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openvpn/ssl.h
Adriaan de Jong 67d8a0d4e9 Refactored tls_options, key_state, and key_source data structures 
Signed-off-by: Adriaan de Jong <dejong@fox-it.com>
Acked-by: James Yonan <james@openvpn.net>
Signed-off-by: David Sommerseth <davids@redhat.com>
2011-10-21 10:53:31 +02:00

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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) 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 SSL/Data channel negotiation module
*/
#ifndef OPENVPN_SSL_H
#define OPENVPN_SSL_H
#if defined(USE_CRYPTO) && defined(USE_SSL)
#include <openssl/ssl.h>
#include <openssl/bio.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/pkcs12.h>
#include <openssl/x509v3.h>
#include "basic.h"
#include "common.h"
#include "crypto.h"
#include "packet_id.h"
#include "session_id.h"
#include "reliable.h"
#include "socket.h"
#include "mtu.h"
#include "options.h"
#include "plugin.h"
#include "ssl_common.h"
#include "ssl_verify.h"
#include "ssl_backend.h"
/* Used in the TLS PRF function */
#define KEY_EXPANSION_ID "OpenVPN"
/* packet opcode (high 5 bits) and key-id (low 3 bits) are combined in one byte */
#define P_KEY_ID_MASK 0x07
#define P_OPCODE_SHIFT 3
/* packet opcodes -- the V1 is intended to allow protocol changes in the future */
#define P_CONTROL_HARD_RESET_CLIENT_V1 1 /* initial key from client, forget previous state */
#define P_CONTROL_HARD_RESET_SERVER_V1 2 /* initial key from server, forget previous state */
#define P_CONTROL_SOFT_RESET_V1 3 /* new key, graceful transition from old to new key */
#define P_CONTROL_V1 4 /* control channel packet (usually TLS ciphertext) */
#define P_ACK_V1 5 /* acknowledgement for packets received */
#define P_DATA_V1 6 /* data channel packet */
/* indicates key_method >= 2 */
#define P_CONTROL_HARD_RESET_CLIENT_V2 7 /* initial key from client, forget previous state */
#define P_CONTROL_HARD_RESET_SERVER_V2 8 /* initial key from server, forget previous state */
/* define the range of legal opcodes */
#define P_FIRST_OPCODE 1
#define P_LAST_OPCODE 8
/** @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 */
#define DECRYPT_KEY_ENABLED(multi, ks) ((ks)->state >= (S_GOT_KEY - (multi)->opt.server))
/**< Check whether the \a ks \c key_state
* is ready to receive data channel
* packets.
* @ingroup data_crypto
*
* If true, it is safe to assume that
* this session has been authenticated
* by TLS.
*
* @note This macro only works if
* S_SENT_KEY + 1 == S_GOT_KEY. */
/* Should we aggregate TLS
* acknowledgements, and tack them onto
* control packets? */
#define TLS_AGGREGATE_ACK
/*
* If TLS_AGGREGATE_ACK, set the
* max number of acknowledgments that
* can "hitch a ride" on an outgoing
* non-P_ACK_V1 control packet.
*/
#define CONTROL_SEND_ACK_MAX 4
/*
* Define number of buffers for send and receive in the reliability layer.
*/
#define TLS_RELIABLE_N_SEND_BUFFERS 4 /* also window size for reliablity layer */
#define TLS_RELIABLE_N_REC_BUFFERS 8
/*
* Various timeouts
*/
#define TLS_MULTI_REFRESH 15 /* call tls_multi_process once every n seconds */
#define TLS_MULTI_HORIZON 2 /* call tls_multi_process frequently for n seconds after
every packet sent/received action */
/* The SSL/TLS worker thread will wait at most this many seconds for the interprocess
communication pipe to the main thread to be ready to accept writes. */
#define TLS_MULTI_THREAD_SEND_TIMEOUT 5
/* Interval that tls_multi_process should call tls_authentication_status */
#define TLS_MULTI_AUTH_STATUS_INTERVAL 10
/*
* Buffer sizes (also see mtu.h).
*/
/* Maximum length of the username in cert */
#define TLS_USERNAME_LEN 64
/* Legal characters in an X509 or common name */
#define X509_NAME_CHAR_CLASS (CC_ALNUM|CC_UNDERBAR|CC_DASH|CC_DOT|CC_AT|CC_COLON|CC_SLASH|CC_EQUAL)
#define COMMON_NAME_CHAR_CLASS (CC_ALNUM|CC_UNDERBAR|CC_DASH|CC_DOT|CC_AT|CC_SLASH)
/* Maximum length of OCC options string passed as part of auth handshake */
#define TLS_OPTIONS_LEN 512
/* Default field in X509 to be username */
#define X509_USERNAME_FIELD_DEFAULT "CN"
/*
* Range of key exchange methods
*/
#define KEY_METHOD_MIN 1
#define KEY_METHOD_MAX 2
/* key method taken from lower 4 bits */
#define KEY_METHOD_MASK 0x0F
/*
* Measure success rate of TLS handshakes, for debugging only
*/
/* #define MEASURE_TLS_HANDSHAKE_STATS */
/*
* Keep track of certificate hashes at various depths
*/
/* Maximum certificate depth we will allow */
#define MAX_CERT_DEPTH 16
struct cert_hash {
unsigned char sha1_hash[SHA_DIGEST_LENGTH];
};
struct cert_hash_set {
struct cert_hash *ch[MAX_CERT_DEPTH];
};
/*
* Prepare the SSL library for use
*/
void init_ssl_lib (void);
/*
* Free any internal state that the SSL library might have
*/
void free_ssl_lib (void);
#ifdef ENABLE_X509_TRACK
struct x509_track
{
const struct x509_track *next;
const char *name;
# define XT_FULL_CHAIN (1<<0)
unsigned int flags;
int nid;
};
void x509_track_add (const struct x509_track **ll_head, const char *name, int msglevel, struct gc_arena *gc);
#endif
/** @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 */
const 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
{
/* 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
/*
* Our session objects.
*/
struct tls_session session[TM_SIZE];
/**< Array of \c tls_session objects
* representing control channel
* sessions with the remote peer. */
};
/*
* Used in --mode server mode to check tls-auth signature on initial
* packets received from new clients.
*/
struct tls_auth_standalone
{
struct key_ctx_bi tls_auth_key;
struct crypto_options tls_auth_options;
struct frame frame;
};
void init_ssl_lib (void);
void free_ssl_lib (void);
/**
* Build master SSL context object that serves for the whole of OpenVPN
* instantiation
*/
void init_ssl (const struct options *options, struct tls_root_ctx *ctx);
struct tls_multi *tls_multi_init (struct tls_options *tls_options);
struct tls_auth_standalone *tls_auth_standalone_init (struct tls_options *tls_options,
struct gc_arena *gc);
void tls_auth_standalone_finalize (struct tls_auth_standalone *tas,
const struct frame *frame);
void tls_multi_init_finalize(struct tls_multi *multi,
const struct frame *frame);
void tls_multi_init_set_options(struct tls_multi* multi,
const char *local,
const char *remote);
#define TLSMP_INACTIVE 0
#define TLSMP_ACTIVE 1
#define TLSMP_KILL 2
int tls_multi_process (struct tls_multi *multi,
struct buffer *to_link,
struct link_socket_actual **to_link_addr,
struct link_socket_info *to_link_socket_info,
interval_t *wakeup);
void tls_multi_free (struct tls_multi *multi, bool clear);
/**************************************************************************/
/**
* Determine whether an incoming packet is a data channel or control
* channel packet, and process accordingly.
* @ingroup external_multiplexer
*
* When OpenVPN is in TLS mode, this is the first function to process an
* incoming packet. It inspects the packet's one-byte header which
* contains the packet's opcode and key ID. Depending on the opcode, the
* packet is processed as a data channel or as a control channel packet.
*
* @par Data channel packets
*
* If the opcode indicates the packet is a data channel packet, then the
* packet's key ID is used to find the local TLS state it is associated
* with. This state is checked whether it is active, authenticated, and
* its remote peer is the source of this packet. If these checks passed,
* the state's security parameters are loaded into the \a opt crypto
* options so that \p openvpn_decrypt() can later use them to authenticate
* and decrypt the packet.
*
* This function then returns false. The \a buf buffer has not been
* modified, except for removing the header.
*
* @par Control channel packets
*
* If the opcode indicates the packet is a control channel packet, then
* this function will process it based on its plaintext header. depending
* on the packet's opcode and session ID this function determines if it is
* destined for an active TLS session, or whether a new TLS session should
* be started. This function also initiates data channel session key
* renegotiation if the received opcode requests that.
*
* If the incoming packet is destined for an active TLS session, then the
* packet is inserted into the Reliability Layer and will be handled
* later.
*
* @param multi - The TLS multi structure associated with the VPN tunnel
* of this packet.
* @param from - The source address of the packet.
* @param buf - A buffer structure containing the incoming packet.
* @param opt - A crypto options structure that will be loaded with the
* appropriate security parameters to handle the packet if it is a
* data channel packet.
*
* @return
* @li True if the packet is a control channel packet that has been
* processed successfully.
* @li False if the packet is a data channel packet, or if an error
* occurred during processing of a control channel packet.
*/
bool tls_pre_decrypt (struct tls_multi *multi,
const struct link_socket_actual *from,
struct buffer *buf,
struct crypto_options *opt);
/**************************************************************************/
/** @name Functions for managing security parameter state for data channel packets
* @{ */
/**
* Inspect an incoming packet for which no VPN tunnel is active, and
* determine whether a new VPN tunnel should be created.
* @ingroup data_crypto
*
* This function receives the initial incoming packet from a client that
* wishes to establish a new VPN tunnel, and determines the packet is a
* valid initial packet. It is only used when OpenVPN is running in
* server mode.
*
* The tests performed by this function are whether the packet's opcode is
* correct for establishing a new VPN tunnel, whether its key ID is 0, and
* whether its size is not too large. This function also performs the
* initial HMAC firewall test, if configured to do so.
*
* The incoming packet and the local VPN tunnel state are not modified by
* this function. Its sole purpose is to inspect the packet and determine
* whether a new VPN tunnel should be created. If so, that new VPN tunnel
* instance will handle processing of the packet.
*
* @param tas - The standalone TLS authentication setting structure for
* this process.
* @param from - The source address of the packet.
* @param buf - A buffer structure containing the incoming packet.
*
* @return
* @li True if the packet is valid and a new VPN tunnel should be created
* for this client.
* @li False if the packet is not valid, did not pass the HMAC firewall
* test, or some other error occurred.
*/
bool tls_pre_decrypt_lite (const struct tls_auth_standalone *tas,
const struct link_socket_actual *from,
const struct buffer *buf);
/**
* Choose the appropriate security parameters with which to process an
* outgoing packet.
* @ingroup data_crypto
*
* If no appropriate security parameters can be found, or if some other
* error occurs, then the buffer is set to empty.
*
* @param multi - The TLS state for this packet's destination VPN tunnel.
* @param buf - The buffer containing the outgoing packet.
* @param opt - The crypto options structure into which the appropriate
* security parameters should be loaded.
*/
void tls_pre_encrypt (struct tls_multi *multi,
struct buffer *buf, struct crypto_options *opt);
/**
* Prepend the one-byte OpenVPN header to the packet, and perform some
* accounting for the key state used.
* @ingroup data_crypto
*
* @param multi - The TLS state for this packet's destination VPN tunnel.
* @param buf - The buffer containing the outgoing packet.
*/
void tls_post_encrypt (struct tls_multi *multi, struct buffer *buf);
/** @} name Functions for managing security parameter state for data channel packets */
void pem_password_setup (const char *auth_file);
int pem_password_callback (char *buf, int size, int rwflag, void *u);
void auth_user_pass_setup (const char *auth_file, const struct static_challenge_info *sc_info);
void ssl_set_auth_nocache (void);
void ssl_set_auth_token (const char *token);
void ssl_purge_auth (const bool auth_user_pass_only);
#ifdef ENABLE_CLIENT_CR
/*
* ssl_get_auth_challenge will parse the server-pushed auth-failed
* reason string and return a dynamically allocated
* auth_challenge_info struct.
*/
void ssl_purge_auth_challenge (void);
void ssl_put_auth_challenge (const char *cr_str);
#endif
void tls_set_verify_command (const char *cmd);
void tls_set_crl_verify (const char *crl);
void tls_set_verify_x509name (const char *x509name);
void tls_adjust_frame_parameters(struct frame *frame);
bool tls_send_payload (struct tls_multi *multi,
const uint8_t *data,
int size);
bool tls_rec_payload (struct tls_multi *multi,
struct buffer *buf);
const char *tls_common_name (const struct tls_multi* multi, const bool null);
const char *tls_username(const struct tls_multi *multi, const bool null);
void tls_set_common_name (struct tls_multi *multi, const char *common_name);
void tls_lock_common_name (struct tls_multi *multi);
void tls_lock_cert_hash_set (struct tls_multi *multi);
#define TLS_AUTHENTICATION_SUCCEEDED 0
#define TLS_AUTHENTICATION_FAILED 1
#define TLS_AUTHENTICATION_DEFERRED 2
#define TLS_AUTHENTICATION_UNDEFINED 3
int tls_authentication_status (struct tls_multi *multi, const int latency);
void tls_deauthenticate (struct tls_multi *multi);
#ifdef MANAGEMENT_DEF_AUTH
bool tls_authenticate_key (struct tls_multi *multi, const unsigned int mda_key_id, const bool auth, const char *client_reason);
static inline char *
tls_get_peer_info(const struct tls_multi *multi)
{
return multi->peer_info;
}
#endif
/*
* inline functions
*/
static inline bool
tls_initial_packet_received (const struct tls_multi *multi)
{
return multi->n_sessions > 0;
}
static inline bool
tls_test_auth_deferred_interval (const struct tls_multi *multi)
{
if (multi)
{
const struct key_state *ks = &multi->session[TM_ACTIVE].key[KS_PRIMARY];
return now < ks->auth_deferred_expire;
}
return false;
}
static inline int
tls_test_payload_len (const struct tls_multi *multi)
{
if (multi)
{
const struct key_state *ks = &multi->session[TM_ACTIVE].key[KS_PRIMARY];
if (ks->state >= S_ACTIVE)
return BLEN (&ks->plaintext_read_buf);
}
return 0;
}
static inline void
tls_set_single_session (struct tls_multi *multi)
{
if (multi)
multi->opt.single_session = true;
}
static inline const char *
tls_client_reason (struct tls_multi *multi)
{
#ifdef ENABLE_DEF_AUTH
return multi->client_reason;
#else
return NULL;
#endif
}
#ifdef ENABLE_PF
static inline bool
tls_common_name_hash (const struct tls_multi *multi, const char **cn, uint32_t *cn_hash)
{
if (multi)
{
const struct tls_session *s = &multi->session[TM_ACTIVE];
if (s->common_name && s->common_name[0] != '\0')
{
*cn = s->common_name;
*cn_hash = s->common_name_hashval;
return true;
}
}
return false;
}
#endif
/*
* protocol_dump() flags
*/
#define PD_TLS_AUTH_HMAC_SIZE_MASK 0xFF
#define PD_SHOW_DATA (1<<8)
#define PD_TLS (1<<9)
#define PD_VERBOSE (1<<10)
const char *protocol_dump (struct buffer *buffer,
unsigned int flags,
struct gc_arena *gc);
/*
* debugging code
*/
#ifdef MEASURE_TLS_HANDSHAKE_STATS
void show_tls_performance_stats(void);
#endif
/*#define EXTRACT_X509_FIELD_TEST*/
void extract_x509_field_test (void);
#endif /* USE_CRYPTO && USE_SSL */
#endif
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