From: "Theo de Raadt" <deraadt@openbsd.org>
Subject: Re: finger: handle UTF-8 characters in .plan and .project
To: tech@openbsd.org
Date: Sun, 25 Aug 2024 16:41:00 -0600

Lucas Gabriel Vuotto <lucas@sexy.is> wrote:

> -	while ((ch = getc(fp)) != EOF)
> -		vputc(lastc = ch);

                ^^^^^^^^

Did you misunderstand the purpose of that vis(3) approach?

The finger protocol is not UTF8.  It is potentially garbage from some
server.

Now you are putting it through UTF-8 processing and potentially
sending this to tty which are not prepared for UTF-8.

I thought that is how this works, and a lot more care is needed.
And in places where care cannot be provided, we just don't do UTF-8.