diff options
Diffstat (limited to 'openvpn/doc/doxygen/doc_protocol_overview.h')
| -rw-r--r-- | openvpn/doc/doxygen/doc_protocol_overview.h | 199 |
1 files changed, 0 insertions, 199 deletions
diff --git a/openvpn/doc/doxygen/doc_protocol_overview.h b/openvpn/doc/doxygen/doc_protocol_overview.h deleted file mode 100644 index 26fed331..00000000 --- a/openvpn/doc/doxygen/doc_protocol_overview.h +++ /dev/null @@ -1,199 +0,0 @@ -/* - * OpenVPN -- An application to securely tunnel IP networks - * over a single TCP/UDP port, with support for SSL/TLS-based - * session authentication and key exchange, - * packet encryption, packet authentication, and - * packet compression. - * - * Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com> - * - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 - * 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 General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program (see the file COPYING included with this - * distribution); if not, write to the Free Software Foundation, Inc., - * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA - */ - -/** - * @file Network protocol overview documentation file. - */ - -/** - * @page network_protocol OpenVPN's network protocol - * - * Description of packet structure in OpenVPN's network protocol. - * - * This document describes the structure of packets exchanged between - * OpenVPN peers. It is based on the protocol description in the \c ssl.h - * file. - * - * @section network_protocol_external Outer structure of packets exchanged between OpenVPN peers - * - * VPN tunnel packets are transported between OpenVPN peers using the UDP - * or TCP protocols. Their structure is described below. - * - * @subsection network_protocol_external_structure External packet structure - * - * - packet length (16 bits, unsigned) [TCP-mode only]: always sent as - * plain text. Since TCP is a stream protocol, this packet length - * defines the packetization of the stream. - * - packet opcode and key_id (8 bits) [TLS-mode only]: - * - package message type (high 5 bits) - * - key_id (low 3 bits): the key_id refers to an already negotiated - * TLS session. OpenVPN seamlessly renegotiates the TLS session by - * using a new key_id for the new session. Overlap (controlled by - * user definable parameters) between old and new TLS sessions is - * allowed, providing a seamless transition during tunnel operation. - * - payload (n bytes) - * - * @subsection network_protocol_external_types Message types - * - * The type of a VPN tunnel packet is indicated by its opcode. The - * following describes the various opcodes available. - * - * - Control channel messages: - * - \c P_CONTROL_HARD_RESET_CLIENT_V1 -- %Key method 1, initial %key - * from client, forget previous state. - * - \c P_CONTROL_HARD_RESET_SERVER_V1 -- %Key method 1, initial %key - * from server, forget previous state. - * - \c P_CONTROL_HARD_RESET_CLIENT_V2 -- %Key method 2, initial %key - * from client, forget previous state. - * - \c P_CONTROL_HARD_RESET_SERVER_V2 -- %Key method 2, initial %key - * from server, forget previous state. - * - \c P_CONTROL_SOFT_RESET_V1 -- New %key, with a graceful - * transition from old to new %key in the sense that a transition - * window exists where both the old or new key_id can be used. - * - \c P_CONTROL_V1 -- Control channel packet (usually TLS - * ciphertext). - * - \c P_ACK_V1 -- Acknowledgement for control channel packets - * received. - * - Data channel messages: - * - \c P_DATA_V1 -- Data channel packet containing data channel - * ciphertext. - * - * @subsection network_protocol_external_key_id Session IDs and Key IDs - * - * OpenVPN uses two different forms of packet identifiers: - * - The first form is 64 bits and is used for all control channel - * messages. This form is referred to as a \c session_id. - * - Data channel messages on the other hand use a shortened form of 3 - * bits for efficiency reasons since the vast majority of OpenVPN - * packets in an active tunnel will be data channel messages. This - * form is referred to as a \c key_id. - * - * The control and data channels use independent packet-id sequences, - * because the data channel is an unreliable channel while the control - * channel is a %reliable channel. Each use their own independent HMAC - * keys. - * - * @subsection network_protocol_external_reliable Control channel reliability layer - * - * Control channel messages (\c P_CONTROL_* and \c P_ACK_* message types) - * are TLS ciphertext packets which have been encapsulated inside of a - * reliability layer. The reliability layer is implemented as a - * straightforward acknowledge and retransmit model. - * - * Acknowledgments of received messages can be encoded in either the - * dedicated \c P_ACK_* record or they can be prepended to a \c - * P_CONTROL_* message. - * - * See the \link reliable Reliability Layer\endlink module for a detailed - * description. - * - * @section network_protocol_control Structure of control channel messages - * - * @subsection network_protocol_control_ciphertext Structure of ciphertext control channel messages - * - * Control channel packets in ciphertext form consist of the following - * parts: - * - * - local \c session_id (random 64 bit value to identify TLS session). - * - HMAC signature of entire encapsulation header for HMAC firewall - * [only if \c --tls-auth is specified] (usually 16 or 20 bytes). - * - packet-id for replay protection (4 or 8 bytes, includes sequence - * number and optional \c time_t timestamp). - * - acknowledgment packet-id array length (1 byte). - * - acknowledgment packet-id array (if length > 0). - * - acknowledgment remote session-id (if length > 0). - * - packet-id of this message (4 bytes). - * - TLS payload ciphertext (n bytes) (only for \c P_CONTROL_V1). - * - * Note that when \c --tls-auth is used, all message types are protected - * with an HMAC signature, even the initial packets of the TLS handshake. - * This makes it easy for OpenVPN to throw away bogus packets quickly, - * without wasting resources on attempting a TLS handshake which will - * ultimately fail. - * - * @subsection network_protocol_control_key_methods Control channel key methods and - * - * Once the TLS session has been initialized and authenticated, the TLS - * channel is used to exchange random %key material for bidirectional - * cipher and HMAC keys which will be used to secure data channel packets. - * OpenVPN currently implements two %key methods. %Key method 1 directly - * derives keys using random bits obtained from the \c RAND_bytes() - * OpenSSL function. %Key method 2 mixes random %key material from both - * sides of the connection using the TLS PRF mixing function. %Key method - * 2 is the preferred method and is the default for OpenVPN 2.0. - * - * The @ref key_generation "Data channel key generation" related page - * describes the %key methods in more detail. - * - * @subsection network_protocol_control_plaintext Structure of plaintext control channel messages - * - * - %Key method 1: - * - Cipher %key length in bytes (1 byte). - * - Cipher %key (n bytes). - * - HMAC %key length in bytes (1 byte). - * - HMAC %key (n bytes). - * - %Options string (n bytes, null terminated, client/server %options - * string should match). - * - %Key method 2: - * - Literal 0 (4 bytes). - * - %Key method (1 byte). - * - \c key_source structure (\c key_source.pre_master only defined - * for client -> server). - * - %Options string length, including null (2 bytes). - * - %Options string (n bytes, null terminated, client/server %options - * string must match). - * - [The username/password data below is optional, record can end at - * this point.] - * - Username string length, including null (2 bytes). - * - Username string (n bytes, null terminated). - * - Password string length, including null (2 bytes). - * - Password string (n bytes, null terminated). - * - * @section network_protocol_data Structure of data channel messages - * - * @subsection network_protocol_data_ciphertext Structure of ciphertext data channel messages - * - * The P_DATA_* payload represents encrypted, encapsulated tunnel packets - * which tend to be either IP packets or Ethernet frames. This is - * essentially the "payload" of the VPN. - * - * Data channel packets in ciphertext form consist of the following parts: - * - HMAC of ciphertext IV + ciphertext (if not disabled by \c --auth - * none). - * - Ciphertext IV (size is cipher-dependent, if not disabled by \c - * --no-iv). - * - Tunnel packet ciphertext. - * - * @subsection network_protocol_data_plaintext Structure of plaintext data channel messages - * - * Data channel packets in plaintext form consist of the following parts: - * - packet-id (4 or 8 bytes, if not disabled by --no-replay). - * - In TLS mode, 4 bytes are used because the implementation can - * force a TLS renegotation before \c 2^32 packets are sent. - * - In pre-shared %key mode, 8 bytes are used (sequence number and \c - * time_t value) to allow long-term %key usage without packet-id - * collisions. - * - User plaintext (n bytes). - */ |