* packet encryption, packet authentication, and
* packet compression.
*
- * Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
+ * Copyright (C) 2010-2014 Fox Crypto B.V. <openvpn@fox-it.com>
*
*
* This program is free software; you can redistribute it and/or modify
* following describes the various opcodes available.
*
* - Control channel messages:
- * - \c P_CONTROL_HARD_RESET_CLIENT_V1 -- %Key method 1, initial %key
+ * - \ref 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
+ * - \ref 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
+ * - \ref 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
+ * - \ref 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
+ * - \ref 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
+ * - \ref P_CONTROL_V1 -- Control channel packet (usually TLS
* ciphertext).
- * - \c P_ACK_V1 -- Acknowledgement for control channel packets
+ * - \ref P_ACK_V1 -- Acknowledgement for control channel packets
* received.
* - Data channel messages:
- * - \c P_DATA_V1 -- Data channel packet containing data channel
+ * - \ref P_DATA_V1 -- Data channel packet containing data channel
* ciphertext.
+ * - \ref P_DATA_V2 -- Data channel packet containing peer-id and data
+ * channel ciphertext.
*
* @subsection network_protocol_external_key_id Session IDs and Key IDs
*
* 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.
+ * derives keys using random bits obtained from the \c rand_bytes() 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.
*
* @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).
+ * The P_DATA_* payload represents encapsulated tunnel packets which tend to be
+ * either IP packets or Ethernet frames. This is essentially the "payload" of
+ * the VPN. Data channel packets consist of a data channel header, and a
+ * payload. There are two possible formats:
+ *
+ * @par P_DATA_V1
+ * P_DATA_V1 packets have a 1-byte header, carrying the \ref P_DATA_V1 \c opcode
+ * and \c key_id, followed by the payload:\n
+ * <tt> [ 5-bit opcode | 3-bit key_id ] [ payload ] </tt>
+ *
+ * @par P_DATA_V2
+ * P_DATA_V2 packets have the same 1-byte opcode/key_id, but carrying the \ref
+ * P_DATA_V2 opcode, followed by a 3-byte peer-id, which uniquely identifies
+ * the peer:\n
+ * <tt> [ 5-bit opcode | 3-bit key_id ] [ 24-bit peer-id ] [ payload ] </tt>
+ *
+ * See @ref data_crypto for details on the data channel payload format.
+ *
*/
* packet compression.
*
* Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
- * Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
+ * Copyright (C) 2010-2014 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
/**
* @file Data Channel Cryptography Module
+ *
+ * @addtogroup data_crypto Data Channel Crypto module
+ *
+ * @par Crypto packet formats
+ * The Data Channel Crypto module supports a number of crypto modes and
+ * configurable options. The actual packet format depends on these options. A
+ * Data Channel packet can consist of:
+ * - \b Opcode, one byte specifying the packet type (see @ref network_protocol
+ * "Network protocol").
+ * - \b Peer-id, if using the v2 data channel packet format (see @ref
+ * network_protocol "Network protocol").
+ * - \b HMAC, covering the ciphertext IV + ciphertext. The HMAC size depends
+ * on the \c \-\-auth option. If \c \-\-auth \c none is specified, there is no
+ * HMAC at all.
+ * - \b Ciphertext \b IV, if not disabled by \c \-\-no-iv. The IV size depends on
+ * the \c \-\-cipher option.
+ * - \b Packet \b ID, a 32-bit incrementing packet counter that provides replay
+ * protection (if not disabled by \c \-\-no-replay).
+ * - \b Timestamp, a 32-bit timestamp of the current time.
+ * - \b Payload, the plain text network packet to be encrypted (unless
+ * encryption is disabled by using \c \-\-cipher \c none). The payload might
+ * already be compressed (see @ref compression "Compression module").
+ *
+ * @par
+ * This section does not discuss the opcode and peer-id, since those do not
+ * depend on the data channel crypto. See @ref network_protocol
+ * "Network protocol" for more information on those.
+ *
+ * @par
+ * \e Legenda \n
+ * <tt>[ xxx ]</tt> = unprotected \n
+ * <tt>[ - xxx - ]</tt> = authenticated \n
+ * <tt>[ * xxx * ]</tt> = encrypted and authenticated
+ *
+ * @par
+ * <b>CBC data channel cypto format</b> \n
+ * In CBC mode, both TLS-mode and static key mode are supported. The IV
+ * consists of random bits to provide unpredictable IVs. \n
+ * <i>CBC IV format:</i> \n
+ * <tt> [ - random - ] </tt> \n
+ * <i>CBC data channel crypto format in TLS-mode:</i> \n
+ * <tt> [ HMAC ] [ - IV - ] [ * packet ID * ] [ * packet payload * ] </tt> \n
+ * <i>CBC data channel crypto format in static key mode:</i> \n
+ * <tt> [ HMAC ] [ - IV - ] [ * packet ID * ] [ * timestamp * ]
+ * [ * packet payload * ] </tt>
+ *
+ * @par
+ * <b>CFB/OFB data channel crypto format</b> \n
+ * CFB and OFB modes are only supported in TLS mode. In these modes, the IV
+ * consists of the packet counter and a timestamp. If the IV is more than 8
+ * bytes long, the remaining space is filled with zeroes. The packet counter may
+ * not roll over within a single TLS sessions. This results in a unique IV for
+ * each packet, as required by the CFB and OFB cipher modes.
+ *
+ * @par
+ * <i>CFB/OFB IV format:</i> \n
+ * <tt> [ - packet ID - ] [ - timestamp - ] [ - opt: zero-padding - ] </tt>\n
+ * <i>CFB/OFB data channel crypto format:</i> \n
+ * <tt> [ HMAC ] [ - IV - ] [ * packet payload * ] </tt>
+ *
+ * @par
+ * <b>No-crypto data channel format</b> \n
+ * In no-crypto mode (\c \-\-cipher \c none is specified), both TLS-mode and
+ * static key mode are supported. No encryption will be performed on the packet,
+ * but packets can still be authenticated. This mode does not require an IV.\n
+ * <i>No-crypto data channel crypto format in TLS-mode:</i> \n
+ * <tt> [ HMAC ] [ - packet ID - ] [ - packet payload - ] </tt> \n
+ * <i>No-crypto data channel crypto format in static key mode:</i> \n
+ * <tt> [ HMAC ] [ - packet ID - ] [ - timestamp - ] [ - packet payload - ] </tt>
+ *
*/
#ifndef CRYPTO_H
projects / thirdparty / openvpn.git / commitdiff
