This article provides the context and the solution for the following SAML error message that might be received by end-users:

SAML Response is missing "InResponseTo" attribute.

• Secure Assertion Markup Language (SAML)
• Custom SAML
• Single Sign-On (SSO)
• Datadog
• NameID Format

This issue occurs on the Datadog Catalog application since it is restricted to a customized Datadog NameID format. The requirements for Datadog are mandatory, and the  NameID must use the format:

urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress

The best method to satisfy the Datadog requirements is with Custom SAML integration since the Name ID Format is customizable. 

These steps need to be followed accordingly for a successful integration:

1. Click on Create App Integration and select SAML 2.0.
2. Name the application as desired.
3. Input the ACS URL and SP Entity ID, which can be found in the Datadog Login method settings under SAML, as shown in the screenshot below:

NOTE: For the moment, copy the ACS URL (1) since the SAML configuration within Datadog is not yet configured.

4. The NameID format is required by Datadog to be set as EmailAddress, just like in the screenshot below:

5. Click Next and complete the feedback, then Finish.
6. Press the Sign On tab and click on View SAML Setup Instructions.

7. Scroll down to the bottom of the page until IdP metadata is found > click on the text > CTRL/CMD + A to select all text > CTRL/CMD + C to copy the text > open a new text > then CTRL/CMD + V to paste the text from the clipboard > save the text as an .XML file.

8. Once the file has been saved, access the Datadog Admin Panel > hover on the name > click on Organization Settings > access Login Methods under the Authentication tab, and click on the Configure button on the SAML tab. If the SAML was previously configured, an Update button will appear instead.

9. There will be a redirect to the SAML configuration page. On the top, click Choose file and upload the .XML file previously created.

10. Once the message that the file has been uploaded and SAML Enabled, the ACS URL for IdP-initiated SAML will be provided, as shown in the screenshot below:

11. Copy the link and paste it on the initial ACS URL configured in the 3rd step.
12. Ensure that the SAML Login Method in Datadog is enabled. 

NOTE: If the SAML Login Method is not enabled by default, the following error might be encountered: 

SAML is not enabled for this org