[openssl-users] [EXTERNAL] Re: Self-signed error when using SSL_CTX_load_verify_locations CApath

[Viktor Dukhovni]

> On Dec 3, 2018, at 1:47 PM, Sands, Daniel via openssl-users <openssl-users at openssl.org> wrote:
> 
> Just wondering, is there a different error for an untrusted cross-
> signed root?  If it's the same error, then maybe remove "self-signed"
> from the above message too, because that would not always be the case
> either.

A cross-signed CA certificate is not self-signed (or even self-issued),
the two are mutually exclusive:

   This specification covers two classes of certificates: CA
   certificates and end entity certificates.  CA certificates may be
   further divided into three classes: cross-certificates, self-issued

  Cooper, et al.              Standards Track                    [Page 12]
 
  RFC 5280            PKIX Certificate and CRL Profile            May 2008

   certificates, and self-signed certificates.  Cross-certificates are
   CA certificates in which the issuer and subject are different
   entities.  Cross-certificates describe a trust relationship between
   the two CAs.  Self-issued certificates are CA certificates in which
   the issuer and subject are the same entity.  Self-issued certificates
   are generated to support changes in policy or operations.  Self-
   signed certificates are self-issued certificates where the digital
   signature may be verified by the public key bound into the
   certificate.  Self-signed certificates are used to convey a public
   key for use to begin certification paths.  End entity certificates
   are issued to subjects that are not authorized to issue certificates.

In OpenSSL there's no such thing as a "cross-signed root", the constructed
chain contains a leaf certificate, some set of cross-signed or self-issued
intermediate certificates, and finally a self-signed "root" (ignoring
for the moment support for "partial chains" and DANE).

-- 
	Viktor.