30 Jan
2024
30 Jan
'24
3:10 a.m.
On 11/01/2024 14.03, Simon Josefsson wrote:
tor 2024-01-11 klockan 13:48 +0100 skrev Florian
Schmaus:
It's a few lines of code in Java to extract the channel-binding data for
tls-server-end-point from a SSLSession using only API from Java's
runtime library [1].
The situation is vastly different for tls-exporter. Last time I've
checked, there was no API in the Java's runtime library to retrieve the
tls-exporter. So you have to resort to third party libraries, which
increases your code complexity (it's usually nicer if you can just rely
on the API of the standard library of your programming language's ecosystem.
In my experience you find APIs to retrieve the tls-server-end-point data
pretty easily. Getting the tls-exporter data can be tricky. It can even
be impossible, I believe, though the situation may has improved over the
last years.
Hi Simon,
thanks for your mail.
On 11/01/2024 13.39, Holger Weiß wrote:
Thanks Florian. Extracting the correct certificate from the TLS
library, hashing it using the right algorithm, and getting that into a
SCRAM library that support tls-server-end-point may be as easy or
challenging as support for tls-exporter. So I'm not as convinced tls-
server-end-point is minimal effort.
* Simon Josefsson <simon(a)josefsson.org>
[2024-01-11 13:10]:
Additionally, implementing tls-server-end-point demands minimal
effort
since it is just based on the hash of the certificate. I believe that
not making it mandatory won't deter anyone who is inclined to
implement
it, as it is a low hanging fruit.
Furthermore, we hope to achieve a high success rate by making it
mandatory to implement for servers.
You are correct, one should aim for better altnatives than
tls-server-end-point when implementing XEP-0440, and this should be
explicitly mentioned in the XEP. As it stands, the XEP does not
clearly
convey this. I intend to propose a revision to rectify this in the
near
future.
I believe tls-server-end-point is generally best
left
unimplemented to
guide efforts towards supporting the stronger tls-exporter.
One use case I see for tls-server-end-point is that it allows for
supporting channel binding by setups where TLS is terminated by
some
reverse proxy, thereby protecting against _some_ but not all attack
vectors that tls-exporter protects against.
What do you think about a compromise to mandate
support for both tls-
server-end-point and tls-exporter? I'd prefer only tls-exporter
though.
Mandating tls-exporter gets you nothing if people can not implement it.
I think this is fallacy many standards organizations fall for. We also
have to look at the software ecosystem and its capabilities.
Are you positive that it is sufficiently easy to retrieve tls-exporter
data from a TLS session in all ecosystems of "relevant" programming
languages?
If we are not positive about it, then why should be push implementations
into non-compliance by mandating it, when we simply could (strongly)
recommend it?
- Flow
1:
https://github.com/igniterealtime/Smack/blob/e504bc23cfe601e4e414aac1aff54c…