From 1e2fbec50017f68f3cde7881de40322659ab5353 Mon Sep 17 00:00:00 2001
From: Joseph Birr-Pixton <jpixton@gmail.com>
Date: Wed, 17 Apr 2024 10:57:53 +0100
Subject: [PATCH] Implement `SSL_session_reused`

---
 rustls-libssl/MATRIX.md    |  2 +-
 rustls-libssl/src/entry.rs | 14 ++++++++++----
 rustls-libssl/src/lib.rs   | 11 +++++++++--
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/rustls-libssl/MATRIX.md b/rustls-libssl/MATRIX.md
index ae23b7d..1c14d76 100644
--- a/rustls-libssl/MATRIX.md
+++ b/rustls-libssl/MATRIX.md
@@ -410,7 +410,7 @@
 | `SSL_rstate_string_long`  |  |  |  |
 | `SSL_select_next_proto`  |  | :white_check_mark: | :white_check_mark: |
 | `SSL_sendfile`  |  |  |  |
-| `SSL_session_reused`  |  | :white_check_mark: | :exclamation: [^stub] |
+| `SSL_session_reused`  |  | :white_check_mark: | :white_check_mark: |
 | `SSL_set0_CA_list`  |  |  |  |
 | `SSL_set0_rbio`  |  |  | :white_check_mark: |
 | `SSL_set0_security_ex_data`  |  |  |  |
diff --git a/rustls-libssl/src/entry.rs b/rustls-libssl/src/entry.rs
index 5bdfaf2..a49c852 100644
--- a/rustls-libssl/src/entry.rs
+++ b/rustls-libssl/src/entry.rs
@@ -1633,6 +1633,16 @@ entry! {
     }
 }
 
+entry! {
+    pub fn _SSL_session_reused(ssl: *const SSL) -> c_int {
+        let ssl = try_clone_arc!(ssl);
+        ssl.lock()
+            .ok()
+            .map(|ssl| ssl.was_session_reused() as c_int)
+            .unwrap_or_default()
+    }
+}
+
 impl Castable for SSL {
     type Ownership = OwnershipArc;
     type RustType = Mutex<SSL>;
@@ -1891,10 +1901,6 @@ entry_stub! {
     pub fn _SSL_set_session(_ssl: *mut SSL, _session: *mut SSL_SESSION) -> c_int;
 }
 
-entry_stub! {
-    pub fn _SSL_session_reused(_ssl: *const SSL) -> c_int;
-}
-
 entry_stub! {
     pub fn _SSL_get1_session(_ssl: *mut SSL) -> *mut SSL_SESSION;
 }
diff --git a/rustls-libssl/src/lib.rs b/rustls-libssl/src/lib.rs
index 4eb3c95..fca936a 100644
--- a/rustls-libssl/src/lib.rs
+++ b/rustls-libssl/src/lib.rs
@@ -16,8 +16,8 @@ use rustls::crypto::aws_lc_rs as provider;
 use rustls::pki_types::{CertificateDer, ServerName};
 use rustls::server::{Accepted, Acceptor};
 use rustls::{
-    CipherSuite, ClientConfig, ClientConnection, Connection, ProtocolVersion, RootCertStore,
-    ServerConfig,
+    CipherSuite, ClientConfig, ClientConnection, Connection, HandshakeKind, ProtocolVersion,
+    RootCertStore, ServerConfig,
 };
 
 mod bio;
@@ -1216,6 +1216,13 @@ impl Ssl {
             None => HandshakeState::Before,
         }
     }
+
+    fn was_session_reused(&self) -> bool {
+        match self.conn() {
+            Some(conn) => conn.handshake_kind() == Some(HandshakeKind::Resumed),
+            None => false,
+        }
+    }
 }
 
 /// This is a reduced-fidelity version of `OSSL_HANDSHAKE_STATE`.