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Call for AV-98 testing

solderpunk <solderpunk (a) SDF.ORG>

Hey folks,

I'm preparing to finally do a 1.0.0 release of AV-98 this weekend and
would appreciate people helping me kick the tyres.  Once the release is
made you'll be able to install it with pip, but for now you need to
clone the repo:

https://tildegit.org/solderpunk/AV-98/

There's a setup.py in there if you want to install it yourself, but it
has no essential third party dependencies and it's all in a single file
so you can just run av98.py from right where you clone it, easy peasy.

The release is mostly for the sake of easier installation, and for
everyday use you won't notice much new if you are already used to how
AV-98 works.  But there have been substantial changes to the TLS-side
of things.

Firstly, you can now toggle between two methods of TLS certificate
validation (AV-98, until now, did no verification whatsoever, an
embarrassing reminder of it's "hacked together quickly in response to
the surprise experience of an actual, live Gemini server" legacy).

With `set tls_mode tofu` (the default), you get the TOFU validation mode
I initially envisioned for Gemini.  When you first visit a server, the
received certificate is blindly trusted.  An SQLite database is
maintained with the fingerprints of trusted certificates, a count of how
many times they've been seen and the dates they were first and most
recently seen.  If you ever subsequently see a different certificate for
that host, you get a warning with details on how often the previous cert
was seen and when it is/was due to expire, to inform your decision on
whether or not to accept it.

Note that it's not required, but the TOFU mode works beter if you have
the `cryptography` module installed - certificates won't be blindly
accepted if they are expired, or not yet valid, or don't have a common
name or subject alternate name matching the expected hostname.  Python's
standard `ssl` module doesn't let you check this for self-signed
certificates (really!).

In TOFU-mode there's a lot of creation of files and directories and this
is largely what I'm hoping to discover bugs in by getting people to try
this out.

With `set tls_mode ca` (which you can stick in an RC file to make your
permanent setting), AV-98 will do typical CA-based validation using your
platform's default trusted certificates, and will refuse to accept
self-signed certificates.

For now I'm still wimping out on setting a hard requirement on TLS cert
validation in the spec (which allows whatever the client likes - but
clients really should be extremely upfront with users about what they
are doing!).  But for my part I am pretty committed to experimenting
with less centralised and less commercial alternatives to the CA system
and I'll probably end up building a lot more options into AV-98's TOFU
mode to reduce the risk associated with the initial acceptance.  I'm
taking a lot of inspiration and ideas from DNS-based solutions like
DANE, and from projects like Perspectives and Convergence.  I'm happy to
discuss them with interested folks.

Secondly, there is now a "client certificate manager" which is accessed
via the `cert` command.  Use of client certificates in Gemini is
currently under-specced and (perhaps as a partial consequence)
under-used, and I want to correct this in the near future.  So I threw
some stuff together in AV-98 to give us concrete ideas to discuss and
test.  None of how this functions is "canonical" yet - I'm embracing the
notion of AV-98 as an experimental client where we test stuff out.

For now, the client certificate manager relies on the `openssl` command
line tool being available to run with `system()`, because this is a
whole world of pain less than doing it in Python.

When it receives a 60, 61 or 62 status code, AV-98 will pop up a
notification and give the use the option to generate a client
certificate to use when re-requesting the resource, or to load a
previously generated (non-transient!) certificate from the filesystem.
When client certificates are *not* being used, the AV-98> prompt now
appears in a happy, friendly lime green colour.  As soon as a client
certificate is loaded, the prompt becomes a scary deep red and displays
as "AV-98+cert>".  If, while a client cert is loaded, you try to
navigate away to a different domain, AV-98 will warn you and give you a
Y/N dialogue to deactivate the cert before continuing, to avoid
"identity leak".  If you subsequently navigate back, during the same
session (I mean AV-98 session here, i.e. you haven't exited and
restarted the program), to a domain where you previously used a client
cert, you'll be asked if you want to load it again.  You can use the
`cert` command to explicitly end a client certificate session any time
you like.

It's all a bit clunky and explicit for now (although to some extent
that's a good thing because people should be *aware* of how they use
client certs), but it's definitely a huge improvement over previous
options for occasionally keeping an eye on your astrobotany plant!

I will make a separate more detailed post later about client
certificates and the things we should think about with regard to them.

That's about it!  Thanks to anybody who tests out, bug reports welcome
via email or at https://tildegit.org/solderpunk/AV-98/issues.

Cheers,
Solderpunk

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solderpunk <solderpunk (a) SDF.ORG>

On Sat, May 23, 2020 at 01:28:39PM +0000, solderpunk wrote:
 
> I'm preparing to finally do a 1.0.0 release of AV-98 this weekend and
> would appreciate people helping me kick the tyres.  Once the release is
> made you'll be able to install it with pip, but for now you need to
> clone the repo:

Just to follow up on this now "overdue" release:  I've been getting lots
of helpful bug reports, pull requests and suggestions from people, which
is great.  Thank you all!  I decided to put off the release until a few
days went by without any such thing coming in, which will hopefully
happen soon.

Cheers,
Solderpunk

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