Update upstream source from tag 'upstream/2.5_beta1'

Update to upstream version '2.5~beta1'
with Debian dir d53f9a482ac24eb491a294b26c24bb1d87afad24

1 files changed, 184 insertions, 0 deletions

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+/*
+ *  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) 2010-2018 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; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * Control Channel Processor module documentation file.
+ */
+
+/**
+ * @defgroup control_processor Control Channel Processor module
+ *
+ * This module controls the setup and maintenance of VPN tunnels and the
+ * associated security parameters.
+ *
+ * @par This module's role
+ * The Control Channel Processor module lies at the core of OpenVPN's
+ * activities.  It handles the setup of new VPN tunnels, the negotiation
+ * of data channel security parameters, the managing of active VPN
+ * tunnels, and finally the cleanup of expired VPN tunnels.
+ *
+ * @par State structures
+ * A large amount of VPN tunnel state information must be stored within an
+ * OpenVPN process.  A wide variety of container structures are used by
+ * this module for that purpose.  Several of these structures are listed
+ * below, and the function of the first three VPN tunnel state containers
+ * is described in more detail later.
+ *  - VPN tunnel state containers:
+ *     - \c tls_multi, security parameter state for a single VPN tunnel.
+ *       Contains three instances of the \c tls_session structure.
+ *     - \c tls_session, security parameter state of a single session
+ *       within a VPN tunnel.  Contains two instances of the \c key_state
+ *       structure.
+ *     - \c key_state, security parameter state of one TLS and data
+ *       channel %key set.
+ *  - Data channel security parameter containers:
+ *     - \c key_ctx_bi, container for two sets of OpenSSL cipher and/or
+ *       HMAC context (both directions).  Contains two instances of the \c
+ *       key_ctx structure.
+ *     - \c key_ctx, container for one set of OpenSSL cipher and/or HMAC
+ *       context (one directions.
+ *  - Key material containers:
+ *     - \c key2, container for two sets of cipher and/or HMAC %key
+ *       material (both directions).  Contains two instances of the \c key
+ *       structure.
+ *     - \c key, container for one set of cipher and/or HMAC %key material
+ *       (one direction).
+ *     - \c key_direction_state, ordering of %key material within the \c
+ *       key2.key array.
+ *  - Key method 2 random material containers:
+ *     - \c key_source2, container for both halves of random material used
+ *       for %key method 2.  Contains two instances of the \c key_source
+ *       structure.
+ *     - \c key_source, container for one half of random material used for
+ *       %key method 2.
+ *
+ * @par The life of a \c tls_multi object
+ * A \c tls_multi structure contains all the security parameter state
+ * information related to the control and data channels of one VPN tunnel.
+ * Its life cycle can be summarized as follows:
+ *  -# Initialization: \c tls_multi_init() and \c
+ *     tls_multi_init_finalize(), which are called (indirectly) from \c
+ *     init_instance() when initializing a new \c context structure.
+ *     - Initializes a \c tls_multi structure.
+ *     - Allocates the three \c tls_session objects contained by the \c
+ *       tls_multi structure, and initializes as appropriate.
+ *  -# Management: \c tls_multi_process() and \c tls_pre_decrypt()
+ *     - If a new session is initiated by the remote peer, then \c
+ *       tls_pre_decrypt() starts the new session negotiation in the
+ *       un-trusted \c tls_session.
+ *     - If the, as yet, un-trusted \c tls_session authenticates
+ *       successfully, then \c tls_multi_process() moves it so as to be
+ *       the active \c tls_session.
+ *     - If an error occurs during processing of a \c key_state object,
+ *       then \c tls_multi_process() cleans up and initializes the
+ *       associated \c tls_session object.  If the error occurred in the
+ *       active \c key_state of the active \c tls_session and the
+ *       lame-duck \c key_state of that \c tls_session has not yet
+ *       expired, it is preserved as fallback.
+ *  -# Cleanup: \c tls_multi_free(), which is called (indirectly) from \c
+ *     close_instance() when cleaning up a \c context structure.
+ *     - Cleans up a \c tls_multi structure.
+ *     - Cleans up the three \c tls_session objects contained by the \c
+ *       tls_multi structure.
+ *
+ * @par The life of a \c tls_session object
+ * A \c tls_session structure contains the state information related to an
+ * active and a lame-duck \c key_state.  Its life cycle can be summarized
+ * as follows:
+ *  -# Initialization: \c tls_session_init()
+ *     - Initializes a \c tls_session structure.
+ *     - Initializes the primary \c key_state by calling \c
+ *       key_state_init().
+ *  -# Renegotiation: \c key_state_soft_reset()
+ *     - Cleans up the old lame-duck \c key_state by calling \c
+ *       key_state_free().
+ *     - Moves the old primary \c key_state to be the new lame-duck \c
+ *       key_state.
+ *     - Initializes a new primary \c key_state by calling \c
+ *       key_state_init().
+ *  -# Cleanup: \c tls_session_free()
+ *     - Cleans up a \c tls_session structure.
+ *     - Cleans up all \c key_state objects associated with the session by
+ *       calling \c key_state_free() for each.
+ *
+ * @par The life of a \c key_state object
+ * A \c key_state structure represents one control and data channel %key
+ * set.  It contains an OpenSSL TLS object that encapsulates the control
+ * channel, and the data channel security parameters needed by the \link
+ * data_crypto Data Channel Crypto module\endlink to perform cryptographic
+ * operations on data channel packets.  Its life cycle can be summarized
+ * as follows:
+ *  -# Initialization: \c key_state_init()
+ *     - Initializes a \c key_state structure.
+ *     - Creates a new OpenSSL TLS object to encapsulate this new control
+ *       channel session.
+ *     - Sets \c key_state.state to \c S_INITIAL.
+ *     - Allocates several internal buffers.
+ *     - Initializes new reliability layer structures for this key set.
+ *  -# Negotiation: \c tls_process()
+ *     - The OpenSSL TLS object negotiates a TLS session between itself
+ *       and the remote peer's TLS object.
+ *     - Key material is generated and exchanged through the TLS session
+ *       between OpenVPN peers.
+ *     - Both peers initialize their data channel cipher and HMAC key
+ *       contexts.
+ *     - On successful negotiation, the \c key_state.state will progress
+ *       from \c S_INITIAL to \c S_ACTIVE and \c S_NORMAL.
+ *  -# Active tunneling: \link data_crypto Data Channel Crypto
+ *     module\endlink
+ *     - Data channel packet to be sent to a remote OpenVPN peer:
+ *        - \c tls_pre_encrypt() loads the security parameters from the \c
+ *          key_state into a \c crypto_options structure.
+ *        - \c openvpn_encrypt() uses the \c crypto_options to an encrypt
+ *          and HMAC sign the data channel packet.
+ *     - Data channel packet received from a remote OpenVPN peer:
+ *        - \c tls_pre_decrypt() loads the security parameters from the \c
+ *          key_state into a \c crypto_options structure.
+ *        - \c openvpn_encrypt() uses the \c crypto_options to
+ *          authenticate and decrypt the data channel packet.
+ *  -# Cleanup: \c key_state_free()
+ *     - Cleans up a \c key_state structure together with its OpenSSL TLS
+ *       object, key material, internal buffers, and reliability layer
+ *       structures.
+ *
+ * @par Control functions
+ * The following two functions drive the Control Channel Processor's
+ * activities.
+ *  - \c tls_multi_process(), iterates through the \c tls_session objects
+ *    within a given \c tls_multi of a VPN tunnel, and calls \c
+ *    tls_process() for each \c tls_session which is being set up, is
+ *    already active, or is busy expiring.
+ *  - \c tls_process(), performs the Control Channel Processor module's
+ *    core handling of received control channel messages, and generates
+ *    appropriate messages to be sent.
+ *
+ * @par Functions which control data channel key generation
+ *  - Key method 1 key exchange functions were removed from OpenVPN 2.5
+ *  - Key method 2 key exchange functions:
+ *     - \c key_method_2_write(), generates and processes key material to
+ *       be sent to the remote OpenVPN peer.
+ *     - \c key_method_2_read(), processes key material received from the
+ *       remote OpenVPN peer.
+ */