Azure Storage TLS: Changes are coming! (…and why you care)

Microsoft is updating Azure services in a phased manner to use TLS certificates from a different set of Certificate Authorities (CAs) beginning August 13, 2020 and concluding approximately on October 26, 2020. We expect that most Azure Storage customers will not be impacted; however, your application may be impacted if you explicitly specify a list of acceptable CAs (a practice known as “certificate pinning”). This change is limited to services in public Azure cloud and US Government cloud. There are no changes in other sovereign clouds like Azure China. 

This change is being made because the current CA certificates do not comply with one of the CA/Browser Forum Baseline requirements. This was reported on July 1, 2020 and impacts multiple popular Public Key Infrastructure (PKI) providers worldwide. Today, most of the TLS certificates used by Azure services are issued from the "Baltimore CyberTrust Root" PKI.  

Azure Storage services will remain chained to the Baltimore CyberTrust Root*, but the TLS server certificates will be issued by new Intermediate Certificate Authorities (ICAs) starting October 26, 2020. 

If any client application has pinned to an Intermediate CA rather than the Baltimore CyberTrust Root, immediate action is required to prevent disruption to connectivity to Azure Storage.  

* Other Azure service TLS certificates may be issued by a different PKI. 

Certificate Renewal Summary 

The table below provides information about the certificates that are being rolled. Depending on which certificate your service uses for establishing TLS connections, action may be needed to prevent loss of connectivity.  

Note: Intermediate certificates are expected to change frequently. We recommend not taking dependencies on them and instead pinning the root certificate as it rolls less frequently.  

Action Required 

1. If your client application has pinned to an Intermediate CA listed in the table, then Search your source code for the thumbprint, Common Name, and other cert properties of any of the 4 Microsoft IT TLS CAs listed above. If there is a match, then your application will be impacted, immediate action is required:  
   1. To resolve this problem, update the source code to include the new intermediate CAs. To continue pinning intermediaries, replace the existing certificates with the new intermediates CAs: 
      1. Microsoft RSA TLS CA 01  
         (Thumbprint: 703d7a8f0ebf55aaa59f98eaf4a206004eb2516a) 
      2. Microsoft RSA TLS CA 02  
         (Thumbprint: b0c2d2d13cdd56cdaa6ab6e2c04440be4a429c75) 
   2. If you have completed the step 1.a. and need to validate your changes, we will provide a test storage account on demand for your convenience to try out before we roll these certificates in production environments. To request a test storage account, please open a support request with the options below and a member from our engineering team will get back to you. 
      • Issue Type: Technical 
      • Service: Azure Storage 
      • Problem type: Connectivity 
      • Problem subtype: Dropped or terminated connections 

Additional Information 

Microsoft wide communications: To broadly notify customers, Microsoft had sent a Service Health portal notification on Aug 3rd, 2020 and released a public document that includes timelines, actions that need to be taken, and details regarding the upcoming changes to our Public Key Infrastructure (PKI).