husk-milter/src/daemon/mod.rs

//
// Husk milter
//
// the actual daemon
//

use anyhow;
use bytes::Bytes;
use std::ffi::CString;
use tokio::signal;
use tokio::net::TcpListener;

use indymilter::{
    Actions,
    Callbacks,
    Context,
    EomContext,
    Macros,
    NegotiateContext,
    ProtoOpts,
    SocketInfo,
    Status,
    Config,
    ContextActions,
};

use crate::types::husk_context::HuskContext;
use crate::config::{HuskConfig, HuskConfigContainer};
use crate::mail;
use crate::crypto;
use crate::types::mail_context::ProtectionPossibility;

pub struct Daemon { }

impl Daemon {

    pub async fn run(config_container: HuskConfigContainer) -> anyhow::Result<()> {

        let config: HuskConfig = config_container.clone().into();

        let listener = TcpListener::bind(&config.connection)
            .await
            .expect(" opening milter socket");

        let callbacks = Callbacks::new()
            .on_negotiate(|cx, actions, opts| Box::pin(Self::handle_negotiate(cx, actions, opts)))
            .on_connect(|cx, hostname, socket_info| Box::pin(Self::handle_connect(cx, hostname, socket_info)))
            .on_helo(move |cx, hostname| Box::pin(Self::handle_helo(cx, config_container.clone(), hostname)))
            .on_mail(|cx, args| Box::pin(Self::handle_mail(cx, args)))
            .on_rcpt(|cx, args| Box::pin(Self::handle_rcpt(cx, args)))
            .on_data(|cx| Box::pin(Self::handle_data(cx)))
            .on_header(|cx, name, value| Box::pin(Self::handle_header(cx, name, value)))
            .on_eoh(|cx| Box::pin(Self::handle_eoh(cx)))
            .on_body(|cx, chunk| Box::pin(Self::handle_body(cx, chunk)))
            .on_eom(|cx| Box::pin(Self::handle_eom(cx)))
            .on_abort(|cx| Box::pin(Self::handle_abort(cx)))
            .on_close(|cx| Box::pin(Self::handle_close(cx)))
            .on_unknown(|cx, arg| Box::pin(Self::handle_unknown(cx, arg)));

        let config = Default::default();

        indymilter::run(listener, callbacks, config, signal::ctrl_c())
            .await
            .expect("milter execution failed");

        Ok(())
    }

    async fn handle_negotiate(
        _cx: &mut NegotiateContext<HuskContext<'_>>,
        actions: Actions,
        opts: ProtoOpts,
    ) -> Status {
        log::debug!("NEGOTIATE: actions: {actions:?} - opts: {opts:?}");

        Status::AllOpts
    }

    async fn handle_connect(
        _cx: &mut Context<HuskContext<'_>>,
        hostname: CString,
        socket_info: SocketInfo,
    ) -> Status {
        log::debug!("CONNECT: hostname: {hostname:?} - socket_info: {socket_info:?}");
        //Self::print_macros(&cx.macros);

        Status::Continue
    }

    async fn handle_helo(cx: &mut Context<HuskContext<'_>>, config_container: HuskConfigContainer, hostname: CString) -> Status {
        log::debug!("HELO: hostname: {hostname:?}");

        let config: HuskConfig = config_container.into();

        // setup Context
        match HuskContext::new(&config) {
            Ok(context) => {
                log::debug!("found introducers: {:?}", context.introducers);
                cx.data = Some(context).take();
                Status::Continue
            },
            Err(e) => {
                log::error!("{}", e);
                Status::Tempfail
            }
        }
    }

    async fn handle_mail(cx: &mut Context<HuskContext<'_>>, args: Vec<CString>) -> Status {
        log::debug!("MAIL: {args:?}");

        let mut sender: Option<String> = None;

        for arg in args {
            if let Some(s) = mail::to_email(&arg) {
                sender = Some(s);
                break;
            }
        }
        if sender.is_none() { return Status::Tempfail; }

        if let Some(ref mut context) = cx.data {
            context.reset_mail();
            context.set_sender(sender.unwrap());
            Status::Continue
        } else {
            Status::Tempfail
        }
    }

    async fn handle_rcpt(cx: &mut Context<HuskContext<'_>>, args: Vec<CString>) -> Status {
        log::debug!("RCPT: {args:?}");

        if let Some(ref mut context) = cx.data {

            let mut rcpt: Option<String> = None;
            for arg in args {
                if let Some(s) = mail::to_email(&arg) {
                    rcpt = Some(s);
                    break;
                }
            }
            if rcpt.is_none() {
                Status::Tempfail
            } else {
                context.add_recipient(rcpt.unwrap()).await;
                Status::Continue
            }

        } else {
            Status::Tempfail
        }
    }

    async fn handle_data(cx: &mut Context<HuskContext<'_>>) -> Status {
        log::debug!("DATA");

        if let Some(ref mut _context) = cx.data {
            // XXX: check for early accepting
            // if there are no recipients with authenticated certificates
            // tell the MTA that this milter is done and the mail can be further
            // processed.
            Status::Continue
        } else {
            Status::Tempfail
        }
    }

    async fn handle_header(_cx: &mut Context<HuskContext<'_>>, name: CString, value: CString) -> Status {
        log::debug!("HEADER: {name:?} = {value:?}");

        Status::Continue
    }

    async fn handle_eoh(_cx: &mut Context<HuskContext<'_>>) -> Status {
        log::debug!("EOH");

        Status::Continue
    }

    async fn handle_body(cx: &mut Context<HuskContext<'_>>, chunk: Bytes) -> Status {
        log::debug!("BODY: chunk with {:?} bytes received", &chunk.len());

        if let Some(ref mut context) = cx.data {
            context.mail.add_chunk(chunk);
            Status::Continue
        } else {
            Status::Tempfail
        }
    }

    async fn handle_eom(cx: &mut EomContext<HuskContext<'_>>) -> Status {
        log::debug!("EOM");

        if let Some(ref mut context) = cx.data {
            log::debug!("Mail from {:?} complete", context.mail.sender);
            log::debug!("recipients: {:?}", context.mail.recipients);
            log::debug!("body size: {}", context.mail.body_size);

            let body = context.mail.collect_body();

            // check if mail is already encrypted. If it is, keep it as such.
            if crypto::is_encrypted(&body) {
                log::info!("encrypted mail detected");
                return Status::Accept;
            }


            // possible protection
            // none -> accept
            // partial -> accept (later: split)
            // full -> encrypt

            let protection = ProtectionPossibility::from(&context.mail);

            if protection == ProtectionPossibility::Full {
                // if an error occures the body is not exchanged
                match crypto::encrypt(&context, &body, &context.mail.recipients) {
                    Ok(encrypted) => {
                        if cx.actions.replace_body(&encrypted).await.is_err() {
                            log::error!("Cannot exchange body");
                        }
                    },
                    Err(e) => {
                        log::error!("{}", e);
                    }
                }
            }
        }

        Status::Continue
    }

    async fn handle_abort(_cx: &mut Context<HuskContext<'_>>) -> Status {
        log::debug!("ABORT");

        Status::Continue
    }

    async fn handle_close(_cx: &mut Context<HuskContext<'_>>) -> Status {
        log::debug!("CLOSE");

        Status::Continue
    }

    async fn handle_unknown(_cx: &mut Context<HuskContext<'_>>, arg: CString) -> Status {
        log::debug!("UNKNOWN: {arg:?}");

        Status::Continue
    }

    fn print_macros(macros: &Macros) {
        println!("  macros: {:?}", macros.to_hash_map());
    }

}