CA/EV Processing for CAs

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EV TLS Capable

Mozilla considers an intermediate certificate to be capable of issuing EV TLS certificates when all of the following are true. The intermediate certificate:

  • is signed by an EV TLS Capable certificate (when not directly signed by the root certificate)
  • either directly or transitively chains up to a root certificate included in Mozilla's root store with the TLS (Websites) trust bit turned on, and EV enabled
  • is not revoked and not expired
  • does not have an Extended Key Usage (EKU) extension or does have an EKU extension containing KeyPurposeIds: anyExtendedKeyUsage or id-kp-serverAuth
  • has the CA/Browser Forum Certificate Policy Object Identifier (OID) of 2.23.140.1.1 (CABF EV OID).

Firefox EV Processing Logic

Firefox determines whether to display the Extended Validation TLS UI for a given website by performing policy validation during certificate path building and verification. Firefox ships with a list of trust anchors (root certificates), some of which are each trusted for the CA/Browser Forum EV policy OID of 2.23.140.1.1. If Firefox can build a trusted path from the end entity certificate to a root certificate that is trusted for the EV policy OID and where each certificate in the chain has that policy OID in the certificatePolicies extension (or, where allowed for intermediate and root certificates, the anyPolicy OID), then that certificate is considered an EV certificate. Additional details are as follows.

Historical Note

Firefox previously recognized a set of CA-specific EV policy OIDs associated with some root certificates in the Mozilla Root CA Program, in addition to the CA/Browser Forum EV policy OID (2.23.140.1.1). Over time, our policy has evolved to require that EV CAs use only the CA/Browser Forum EV policy OID.

As of Firefox version 103 and later, Firefox attempts to build a certificate path using the recognized EV OID found in the end-entity certificate until it identifies a valid path. (This behavior was implemented via Bugzilla #1769150). In older versions (102 or earlier), Firefox processed only the first recognized EV policy OID listed in the certificatePolicies extension of the end-entity certificate. If path-building failed using this first OID, the certificate would not be considered EV, even if other recognized OIDs were present.

We eventually standardized on the CA/Browser Forum EV policy OID (2.23.140.1.1). Consequently, Mozilla stopped adding CA-specific EV policy OIDs to ExtendedValidation.cpp, and new EV enablement requests are approved only if they use the 2.23.140.1.1 OID.

It remains acceptable for CAs to include their CA-specific EV policy OID(s) in their certificates; however, the CA/Browser Forum EV policy OID (2.23.140.1.1) must also be present.

Current EV Processing

EV CAs must use the CA/Browser Forum EV policy OID (2.23.140.1.1). Mozilla no longer processes CA-specific EV policy OIDs. Any intermediate CA certificate or issuing CA certificate must include either the EV policy OID of 2.23.140.1.1 or the anyPolicy OID (2.5.29.32.0), provided that the EV Guidelines permit the use of the anyPolicy OID in the given situation.

All end-entity EV certificates must assert the EV policy OID. This means one of the following must be true for each intermediate CA certificate in the chain:

  • The certificatePolicies extension includes the anyPolicy OID (2.5.29.32.0). (Note: If the inhibitAnyPolicy extension is present, Firefox will reject the anyPolicy OID regardless of the value set for inhibitAnyPolicy.)
  • The certificatePolicies extension includes the CA/Browser Forum EV policy OID (2.23.140.1.1).

For EV certificates that chain to multiple roots via cross-certification, the same rules apply. Special care should be taken, as mismatches between policy OIDs in end-entity certificates and CA certificates using the path building algorithm may cause issues. The best practice is to rely exclusively on the CA/Browser Forum EV policy OID (2.23.140.1.1) and ensure that it is prominently placed in the certificatePolicies extension of all end-entity EV certificates.


Revocation Checking

An additional consideration for receiving the EV UI is that revocation checking must succeed via OCSP (or some future revocation checking mechanism) for the end-entity and intermediate CA certificate(s). If the security.OCSP.enabled preference is set to ‘0’, OCSP checking is not performed and the EV UI will not appear for otherwise valid EV certificates.

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