sasl - SASL authentication encoders

Import with import "sasl.j" as sasl;. The crypto-free SASL mechanisms as pure base64 encoders, shared by the mail clients (smtp / pop / imap). These format the client tokens; the protocol clients run the mechanism-specific wire dialogue around them. No networking and no crypto, so this module is TinyGo-clean and runs on either binary.

import "sasl.j" as sasl;

def p as string init sasl.plain("me@example.com", "secret");     # SASL PLAIN
def b as string init sasl.bearer("me@gmail.com", accessToken);   # SASL XOAUTH2

Runnable: examples/modules/sasl_demo.j (and it is exercised end to end by the mail clients’ demos, e.g. smtp_demo.j).

Surface

XOAUTH2 (the “use a token” half of OAuth2)

sasl.bearer(user, token) builds the SASL XOAUTH2 initial response - base64("user=" user 0x01 "auth=Bearer " token 0x01 0x01) - which is how Google and Microsoft 365 authenticate mail now that both have retired password auth. The mail clients accept it via Options.auth = "xoauth2" (with the access token in pass):

def opts as smtp.Options init smtp.Options{host: "smtp.gmail.com", port: 587,
    security: "starttls", clientName: "me.example", user: "me@gmail.com",
    pass: accessToken, auth: "xoauth2"};
smtp.send($opts, "me@gmail.com", ["you@example.com"], $message);

The function is named bearer, not xoauth2, because a Jennifer method name is letters-only (no digit); the wire mechanism name "XOAUTH2" is a string the client sends. Getting the token itself is the other half of OAuth2 - the job of the generic oauth client (planned, M18.7.3).

Out of scope

• Crypto-free mechanisms only. The challenge-response mechanisms (SCRAM-SHA-256, CRAM-MD5) need HMAC / PBKDF2 and join this module when the crypto library (M20.1) lands.
• Encoders, not transport. sasl formats tokens; the SMTP AUTH, IMAP AUTHENTICATE, and POP3 AUTH dialogue lives in the respective clients.

See also

• smtp.md / pop.md / imap.md - the mail clients that consume these encoders.
• encoding.md - the base64 codec sasl builds on.
• modules/index.md - the module catalog and import rules.