Hello @Moshe Reubinoff,
Thank you for posting your query on Microsoft Q&A.
Based on your description, it seems you configured the AWS Single-Account gallery application in Azure through Enterprise Applications, and you can access the app from the Azure portal. However, when attempting to access it from the AWS workspace, it fails with an error message: "AADSTS750054 — SAMLRequest or SAMLResponse must be present as query string parameters in the HTTP request for SAML Redirect binding" during SAML Single Sign-On.
The error happens when Entra ID wasn’t able to identify the SAML request within the URL parameters in the HTTP request. This can happen if the application is not using HTTP redirect binding when sending the SAML request to Azure AD.
Below is a diagram of SAML SSO.
Azure single sign-on SAML protocol — Microsoft Entra | Microsoft Docs
If SAML SSO is started from step 1, it is called SP-initiated SAML SSO as SAML SSO is initiated by Application (Service Provider). If a user goes to IdP first, IdP will initiate SAML SSO from step 4 (Technically, IdP will send SAML Request itself.)
Step 1, a user goes to the Application (Service Provider).
Step 2, Application finds the Identity Provider (IdP) based on the URL or domain of the user (Home realm discovery).
From step 3, Application (Service Provider) generates SAML Request and redirect the user’s browser to Azure AD SAML single sign-on URL (https://login.microsoftonline.com/<TenantID>/saml2). However, somehow the application doesn’t send SAML Request in the header, Entra ID throws AADSTS750054 error because Entra ID is not able to proceed SAML SSO.
The solution is that the Application (Service Provider), usually an application vendor, send SAML Request in the header.
Once the Application (Service Provider) sends AML Request in the header, Entra ID will proceed the next step of SAML SSO.
Please refer the below document more information on this issue.
I hope this information is helpful. Please feel free to reach out if you have any further questions.
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Thanks,
Raja Pothuraju.