Mozilla Security Blog
Categories: CA Program Security

Distrusting New WoSign and StartCom Certificates

Kathleen Wilson

Mozilla has discovered that a Certificate Authority (CA) called WoSign has had a number of technical and management failures. Most seriously, we discovered they were backdating SSL certificates in order to get around the deadline that CAs stop issuing SHA-1 SSL certificates by January 1, 2016. Additionally, Mozilla discovered that WoSign had acquired full ownership of another CA called StartCom and failed to disclose this, as required by Mozilla policy. The representatives of WoSign and StartCom denied and continued to deny both of these allegations until sufficient data was collected to demonstrate that both allegations were correct. The levels of deception demonstrated by representatives of the combined company have led to Mozilla’s decision to distrust future certificates chaining up to the currently-included WoSign and StartCom root certificates.

Specifically, Mozilla is taking the following actions:

  1. Distrust certificates with a notBefore date after October 21, 2016 which chain up to the following affected roots. If additional back-dating is discovered (by any means) to circumvent this control, then Mozilla will immediately and permanently revoke trust in the affected roots.
    • This change will go into the Firefox 51 release train.
    • The code will use the following Subject Distinguished Names to identify the root certificates, so that the control will also apply to cross-certificates of these roots.
      • CN=CA 沃通根证书, OU=null, O=WoSign CA Limited, C=CN
      • CN=Certification Authority of WoSign, OU=null, O=WoSign CA Limited, C=CN
      • CN=Certification Authority of WoSign G2, OU=null, O=WoSign CA Limited, C=CN
        CN=CA WoSign ECC Root, OU=null, O=WoSign CA Limited, C=CN
      • CN=StartCom Certification Authority, OU=Secure Digital Certificate Signing, O=StartCom Ltd., C=IL
      • CN=StartCom Certification Authority G2, OU=null, O=StartCom Ltd., C=IL
  2. Add the previously identified backdated SHA-1 certificates chaining up to these affected roots to OneCRL.
  3. No longer accept audits carried out by Ernst & Young Hong Kong.
  4. Remove these affected root certificates from Mozilla’s root store at some point in the future. If the CA’s new root certificates are accepted for inclusion, then Mozilla may coordinate the removal date with the CA’s plans to migrate their customers to the new root certificates. Otherwise, Mozilla may choose to remove them at any point after March 2017.
  5. Mozilla reserves the right to take further or alternative action.

If you receive a certificate from one of these two CAs after October 21, 2016, your certificate will not validate in Mozilla products such as Firefox 51 and later, until these CAs provide new root certificates with different Subject Distinguished Names, and you manually import the root certificate that your certificate chains up to. Consumers of your website will also have to manually import the new root certificate until it is included by default in Mozilla’s root store.

Each of these CAs may re-apply for inclusion of new (replacement) root certificates as described in Bug #1311824 for WoSign, and Bug #1311832 for StartCom.

We believe that this response is consistent with Mozilla policy and is one which we could apply to any other CA that demonstrated similar levels of deception to circumvent Mozilla’s CA Certificate Policy, the CA/Browser Forum’s Baseline Requirements, and direct inquiries from Mozilla representatives.

Mozilla Security Team