[−][src]Crate samotop

This is an SMTP server library with focus on privacy. There is also an actual SMTP server - see samotop-server

SMTP Relay Server (MTA) library for Rust with focus on spam elimination and privacy. The motivation is to revive e-mail infrastructure and architecture, address current problems and allow new systems to integrate SMTP. It's called SaMoToP, which could be a nice Czech word.

Status

Reaching stable. The API builds on async/await to offer a convenient asynchronous interface.

Installation

Usage

See the docs on docs.rs.

Add this to your Cargo.toml:

[dependencies.samotop]
version = "0"

Note that the API is still unstable. Please use the latest release.

There are a few interesting provisions one could take away from Samotop:

  • The server (through samotop::server::Server) - it takes IP:port's to listen on() and you can then serve() your own implementation of a TcpService.
  • The SMTP service (SmtpService) - it takes an async IO and provides an SMTP service defined by SessionService.
  • The low level SmtpCodec - it translates between IO and a Stram of ReadControl and a Sink of WriteControl. It handles SMTP mail data as well.
  • The SMTP session parser (SmtpParser) - it takes &str and returns parsed commands or session.
  • The SMTP session and domain model (samotop::model::session, samotop::model::smtp) - these describe the domain and behavior.
  • The mail handling stuff that is yet to be written (MailService)...

SMTP Server

You can run a plaintext SMTP service without support for STARTTLS.

extern crate async_std;
extern crate env_logger;
extern crate samotop;
use samotop::server::Server;
use samotop::service::tcp::DummyTcpService;
fn main() {
    env_logger::init();
    let mail = samotop::service::mail::default::DefaultMailService;
    let sess = samotop::service::session::StatefulSessionService::new(mail);
    let svc = samotop::service::tcp::SmtpService::new(sess);
    let svc = samotop::service::tcp::TlsEnabled::disabled(svc);
    let srv = samotop::server::Server::on("localhost:25").serve(svc);
    async_std::task::block_on(srv).unwrap()
}

To enable TLS, provide a rustls TlsAcceptor. Alternatively, implement TlsEnabled for another TLS library. See the samotop-server for fullexample with TLS enabled.

Dummy server

Any TCP service can be served. See the docs for TcpService. Run it with RUST_LOG=trace to display trace log. Use this to understand how networking IO is handled.

extern crate async_std;
extern crate env_logger;
extern crate samotop;
use samotop::server::Server;
use samotop::service::tcp::DummyTcpService;
fn main() {
    env_logger::init();
    let mut srv = Server::on("localhost:0").serve(DummyTcpService);
    async_std::task::block_on(srv).unwrap()
}

Development

Refresh README from docs: $ cargo readme > README.md

Status

We've got a decent SMTP command parser written as a PEG grammar. The model is tightly nit from the RFCs. An async-std based server will hear your SMTP commands, drive the SMTP state machine and correct you if you step aside. Once a mail session is ready, the mail data are currently dumped to the console. After that, you can do it again. See the crate documentation for API status. The samotop crate is published on crates.io. The executable is not very useful yet except for debugging SMTP itself until common MDA/MTA features are implemented.

Done

  • [x] Parse SMTP commands and write responses according to RFCs
  • [x] SMTP state machine - helo, mail, rcpt*, data, rset, quit - must be in correct order according to RFCs
  • [x] DATA are handled and terminated correctly (escape dot, final dot).
  • [x] Async/await with async-std backing
  • [x] Privacy: TLS/STARTTLS supported using rustls
  • [x] MTA: Simple mail relay, logging smtp session to standard output but able to receive mail from common relays
  • [x] MDA: System-wide mailbox - mailbox for all unclaimed domains / addresses - store mail in a folder so it can be processed further
  • [x] Antispam: SPF (through viaspf, todo:async)

To do

  • [ ] Antispam: Strict SMTP (require CRLF, reject if client sends mail before banner or EHLO response)
  • [ ] Antispam: whitelist and blacklist
  • [ ] Antispam: greylisting
  • [ ] Antispam: white/black/grey list with UI - user decides new contact handling
  • [ ] Antispam: is it encrypted?
  • [ ] Antispam: reverse lookup
  • [ ] Antispam: DANE (DNSSEC) with UI - user verifies signatures
  • [ ] Processing: Relay mail to another MTA
  • [ ] Processing: Store mail in Maildir (MDA)
  • [ ] MDA: Domain mailbox - mailbox for unclaimed addresses
  • [ ] MDA: User mailbox - mailbox for specific address or alias
  • [ ] MDA: Smart mailbox - multiple mailbox addresses by convention
  • [ ] Privacy: Refuse unencrypted session
  • [ ] Privacy: Encryption at rests, encrypt e-mails, only the recipient will be able to decrypt
  • [ ] Privacy: Leave no trace, no logs, obfuscated file dates...

Company

In Rust world I have so far found mostly SMTP clients.

SMTP server

  • mailin by Saul Hazledine is quite similar to samotop:
    • same: recent activity (Mailin last commits: Feb 2020)
    • same: enables writing SMTP servers in Rust.
    • same: includes SMTP parsing, responding and an SMTP state machine.
    • different: Samotop uses PEG, Mailin uses Nom to define the SMTP parser.
    • different: Samotop is async while Mailin runs on bare std blocking IO. Async introduces more dependencies, but allows us to shift to the new IO paradigm. In Samotop, the SMTP session is handled as a stream of commands and responses. Mailin uses a threadpool to schedule work, Samotop can run on a single thread thanks to async.
    • not too different: samotop includes a default TCP server and enables the user to implement it differently, mailin expects the user to provide a socket but a TCP server is available in mailin-embedded. Thanks to this, Mailin alone has much smaller dependency footprint. Samotop may follow suit to split the crates.
    • ...
  • smtpbis and rustyknife by Jonathan Bastien-Filiatrault are SMTP libraries on async and tokio.
    • same: async.
    • different: Samotop moved to async-std, smtpbis is on tokio.
    • ...
  • rust-smtp by mneumann, last commit 2014, parser coded manually, looks unfinished and abandoned.
  • rust-smtp fork of the above with progress by synlestidae in 2016

Other

  • lettre is an SMTP client, it seems to be alive and well!
  • segimap by uiri, that's actually an IMAP server.
  • ferric-mail by wraithan, looks abandoned since 2014.
  • new-tokio-smtp is na SMTP client by Philipp Korber, now only pasively maintained

Modules

grammar
model
protocol
server
service