Last Call Review of draft-ietf-dhc-anonymity-profile-06
I am the assigned Gen-ART reviewer for this draft. The General Area
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Reviewer: Brian Carpenter
Review Date: 2016-02
IETF LC End Date: 2016-02-15
IESG Telechat date:
Summary: Almost ready
There is a reciprocal-RAND IPR disclosure against this draft
> 3.5. Client Identifier Option
> In contradiction to [RFC4361], when using the anonymity profile, DHCP
> clients MUST use client identifiers based solely on the link layer
> address that will be used in the underlying connection.
The use of "solely" bothers me. I understand why the ID must be based
on the MAC address, but why can't it be (for example) a hash of that
address with a pseudo-random nonce? "Solely" seems to exclude that
sort of solution.
> There are usages of DHCP where the underlying connection is a point
> to point link, in which case there is no link layer address available
> to construct a non-revealing identifier. If anonymity is desired in
> such networks, the client SHOULD pick a random identifier that is
> unique to the current link, using for example a combination of a
> local secret and an identifier of the connection.
Firstly, s/random/pseudo-random/ and s/unique/highly likely to be unique/
Secondly, this seems underspecified. Something more like
> 4.3. Client Identifier DHCPv6 Option
> When using the anonymity profile without the benefit of randomized
> link-layer addresses, clients that want to protect their privacy
> SHOULD generate a new randomized DUID-LLT every time they attach to a
> new link or detect a possible link change event.
Firstly, again, it's always pseudo-random in a computer.
Secondly, it isn't obvious from the text that you are really abusing the
RFC 3315 format by using a bogus MAC address and bogus timestamp. I suggest
rewriting the sentence:
When using the anonymity profile without the benefit of pseudo-random
link-layer addresses, clients that want to protect their privacy
SHOULD generate a new pseudo-random identifier in DUID-LLT format
every time they attach to a new link or detect a possible link
change event. Syntactically this identifier will conform to [RFC3315]
but its content is meaningless.
> 4.5.2. Prefix delegation
> The interaction between prefix delegation and anonymity require
> further study. For now, the simple solution is to avoid using prefix
> delegation when striving for anonymity. When using the anonymity
> profiles, clients SHOULD NOT use IA_PD, the prefix delegation form of
> address assignment.
I see the issue, but this may be problematic for some scenarios. I think
this choice needs to be reviewed in 6man. I will make that happen.
> 5. Operational Considerations
> The anonymity profile has the effect of hiding the client identity
> from the DHCP server. This is not always desirable. Some DHCP
> servers provide facilities like publishing names and addresses in the
> DNS, or ensuring that returning clients get reassigned the same
Many DHCP servers will only give addresses to pre-registered MAC addresses.
That should probably be noted, because it will prevent all use of
pseudo-random MAC addresses. (Another reason to hash the MAC address
with a nonce.)