deltachat/net/
tls.rs

1//! TLS support.
2use parking_lot::Mutex;
3use std::collections::HashMap;
4use std::sync::Arc;
5
6use anyhow::Result;
7
8use crate::net::session::SessionStream;
9
10use tokio_rustls::rustls::client::ClientSessionStore;
11
12pub async fn wrap_tls<'a>(
13    strict_tls: bool,
14    hostname: &str,
15    port: u16,
16    use_sni: bool,
17    alpn: &str,
18    stream: impl SessionStream + 'static,
19    tls_session_store: &TlsSessionStore,
20) -> Result<impl SessionStream + 'a> {
21    if strict_tls {
22        let tls_stream =
23            wrap_rustls(hostname, port, use_sni, alpn, stream, tls_session_store).await?;
24        let boxed_stream: Box<dyn SessionStream> = Box::new(tls_stream);
25        Ok(boxed_stream)
26    } else {
27        // We use native_tls because it accepts 1024-bit RSA keys.
28        // Rustls does not support them even if
29        // certificate checks are disabled: <https://github.com/rustls/rustls/issues/234>.
30        let alpns = if alpn.is_empty() {
31            Box::from([])
32        } else {
33            Box::from([alpn])
34        };
35        let tls = async_native_tls::TlsConnector::new()
36            .min_protocol_version(Some(async_native_tls::Protocol::Tlsv12))
37            .use_sni(use_sni)
38            .request_alpns(&alpns)
39            .danger_accept_invalid_hostnames(true)
40            .danger_accept_invalid_certs(true);
41        let tls_stream = tls.connect(hostname, stream).await?;
42        let boxed_stream: Box<dyn SessionStream> = Box::new(tls_stream);
43        Ok(boxed_stream)
44    }
45}
46
47/// Map to store TLS session tickets.
48///
49/// Tickets are separated by port and ALPN
50/// to avoid trying to use Postfix ticket for Dovecot and vice versa.
51/// Doing so would not be a security issue,
52/// but wastes the ticket and the opportunity to resume TLS session unnecessarily.
53/// Rustls takes care of separating tickets that belong to different domain names.
54#[derive(Debug)]
55pub(crate) struct TlsSessionStore {
56    sessions: Mutex<HashMap<(u16, String), Arc<dyn ClientSessionStore>>>,
57}
58
59// This is the default for TLS session store
60// as of Rustls version 0.23.16,
61// but we want to create multiple caches
62// to separate them by port and ALPN.
63const TLS_CACHE_SIZE: usize = 256;
64
65impl TlsSessionStore {
66    /// Creates a new TLS session store.
67    ///
68    /// One such store should be created per profile
69    /// to keep TLS sessions independent.
70    pub fn new() -> Self {
71        Self {
72            sessions: Default::default(),
73        }
74    }
75
76    /// Returns session store for given port and ALPN.
77    ///
78    /// Rustls additionally separates sessions by hostname.
79    pub fn get(&self, port: u16, alpn: &str) -> Arc<dyn ClientSessionStore> {
80        Arc::clone(
81            self.sessions
82                .lock()
83                .entry((port, alpn.to_string()))
84                .or_insert_with(|| {
85                    Arc::new(tokio_rustls::rustls::client::ClientSessionMemoryCache::new(
86                        TLS_CACHE_SIZE,
87                    ))
88                }),
89        )
90    }
91}
92
93pub async fn wrap_rustls<'a>(
94    hostname: &str,
95    port: u16,
96    use_sni: bool,
97    alpn: &str,
98    stream: impl SessionStream + 'a,
99    tls_session_store: &TlsSessionStore,
100) -> Result<impl SessionStream + 'a> {
101    let mut root_cert_store = tokio_rustls::rustls::RootCertStore::empty();
102    root_cert_store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
103
104    let mut config = tokio_rustls::rustls::ClientConfig::builder()
105        .with_root_certificates(root_cert_store)
106        .with_no_client_auth();
107    config.alpn_protocols = if alpn.is_empty() {
108        vec![]
109    } else {
110        vec![alpn.as_bytes().to_vec()]
111    };
112
113    // Enable TLS 1.3 session resumption
114    // as defined in <https://www.rfc-editor.org/rfc/rfc8446#section-2.2>.
115    //
116    // Obsolete TLS 1.2 mechanisms defined in RFC 5246
117    // and RFC 5077 have worse security
118    // and are not worth increasing
119    // attack surface: <https://words.filippo.io/we-need-to-talk-about-session-tickets/>.
120    let resumption_store = tls_session_store.get(port, alpn);
121    let resumption = tokio_rustls::rustls::client::Resumption::store(resumption_store)
122        .tls12_resumption(tokio_rustls::rustls::client::Tls12Resumption::Disabled);
123    config.resumption = resumption;
124    config.enable_sni = use_sni;
125
126    let tls = tokio_rustls::TlsConnector::from(Arc::new(config));
127    let name = rustls_pki_types::ServerName::try_from(hostname)?.to_owned();
128    let tls_stream = tls.connect(name, stream).await?;
129    Ok(tls_stream)
130}
deltachat/net/tls.rs

deltachat/net/
tls.rs
