or, perhaps you would like to include user details from a legacy `UserDetailsService`.
In that case, the response authentication converter can come in handy, as can be seen below:

[source,java]
----
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Autowired
    UserDetailsService userDetailsService;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        OpenSamlAuthenticationProvider authenticationProvider = new OpenSamlAuthenticationProvider();
        authenticationProvider.setResponseAuthenticationConverter(responseToken -> {
        	Saml2Authentication authentication = OpenSamlAuthenticationProvider
                    .createDefaultResponseAuthenticationConverter() <1>
                    .convert(responseToken);
        	Assertion assertion = responseToken.getResponse().getAssertions().get(0);
            String username = assertion.getSubject().getNameID().getValue();
            UserDetails userDetails = this.userDetailsService.loadUserByUsername(username); <2>
            return MySaml2Authentication(userDetails, authentication); <3>
        });

        http
            .authorizeRequests(authz -> authz
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(new ProviderManager(authenticationProvider))
            );
    }
}
----
<1> First, call the default converter, which extracts attributes and authorities from the response
<2> Second, call the <<servlet-authentication-userdetailsservice, `UserDetailsService`>> using the relevant information
<3> Third, return a custom authentication that includes the user details

[NOTE]
It's not required to call `OpenSamlAuthenticationProvider` 's default authentication converter.
It returns a `Saml2AuthenticatedPrincipal` containing the attributes it extracted from `AttributeStatement` s as well as the single `ROLE_USER` authority.

[[servlet-saml2login-opensamlauthenticationprovider-additionalvalidation]]
==== Performing Additional Validation

`OpenSamlAuthenticationProvider` performs minimal validation on SAML 2.0 Assertions.
After verifying the signature, it will:

1. Validate `<AudienceRestriction>` and `<DelegationRestriction>` conditions
2. Validate `<SubjectConfirmation>` s, expect for any IP address information

To perform additional validation, you can configure your own assertion validator that delegates to `OpenSamlAuthenticationProvider` 's default and then performs its own.

[[servlet-saml2login-opensamlauthenticationprovider-onetimeuse]]
For example, you can use OpenSAML's `OneTimeUseConditionValidator` to also validate a `<OneTimeUse>` condition, like so:

[source,java]
----
OpenSamlAuthenticationProvider provider = new OpenSamlAuthenticationProvider();
OneTimeUseConditionValidator validator = ...;
provider.setAssertionValidator(assertionToken -> {
    Saml2ResponseValidatorResult result = OpenSamlAuthenticationProvider
            .createDefaultAssertionValidator()
            .convert(assertionToken);
    Assertion assertion = assertionToken.getAssertion();
    OneTimeUse oneTimeUse = assertion.getConditions().getOneTimeUse();
    ValidationContext context = new ValidationContext();
    try {
    	if (validator.validate(oneTimeUse, assertion, context) == ValidationResult.VALID) {
    		return result;
    	}
    } catch (Exception e) {
    	return result.concat(new Saml2Error(INVALID_ASSERTION, e.getMessage()));
    }
    return result.contact(new Saml2Error(INVALID_ASSERTION, context.getValidationFailureMessage()));
});
----

[NOTE]
While recommended, it's not necessary to call `OpenSamlAuthenticationProvider` 's default assertion validator.
A circumstance where you would skip it would be if you don't need it to check the `<AudienceRestriction>` or the `<SubjectConfirmation>` since you are doing those yourself.

[[servlet-saml2login-opensamlauthenticationprovider-decryption]]
==== Customizing Decryption

Spring Security decrypts `<saml2:EncryptedAssertion>`, `<saml2:EncryptedAttribute>`, and `<saml2:EncryptedID>` elements automatically by using the decryption <<servlet-saml2login-rpr-credentials,`Saml2X509Credential` instances>> registered in the <<servlet-saml2login-relyingpartyregistration,`RelyingPartyRegistration`>>.

`OpenSamlAuthenticationProvider` exposes <<servlet-saml2login-architecture,two decryption strategies>>.
The response decrypter is for decrypting encrypted elements of the `<saml2:Response>`, like `<saml2:EncryptedAssertion>`.
The assertion decrypter is for decrypting encrypted elements of the `<saml2:Assertion>`, like `<saml2:EncryptedAttribute>` and `<saml2:EncryptedID>`.

You can replace `OpenSamlAuthenticationProvider`'s default decryption strategy with your own.
For example, if you have a separate service that decrypts the assertions in a `<saml2:Response>`, you can use it instead like so:

[source,java]
----
MyDecryptionService decryptionService = ...;
OpenSamlAuthenticationProvider provider = new OpenSamlAuthenticationProvider();
provider.setResponseElementsDecrypter((responseToken) -> decryptionService.decrypt(responseToken.getResponse()));
----

If you are also decrypting individual elements in a `<saml2:Assertion>`, you can customize the assertion decrypter, too:

[source,java]
----
provider.setAssertionElementsDecrypter((assertionToken) -> decryptionService.decrypt(assertionToken.getAssertion()));
----

NOTE: There are two separate decrypters since assertions can be signed separately from responses.
Trying to decrypt a signed assertion's elements before signature verification may invalidate the signature.
If your asserting party signs the response only, then it's safe to decrypt all elements using only the response decrypter.

[[servlet-saml2login-authenticationmanager-custom]]
==== Using a Custom Authentication Manager

[[servlet-saml2login-opensamlauthenticationprovider-authenticationmanager]]
Of course, the `authenticationManager` DSL method can be also used to perform a completely custom SAML 2.0 authentication.
This authentication manager should expect a `Saml2AuthenticationToken` object containing the SAML 2.0 Response XML data.

[source,java]
----
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        AuthenticationManager authenticationManager = new MySaml2AuthenticationManager(...);
        http
            .authorizeRequests(authorize -> authorize
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(authenticationManager)
            )
        ;
    }
}
----

[[servlet-saml2login-authenticatedprincipal]]
=== Using `Saml2AuthenticatedPrincipal`

With the relying party correctly configured for a given asserting party, it's ready to accept assertions.
Once the relying party validates an assertion, the result is a `Saml2Authentication` with a `Saml2AuthenticatedPrincipal`.

This means that you can access the principal in your controller like so:

[source,java]
----
@Controller
public class MainController {
	@GetMapping("/")
	public String index(@AuthenticationPrincipal Saml2AuthenticatedPrincipal principal, Model model) {
		String email = principal.getFirstAttribute("email");
		model.setAttribute("email", email);
		return "index";
	}
}
----

[TIP]
Because the SAML 2.0 specification allows for each attribute to have multiple values, you can either call `getAttribute` to get the list of attributes or `getFirstAttribute` to get the first in the list.
`getFirstAttribute` is quite handy when you know that there is only one value.

[[servlet-saml2login-metadata]]
=== Producing `<saml2:SPSSODescriptor>` Metadata

You can publish a metadata endpoint by adding the `Saml2MetadataFilter` to the filter chain, as you'll see below:

[source,java]
----
Converter<HttpServletRequest, RelyingPartyRegistration> relyingPartyRegistrationResolver =
        new DefaultRelyingPartyRegistrationResolver(this.relyingPartyRegistrationRepository);
Saml2MetadataFilter filter = new Saml2MetadataFilter(
		relyingPartyRegistrationResolver,
        new OpenSamlMetadataResolver());

http
    // ...
    .saml2Login(withDefaults())
    .addFilterBefore(new Saml2MetadataFilter(r), Saml2WebSsoAuthenticationFilter.class);
----

You can use this metadata endpoint to register your relying party with your asserting party.
This is often as simple as finding the correct form field to supply the metadata endpoint.

By default, the metadata endpoint is `+/saml2/service-provider-metadata/{registrationId}+`.
You can change this by calling the `setRequestMatcher` method on the filter:

[source,java]
----
filter.setRequestMatcher(new AntPathRequestMatcher("/saml2/metadata/{registrationId}", "GET"));
----

ensuring that the `registrationId` hint is at the end of the path.

Or, if you have registered a custom relying party registration resolver in the constructor, then you can specify a path without a `registrationId` hint, like so:

[source,java]
----
filter.setRequestMatcher(new AntPathRequestMatcher("/saml2/metadata", "GET"));
----

[[servlet-saml2login-logout]]
=== Performing Single Logout

Spring Security does not yet support single logout.

Generally speaking, though, you can achieve this by creating and registering a custom `LogoutSuccessHandler` and `RequestMatcher`:

[source,java]
----
http
    // ...
    .logout(logout -> logout
        .logoutSuccessHandler(myCustomSuccessHandler())
        .logoutRequestMatcher(myRequestMatcher())
    )
----

The success handler will send logout requests to the asserting party.

The request matcher will detect logout requests from the asserting party.
