Merge commit '86cc97e55fe346502462284d2e636a2b3708163e' as 'Sources/OpenVPN3'

Sources/OpenVPN3/openvpn/ssl/is_openvpn_protocol.hpp

@@ -0,0 +1,58 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+//
+
+#ifndef OPENVPN_SSL_IS_OPENVPN_PROTOCOL_H
+#define OPENVPN_SSL_IS_OPENVPN_PROTOCOL_H
+
+#include <algorithm>                // for std::min
+
+#include <openvpn/common/size.hpp>  // for size_t
+
+namespace openvpn {
+
+  // Peek at the first few bytes of a session and
+  // distinguishing between OpenVPN or SSL protocols.
+  inline bool is_openvpn_protocol(const unsigned char *p, const size_t len)
+  {
+    const int CONTROL_HARD_RESET_CLIENT_V2 = 7;
+    const int CONTROL_HARD_RESET_CLIENT_V3 = 10;
+    const int OPCODE_SHIFT = 3;
+    const int MIN_INITIAL_PKT_SIZE = 14;
+
+    switch (std::min(len, size_t(3)))
+      {
+      case 3:
+	return p[0] == 0
+	  && p[1] >= MIN_INITIAL_PKT_SIZE
+	  && (p[2] == (CONTROL_HARD_RESET_CLIENT_V2 << OPCODE_SHIFT)
+	      || p[2] == (CONTROL_HARD_RESET_CLIENT_V3 << OPCODE_SHIFT));
+      case 2:
+	return p[0] == 0 && p[1] >= MIN_INITIAL_PKT_SIZE;
+      case 1:
+	return p[0] == 0;
+      default:
+	return true;
+      }
+  }
+
+}
+#endif