Enable session resumption

This implements `SSL_CTX_sess_set_cache_size`, `SSL_CTX_sess_get_cache_size` &
`SSL_CTX_set_session_id_context`.

TODO: need to implement `SSL_CTX_set_session_cache_mode`

rustls-libssl/MATRIX.md

@@ -179,7 +179,7 @@
 | `SSL_CTX_set_recv_max_early_data`  |  |  |  |
 | `SSL_CTX_set_security_callback`  |  |  |  |
 | `SSL_CTX_set_security_level`  |  |  |  |
-| `SSL_CTX_set_session_id_context`  |  | :white_check_mark: | :exclamation: [^stub] |
+| `SSL_CTX_set_session_id_context`  |  | :white_check_mark: | :white_check_mark: |
 | `SSL_CTX_set_session_ticket_cb`  |  |  |  |
 | `SSL_CTX_set_srp_cb_arg` [^deprecatedin_3_0] [^srp] |  |  |  |
 | `SSL_CTX_set_srp_client_pwd_callback` [^deprecatedin_3_0] [^srp] |  |  |  |
@@ -461,7 +461,7 @@
 | `SSL_set_security_callback`  |  |  |  |
 | `SSL_set_security_level`  |  |  |  |
 | `SSL_set_session`  | :white_check_mark: | :white_check_mark: | :exclamation: [^stub] |
-| `SSL_set_session_id_context`  |  |  | :exclamation: [^stub] |
+| `SSL_set_session_id_context`  |  |  |  |
 | `SSL_set_session_secret_cb`  |  |  |  |
 | `SSL_set_session_ticket_ext`  |  |  |  |
 | `SSL_set_session_ticket_ext_cb`  |  |  |  |

rustls-libssl/build.rs

@@ -174,7 +174,6 @@ const ENTRYPOINTS: &[&str] = &[
     "SSL_set_post_handshake_auth",
     "SSL_set_quiet_shutdown",
     "SSL_set_session",
-    "SSL_set_session_id_context",
     "SSL_set_shutdown",
     "SSL_set_SSL_CTX",
     "SSL_set_verify",

rustls-libssl/src/cache.rs

@@ -0,0 +1,79 @@
+use std::sync::Arc;
+
+use rustls::client::ClientSessionMemoryCache;
+use rustls::client::ClientSessionStore;
+use rustls::server::ServerSessionMemoryCache;
+use rustls::server::{ProducesTickets, StoresServerSessions};
+
+/// A container for session caches that can live inside
+/// an `SSL_CTX` but outlive a rustls `ServerConfig`/`ClientConfig`
+pub struct SessionCaches {
+    size: usize,
+    context: Vec<u8>,
+    client: Option<Arc<dyn ClientSessionStore + Send + Sync>>,
+    server: Option<Arc<dyn StoresServerSessions + Send + Sync>>,
+    ticketer: Option<Arc<dyn ProducesTickets>>,
+}
+
+impl SessionCaches {
+    pub fn with_size(size: usize) -> Self {
+        // a user who has one `SSL_CTX` for both clients and servers will end
+        // up with twice as many sessions as this, since rustls caches
+        // client and server sessions separately.
+        //
+        // the common case is to have those separate (it is, for example,
+        // impossible to configure certs/keys separately for client and
+        // servers in a given `SSL_CTX`) so this should be ok.
+        Self {
+            size,
+            context: vec![],
+            client: None,
+            server: None,
+            ticketer: None,
+        }
+    }
+
+    pub fn get_client(&mut self) -> Arc<dyn ClientSessionStore + Send + Sync> {
+        Arc::clone(
+            self.client
+                .get_or_insert_with(|| Arc::new(ClientSessionMemoryCache::new(self.size))),
+        )
+    }
+
+    pub fn get_server(&mut self) -> Arc<dyn StoresServerSessions + Send + Sync> {
+        Arc::clone(
+            self.server
+                .get_or_insert_with(|| ServerSessionMemoryCache::new(self.size)),
+        )
+    }
+
+    pub fn get_ticketer(&mut self) -> Arc<dyn ProducesTickets> {
+        Arc::clone(
+            self.ticketer
+                .get_or_insert_with(|| crate::provider::Ticketer::new().unwrap()),
+        )
+    }
+
+    pub fn set_context(&mut self, context: &[u8]) {
+        // This is a different behaviour to that described by `SSL_set_session_id_context()`:
+        // the context isn't bound to an individual session but instead is an epoch for
+        // the entire set of stored sessions & ticketer keying.
+        if context != self.context {
+            context.clone_into(&mut self.context);
+            self.client = None;
+            self.server = None;
+            self.ticketer = None;
+        }
+    }
+
+    pub fn size(&self) -> usize {
+        self.size
+    }
+}
+
+impl Default for SessionCaches {
+    fn default() -> Self {
+        // this is SSL_SESSION_CACHE_MAX_SIZE_DEFAULT
+        Self::with_size(1024 * 20)
+    }
+}

rustls-libssl/src/entry.rs

@@ -258,6 +258,14 @@ entry! {
                     inner.set_servername_callback_context(parg);
                     C_INT_SUCCESS as c_long
                 }
+                Ok(SslCtrl::SetSessCacheSize) => {
+                    if larg < 0 {
+                        return 0;
+                    }
+                    inner.set_session_cache_size(larg as usize);
+                    C_INT_SUCCESS as c_long
+                }
+                Ok(SslCtrl::GetSessCacheSize) => inner.get_session_cache_size() as c_long,
                 Err(()) => {
                     log::warn!("unimplemented _SSL_CTX_ctrl(..., {cmd}, {larg}, ...)");
                     0
@@ -763,6 +771,26 @@ entry! {
     }
 }
 
+entry! {
+    pub fn _SSL_CTX_set_session_id_context(
+        ctx: *mut SSL_CTX,
+        sid_ctx: *const c_uchar,
+        sid_ctx_len: c_uint,
+    ) -> c_int {
+        let ctx = try_clone_arc!(ctx);
+        let sid_ctx = try_slice!(sid_ctx, sid_ctx_len);
+
+        match ctx
+            .lock()
+            .map_err(|_| Error::cannot_lock())
+            .map(|mut ctx| ctx.set_session_id_context(sid_ctx))
+        {
+            Err(e) => e.raise().into(),
+            Ok(()) => C_INT_SUCCESS,
+        }
+    }
+}
+
 impl Castable for SSL_CTX {
     type Ownership = OwnershipArc;
     type RustType = Mutex<SSL_CTX>;
@@ -895,7 +923,10 @@ entry! {
                     C_INT_SUCCESS as i64
                 }
                 // not a defined operation in the OpenSSL API
-                Ok(SslCtrl::SetTlsExtServerNameCallback) | Ok(SslCtrl::SetTlsExtServerNameArg) => 0,
+                Ok(SslCtrl::SetTlsExtServerNameCallback)
+                | Ok(SslCtrl::SetTlsExtServerNameArg)
+                | Ok(SslCtrl::SetSessCacheSize)
+                | Ok(SslCtrl::GetSessCacheSize) => 0,
                 Err(()) => {
                     log::warn!("unimplemented _SSL_ctrl(..., {cmd}, {larg}, ...)");
                     0
@@ -1815,6 +1846,8 @@ num_enum! {
     enum SslCtrl {
         Mode = 33,
         SetMsgCallbackArg = 16,
+        SetSessCacheSize = 42,
+        GetSessCacheSize = 43,
         SetTlsExtServerNameCallback = 53,
         SetTlsExtServerNameArg = 54,
         SetTlsExtHostname = 55,
@@ -1897,23 +1930,6 @@ entry_stub! {
 pub type SSL_CTX_sess_remove_cb =
     Option<unsafe extern "C" fn(ctx: *mut SSL_CTX, sess: *mut SSL_SESSION)>;
 
-entry_stub! {
-    pub fn _SSL_CTX_set_session_id_context(
-        _ctx: *mut SSL_CTX,
-        _sid_ctx: *const c_uchar,
-        _sid_ctx_len: c_uint,
-    ) -> c_int;
-}
-
-entry_stub! {
-
-    pub fn _SSL_set_session_id_context(
-        _ssl: *mut SSL,
-        _sid_ctx: *const c_uchar,
-        _sid_ctx_len: c_uint,
-    ) -> c_int;
-}
-
 entry_stub! {
     pub fn _SSL_CTX_set_keylog_callback(_ctx: *mut SSL_CTX, _cb: SSL_CTX_keylog_cb_func);
 }

rustls-libssl/src/lib.rs

@@ -11,6 +11,7 @@ use openssl_sys::{
     EVP_PKEY, SSL_ERROR_NONE, SSL_ERROR_SSL, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE, X509,
     X509_STORE, X509_V_ERR_UNSPECIFIED,
 };
+use rustls::client::Resumption;
 use rustls::crypto::aws_lc_rs as provider;
 use rustls::pki_types::{CertificateDer, ServerName};
 use rustls::server::{Accepted, Acceptor};
@@ -20,6 +21,7 @@ use rustls::{
 };
 
 mod bio;
+mod cache;
 mod callbacks;
 #[macro_use]
 mod constants;
@@ -215,6 +217,7 @@ pub struct SslContext {
     method: &'static SslMethod,
     ex_data: ex_data::ExData,
     versions: EnabledVersions,
+    caches: cache::SessionCaches,
     raw_options: u64,
     verify_mode: VerifyMode,
     verify_depth: c_int,
@@ -236,6 +239,7 @@ impl SslContext {
             method,
             ex_data: ex_data::ExData::default(),
             versions: EnabledVersions::default(),
+            caches: cache::SessionCaches::default(),
             raw_options: 0,
             verify_mode: VerifyMode::default(),
             verify_depth: -1,
@@ -264,6 +268,11 @@ impl SslContext {
         self.ex_data.get(idx)
     }
 
+    fn option_is_set(&self, opt: SslOption) -> bool {
+        let mask = opt as u64;
+        self.raw_options & mask == mask
+    }
+
     fn get_options(&self) -> u64 {
         self.raw_options
     }
@@ -308,6 +317,19 @@ impl SslContext {
             .unwrap_or_default()
     }
 
+    fn get_session_cache_size(&self) -> usize {
+        self.caches.size()
+    }
+
+    fn set_session_cache_size(&mut self, size: usize) {
+        // divergence: OpenSSL can adjust the cache size without emptying it.
+        self.caches = cache::SessionCaches::with_size(size);
+    }
+
+    fn set_session_id_context(&mut self, context: &[u8]) {
+        self.caches.set_context(context);
+    }
+
     fn set_max_early_data(&mut self, max: u32) {
         self.max_early_data = max;
     }
@@ -748,11 +770,7 @@ impl Ssl {
             None => ServerName::try_from("0.0.0.0").unwrap(),
         };
 
-        let method = self
-            .ctx
-            .lock()
-            .map(|ctx| ctx.method)
-            .map_err(|_| error::Error::cannot_lock())?;
+        let mut ctx = self.ctx.lock().map_err(|_| error::Error::cannot_lock())?;
 
         let provider = Arc::new(provider::default_provider());
         let verifier = Arc::new(verifier::ServerVerifier::new(
@@ -762,7 +780,7 @@ impl Ssl {
             &self.verify_server_name,
         ));
 
-        let versions = self.versions.reduce_versions(method.client_versions)?;
+        let versions = self.versions.reduce_versions(ctx.method.client_versions)?;
 
         let wants_resolver = ClientConfig::builder_with_provider(provider)
             .with_protocol_versions(&versions)
@@ -777,6 +795,7 @@ impl Ssl {
         };
 
         config.alpn_protocols.clone_from(&self.alpn);
+        config.resumption = Resumption::store(ctx.caches.get_client());
 
         let client_conn = ClientConnection::new(Arc::new(config), sni_server_name.clone())
             .map_err(error::Error::from_rustls)?;
@@ -843,11 +862,7 @@ impl Ssl {
     }
 
     fn init_server_conn(&mut self) -> Result<(), error::Error> {
-        let method = self
-            .ctx
-            .lock()
-            .map(|ctx| ctx.method)
-            .map_err(|_| error::Error::cannot_lock())?;
+        let mut ctx = self.ctx.lock().map_err(|_| error::Error::cannot_lock())?;
 
         let provider = Arc::new(provider::default_provider());
         let verifier = Arc::new(
@@ -864,7 +879,7 @@ impl Ssl {
             .server_resolver()
             .ok_or_else(|| error::Error::bad_data("missing server keys"))?;
 
-        let versions = self.versions.reduce_versions(method.server_versions)?;
+        let versions = self.versions.reduce_versions(ctx.method.server_versions)?;
 
         let mut config = ServerConfig::builder_with_provider(provider)
             .with_protocol_versions(&versions)
@@ -874,6 +889,10 @@ impl Ssl {
 
         config.alpn_protocols = mem::take(&mut self.alpn);
         config.max_early_data_size = self.max_early_data;
+        config.session_storage = ctx.caches.get_server();
+        if !ctx.option_is_set(SslOption::NoTicket) {
+            config.ticketer = ctx.caches.get_ticketer();
+        }
 
         let accepted = match mem::replace(&mut self.conn, ConnState::Nothing) {
             ConnState::Accepted(accepted) => accepted,
@@ -1380,6 +1399,12 @@ impl EnabledVersions {
     }
 }
 
+/// Subset of SSL_OP values that we interpret.
+#[repr(u64)]
+enum SslOption {
+    NoTicket = 1 << 14,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;