ssl_common.h

/*
 *  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) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *  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 Control Channel Common Data Structures
 */

#ifndef SSL_COMMON_H_
#define SSL_COMMON_H_

#include "session_id.h"
#include "socket.h"
#include "packet_id.h"
#include "crypto.h"
#include "options.h"

#include "ssl_backend.h"

/* passwords */
#define UP_TYPE_AUTH        "Auth"
#define UP_TYPE_PRIVATE_KEY "Private Key"

/** @addtogroup control_processor
 *  @{ */
/**
 * @name Control channel negotiation states
 *
 * These states represent the different phases of control channel
 * negotiation between OpenVPN peers.  OpenVPN servers and clients
 * progress through the states in a different order, because of their
 * different roles during exchange of random material.  The references to
 * the \c key_source2 structure in the list below is only valid if %key
 * method 2 is being used.  See the \link key_generation data channel key
 * generation\endlink related page for more information.
 *
 * Clients follow this order:
 *   -# \c S_INITIAL, ready to begin three-way handshake and control
 *      channel negotiation.
 *   -# \c S_PRE_START, have started three-way handshake, waiting for
 *      acknowledgment from remote.
 *   -# \c S_START, initial three-way handshake complete.
 *   -# \c S_SENT_KEY, have sent local part of \c key_source2 random
 *      material.
 *   -# \c S_GOT_KEY, have received remote part of \c key_source2 random
 *      material.
 *   -# \c S_ACTIVE, normal operation during remaining handshake window.
 *   -# \c S_NORMAL_OP, normal operation.
 *
 * Servers follow the same order, except for \c S_SENT_KEY and \c
 * S_GOT_KEY being reversed, because the server first receives the
 * client's \c key_source2 random material before generating and sending
 * its own.
 *
 * @{
 */
#define S_ERROR          -1     /**< Error state.  */
#define S_UNDEF           0     /**< Undefined state, used after a \c
                                 *   key_state is cleaned up. */
#define S_INITIAL         1     /**< Initial \c key_state state after
                                 *   initialization by \c key_state_init()
                                 *   before start of three-way handshake. */
#define S_PRE_START       2     /**< Waiting for the remote OpenVPN peer
                                 *   to acknowledge during the initial
                                 *   three-way handshake. */
#define S_START           3     /**< Three-way handshake is complete,
                                 *   start of key exchange. */
#define S_SENT_KEY        4     /**< Local OpenVPN process has sent its
                                 *   part of the key material. */
#define S_GOT_KEY         5     /**< Local OpenVPN process has received
                                 *   the remote's part of the key
                                 *   material. */
#define S_ACTIVE          6     /**< Operational \c key_state state
                                 *   immediately after negotiation has
                                 *   completed while still within the
                                 *   handshake window. */
/* ready to exchange data channel packets */
#define S_NORMAL_OP       7     /**< Normal operational \c key_state
                                 *   state. */
/** @} name Control channel negotiation states */
/** @} addtogroup control_processor */

/**
 * Container for one half of random material to be used in %key method 2
 * \ref key_generation "data channel key generation".
 * @ingroup control_processor
 */
struct key_source {
  uint8_t pre_master[48];       /**< Random used for master secret
                                 *   generation, provided only by client
                                 *   OpenVPN peer. */
  uint8_t random1[32];          /**< Seed used for master secret
                                 *   generation, provided by both client
                                 *   and server. */
  uint8_t random2[32];          /**< Seed used for key expansion, provided
                                 *   by both client and server. */
};


/**
 * Container for both halves of random material to be used in %key method
 * 2 \ref key_generation "data channel key generation".
 * @ingroup control_processor
 */
struct key_source2 {
  struct key_source client;     /**< Random provided by client. */
  struct key_source server;     /**< Random provided by server. */
};

/**
 * Security parameter state of one TLS and data channel %key session.
 * @ingroup control_processor
 *
 * This structure represents one security parameter session between
 * OpenVPN peers.  It includes the control channel TLS state and the data
 * channel crypto state.  It also contains the reliability layer
 * structures used for control channel messages.
 *
 * A new \c key_state structure is initialized for each hard or soft
 * reset.
 *
 * @see
 *  - This structure should be initialized using the \c key_state_init()
 *    function.
 *  - This structure should be cleaned up using the \c key_state_free()
 *    function.
 */
struct key_state
{
  int state;
  int key_id;			/* inherited from struct tls_session below */

  struct key_state_ssl ks_ssl;	/* contains SSL object and BIOs for the control channel */

  time_t established;		/* when our state went S_ACTIVE */
  time_t must_negotiate;	/* key negotiation times out if not finished before this time */
  time_t must_die;		/* this object is destroyed at this time */

  int initial_opcode;		/* our initial P_ opcode */
  struct session_id session_id_remote;   /* peer's random session ID */
  struct link_socket_actual remote_addr; /* peer's IP addr */
  struct packet_id packet_id;	       /* for data channel, to prevent replay attacks */

  struct key_ctx_bi key;	       /* data channel keys for encrypt/decrypt/hmac */

  struct key_source2 *key_src;         /* source entropy for key expansion */

  struct buffer plaintext_read_buf;
  struct buffer plaintext_write_buf;
  struct buffer ack_write_buf;

  struct reliable *send_reliable; /* holds a copy of outgoing packets until ACK received */
  struct reliable *rec_reliable;  /* order incoming ciphertext packets before we pass to TLS */
  struct reliable_ack *rec_ack;	  /* buffers all packet IDs we want to ACK back to sender */

  struct buffer_list *paybuf;

  counter_type n_bytes;			 /* how many bytes sent/recvd since last key exchange */
  counter_type n_packets;		 /* how many packets sent/recvd since last key exchange */

  /*
   * If bad username/password, TLS connection will come up but 'authenticated' will be false.
   */
  bool authenticated;
  time_t auth_deferred_expire;

#ifdef ENABLE_DEF_AUTH
  /* If auth_deferred is true, authentication is being deferred */
  bool auth_deferred;
#ifdef MANAGEMENT_DEF_AUTH
  unsigned int mda_key_id;
  unsigned int mda_status;
#endif
#ifdef PLUGIN_DEF_AUTH
  unsigned int auth_control_status;
  time_t acf_last_mod;
  char *auth_control_file;
#endif
#endif
};

/*
 * Our const options, obtained directly or derived from
 * command line options.
 */
struct tls_options
{
  /* our master TLS context from which all SSL objects derived */
  struct tls_root_ctx ssl_ctx;

  /* data channel cipher, hmac, and key lengths */
  struct key_type key_type;

  /* true if we are a TLS server, client otherwise */
  bool server;

  /* if true, don't xmit until first packet from peer is received */
  bool xmit_hold;

#ifdef ENABLE_OCC
  /* local and remote options strings
     that must match between client and server */
  const char *local_options;
  const char *remote_options;
#endif

  /* from command line */
  int key_method;
  bool replay;
  bool single_session;
#ifdef ENABLE_OCC
  bool disable_occ;
#endif
#ifdef ENABLE_PUSH_PEER_INFO
  int push_peer_info_detail;
#endif
  int transition_window;
  int handshake_window;
  interval_t packet_timeout;
  int renegotiate_bytes;
  int renegotiate_packets;
  interval_t renegotiate_seconds;

  /* cert verification parms */
  const char *verify_command;
  const char *verify_export_cert;
  int verify_x509_type;
  const char *verify_x509_name;
  const char *crl_file;
  int ns_cert_type;
  unsigned remote_cert_ku[MAX_PARMS];
  const char *remote_cert_eku;
  uint8_t *verify_hash;
  char *x509_username_field;

  /* allow openvpn config info to be
     passed over control channel */
  bool pass_config_info;

  /* struct crypto_option flags */
  unsigned int crypto_flags_and;
  unsigned int crypto_flags_or;

  int replay_window;                   /* --replay-window parm */
  int replay_time;                     /* --replay-window parm */
  bool tcp_mode;

  /* packet authentication for TLS handshake */
  struct crypto_options tls_auth;
  struct key_ctx_bi tls_auth_key;

  /* frame parameters for TLS control channel */
  struct frame frame;

  /* used for username/password authentication */
  const char *auth_user_pass_verify_script;
  bool auth_user_pass_verify_script_via_file;
  const char *tmp_dir;
  const char *auth_user_pass_file;

  /* use the client-config-dir as a positive authenticator */
  const char *client_config_dir_exclusive;

  /* instance-wide environment variable set */
  struct env_set *es;
  const struct plugin_list *plugins;

  /* configuration file SSL-related boolean and low-permutation options */
# define SSLF_CLIENT_CERT_NOT_REQUIRED (1<<0)
# define SSLF_USERNAME_AS_COMMON_NAME  (1<<1)
# define SSLF_AUTH_USER_PASS_OPTIONAL  (1<<2)
# define SSLF_OPT_VERIFY               (1<<4)
# define SSLF_CRL_VERIFY_DIR           (1<<5)
# define SSLF_TLS_VERSION_MIN_SHIFT    6
# define SSLF_TLS_VERSION_MIN_MASK     0xF /* (uses bit positions 6 to 9) */
# define SSLF_TLS_VERSION_MAX_SHIFT    10
# define SSLF_TLS_VERSION_MAX_MASK     0xF /* (uses bit positions 10 to 13) */
  unsigned int ssl_flags;

#ifdef MANAGEMENT_DEF_AUTH
  struct man_def_auth_context *mda_context;
#endif

#ifdef ENABLE_X509_TRACK
  const struct x509_track *x509_track;
#endif

#ifdef ENABLE_CLIENT_CR
  const struct static_challenge_info *sci;
#endif

  /* --gremlin bits */
  int gremlin;
};

/** @addtogroup control_processor
 *  @{ */
/** @name Index of key_state objects within a tls_session structure
 *
 *  This is the index of \c tls_session.key
 *
 *  @{ */
#define KS_PRIMARY    0         /**< Primary %key state index. */
#define KS_LAME_DUCK  1         /**< %Key state index that will retire
                                 *   soon. */
#define KS_SIZE       2         /**< Size of the \c tls_session.key array. */
/** @} name Index of key_state objects within a tls_session structure */
/** @} addtogroup control_processor */


/**
 * Security parameter state of a single session within a VPN tunnel.
 * @ingroup control_processor
 *
 * This structure represents an OpenVPN peer-to-peer control channel
 * session.
 *
 * A \c tls_session remains over soft resets, but a new instance is
 * initialized for each hard reset.
 *
 * @see
 *  - This structure should be initialized using the \c tls_session_init()
 *    function.
 *  - This structure should be cleaned up using the \c tls_session_free()
 *    function.
 */
struct tls_session
{
  /* const options and config info */
  struct tls_options *opt;

  /* during hard reset used to control burst retransmit */
  bool burst;

  /* authenticate control packets */
  struct crypto_options tls_auth;
  struct packet_id tls_auth_pid;

  int initial_opcode;		/* our initial P_ opcode */
  struct session_id session_id;	/* our random session ID */
  int key_id;			/* increments with each soft reset (for key renegotiation) */

  int limit_next;               /* used for traffic shaping on the control channel */

  int verify_maxlevel;

  char *common_name;

  struct cert_hash_set *cert_hash_set;

#ifdef ENABLE_PF
  uint32_t common_name_hashval;
#endif

  bool verified;                /* true if peer certificate was verified against CA */

  /* not-yet-authenticated incoming client */
  struct link_socket_actual untrusted_addr;

  struct key_state key[KS_SIZE];
};

/** @addtogroup control_processor
 *  @{ */
/** @name Index of tls_session objects within a tls_multi structure
 *
 *  This is the index of \c tls_multi.session
 *
 *  Normally three tls_session objects are maintained by an active openvpn
 *  session.  The first is the current, TLS authenticated session, the
 *  second is used to process connection requests from a new client that
 *  would usurp the current session if successfully authenticated, and the
 *  third is used as a repository for a "lame-duck" %key in the event that
 *  the primary session resets due to error while the lame-duck %key still
 *  has time left before its expiration.  Lame duck keys are used to
 *  maintain the continuity of the data channel connection while a new %key
 *  is being negotiated.
 *
 *  @{ */
#define TM_ACTIVE    0          /**< Active \c tls_session. */
#define TM_UNTRUSTED 1          /**< As yet un-trusted \c tls_session
                                 *   being negotiated. */
#define TM_LAME_DUCK 2          /**< Old \c tls_session. */
#define TM_SIZE      3          /**< Size of the \c tls_multi.session
                                 *   array. */
/** @} name Index of tls_session objects within a tls_multi structure */
/** @} addtogroup control_processor */


/*
 * The number of keys we will scan on encrypt or decrypt.  The first
 * is the "active" key.  The second is the lame_duck or retiring key
 * associated with the active key's session ID.  The third is a detached
 * lame duck session that only occurs in situations where a key renegotiate
 * failed on the active key, but a lame duck key was still valid.  By
 * preserving the lame duck session, we can be assured of having a data
 * channel key available even when network conditions are so bad that
 * we can't negotiate a new key within the time allotted.
 */
#define KEY_SCAN_SIZE 3


/**
 * Security parameter state for a single VPN tunnel.
 * @ingroup control_processor
 *
 * An active VPN tunnel running with TLS enabled has one \c tls_multi
 * object, in which it stores all control channel and data channel
 * security parameter state.  This structure can contain multiple,
 * possibly simultaneously active, \c tls_context objects to allow for
 * interruption-less transitions during session renegotiations.  Each \c
 * tls_context represents one control channel session, which can span
 * multiple data channel security parameter sessions stored in \c
 * key_state structures.
 */
struct tls_multi
{
  /* used to coordinate access between main thread and TLS thread */
  /*MUTEX_PTR_DEFINE (mutex);*/

  /* const options and config info */
  struct tls_options opt;

  struct key_state* key_scan[KEY_SCAN_SIZE];
                                /**< List of \c key_state objects in the
                                 *   order they should be scanned by data
                                 *   channel modules. */

  /*
   * used by tls_pre_encrypt to communicate the encrypt key
   * to tls_post_encrypt()
   */
  struct key_state *save_ks;	/* temporary pointer used between pre/post routines */

  /*
   * Used to return outgoing address from
   * tls_multi_process.
   */
  struct link_socket_actual to_link_addr;

  int n_sessions;               /**< Number of sessions negotiated thus
                                 *   far. */

  /*
   * Number of errors.
   */
  int n_hard_errors;   /* errors due to TLS negotiation failure */
  int n_soft_errors;   /* errors due to unrecognized or failed-to-authenticate incoming packets */

  /*
   * Our locked common name, username, and cert hashes (cannot change during the life of this tls_multi object)
   */
  char *locked_cn;
  char *locked_username;
  struct cert_hash_set *locked_cert_hash_set;

#ifdef ENABLE_DEF_AUTH
  /*
   * An error message to send to client on AUTH_FAILED
   */
  char *client_reason;

  /*
   * A multi-line string of general-purpose info received from peer
   * over control channel.
   */
  char *peer_info;

  /* Time of last call to tls_authentication_status */
  time_t tas_last;
#endif

  /* For P_DATA_V2 */
  uint32_t peer_id;
  bool use_peer_id;

  /*
   * Our session objects.
   */
  struct tls_session session[TM_SIZE];
                                /**< Array of \c tls_session objects
                                 *   representing control channel
                                 *   sessions with the remote peer. */
};


#define SHOW_TLS_CIPHER_LIST_WARNING \
  "Be aware that that whether a cipher suite in this list can actually work\n" \
  "depends on the specific setup of both peers. See the man page entries of\n" \
  "--tls-cipher and --show-tls for more details.\n\n"

#endif /* SSL_COMMON_H_ */