Authenticating <saml2:Response>s

To verify SAML 2.0 Responses, Spring Security uses Saml2AuthenticationTokenConverter to populate the Authentication request and OpenSaml4AuthenticationProvider to authenticate it.

You can configure this in a number of ways including:

  1. Changing the way the RelyingPartyRegistration is Looked Up

  2. Setting a clock skew to timestamp validation

  3. Mapping the response to a list of GrantedAuthority instances

  4. Customizing the strategy for validating assertions

  5. Customizing the strategy for decrypting response and assertion elements

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

Changing the SAML Response Processing Endpoint

The default endpoint is /login/saml2/sso/{registrationId}. You can change this in the DSL and in the associated metadata like so:

  • Java

  • Kotlin

@Bean
SecurityFilterChain securityFilters(HttpSecurity http) throws Exception {
	http
        // ...
        .saml2Login((saml2) -> saml2.loginProcessingUrl("/saml2/login/sso"))
        // ...

    return http.build();
}
@Bean
fun securityFilters(val http: HttpSecurity): SecurityFilterChain {
	http {
        // ...
        .saml2Login {
            loginProcessingUrl = "/saml2/login/sso"
        }
        // ...
    }

    return http.build()
}

and:

  • Java

  • Kotlin

relyingPartyRegistrationBuilder.assertionConsumerServiceLocation("/saml/SSO")
relyingPartyRegistrationBuilder.assertionConsumerServiceLocation("/saml/SSO")

Changing RelyingPartyRegistration lookup

By default, this converter will match against any associated <saml2:AuthnRequest> or any registrationId it finds in the URL. Or, if it cannot find one in either of those cases, then it attempts to look it up by the <saml2:Response#Issuer> element.

There are a number of circumstances where you might need something more sophisticated, like if you are supporting ARTIFACT binding. In those cases, you can customize lookup through a custom AuthenticationConverter, which you can customize like so:

  • Java

  • Kotlin

@Bean
SecurityFilterChain securityFilters(HttpSecurity http, AuthenticationConverter authenticationConverter) throws Exception {
	http
        // ...
        .saml2Login((saml2) -> saml2.authenticationConverter(authenticationConverter))
        // ...

    return http.build();
}
@Bean
fun securityFilters(val http: HttpSecurity, val converter: AuthenticationConverter): SecurityFilterChain {
	http {
        // ...
        .saml2Login {
            authenticationConverter = converter
        }
        // ...
    }

    return http.build()
}

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 OpenSaml4AuthenticationProvider's default assertion validator with some tolerance:

  • Java

  • Kotlin

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        OpenSaml4AuthenticationProvider authenticationProvider = new OpenSaml4AuthenticationProvider();
        authenticationProvider.setAssertionValidator(OpenSaml4AuthenticationProvider
                .createDefaultAssertionValidator(assertionToken -> {
                    Map<String, Object> params = new HashMap<>();
                    params.put(CLOCK_SKEW, Duration.ofMinutes(10).toMillis());
                    // ... other validation parameters
                    return new ValidationContext(params);
                })
        );

        http
            .authorizeHttpRequests(authz -> authz
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(new ProviderManager(authenticationProvider))
            );
        return http.build();
    }
}
@Configuration
@EnableWebSecurity
open class SecurityConfig {
    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        val authenticationProvider = OpenSaml4AuthenticationProvider()
        authenticationProvider.setAssertionValidator(
            OpenSaml4AuthenticationProvider
                .createDefaultAssertionValidator(Converter<OpenSaml4AuthenticationProvider.AssertionToken, ValidationContext> {
                    val params: MutableMap<String, Any> = HashMap()
                    params[CLOCK_SKEW] =
                        Duration.ofMinutes(10).toMillis()
                    ValidationContext(params)
                })
        )
        http {
            authorizeRequests {
                authorize(anyRequest, authenticated)
            }
            saml2Login {
                authenticationManager = ProviderManager(authenticationProvider)
            }
        }
        return http.build()
    }
}

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:

  • Java

  • Kotlin

@Configuration
@EnableWebSecurity
public class SecurityConfig {
    @Autowired
    UserDetailsService userDetailsService;

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        OpenSaml4AuthenticationProvider authenticationProvider = new OpenSaml4AuthenticationProvider();
        authenticationProvider.setResponseAuthenticationConverter(responseToken -> {
            Saml2Authentication authentication = OpenSaml4AuthenticationProvider
                    .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
            .authorizeHttpRequests(authz -> authz
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(new ProviderManager(authenticationProvider))
            );
        return http.build();
    }
}
@Configuration
@EnableWebSecurity
open class SecurityConfig {
    @Autowired
    var userDetailsService: UserDetailsService? = null

    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        val authenticationProvider = OpenSaml4AuthenticationProvider()
        authenticationProvider.setResponseAuthenticationConverter { responseToken: OpenSaml4AuthenticationProvider.ResponseToken ->
            val authentication = OpenSaml4AuthenticationProvider
                .createDefaultResponseAuthenticationConverter() (1)
                .convert(responseToken)
            val assertion: Assertion = responseToken.response.assertions[0]
            val username: String = assertion.subject.nameID.value
            val userDetails = userDetailsService!!.loadUserByUsername(username) (2)
            MySaml2Authentication(userDetails, authentication) (3)
        }
        http {
            authorizeRequests {
                authorize(anyRequest, authenticated)
            }
            saml2Login {
                authenticationManager = ProviderManager(authenticationProvider)
            }
        }
        return http.build()
    }
}
1 First, call the default converter, which extracts attributes and authorities from the response
2 Second, call the UserDetailsService using the relevant information
3 Third, return a custom authentication that includes the user details
It’s not required to call OpenSaml4AuthenticationProvider's default authentication converter. It returns a Saml2AuthenticatedPrincipal containing the attributes it extracted from AttributeStatements as well as the single ROLE_USER authority.

Performing Additional Response Validation

OpenSaml4AuthenticationProvider validates the Issuer and Destination values right after decrypting the Response. You can customize the validation by extending the default validator concatenating with your own response validator, or you can replace it entirely with yours.

For example, you can throw a custom exception with any additional information available in the Response object, like so:

OpenSaml4AuthenticationProvider provider = new OpenSaml4AuthenticationProvider();
provider.setResponseValidator((responseToken) -> {
	Saml2ResponseValidatorResult result = OpenSamlAuthenticationProvider
		.createDefaultResponseValidator()
		.convert(responseToken)
		.concat(myCustomValidator.convert(responseToken));
	if (!result.getErrors().isEmpty()) {
		String inResponseTo = responseToken.getInResponseTo();
		throw new CustomSaml2AuthenticationException(result, inResponseTo);
	}
	return result;
});

Performing Additional Assertion Validation

OpenSaml4AuthenticationProvider 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 OpenSaml4AuthenticationProvider's default and then performs its own.

For example, you can use OpenSAML’s OneTimeUseConditionValidator to also validate a <OneTimeUse> condition, like so:

  • Java

  • Kotlin

OpenSaml4AuthenticationProvider provider = new OpenSaml4AuthenticationProvider();
OneTimeUseConditionValidator validator = ...;
provider.setAssertionValidator(assertionToken -> {
    Saml2ResponseValidatorResult result = OpenSaml4AuthenticationProvider
            .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.concat(new Saml2Error(INVALID_ASSERTION, context.getValidationFailureMessage()));
});
var provider = OpenSaml4AuthenticationProvider()
var validator: OneTimeUseConditionValidator = ...
provider.setAssertionValidator { assertionToken ->
    val result = OpenSaml4AuthenticationProvider
        .createDefaultAssertionValidator()
        .convert(assertionToken)
    val assertion: Assertion = assertionToken.assertion
    val oneTimeUse: OneTimeUse = assertion.conditions.oneTimeUse
    val context = ValidationContext()
    try {
        if (validator.validate(oneTimeUse, assertion, context) = ValidationResult.VALID) {
            return@setAssertionValidator result
        }
    } catch (e: Exception) {
        return@setAssertionValidator result.concat(Saml2Error(INVALID_ASSERTION, e.message))
    }
    result.concat(Saml2Error(INVALID_ASSERTION, context.validationFailureMessage))
}
While recommended, it’s not necessary to call OpenSaml4AuthenticationProvider'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.

Customizing Decryption

Spring Security decrypts <saml2:EncryptedAssertion>, <saml2:EncryptedAttribute>, and <saml2:EncryptedID> elements automatically by using the decryption Saml2X509Credential instances registered in the RelyingPartyRegistration.

OpenSaml4AuthenticationProvider exposes 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 OpenSaml4AuthenticationProvider'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:

  • Java

  • Kotlin

MyDecryptionService decryptionService = ...;
OpenSaml4AuthenticationProvider provider = new OpenSaml4AuthenticationProvider();
provider.setResponseElementsDecrypter((responseToken) -> decryptionService.decrypt(responseToken.getResponse()));
val decryptionService: MyDecryptionService = ...
val provider = OpenSaml4AuthenticationProvider()
provider.setResponseElementsDecrypter { responseToken -> decryptionService.decrypt(responseToken.response) }

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

  • Java

  • Kotlin

provider.setAssertionElementsDecrypter((assertionToken) -> decryptionService.decrypt(assertionToken.getAssertion()));
provider.setAssertionElementsDecrypter { assertionToken -> decryptionService.decrypt(assertionToken.assertion) }
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.

Using a Custom Authentication Manager

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.

  • Java

  • Kotlin

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        AuthenticationManager authenticationManager = new MySaml2AuthenticationManager(...);
        http
            .authorizeHttpRequests(authorize -> authorize
                .anyRequest().authenticated()
            )
            .saml2Login(saml2 -> saml2
                .authenticationManager(authenticationManager)
            )
        ;
        return http.build();
    }
}
@Configuration
@EnableWebSecurity
open class SecurityConfig {
    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        val customAuthenticationManager: AuthenticationManager = MySaml2AuthenticationManager(...)
        http {
            authorizeRequests {
                authorize(anyRequest, authenticated)
            }
            saml2Login {
                authenticationManager = customAuthenticationManager
            }
        }
        return http.build()
    }
}

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:

  • Java

  • Kotlin

@Controller
public class MainController {
	@GetMapping("/")
	public String index(@AuthenticationPrincipal Saml2AuthenticatedPrincipal principal, Model model) {
		String email = principal.getFirstAttribute("email");
		model.setAttribute("email", email);
		return "index";
	}
}
@Controller
class MainController {
    @GetMapping("/")
    fun index(@AuthenticationPrincipal principal: Saml2AuthenticatedPrincipal, model: Model): String {
        val email = principal.getFirstAttribute<String>("email")
        model.setAttribute("email", email)
        return "index"
    }
}
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.