Hello Imran,
OSS message is not needed to get the CA signed from SAP.
SAP hardly gives something for free 
It is chargeable, and SAP charges 260 Euros + Tax for 2 years validity.
If not SAP, you can also try out other third parties who can provide you the CA signed certificates like Digicert.
You can follow the below link to generate it -
SSL Server Certificates | SAP Support Portal
Regards,
Nitin Deshpande