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Re: [ietf-dkim] draft-ietf-dkim-base-02 // Parent signing security considerations

2006-06-01 15:16:11
Douglas Otis wrote:
[]

My suggestion this morning was that if we include this in the security considerations at all, that we just lift it from the -threats draft since that has already been vetted.
Here's what's there now:

4.1.18.  Key Publication by Higher Level Domain

  In order to support the ability of a domain to sign for subdomains
  under its administrative control, DKIM permits the domain of a
  signature (d= tag) to be any higher-level domain than the signature's
  address (i= or equivalent).  However, since there is no mechanism for
  determining common administrative control of a subdomain, it is
  possible for a parent to publish keys which are valid for any domain
  below them in the DNS hierarchy.  In other words, mail from the
  domain example.anytown.ny.us could be signed using keys published by
  anytown.ny.us, ny.us, or us, in addition to the domain itself.
  Operation of a domain always requires a trust relationship with
  higher level domains.  Higher level domains already have ultimate
  power over their subdomains:  they could change the name server
  delegation for the domain or disenfranchise it entirely.  So it is
  unlikely that a higher level domain would intentionally compromise a
  subdomain in this manner.  However, if higher level domains send mail
  on their own behalf, they may wish to publish keys at their own
  level.  Higher level domains must employ special care in the
  delegation of keys they publish to ensure that any of their
  subdomains are not compromised by misuse of such keys.


FWIW, I'm neutral as to whether we need to include this threat in -base or not.

      Mike
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