Hi there, I note that this mail was cc'd to the HTTP WG mailing list (ietf-http-wg@xxxxxx), but apparently didn't make it there (see <https://lists.w3.org/Archives/Public/ietf-http-wg/2020AprJun/>). We really should find out what went wrong here. (the same seems to have happened for the LC on draft-ietf-httpbis-client-hints-13 a few days later) I'll use that as somewhat lame excuse for a very late comment on the document (I've been working on an implementation and this came up just yesterday): <https://tools.ietf.org/html/draft-ietf-httpbis-header-structure-18#section-4.2> says:
When generating input_bytes, parsers MUST combine all lines in the same section (header or trailer) that case-insensitively match the field name into one comma-separated field-value, as per [RFC7230], Section 3.2.2; this assures that the entire field value is processed correctly.
It doesn't require *how* to combine these values (and that's ok because it can't). Later on it says:
Strings split across multiple field lines will have unpredictable results, because comma(s) and whitespace inserted upon combination will become part of the string output by the parser. Since concatenation might be done by an upstream intermediary, the results are not under the control of the serializer or the parser.
So there are HTTP messages that can lead to different parsing results, depending on what intermediaries do (how *they* combine the lines), and what the final recipient does. That this can happen for certain inputs is a given; *this* spec can't do anything about that as it doesn't control the other parts in the transmission chain. What bugs me is that we have an invalid message to start with, but the spec apparently *requires* receivers to accept it, albeit with potentially unpredictable results. IMHO it would be better to allow those recipients that *can* detect the brokenness to reject these fields. If it is really intended to forbid that it might be good to add a short explanation why this is the case. Best regards, Julian -- last-call mailing list last-call@xxxxxxxx https://www.ietf.org/mailman/listinfo/last-call
