Re: [TLS] Narrowing allowed characters in ALPN ?

Viktor Dukhovni <> Thu, 20 May 2021 05:55 UTC

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Date: Thu, 20 May 2021 01:55:09 -0400
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Subject: Re: [TLS] Narrowing allowed characters in ALPN ?
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On Wed, May 19, 2021 at 10:29:43PM +0000, Salz, Rich wrote:

> I support limiting it.

I concur.  These are not strings used between users to communicate in
their native language.  They are machine-to-machine protocol
identifiers, and use of the narrowest reasonable character set promotes

We don't want to embed ASCII NUL bytes in these, worry about potential
corruption when they get embedded in text strings and undergo transforms
from ISO-Latin to UTF-8 or back, ...

The more vanilla the character set the better.  The HTTPS record
constructs comma-separated lists of these in quotes, so it has to
deal with escaping quotes and commas, and other needless pain.

We're not helping anyone by insisting that the original definition was
wise.  It can and should be revised.