>>> Hal Murray <hmurray@xxxxxxxxxxxxxxx> schrieb am 09.02.2021 um 10:34 in
Nachricht <20210209093446.E11F8406061@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
> daedulus@xxxxxxxxxxxxx said:
>> RFC8573 seems clear that MD5 must not be used to effect security for NTP
> but
>> this I‑D imports iana‑crypt‑hash which allows MD5 without any
restriction,
>> so is MD5 allowed or not?
>
> "Allowed" is the key word. Just because somebody published an RFC doesn't
> mean that all the gear out in the field will get updated. As Harlan pointed
>
> out, there is a very very long tail on NTP deployments.
>
> I think it makes sense for iana‑crypt‑hash to include slots for historic
> items. If nothing else, it is a good place to say "historic" or
> "deprecated"
> and give references to the details.
>
> If you think a Yang model should discourage using MD5, then I suggest adding
>
> words to say that. Better would be to phrase things so that it also
> includes
> other algorithms that get kicked out of the club after the RFC is published.
>
> I don't know of any place that publishes an up‑to‑date list of
crypto‑hashing
> algorithms and their status.
>
> ‑‑‑‑‑‑‑‑‑‑
>
> I'm looking at iana‑crypt‑hash@2014‑08‑06.yang
>
> It says:
> id | hash function | feature
> ‑‑‑+‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑+‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑
> 1 | MD5 | crypt‑hash‑md5
> 5 | SHA‑256 | crypt‑hash‑sha‑256
> 6 | SHA‑512 | crypt‑hash‑sha‑512
AFAIK DES does no longer work with NTPv4, but it probably would in NTPv3. So
would leaving out DES actually break NTPv3 compatibility? (Not that I suggest
to use DES, but who knows what old NTPv3 gear actually does).
It seems as per RFC 1305 DES is the only algorithm supported ("Cryptographic
Keys (sys.key): This is a set of 64-bit DES keys." on page 64)
>
> If NTP is the only use, then I'd suggest adding a deprecated note. But I
> assume that is used by other than NTP so that may not be appropriate. But
> maybe if MD5 is deprecated for NTP it should be deprecated for other uses
> too.
> ???
>
> What happened to slots 2, 3, and 4?
>
> Existing NTP code also supports SHA‑1
>
> RFC 8573 that deprecated using MD5 with NTP suggests using AES‑CMAC. Note
> that is CMAC rather than HMAC and that NTP uses it's own scheme rather than
> HMAC as described in RFC 6151.
>
> The NTPsec code supports any hash (or CMAC) algorithm that the underlying
> library from OpenSSL supports.
>
> ‑‑
> These are my opinions. I hate spam.
>
>
>
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