Re: Re: changing NSEC3 salt

[Timothe Litt]

On 06-Feb-14 09:14, Klaus Darilion wrote:

On 06.02.2014 14:58, Cathy Almond wrote:

On 06/02/2014 12:58, Timothe Litt wrote:

On 06-Feb-14 05:56, Cathy Almond wrote:

On 05/02/2014 18:54, David Newman wrote:

The Michael W. Lucas DNSSEC book recommends changing NSEC3 salt every
time a zone's ZSK changes.


needed to remove the old salt?

thanks

dn

Is this just a matter of a new 'rndc signing' command, or is some action

rndc signing -nsec3param ...

I would expect the old NSEC3 chain and old NSEC3PARAM record to be
removed, once the new chain is in place.


the new NSEC3 chain has been completely generated).

Cathy

(Similarly, the new NSEC3PARAM record will not appear in the zone until

This seems silly.  Why should a person have to select a salt at all?
It's just a random number, and people are really bad at picking random
numbers.  Seems like a miss in 'DNSSEC for humans' :-)

There should be a mechanism to tell named to pick a random number and

already has to know how to get random numbers, so this should not be
difficult.  It should work for records supplied in UPDATE transactions
as well as rndc signing.


that doesn't seem unreasonable.  (E.g. if read from a zone file, pick a
salt, treat the record as if loaded with that value, and do all the
requisite (re-)signing.)


list if you comment on this. (Careful with that 'reply all'!)

Timothe Litt
ACM Distinguished Engineer

use it for the salt. (I suggest '*' - '-' already means 'none'.) named A bit more work to have it function when loaded from a zone file, though I'm copying bind9-bugs so this doesn't get lost. Please don't copy that

Sounds like a good idea - thanks.

regards
Klaus

Indeed. It would also solve the theoretical problem of NSEC3 hash collisions (see my email from 3. Feb 2014)

Not quite. It would enable a solution, but it doesn't solve it unless named also checks for a collision, picking a new salt and re-trying in that case. That would be a good idea (though creating a test case would be a good student challenge). [If it isn't tested, it doesn't work...]

Note also the RFC 5155 recommendation:

The salt SHOULD be at least 64 bits long and unpredictable, so that
an attacker cannot anticipate the value of the salt and compute the
next set of dictionaries before the zone is published.

In case it wasn't obvious, I should have noted that the length would be a config file entry.

Timothe Litt
ACM Distinguished Engineer
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This communication may not represent my employer's views,
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