> But applying a label to the data does not change the nature of the data.

This is not about applying a label, this is about type-tagging. The label is irrelevant, the type tag is not.

> In the larger context, the data was created as a text representation of an IP address, was never used in a DNS context

Except that it was. As per the SNI specification, putting something into the SNI hostname field is "using it in a DNS context", which is why doing so is a bug. It's the exact same bug as putting plain text into HTML. The fact that "<" represents a "less than sign" in plain text is irrelevant to what "<" means when it appears in HTML. The semantics of HTML are not governed by the spec of plain text. Using plain text where HTML is expected is a bug. The fact that a human with a larger context might be able to recognize that the string "3 < a / b = 42" appearing in an HTML document was probably not intended to contain a malformed HTML tag does not change that it in fact does.

> Just as "Alice" remains a first name even if it is mislabeled or misused.

Essentialism, anyone?

> "Alice" is a first name, but it is also a valid hostname. It is not a hostname just by virtue of being validly parseable as such.

Exactly! It is by virtue of the context in which it appears. And the context of the SNI host name field makes whatever appears in it a DNS FQDN.

> And if I wanted to know the first names of people here at HN, but asked for their hostnames, I would generally not get the answer I wanted.

Yep. And equally, when the server implementing SNI asks you for a DNS hostname, but you supply an IP address, you are not answering the question being asked, and you should expect whatever your reply is to be treated as a DNS hostname.

> If some awful code somewhere misused first names as hostnames, the network guy with very limited context might say "I see a query for hostname 'Alice'", but the people with larger context would ask "Why is this firstname being misused as a hostname?".

Sure, they might. That doesn't change the fact that as far as the protocol is concerned, it still is a hostname, which is precisely why it will fail to work.

> This HN thread was never a SNI spec internal debate, and no one here benefits from assuming that highly restrictive context.

You claimed that you could specify IP addresses in SNI messages. You still can't.

> I have had discussions with some of the langsec folks in the past. I greatly respect their work, and they are wise enough to know that their context is not useful in general discussion.

So, this is not a discussion about whether or not you can specify IP addresses in the SNI hostname field?

> Your initial statement was condescending and misleading. As the conversation continues, it becomes clear that this was intentional, and you are willing to die on the hill of tiny irrelevant context. Noted.

You are still wrong and apparently massively confused.

Let's assume we have a server that has a certificate for the host name 1.2.3.4. That is, a certificate with a subject alternative name of type dNSName, value "1.2.3.4". Now, an HTTP client is instructed to request the URI https://1.2.3.4/foobar, POSTing a valuable secret to that URI. This HTTP client puts "1.2.3.4" into the SNI dns hostname field, as you seem to be believe to be correct behaviour according to the RFC, right? Now, the server will correctly respond to that with said certificate, right?

What happens next? Should the client accept that certificate or not? Why should it? Why not?