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;
9use crate::sql::Sql;
10use crate::tools::time;
11
12use tokio_rustls::rustls;
13use tokio_rustls::rustls::client::ClientSessionStore;
14use tokio_rustls::rustls::server::ParsedCertificate;
15
16mod danger;
17use danger::CustomCertificateVerifier;
18
19mod spki;
20pub use spki::SpkiHashStore;
21
22#[expect(clippy::too_many_arguments)]
23pub async fn wrap_tls<'a>(
24    strict_tls: bool,
25    hostname: &str,
26    port: u16,
27    use_sni: bool,
28    alpn: &str,
29    stream: impl SessionStream + 'static,
30    tls_session_store: &TlsSessionStore,
31    spki_hash_store: &SpkiHashStore,
32    sql: &Sql,
33) -> Result<impl SessionStream + 'a> {
34    if strict_tls {
35        let tls_stream = wrap_rustls(
36            hostname,
37            port,
38            use_sni,
39            alpn,
40            stream,
41            tls_session_store,
42            spki_hash_store,
43            sql,
44        )
45        .await?;
46        let boxed_stream: Box<dyn SessionStream> = Box::new(tls_stream);
47        Ok(boxed_stream)
48    } else {
49        // We use native_tls because it accepts 1024-bit RSA keys.
50        // Rustls does not support them even if
51        // certificate checks are disabled: <https://github.com/rustls/rustls/issues/234>.
52        let alpns = if alpn.is_empty() {
53            Box::from([])
54        } else {
55            Box::from([alpn])
56        };
57        let tls = async_native_tls::TlsConnector::new()
58            .min_protocol_version(Some(async_native_tls::Protocol::Tlsv12))
59            .use_sni(use_sni)
60            .request_alpns(&alpns)
61            .danger_accept_invalid_hostnames(true)
62            .danger_accept_invalid_certs(true);
63        let tls_stream = tls.connect(hostname, stream).await?;
64        let boxed_stream: Box<dyn SessionStream> = Box::new(tls_stream);
65        Ok(boxed_stream)
66    }
67}
68
69/// Map to store TLS session tickets.
70///
71/// Tickets are separated by port and ALPN
72/// to avoid trying to use Postfix ticket for Dovecot and vice versa.
73/// Doing so would not be a security issue,
74/// but wastes the ticket and the opportunity to resume TLS session unnecessarily.
75/// Rustls takes care of separating tickets that belong to different domain names.
76#[derive(Debug)]
77pub(crate) struct TlsSessionStore {
78    sessions: Mutex<HashMap<(u16, String), Arc<dyn ClientSessionStore>>>,
79}
80
81// This is the default for TLS session store
82// as of Rustls version 0.23.16,
83// but we want to create multiple caches
84// to separate them by port and ALPN.
85const TLS_CACHE_SIZE: usize = 256;
86
87impl TlsSessionStore {
88    /// Creates a new TLS session store.
89    ///
90    /// One such store should be created per profile
91    /// to keep TLS sessions independent.
92    pub fn new() -> Self {
93        Self {
94            sessions: Default::default(),
95        }
96    }
97
98    /// Returns session store for given port and ALPN.
99    ///
100    /// Rustls additionally separates sessions by hostname.
101    pub fn get(&self, port: u16, alpn: &str) -> Arc<dyn ClientSessionStore> {
102        Arc::clone(
103            self.sessions
104                .lock()
105                .entry((port, alpn.to_string()))
106                .or_insert_with(|| {
107                    Arc::new(rustls::client::ClientSessionMemoryCache::new(
108                        TLS_CACHE_SIZE,
109                    ))
110                }),
111        )
112    }
113}
114
115#[expect(clippy::too_many_arguments)]
116pub async fn wrap_rustls<'a>(
117    hostname: &str,
118    port: u16,
119    use_sni: bool,
120    alpn: &str,
121    stream: impl SessionStream + 'a,
122    tls_session_store: &TlsSessionStore,
123    spki_hash_store: &SpkiHashStore,
124    sql: &Sql,
125) -> Result<impl SessionStream + 'a> {
126    let root_cert_store =
127        rustls::RootCertStore::from_iter(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
128
129    let mut config = rustls::ClientConfig::builder()
130        .with_root_certificates(root_cert_store)
131        .with_no_client_auth();
132    config.alpn_protocols = if alpn.is_empty() {
133        vec![]
134    } else {
135        vec![alpn.as_bytes().to_vec()]
136    };
137
138    // Enable TLS 1.3 session resumption
139    // as defined in <https://www.rfc-editor.org/rfc/rfc8446#section-2.2>.
140    //
141    // Obsolete TLS 1.2 mechanisms defined in RFC 5246
142    // and RFC 5077 have worse security
143    // and are not worth increasing
144    // attack surface: <https://words.filippo.io/we-need-to-talk-about-session-tickets/>.
145    let resumption_store = tls_session_store.get(port, alpn);
146    let resumption = rustls::client::Resumption::store(resumption_store)
147        .tls12_resumption(rustls::client::Tls12Resumption::Disabled);
148    config.resumption = resumption;
149    config.enable_sni = use_sni;
150
151    config
152        .dangerous()
153        .set_certificate_verifier(Arc::new(CustomCertificateVerifier::new(
154            spki_hash_store.get_spki_hash(hostname, sql).await?,
155        )));
156
157    let tls = tokio_rustls::TlsConnector::from(Arc::new(config));
158    let name = tokio_rustls::rustls::pki_types::ServerName::try_from(hostname)?.to_owned();
159    let tls_stream = tls.connect(name, stream).await?;
160
161    // Successfully connected.
162    // Remember SPKI hash to accept it later if certificate expires.
163    let (_io, client_connection) = tls_stream.get_ref();
164    if let Some(end_entity) = client_connection
165        .peer_certificates()
166        .and_then(|certs| certs.first())
167    {
168        let now = time();
169        let parsed_certificate = ParsedCertificate::try_from(end_entity)?;
170        let spki = parsed_certificate.subject_public_key_info();
171        spki_hash_store.save_spki(hostname, &spki, sql, now).await?;
172    }
173
174    Ok(tls_stream)
175}
deltachat/net/tls.rs

deltachat/net/
tls.rs
