vtls: Only call add/getsession if session id is enabled

Prior to this change we called Curl_ssl_getsessionid and
Curl_ssl_addsessionid regardless of whether session ID reusing was
enabled. According to comments that is in case session ID reuse was
disabled but then later enabled.

The old way was not intuitive and probably not something users expected.
When a user disables session ID caching I'd guess they don't expect the
session ID to be cached anyway in case the caching is later enabled.

1 files changed, 39 insertions, 32 deletions

diff --git a/lib/vtls/cyassl.c b/lib/vtls/cyassl.c
index c189af772..96d025746 100644
--- a/lib/vtls/cyassl.c
+++ b/lib/vtls/cyassl.c
@@ -137,7 +137,6 @@ cyassl_connect_step1(struct connectdata *conn,
   struct SessionHandle *data = conn->data;
   struct ssl_connect_data* conssl = &conn->ssl[sockindex];
   SSL_METHOD* req_method = NULL;
-  void* ssl_sessionid = NULL;
   curl_socket_t sockfd = conn->sock[sockindex];
 #ifdef HAVE_SNI
   bool sni = FALSE;
@@ -378,19 +377,24 @@ cyassl_connect_step1(struct connectdata *conn,
 #endif /* HAVE_ALPN */
 
   /* Check if there's a cached ID we can/should use here! */
-  Curl_ssl_sessionid_lock(conn);
-  if(!Curl_ssl_getsessionid(conn, &ssl_sessionid, NULL)) {
-    /* we got a session id, use it! */
-    if(!SSL_set_session(conssl->handle, ssl_sessionid)) {
-      Curl_ssl_sessionid_unlock(conn);
-      failf(data, "SSL: SSL_set_session failed: %s",
-            ERR_error_string(SSL_get_error(conssl->handle, 0), error_buffer));
-      return CURLE_SSL_CONNECT_ERROR;
+  if(conn->ssl_config.sessionid) {
+    void *ssl_sessionid = NULL;
+
+    Curl_ssl_sessionid_lock(conn);
+    if(!Curl_ssl_getsessionid(conn, &ssl_sessionid, NULL)) {
+      /* we got a session id, use it! */
+      if(!SSL_set_session(conssl->handle, ssl_sessionid)) {
+        Curl_ssl_sessionid_unlock(conn);
+        failf(data, "SSL: SSL_set_session failed: %s",
+              ERR_error_string(SSL_get_error(conssl->handle, 0),
+              error_buffer));
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+      /* Informational message */
+      infof (data, "SSL re-using session ID\n");
     }
-    /* Informational message */
-    infof (data, "SSL re-using session ID\n");
+    Curl_ssl_sessionid_unlock(conn);
   }
-  Curl_ssl_sessionid_unlock(conn);
 
   /* pass the raw socket into the SSL layer */
   if(!SSL_set_fd(conssl->handle, (int)sockfd)) {
@@ -574,36 +578,39 @@ cyassl_connect_step3(struct connectdata *conn,
                      int sockindex)
 {
   CURLcode result = CURLE_OK;
-  void *old_ssl_sessionid=NULL;
   struct SessionHandle *data = conn->data;
   struct ssl_connect_data *connssl = &conn->ssl[sockindex];
-  bool incache;
-  SSL_SESSION *our_ssl_sessionid;
 
   DEBUGASSERT(ssl_connect_3 == connssl->connecting_state);
 
-  our_ssl_sessionid = SSL_get_session(connssl->handle);
+  if(conn->ssl_config.sessionid) {
+    bool incache;
+    SSL_SESSION *our_ssl_sessionid;
+    void *old_ssl_sessionid = NULL;
 
-  Curl_ssl_sessionid_lock(conn);
-  incache = !(Curl_ssl_getsessionid(conn, &old_ssl_sessionid, NULL));
-  if(incache) {
-    if(old_ssl_sessionid != our_ssl_sessionid) {
-      infof(data, "old SSL session ID is stale, removing\n");
-      Curl_ssl_delsessionid(conn, old_ssl_sessionid);
-      incache = FALSE;
+    our_ssl_sessionid = SSL_get_session(connssl->handle);
+
+    Curl_ssl_sessionid_lock(conn);
+    incache = !(Curl_ssl_getsessionid(conn, &old_ssl_sessionid, NULL));
+    if(incache) {
+      if(old_ssl_sessionid != our_ssl_sessionid) {
+        infof(data, "old SSL session ID is stale, removing\n");
+        Curl_ssl_delsessionid(conn, old_ssl_sessionid);
+        incache = FALSE;
+      }
     }
-  }
 
-  if(!incache) {
-    result = Curl_ssl_addsessionid(conn, our_ssl_sessionid,
-                                   0 /* unknown size */);
-    if(result) {
-      Curl_ssl_sessionid_unlock(conn);
-      failf(data, "failed to store ssl session");
-      return result;
+    if(!incache) {
+      result = Curl_ssl_addsessionid(conn, our_ssl_sessionid,
+                                     0 /* unknown size */);
+      if(result) {
+        Curl_ssl_sessionid_unlock(conn);
+        failf(data, "failed to store ssl session");
+        return result;
+      }
     }
+    Curl_ssl_sessionid_unlock(conn);
   }
-  Curl_ssl_sessionid_unlock(conn);
 
   connssl->connecting_state = ssl_connect_done;