Contribute to cyrusimap/cyrus-sasl

[stbischof]

Hi @moriyoshi,

would you may add an PR of your cyrus-sasl-xoauth2-plugin to
https://github.com/cyrusimap/cyrus-sasl

ref: cyrusimap/cyrus-sasl#522

[moriyoshi]

Thanks for the heads-up. There are several points worth a note:

1. The issue OAUTHBEARER SASL mechanism support cyrusimap/cyrus-sasl#522 refers to RFC 7628, which describes a mechanism similar to XOAUTH2, but those are different in how to build the payload sent to the server. OAUTHBEARER uses base64-encoded HTTP-esque key-value pairs while XOAUTH2 uses plain base64-encoded KV.
2. Addition of XOAUTH2 to cyrus-sasl was discussed before on the list.
   https://lists.andrew.cmu.edu/pipermail/cyrus-sasl/2018-May/003132.html
   The key point is the client plugin needs some external mechanism that initiates initial token retrieval and subsequent token refreshment and it isn't standardized at the moment.

FYI: #4 implements a conversation protocol with the external credential provider. For now it isn't my intention to make it official.