Re: [TLS] [EXTERNAL] Re: Narrowing allowed characters in ALPN ?

Viktor Dukhovni <ietf-dane@dukhovni.org> Thu, 20 May 2021 22:56 UTC

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From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Subject: Re: [TLS] [EXTERNAL] Re: Narrowing allowed characters in ALPN ?
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On Thu, May 20, 2021 at 11:52:50AM -0700, Nick Harper wrote:

> > Since the likelihood of actually adding exotic ALPN values to the
> > registry appears slim, why not say so.  That would leave the exotic
> > values for private on-the-wire use, while allowing DNS and other
> > configuration serialisation forms to avail themselves of more
> > straight-forward parsers.
> 
> Encoding ALPN identifiers in hex for these configuration files sounds like
> a very straightforward way to support all valid ALPN identifiers. We
> already have "exotic" ALPN identifiers in the registry (for GREASE). Any
> new scheme that handles ALPN should be designed to handle all possible
> values. Not doing so will lead to interoperability issues that others have
> already mentioned.

I agree it is a straight-forwarding encoding for machines, and it is
well suited for the GREASE code points.

But, it makes for a fairly terrible user interface for the human
operator.  Compare:

    * managesieve
    * 6d616e6167657369657665

Typos in hex values are easy to make and hard to recognise.

-- 
    Viktor.