Bug 2210: TLS session resumption is not working for subsequent FTP data connections with TLS 1.3 with some servers

https://winscp.net/tracker/2210

Undoes related and obsolete Bug 2018

Source commit: 8ebb50c550bc2b7c93e2aa552deb3bf3f036ce98

source/filezilla/AsyncSslSocketLayer.cpp

@@ -53,11 +53,13 @@ CAsyncSslSocketLayer::CAsyncSslSocketLayer()
   m_onCloseCalled = false;
   m_Main = NULL;
   m_sessionid = NULL;
+  m_sessionidSerialized = NULL;
   m_sessionreuse = true;
   m_sessionreuse_failed = false;
 
   FCertificate = NULL;
   FPrivateKey = NULL;
+  m_CriticalSection.reset(new  TCriticalSection());
 }
 
 CAsyncSslSocketLayer::~CAsyncSslSocketLayer()
@@ -627,6 +629,28 @@ BOOL CAsyncSslSocketLayer::Connect(LPCTSTR lpszHostAddress, UINT nHostPort)
   return res;
 }
 
+void CAsyncSslSocketLayer::SetSession(SSL_SESSION * Session)
+{
+  TGuard Guard(m_CriticalSection.get());
+  if (m_sessionid != NULL)
+  {
+    SSL_SESSION_free(m_sessionid);
+  }
+  if (m_sessionidSerialized != NULL)
+  {
+    delete[] m_sessionidSerialized;
+    m_sessionidSerialized = NULL;
+  }
+  m_sessionid = Session;
+  if (m_sessionid != NULL)
+  {
+    m_sessionidSerializedLen = i2d_SSL_SESSION(m_sessionid, NULL);
+    m_sessionidSerialized = new unsigned char[m_sessionidSerializedLen];
+    unsigned char * P = m_sessionidSerialized;
+    i2d_SSL_SESSION(m_sessionid, &P);
+  }
+}
+
 bool CAsyncSslSocketLayer::HandleSession(SSL_SESSION * Session)
 {
   bool Result = false;
@@ -648,30 +672,22 @@ bool CAsyncSslSocketLayer::HandleSession(SSL_SESSION * Session)
             m_Main->m_sessionreuse_failed = true;
           }
         }
-        LogSocketMessageRaw(FZ_LOG_DEBUG, L"Saving session ID");
       }
       else
       {
-        SSL_SESSION_free(m_sessionid);
         LogSocketMessageRaw(FZ_LOG_INFO, L"Session ID changed");
       }
-      m_sessionid = Session;
-      // Some TLS 1.3 servers require reuse of the session of the previous data connection, not of the main session.
-      // It seems that it's safe to do this even for older TLS versions, but let's not for now.
-      // Once we do, we can simply always use main session's m_sessionid field in the code above.
-      if ((SSL_version(m_ssl) >= TLS1_3_VERSION) && (m_Main != NULL))
+
+      if (m_Main == NULL)
+      {
+        LogSocketMessageRaw(FZ_LOG_INFO, L"Saving session ID");
+        SetSession(Session);
+        Result = true;
+      }
+      else
       {
-        if (m_Main->m_sessionid != NULL)
-        {
-          SSL_SESSION_free(m_Main->m_sessionid);
-        }
-        m_Main->m_sessionid = Session;
-        if (Session != NULL)
-        {
-          SSL_SESSION_up_ref(Session);
-        }
+        m_sessionid = Session;
       }
-      Result = true;
     }
   }
   return Result;
@@ -814,14 +830,22 @@ int CAsyncSslSocketLayer::InitSSLConnection(bool clientMode,
   m_sessionreuse = sessionreuse;
   if ((m_Main != NULL) && m_sessionreuse)
   {
-    if (m_Main->m_sessionid == NULL)
+    TGuard Guard(m_Main->m_CriticalSection.get());
+    if (m_Main->m_sessionidSerialized == NULL)
     {
       DebugFail();
       SSL_set_session(m_ssl, NULL);
     }
     else if (!m_Main->m_sessionreuse_failed)
     {
-      if (!SSL_set_session(m_ssl, m_Main->m_sessionid))
+      // This is what Python SSL module does, instead of directly using SSL_SESSION of the other session,
+      // claiming a bug in OpenSSL 1.1.1 and newer. See PySSL_get_session/PySSL_set_session.
+      // OpenSSL refutes this as a bug in Python session handling.
+      // https://github.com/openssl/openssl/issues/1550
+      // But it works for us too.
+      const unsigned char * P = m_Main->m_sessionidSerialized;
+      SSL_SESSION * Session = DebugNotNull(d2i_SSL_SESSION(NULL, &P, m_Main->m_sessionidSerializedLen));
+      if (!SSL_set_session(m_ssl, Session))
       {
         LogSocketMessageRaw(FZ_LOG_INFO, L"SSL_set_session failed");
         return SSL_FAILURE_INITSSL;
@@ -943,11 +967,7 @@ void CAsyncSslSocketLayer::ResetSslSession()
       cur = cur->pNext;
     }
 
-  if (m_sessionid != NULL)
-  {
-    SSL_SESSION_free(m_sessionid);
-    m_sessionid = NULL;
-  }
+  SetSession(NULL);
   m_sessionreuse = true;
   m_sessionreuse_failed = false;
 
@@ -1195,13 +1215,11 @@ void CAsyncSslSocketLayer::apps_ssl_info_callback(const SSL *s, int where, int r
   {
     // For 1.2 and older, session is always established at this point.
     // For 1.3, session can be restarted later, so this is handled in NewSessionCallback.
-    if (SSL_version(pLayer->m_ssl) < TLS1_3_VERSION)
+    // But at least with Cerberus server, it is not, so if we want to have "reuse" logged, we need to do it here.
+    SSL_SESSION * sessionid = SSL_get1_session(pLayer->m_ssl);
+    if (!pLayer->HandleSession(sessionid))
     {
-      SSL_SESSION * sessionid = SSL_get1_session(pLayer->m_ssl);
-      if (!pLayer->HandleSession(sessionid))
-      {
-        SSL_SESSION_free(sessionid);
-      }
+      SSL_SESSION_free(sessionid);
     }
     int error = SSL_get_verify_result(pLayer->m_ssl);
     pLayer->DoLayerCallback(LAYERCALLBACK_LAYERSPECIFIC, SSL_VERIFY_CERT, error);

source/filezilla/AsyncSslSocketLayer.h

@@ -158,6 +158,7 @@ private:
   BOOL ShutDownComplete();
   int InitSSL();
   void PrintLastErrorMsg();
+  void SetSession(SSL_SESSION * Session);
   bool HandleSession(SSL_SESSION * Session);
   int ProcessSendBuffer();
 
@@ -176,6 +177,7 @@ private:
 
   // Critical section for thread synchronization
   static std::unique_ptr<TCriticalSection> m_sCriticalSection;
+  std::unique_ptr<TCriticalSection> m_CriticalSection;
 
   // Status variables
   static bool m_bSslInitialized;
@@ -198,6 +200,8 @@ private:
   SSL_CTX* m_ssl_ctx;  // SSL context
   SSL* m_ssl;      // current session handle
   SSL_SESSION * m_sessionid;
+  int m_sessionidSerializedLen;
+  unsigned char * m_sessionidSerialized;
   bool m_sessionreuse;
   bool m_sessionreuse_failed;
   CAsyncSslSocketLayer * m_Main;