[Ovmsdev] TLS CA question

Stephen Casner casner at acm.org
Thu Mar 4 12:09:45 HKT 2021


Thanks for that reply.  As I mentioned, if I don't configure
WOLFSSL_ALT_CERT_CHAIN then I get an "ASN no signer to confirm"
error.  Do you have any idea why that might be?  That is, am I likely
to be missing access to some key?  Of some key not being present in a
cert when it should be there?

                                                        -- Steve

On Thu, 4 Mar 2021, Mark Webb-Johnson wrote:

> Steve,
> A thorny issue. Servers are _supposed_ to provide intermediate certificates, up to a trusted root. When you are issued a certificate, it includes a bundle of these intermediary certificates to be installed at the same time.  In practice, servers are often mis-configured so they do not. This is made worse by browsers silently detecting this, then downloading the missing intermediate certificates (the child certificate contains a URL to its parent's cert).
> For Open Vehicles, I don't think we need to deal with this, and we certainly don't need the complexity of automatically downloading intermediate certificates. I think if the user wants to access a server misconfigured in that way, he can simply import and trust the intermediate certificate directly.
> I don't think we should set WOLFSSL_ALT_CERT_CHAIN.
> Regarding your question, in normal operation OVMS as a client must validate the server certificates it connect to. I don't think OVMS currently supports client certificates, although if it did we would have to correctly provide those to the server on connection.
> Regards, Mark.
> > On 4 Mar 2021, at 9:00 AM, Stephen Casner <casner at acm.org> wrote:
> >
> > I find that I need to enable the following option in my testing of the
> > possible replacement of MEDTLS with WolfSSL, otherwise I get an "ASN
> > no signer to confirm" error:
> >
> >    WOLFSSL_ALT_CERT_CHAIN allows CA's to be presented by peer, but
> >    not part of a valid chain. Default wolfSSL behavior is to require
> >    validation of all presented peer certificates. This also allows
> >    loading intermediate CA's as trusted and ignoring no signer
> >    failures for CA's up the chain to root. The alternate certificate
> >    chain mode only requires that the peer certificate validate to a
> >    trusted CA.
> >
> > Is that expected for the trust arrangements we are using?
> >
> > A possibly related question: do we expect the server to validate
> > clients, or only the clients to validate the server?
> >
> >                                                        -- Steve
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> > OvmsDev at lists.openvehicles.com
> > http://lists.openvehicles.com/mailman/listinfo/ovmsdev
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