[kitten] complementary OPAQUE SASL mechanism draft

[Stefan Marsiske <[e-mail]>]

Thanks Rick for triggering me. Please let me introduce my
complementary draft:

https://github.com/stef/sasl-opaque

this draft by far less ambitious than the other introduced a few days ago on
this list. this one only specifies a simple OPAQUE mechanism for SASL and
mostly only the wireformat. there is no channel binding, and no secure layer.
it also does not support cryptographic agility[1], similar to wireguard and
other modern solutions, eliminating footguns, negotiations and other
complexity. it only specifies one configuration, one of the two specified by
the IRTF CFRG draft[2] with one change, the usage of argon2i for the KSF
instead of scrypt (for which i have an issue open to change[3]).

myself i am the author of the first public/libre OPAQUE implementation, and was
following the IRTF CFRG draft closely. then i got funded through the NGI0 PET
Fund under grant agreement No 825310. this funding had the goal to support
OPAQUE in as much languages and protocols as possible, and thus i implemented a
SASL mechanism which works as an out-of-tree module with cyrus SASL[4].  i'm
much more more of an OPAQUE expert than an SASL expert.

having seen the other draft even before it was posted here, i think the two
drafts are complementary with the other draft having a more high-level
SASL/gss-api wrapping focus (including channel binding et al), and mine a lower
level OPAQUE wireformat focus. as such i think it makes sense to either merge
the two drafts, or i think better to have the high-level draft to refer to the
low level draft (and vice versa) for wireformat of the specific OPAQUE
configuration.

best regards,
Stefan Marsiske

[1] https://paragonie.com/blog/2019/10/against-agility-in-cryptography-protocols
[2] https://github.com/cfrg/draft-irtf-cfrg-opaque/blob/master/draft-irtf-cfrg-opaque.md#configurations-configurations
[3] https://github.com/cfrg/draft-irtf-cfrg-opaque/issues/376
[4] https://github.com/stef/libopaque/
[5] https://github.com/stef/libopaque/tree/master/sasl