private Assertion buildSAMLAssertion(
      SAMLSSOAuthnReqDTO authReqDTO, DateTime notOnOrAfter, String sessionId)
      throws IdentityException {
    try {
      DateTime currentTime = new DateTime();
      Assertion samlAssertion = new AssertionBuilder().buildObject();
      samlAssertion.setID(SAMLSSOUtil.createID());
      samlAssertion.setVersion(SAMLVersion.VERSION_20);
      samlAssertion.setIssuer(SAMLSSOUtil.getIssuer());
      samlAssertion.setIssueInstant(currentTime);
      Subject subject = new SubjectBuilder().buildObject();

      NameID nameId = new NameIDBuilder().buildObject();
      if (authReqDTO.getUseFullyQualifiedUsernameAsSubject()) {
        nameId.setValue(authReqDTO.getUsername());
        nameId.setFormat(NameIdentifier.EMAIL);
      } else {
        nameId.setValue(MultitenantUtils.getTenantAwareUsername(authReqDTO.getUsername()));
        nameId.setFormat(authReqDTO.getNameIDFormat());
      }

      subject.setNameID(nameId);

      SubjectConfirmation subjectConfirmation = new SubjectConfirmationBuilder().buildObject();
      subjectConfirmation.setMethod(SAMLSSOConstants.SUBJECT_CONFIRM_BEARER);

      SubjectConfirmationData scData = new SubjectConfirmationDataBuilder().buildObject();
      scData.setRecipient(authReqDTO.getAssertionConsumerURL());
      scData.setNotOnOrAfter(notOnOrAfter);
      scData.setInResponseTo(authReqDTO.getId());
      subjectConfirmation.setSubjectConfirmationData(scData);

      subject.getSubjectConfirmations().add(subjectConfirmation);

      samlAssertion.setSubject(subject);

      AuthnStatement authStmt = new AuthnStatementBuilder().buildObject();
      authStmt.setAuthnInstant(new DateTime());

      AuthnContext authContext = new AuthnContextBuilder().buildObject();
      AuthnContextClassRef authCtxClassRef = new AuthnContextClassRefBuilder().buildObject();
      authCtxClassRef.setAuthnContextClassRef(AuthnContext.PASSWORD_AUTHN_CTX);
      authContext.setAuthnContextClassRef(authCtxClassRef);
      authStmt.setAuthnContext(authContext);
      if (authReqDTO.isDoSingleLogout()) {
        authStmt.setSessionIndex(sessionId);
      }
      samlAssertion.getAuthnStatements().add(authStmt);

      /*
       * If <AttributeConsumingServiceIndex> element is in the
       * <AuthnRequest> and
       * according to the spec 2.0 the subject MUST be in the assertion
       */
      Map<String, String> claims = SAMLSSOUtil.getAttributes(authReqDTO);
      if (claims != null) {
        samlAssertion.getAttributeStatements().add(buildAttributeStatement(claims));
      }

      AudienceRestriction audienceRestriction = new AudienceRestrictionBuilder().buildObject();
      Audience issuerAudience = new AudienceBuilder().buildObject();
      issuerAudience.setAudienceURI(authReqDTO.getIssuer());
      audienceRestriction.getAudiences().add(issuerAudience);
      if (authReqDTO.getRequestedAudiences() != null) {
        for (String requestedAudience : authReqDTO.getRequestedAudiences()) {
          Audience audience = new AudienceBuilder().buildObject();
          audience.setAudienceURI(requestedAudience);
          audienceRestriction.getAudiences().add(audience);
        }
      }
      Conditions conditions = new ConditionsBuilder().buildObject();
      conditions.setNotBefore(currentTime);
      conditions.setNotOnOrAfter(notOnOrAfter);
      conditions.getAudienceRestrictions().add(audienceRestriction);
      samlAssertion.setConditions(conditions);

      if (authReqDTO.getDoSignAssertions()) {
        SAMLSSOUtil.setSignature(
            samlAssertion,
            XMLSignature.ALGO_ID_SIGNATURE_RSA,
            new SignKeyDataHolder(authReqDTO.getUsername()));
      }

      return samlAssertion;
    } catch (Exception e) {
      log.error("Error when reading claim values for generating SAML Response", e);
      throw new IdentityException(
          "Error when reading claim values for generating SAML Response", e);
    }
  }