IPv6 address encoding in commonName

Michael Richardson mcr at sandelman.ca
Wed Aug 14 22:47:41 UTC 2019

Robert Moskowitz <rgm at htt-consult.com> wrote:
    > I am fiddling around with an intermediate CA signing cert that the CA's
    > 'name' is it HIP (RFC 7401) HIT which is a valid IPv6 address. Actually a
    > Hierarchical HIT as in draft-moskowitz-hierarchical-hip (to be revised soon).

    > For a client cert, it would be easy to put the HIT in subjectAltName per RFC
    > 8002 (with a null subjectName), but a CA cert MUST have a non-empty
    > subjectName.

    > Thus all I want in this subjectName is commonName with the HIT.
    > I am looking for examples of IPv6 addresses in commonName.

I thought that RFC3779 did exactly what you want, but it does not define new
Subject DN, but rather a new extension that will be bound to the Subject.
(I was surprised that RFC3779 was not in the SIDR WG's list of documents,but
I guess it preceeded the SIDR working group, and occured in PKIX)

In ANIMA's ACP document, we have an abomination that leverages rfc822Name,
mostly because we figure the odds of getting anything else through
off-the-shelf CAs is nil.
Note to consumed with things in your stomach:

Jakob Bohm via openssl-users <openssl-users at openssl.org> wrote:
    > As the author of a proposal in this area, could you define a notation
    > for IPv6 DNs, perhaps one that actually reflects the hierarchical nature
    > of IPv6 addresses?

RFC3779 does some of that, but not in the DN itself.

    > You could take inspiration from the (unfortunately rarely used)
    > hierarchical DN representation of DNS names (this used the DNS
    > specific DC name components).  Overall the goal is to allow X.500
    > distinguished name restrictions to work correctly.

Yes, we could abuse the DC component.
Were you thinking about:

    > In practice you could follow the nibble notation as already used
    > for delegation of IPv6 reverse lookups in DNS.

so more correctly:

    > However for the CN in the end cert you could perhaps use the full
    > DNS reverse IPv6 name
    > "x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.x.ip6.arpa"
    > or the URL/Mail notation "[xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx]"
    > where the hex notation shall be the shortest form permitted by the
    > IPv6 notation spec.

Bob, this seems like the best immediate hack to me.

]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]     mcr at sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

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