Disable all TLS session tickets

OpenSSL supports two types of session tickets for TLSv1.3, stateless
and stateful. The option we've used only turns off stateless tickets
leaving stateful tickets active. Use the new API introduced in 1.1.1
to disable all types of tickets.

Backpatch to all supported versions.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reported-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20240617173803.6alnafnxpiqvlh3g@awork3.anarazel.de
Backpatch-through: v12

4 files changed, 22 insertions, 6 deletions

diff --git a/configure b/configure
index a13348f3d71..1f8d2a2faef 100755
--- a/configure
+++ b/configure
@@ -13310,12 +13310,13 @@ fi
 done
 
   # Function introduced in OpenSSL 1.1.1.
-  for ac_func in X509_get_signature_info
+  for ac_func in X509_get_signature_info SSL_CTX_set_num_tickets
 do :
-  ac_fn_c_check_func "$LINENO" "X509_get_signature_info" "ac_cv_func_X509_get_signature_info"
-if test "x$ac_cv_func_X509_get_signature_info" = xyes; then :
+  as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
+ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
+if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
   cat >>confdefs.h <<_ACEOF
-#define HAVE_X509_GET_SIGNATURE_INFO 1
+#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
 _ACEOF
 
 fi
diff --git a/configure.ac b/configure.ac
index e41a15253ae..f98209bddc5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1359,7 +1359,7 @@ if test "$with_ssl" = openssl ; then
   # function was removed.
   AC_CHECK_FUNCS([CRYPTO_lock])
   # Function introduced in OpenSSL 1.1.1.
-  AC_CHECK_FUNCS([X509_get_signature_info])
+  AC_CHECK_FUNCS([X509_get_signature_info SSL_CTX_set_num_tickets])
   AC_DEFINE([USE_OPENSSL], 1, [Define to 1 to build with OpenSSL support. (--with-ssl=openssl)])
 elif test "$with_ssl" != no ; then
   AC_MSG_ERROR([--with-ssl must specify openssl])
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 4c7e16ca2ca..ef1b65b443b 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -249,8 +249,20 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/* disallow SSL session tickets */
+	/*
+	 * Disallow SSL session tickets. OpenSSL use both stateful and stateless
+	 * tickets for TLSv1.3, and stateless ticket for TLSv1.2. SSL_OP_NO_TICKET
+	 * is available since 0.9.8f but only turns off stateless tickets. In
+	 * order to turn off stateful tickets we need SSL_CTX_set_num_tickets,
+	 * which is available since OpenSSL 1.1.1. LibreSSL 3.5.4 (from OpenBSD
+	 * 7.1) introduced this API for compatibility, but doesn't support session
+	 * tickets at all so it's a no-op there.
+	 */
+#ifdef HAVE_SSL_CTX_SET_NUM_TICKETS
+	SSL_CTX_set_num_tickets(context, 0);
+#else
 	SSL_CTX_set_options(context, SSL_OP_NO_TICKET);
+#endif
 
 	/* disallow SSL session caching, too */
 	SSL_CTX_set_session_cache_mode(context, SSL_SESS_CACHE_OFF);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 768e3d719c1..e787d2dec2d 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -721,6 +721,9 @@
 /* Define to 1 if you have the `X509_get_signature_nid' function. */
 #undef HAVE_X509_GET_SIGNATURE_NID
 
+/* Define to 1 if you have the `SSL_CTX_set_num_tickets' function. */
+#undef HAVE_SSL_CTX_SET_NUM_TICKETS
+
 /* Define to 1 if the assembler supports X86_64's POPCNTQ instruction. */
 #undef HAVE_X86_64_POPCNTQ