SSO with Atlassian Access and signed requests + X509 certificate

[Julien REBILLARD]

Hi, 

After discussion with Atlassian support, Access is unable to produce signed requests and certificates when setting up SSO between Access and its own IDP.

There is a ticket on this subject, but given the few votes it contains, I have no illusions about the outcome of this request (https://jira.atlassian.com/browse/ACCESS-1213). 

My security department requires the certificate to be present and requests to be signed back from Atlassian.

As Atlassian preconfigures Access for predefined IDPs (Auth0, Onelogin, ...) would it be possible to do the SSO procedure in 2 steps:
Atlassian communicates with Onelogin (for example) which communicates with my IdP (with the certificate and signature)? Would SSO work in this case?

If other people have encountered the same problem, I am interested in the solutions that have been put in place.