husk-milter/src/mail.rs

//! mail functions

use anyhow::Result;
use bytes::Bytes;
use bytes::BytesMut;
use std::ffi::CString;
use sequoia_openpgp::packet::UserID;
use lettre::transport::smtp::{
    client::SmtpConnection, commands::*, extension::ClientId, SMTP_PORT,
};
use lettre::Address;
use tokio::task::JoinSet;
use std::time::Duration;
use chrono::Utc;

use crate::types::cheader::CHeader;
use crate::types::defaults;
use crate::types::errors::HuskError;
use crate::types::recipient::Recipient;

/// Parse the user id fields from a string.
pub fn to_userid(rcpt: &CString) -> Result<UserID> {
    let rcpt = rcpt.to_str()?;
    Ok(UserID::from(rcpt))
}

/// Get the email from the string representation of a user id.
pub fn to_email(rcpt: &CString) -> Result<String> {
    let u = to_userid(rcpt)?;

    if let Some(e) = u.email()? {
        Ok(e.to_string())
    } else {
        Err(HuskError::CannotConvertToEmail(u.to_string()).into())
    }
}

/// Checks if the parameter has a valid email format.
pub fn is_email(email: &str) -> bool {
    let uid = UserID::from(email);

    if let Ok(Some(e)) = uid.email() {
        e == email
    } else {
        false
    }
}

/// Checks if the parameter has a valid domain format.
pub fn is_domain(domain: &str) -> bool {
    is_email(format!("test@{}", domain).as_str())
}

pub async fn smtp_inject(from: String, to: &Vec<Recipient<'_>>, header: CHeader, body: &Bytes) -> Result<()> {

    let mut joinset: JoinSet<Result<()>> = JoinSet::new();

    log::debug!("smtp inject: from {}", from);

    // build message
    let mut header_size = 0;
    for (key, value) in header.iter_lines() {
        header_size += key.count_bytes();
        header_size += value.count_bytes();
        header_size += 4; // 4 is ': ' plus '\r\n'
    }

    // The size of the whole message the sum of header and body size + '\r\n'
    // as the dividing empty line.
    let mut message = BytesMut::with_capacity(header_size + body.len() + 2);
    for (key, value) in header.iter_lines() {
        message.extend_from_slice(key.as_bytes());
        message.extend_from_slice(": ".as_bytes());
        message.extend_from_slice(value.as_bytes());
        message.extend_from_slice("\r\n".as_bytes());
    }
    message.extend_from_slice(b"\r\n");
    message.extend_from_slice(&body[..]);

    // convert addresses
    let from_email = CString::new(from.clone())?;
    let from_email = to_email(&from_email)?;
    let from_email: Address = from_email.try_into()?;

    let mut rcpts: Vec<Address> = Vec::new();
    for rcpt in to {
        let rcpt = rcpt.email.clone();
        rcpts.push(rcpt.try_into()?);
    }

    // XXX: add secret token?
    let my_id = ClientId::Domain(defaults::HELO_REINJECT_ID.to_owned());
    joinset.spawn(async move {

        // XXX
        // We connect to localhost - every other host would require implementing
        // TLS. The milter protocol is unencrypted anyways.
        match SmtpConnection::connect(("localhost", SMTP_PORT), Some(Duration::from_secs(5)), &my_id, None, None) {
            Ok(mut client) => {
                log::debug!("connected - start sending");

                client.command(Mail::new(Some(from_email),vec![]))?;
                for rcpt in rcpts {
                    client.command(Rcpt::new(rcpt, vec![]))?;
                }
                client.command(Data)?;
                client.message(&message)?;
                client.command(Quit)?;

                Ok(())
            },
            Err(e) => {
                log::error!("cannot connect to localhost:{} - {:?}", SMTP_PORT, e);
                Err(e.into())
            }
        }
    });

    match joinset.join_all().await.first() {
        Some(Ok(_)) => {
            log::debug!("mail injection done.");
            Ok(())
        },
        Some(Err(e)) => {
            log::error!("mail injection failed: {:?}", e);
            Err(HuskError::SmtpInjectionFailure(e.to_string()).into())
        },
        _ => {
            log::error!("mail injection failed without reason");
            Err(HuskError::SmtpInjectionFailure("no reason".to_string()).into())
        },
    }
}

pub fn generate_footer(rcpts: &Vec<Recipient>) -> String {
    internal_generate_footer(Utc::now().to_rfc2822(), rcpts)
}

pub(crate) fn internal_generate_footer(now: String, other_rpcts: &Vec<Recipient>) -> String {
    let mut footer = defaults::FOOTER.replace("{date}", now.as_str());

    if ! other_rpcts.is_empty() {
        let rcpts = other_rpcts.iter()
            .map(|r| r.email.clone())
            .collect::<Vec<String>>()
            .join(", ");
        footer.push_str(
            defaults::FOOTER_RECIPIENTS.replace(
                "{rcpts}",
                &rcpts).as_str()
            );
    }
    footer
}


#[cfg(test)]
pub mod tests {

    use crate::mail::internal_generate_footer;
    use crate::types::recipient::Recipient;

    #[test]
    fn test_footer() {

        let rcpts = vec![
            Recipient {
                email: "alice@example.com".to_string(),
                certs: Vec::new()
            },
            Recipient {
                email: "bob@example.com".to_string(),
                certs: Vec::new()
            }
        ];

        let footer = internal_generate_footer(
            "1.1.1970".to_string(),
            &rcpts
        );

        assert!(footer.contains("1.1.1970"));
        assert!(footer.contains("alice@example.com"));
        assert!(footer.contains("bob@example.com"));
    }
}