Re: [Cbor] Do we care about array-tags issue 6, clamped-uint8 arrays?
Sean Leonard <dev+ietf@seantek.com> Wed, 24 July 2019 23:53 UTC
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From: Sean Leonard <dev+ietf@seantek.com>
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Date: Wed, 24 Jul 2019 19:53:11 -0400
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Cc: Carsten Bormann <cabo@tzi.org>, cbor@ietf.org
To: Jeffrey Yasskin <jyasskin=40google.com@dmarc.ietf.org>
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Subject: Re: [Cbor] Do we care about array-tags issue 6, clamped-uint8 arrays?
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I find round-tripping with ES6 TypedArray to be a sufficiently compelling use case, that it should stay in. That being said, the fact that typed arrays is prompted by and mirrors ES6 TypedArrays—a non-CBOR standard—also prompts me to call for having the tags assigned in the > 255 space. If more TypedArray types are defined in that spec, it is easier to assign the tags to CBOR in a larger block of numbers. That issue, I feel, was never actually resolved on the merits. I believe that the assignment of tags in the 1-byte space (40-255) provides less flexibility and extensibility than assigning them in the 2-byte space (256-65535).* The case in point illustrates that between draft-ietf-cbor-array-tags-00 and draft-ietf-cbor-array-tags-03, the tag 1040 got introduced seemingly came out of nowhere and broke up the nice block of numbers. Since 1040 has been introduced anyway, that is a strong indication that everything should be in the 256-65535 space. Sean *or they could be called 2-byte space and 3-byte space: it’s not clear if there is a consistent definition that we have been using. > On Jul 24, 2019, at 6:17 PM, Jeffrey Yasskin <jyasskin=40google.com@dmarc.ietf.org> wrote: > > On Wed, Jul 24, 2019, 4:41 PM Carsten Bormann <cabo@tzi.org <mailto:cabo@tzi.org>> wrote: > To make sure that we don’t create a trap for generations to fall into, a paragraph could be added to the security considerations.. > > That sounds like a good idea. > > Jeffrey > > Generally speaking, an implementation that wants to perform operations on input data will need to validate that to be appropriate for that beforehand. The potential trap here might be that a Uint8ClampedArray might feel a lot more like a Uint8Array than other types do to each other so the validator would be misled. So don’t do that… > > Grüße, Carsten > > > > On Jul 24, 2019, at 16:01, Jeffrey Yasskin <jyasskin=40google.com@dmarc.ietf.org <mailto:40google.com@dmarc.ietf.org>> wrote: > > > > In https://github.com/cbor-wg/array-tags/issues/6 <https://github.com/cbor-wg/array-tags/issues/6> I complained that > > tag 68, marking clamped-uint8 data, is weird, in that clamped-ness is > > a property of further processing rather than the data encoded in CBOR. > > I worried that we might introduce security issues by allowing a > > potentially-malicious sender to decide how the recipient processes the > > received data. > > > > More abstractly, I believe this is the only tag in the document that > > extends the CBOR generic data model. > > > > I don't think the current text adequately describes when a recipient > > should create a Uint8ClampedArray from potentially-untrusted input > > data. But I 1) didn't object during the last call and 2) don't think > > this is a big enough issue to try to hold up the process if other > > folks think it's fine. > > > > So, how do other folks feel about the marker for clamped uint8 arrays? > > > > Thanks, > > Jeffrey > > > > _______________________________________________ > > CBOR mailing list > > CBOR@ietf.org <mailto:CBOR@ietf.org> > > https://www.ietf.org/mailman/listinfo/cbor <https://www.ietf.org/mailman/listinfo/cbor> > > > > _______________________________________________ > CBOR mailing list > CBOR@ietf.org > https://www.ietf.org/mailman/listinfo/cbor
- [Cbor] Do we care about array-tags issue 6, clamp… Jeffrey Yasskin
- Re: [Cbor] Do we care about array-tags issue 6, c… Carsten Bormann
- Re: [Cbor] Do we care about array-tags issue 6, c… Jeffrey Yasskin
- Re: [Cbor] Do we care about array-tags issue 6, c… Sean Leonard
- Re: [Cbor] Do we care about array-tags issue 6, c… Carsten Bormann
- Re: [Cbor] Do we care about array-tags issue 6, c… Sean Leonard
- Re: [Cbor] Do we care about array-tags issue 6, c… Jeffrey Yasskin
- Re: [Cbor] Do we care about array-tags issue 6, c… Carsten Bormann
- Re: [Cbor] Do we care about array-tags issue 6, c… Jim Schaad
- Re: [Cbor] Do we care about array-tags issue 6, c… Sean Solberg