[tech] IPv6 addresses in URLs

mbays mbays at sdf.org
Sun Apr 18 12:17:14 BST 2021

* Sunday, 2021-04-18 at 09:12 +0000 - nervuri <nervuri at disroot.org>:

> On Sat, 2021-04-17, Stephane Bortzmeyer wrote:
> > > No SNI vs empty SNI - we could test to see if servers have a problem
> > > with either.
> > 
> > For instance, egsam.glv.one reacts badly when you don't send a SNI:
> > 
> > % gnutls-cli -p 1965 --disable-sni --insecure egsam.glv.one
> Sure, but I was only referring to capsules accessible using an IP
> address instead of a DNS name.  Makeworld figured it out:
> https://gitlab.com/gemini-specification/protocol/-/issues/33

For the benefit of those who don't want to fire up a javascript browser 
just to see this: I (grudgingly) did it for you, and here's Makeworld's 

>Ok, I figured it out.
>I used Wireshark to analyze curl traffic to and 
>https://example.com. curl only sends the SNI for the latter connection. 
>For the former it omits it entirely. As further clarified in the 
>OpenSSL wiki:
>   SNI has been made mandatory to implement in TLS 1.3 but not mandatory to use.
>I'm not sure if an empty SNI is valid or accepted by spec or existing 
>code, but omitting it certainly is. Most of the TLS libraries geminauts 
>are using would be doing all this by default, and so the spec should 
>reflect that. SNI should be omitted for IP addresses.
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