104 lines
3.6 KiB
Markdown
104 lines
3.6 KiB
Markdown
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# Various issues with RFCs
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## RFC 3597 - "Handling of Unknown DNS Resource Record (RR) Types"
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[Section 5](https://tools.ietf.org/html/rfc3597#section-5) defines a
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generic (master file) format for unknown types, which can also be used
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for (partially) known types to be compatible with other software.
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It also says:
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> An implementation MAY also choose to represent some RRs of known type
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> using the above generic representations for the type, class and/or
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> RDATA, which carries the benefit of making the resulting master file
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> portable to servers where these types are unknown.
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and provides examples:
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> e.example. IN A \# 4 0A000001
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> e.example. CLASS1 TYPE1 10.0.0.2
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I.e. it allows mixing unknown and known format.
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Given that the `\# <len> <hex>` format can also be a valid known
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representation it is a bad idea to mix them (the obvious example being
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`TXT`).
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It is acceptable to use the generic `CLASS...` specifier with known and
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unknown TYPEs, but the generic representation of RDATA must only be used
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with the generic `TYPE...` representation; and the generic `TYPE...`
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representation must always be followed by the generic representation of
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RDATA.
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## RFC 4034
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[Section 3.2](https://tools.ietf.org/html/rfc4034#section-3.2) says:
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> The Signature Expiration Time and Inception Time field values MUST be
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> represented either as an unsigned decimal integer indicating seconds
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> since 1 January 1970 00:00:00 UTC, or in the form YYYYMMDDHHmmSS in
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> UTC, where:
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>
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> - YYYY is the year (0001-9999, but see Section 3.1.5);
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> - MM is the month number (01-12);
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> - DD is the day of the month (01-31);
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> - HH is the hour, in 24 hour notation (00-23);
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> - mm is the minute (00-59); and
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> - SS is the second (00-59).
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But in UTC the second sometimes might be `60` to handle leap seconds;
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these value can't be represented in POSIX time (seconds since epoch
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*without* leap seconds), so the `YYYYMMDDHHmmSS` simply isn't exact UTC.
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## RFC 6895
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[Sectoin 3.1](https://tools.ietf.org/html/rfc6895#section-3.1) says:
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> Allocated RRTYPEs have mnemonics that must be completely disjoint
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> from the mnemonics used for CLASSes and that must match the regular
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> expression below. In addition, the generic CLASS and RRTYPE names
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> specified in Section 5 of [RFC3597] cannot be assigned as new RRTYPE
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> mnemonics.
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>
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> [A-Z][A-Z0-9\-]*[A-Z0-9]
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> but not
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> (TYPE|CLASS)[0-9]*
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TYPE 255 doesn't have a clear mnemonic though; usually `ANY` is used,
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but the official name is `*`.
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Now:
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- `*` doesn't match the required format
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- `ANY` conflicts with CLASS `ANY` (255)
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- but a mnemonic is required because the TYPE is allocated
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RFC 6895 indicates that `*` means `(ALL/ANY)`, so one might read it
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suggests using `ALL` as mnemonic for TYPE 255.
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Side note: RFC 1035 doesn't specify a mnemonic for (Q)CLASS 255 either,
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but the registry put `ANY` between `(`..`)`, the same as it did for the
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other mnemonic from RFC 1035.
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The QCLASS 254 looks different again, but `NONE` is probably a safe
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mnemonic for it.
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See also:
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- Re: [dnsext] WGLC: RFC6195bis IANA guidance (https://mailarchive.ietf.org/arch/msg/dnsext/kKBfBhQIJmRDQ-xb_iJD-A4EeZE)
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### Proposal
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Given the common use of `ANY` for TYPE 255, it should be marked as the
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official mnemonic.
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Since QCLASS `ANY` is basically useless it could be obsoleted.
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BCP 42 (currently RFC 6895) should be updated to say `ANY` is a valid
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mnemonic for both TYPE 255 and CLASS 255, and, if ambiguous, should be
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interpreted as TYPE 255.
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See also:
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- [dnsext] rfc6195bis draft : thoughts on CLASS sub-registry (https://mailarchive.ietf.org/arch/msg/dnsext/fA086yr5V3QrVkmxF7HcuBIX92A)
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