chatmail-core/src/net/tls.rs

//! TLS support.

use anyhow::Result;
use async_native_tls::{Certificate, Protocol, TlsConnector, TlsStream};
use once_cell::sync::Lazy;
use tokio::io::{AsyncRead, AsyncWrite};

// this certificate is missing on older android devices (eg. lg with android6 from 2017)
// certificate downloaded from https://letsencrypt.org/certificates/
static LETSENCRYPT_ROOT: Lazy<Certificate> = Lazy::new(|| {
    Certificate::from_der(include_bytes!(
        "../../assets/root-certificates/letsencrypt/isrgrootx1.der"
    ))
    .unwrap()
});

pub fn build_tls(strict_tls: bool) -> TlsConnector {
    let tls_builder = TlsConnector::new()
        .min_protocol_version(Some(Protocol::Tlsv12))
        .add_root_certificate(LETSENCRYPT_ROOT.clone());

    if strict_tls {
        tls_builder
    } else {
        tls_builder
            .danger_accept_invalid_hostnames(true)
            .danger_accept_invalid_certs(true)
    }
}

pub async fn wrap_tls<T: AsyncRead + AsyncWrite + Unpin>(
    strict_tls: bool,
    hostname: &str,
    stream: T,
) -> Result<TlsStream<T>> {
    let tls = build_tls(strict_tls);
    let tls_stream = tls.connect(hostname, stream).await?;
    Ok(tls_stream)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_build_tls() {
        // we are using some additional root certificates.
        // make sure, they do not break construction of TlsConnector
        let _ = build_tls(true);
        let _ = build_tls(false);
    }
}