chatmail-core/src/provider.rs

//! [Provider database](https://providers.delta.chat/) module.

#![allow(missing_docs)]

mod data;

use crate::config::Config;
use crate::context::Context;
use crate::provider::data::{PROVIDER_DATA, PROVIDER_IDS, PROVIDER_UPDATED};
use anyhow::Result;
use chrono::{NaiveDateTime, NaiveTime};
use trust_dns_resolver::{config, AsyncResolver, TokioAsyncResolver};

#[derive(Debug, Display, Copy, Clone, PartialEq, Eq, FromPrimitive, ToPrimitive)]
#[repr(u8)]
pub enum Status {
    Ok = 1,
    Preparation = 2,
    Broken = 3,
}

#[derive(Debug, Display, PartialEq, Eq, Copy, Clone, FromPrimitive, ToPrimitive)]
#[repr(u8)]
pub enum Protocol {
    Smtp = 1,
    Imap = 2,
}

#[derive(Debug, Display, PartialEq, Eq, Copy, Clone, FromPrimitive, ToPrimitive)]
#[repr(u8)]
pub enum Socket {
    Automatic = 0,
    Ssl = 1,
    Starttls = 2,
    Plain = 3,
}

impl Default for Socket {
    fn default() -> Self {
        Socket::Automatic
    }
}

#[derive(Debug, PartialEq, Eq, Clone)]
#[repr(u8)]
pub enum UsernamePattern {
    Email = 1,
    Emaillocalpart = 2,
}

#[derive(Debug, PartialEq, Eq)]
#[repr(u8)]
pub enum Oauth2Authorizer {
    Yandex = 1,
    Gmail = 2,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Server {
    pub protocol: Protocol,
    pub socket: Socket,
    pub hostname: &'static str,
    pub port: u16,
    pub username_pattern: UsernamePattern,
}

#[derive(Debug, PartialEq, Eq)]
pub struct ConfigDefault {
    pub key: Config,
    pub value: &'static str,
}

#[derive(Debug, PartialEq, Eq)]
pub struct Provider {
    /// Unique ID, corresponding to provider database filename.
    pub id: &'static str,
    pub status: Status,
    pub before_login_hint: &'static str,
    pub after_login_hint: &'static str,
    pub overview_page: &'static str,
    pub server: Vec<Server>,
    pub config_defaults: Option<Vec<ConfigDefault>>,
    pub strict_tls: bool,
    pub max_smtp_rcpt_to: Option<u16>,
    pub oauth2_authorizer: Option<Oauth2Authorizer>,
}

/// Get resolver to query MX records.
///
/// We first try to read the system's resolver from `/etc/resolv.conf`.
/// This does not work at least on some Androids, therefore we fallback
/// to the default `ResolverConfig` which uses eg. to google's `8.8.8.8` or `8.8.4.4`.
fn get_resolver() -> Result<TokioAsyncResolver> {
    if let Ok(resolver) = AsyncResolver::tokio_from_system_conf() {
        return Ok(resolver);
    }
    let resolver = AsyncResolver::tokio(
        config::ResolverConfig::default(),
        config::ResolverOpts::default(),
    )?;
    Ok(resolver)
}

/// Returns provider for the given domain.
///
/// This function looks up domain in offline database first. If not
/// found, it queries MX record for the domain and looks up offline
/// database for MX domains.
///
/// For compatibility, email address can be passed to this function
/// instead of the domain.
pub async fn get_provider_info(
    context: &Context,
    domain: &str,
    skip_mx: bool,
) -> Option<&'static Provider> {
    let domain = domain.rsplit('@').next()?;

    if let Some(provider) = get_provider_by_domain(domain) {
        return Some(provider);
    }

    if !skip_mx {
        if let Some(provider) = get_provider_by_mx(context, domain).await {
            return Some(provider);
        }
    }

    None
}

/// Finds a provider in offline database based on domain.
pub fn get_provider_by_domain(domain: &str) -> Option<&'static Provider> {
    if let Some(provider) = PROVIDER_DATA.get(domain.to_lowercase().as_str()) {
        return Some(*provider);
    }

    None
}

/// Finds a provider based on MX record for the given domain.
///
/// For security reasons, only Gmail can be configured this way.
pub async fn get_provider_by_mx(context: &Context, domain: &str) -> Option<&'static Provider> {
    if let Ok(resolver) = get_resolver() {
        let mut fqdn: String = domain.to_string();
        if !fqdn.ends_with('.') {
            fqdn.push('.');
        }

        if let Ok(mx_domains) = resolver.mx_lookup(fqdn).await {
            for (provider_domain, provider) in PROVIDER_DATA.iter() {
                if provider.id != "gmail" {
                    // MX lookup is limited to Gmail for security reasons
                    continue;
                }

                let provider_fqdn = provider_domain.to_string() + ".";
                let provider_fqdn_dot = ".".to_string() + &provider_fqdn;

                for mx_domain in mx_domains.iter() {
                    let mx_domain = mx_domain.exchange().to_lowercase().to_utf8();

                    if mx_domain == provider_fqdn || mx_domain.ends_with(&provider_fqdn_dot) {
                        return Some(provider);
                    }
                }
            }
        }
    } else {
        warn!(context, "cannot get a resolver to check MX records.");
    }

    None
}

// TODO: uncomment when clippy starts complaining about it
//#[allow(clippy::manual_map)] // Can't use .map() because the lifetime is not propagated
pub fn get_provider_by_id(id: &str) -> Option<&'static Provider> {
    if let Some(provider) = PROVIDER_IDS.get(id) {
        Some(provider)
    } else {
        None
    }
}

// returns update timestamp in seconds, UTC, compatible for comparison with time() and database times
pub fn get_provider_update_timestamp() -> i64 {
    NaiveDateTime::new(*PROVIDER_UPDATED, NaiveTime::from_hms_opt(0, 0, 0).unwrap())
        .timestamp_millis()
        / 1_000
}

#[cfg(test)]
mod tests {
    #![allow(clippy::indexing_slicing)]

    use super::*;
    use crate::test_utils::TestContext;
    use crate::tools::time;
    use chrono::NaiveDate;

    #[test]
    fn test_get_provider_by_domain_unexistant() {
        let provider = get_provider_by_domain("unexistant.org");
        assert!(provider.is_none());
    }

    #[test]
    fn test_get_provider_by_domain_mixed_case() {
        let provider = get_provider_by_domain("nAUta.Cu").unwrap();
        assert!(provider.status == Status::Ok);
    }

    #[test]
    fn test_get_provider_by_domain() {
        let addr = "nauta.cu";
        let provider = get_provider_by_domain(addr).unwrap();
        assert!(provider.status == Status::Ok);
        let server = &provider.server[0];
        assert_eq!(server.protocol, Protocol::Imap);
        assert_eq!(server.socket, Socket::Starttls);
        assert_eq!(server.hostname, "imap.nauta.cu");
        assert_eq!(server.port, 143);
        assert_eq!(server.username_pattern, UsernamePattern::Email);
        let server = &provider.server[1];
        assert_eq!(server.protocol, Protocol::Smtp);
        assert_eq!(server.socket, Socket::Starttls);
        assert_eq!(server.hostname, "smtp.nauta.cu");
        assert_eq!(server.port, 25);
        assert_eq!(server.username_pattern, UsernamePattern::Email);

        let provider = get_provider_by_domain("gmail.com").unwrap();
        assert!(provider.status == Status::Preparation);
        assert!(!provider.before_login_hint.is_empty());
        assert!(!provider.overview_page.is_empty());

        let provider = get_provider_by_domain("googlemail.com").unwrap();
        assert!(provider.status == Status::Preparation);
    }

    #[test]
    fn test_get_provider_by_id() {
        let provider = get_provider_by_id("gmail").unwrap();
        assert!(provider.id == "gmail");
    }

    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
    async fn test_get_provider_info() {
        let t = TestContext::new().await;
        assert!(get_provider_info(&t, "", false).await.is_none());
        assert!(get_provider_info(&t, "google.com", false).await.unwrap().id == "gmail");

        // get_provider_info() accepts email addresses for backwards compatibility
        assert!(
            get_provider_info(&t, "example@google.com", false)
                .await
                .unwrap()
                .id
                == "gmail"
        );
    }

    #[test]
    fn test_get_provider_update_timestamp() {
        let timestamp_past = NaiveDateTime::new(
            NaiveDate::from_ymd_opt(2020, 9, 9).unwrap(),
            NaiveTime::from_hms_opt(0, 0, 0).unwrap(),
        )
        .timestamp_millis()
            / 1_000;
        assert!(get_provider_update_timestamp() <= time());
        assert!(get_provider_update_timestamp() > timestamp_past);
    }

    #[test]
    fn test_get_resolver() -> Result<()> {
        assert!(get_resolver().is_ok());
        Ok(())
    }
}