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authorAlberto Gonzalez Iniesta <agi@inittab.org>2012-11-05 16:28:09 +0100
committerAlberto Gonzalez Iniesta <agi@inittab.org>2012-11-05 16:28:09 +0100
commit8dd0350e1607aa30f7a043c8d5ec7a7eeb874115 (patch)
tree566d0620eb693320cb121dfd93a5675fa704a30b /src/openvpn/crypto.h
parent349cfa7acb95abe865209a28e417ec74b56f9bba (diff)
Imported Upstream version 2.3_rc1
Diffstat (limited to 'src/openvpn/crypto.h')
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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 Data Channel Cryptography Module
+ */
+
+#ifndef CRYPTO_H
+#define CRYPTO_H
+
+#ifdef ENABLE_CRYPTO
+
+#define ALLOW_NON_CBC_CIPHERS
+
+#include "crypto_backend.h"
+#include "basic.h"
+#include "buffer.h"
+#include "packet_id.h"
+#include "mtu.h"
+
+/*
+ * Defines a key type and key length for both cipher and HMAC.
+ */
+struct key_type
+{
+ uint8_t cipher_length; /**< Cipher length, in bytes */
+ uint8_t hmac_length; /**< HMAC length, in bytes */
+ const cipher_kt_t *cipher; /**< Cipher static parameters */
+ const md_kt_t *digest; /**< Message digest static parameters */
+};
+
+/**
+ * Container for unidirectional cipher and HMAC %key material.
+ * @ingroup control_processor
+ */
+struct key
+{
+ uint8_t cipher[MAX_CIPHER_KEY_LENGTH];
+ /**< %Key material for cipher operations. */
+ uint8_t hmac[MAX_HMAC_KEY_LENGTH];
+ /**< %Key material for HMAC operations. */
+};
+
+
+/**
+ * Container for one set of OpenSSL cipher and/or HMAC contexts.
+ * @ingroup control_processor
+ */
+struct key_ctx
+{
+ cipher_ctx_t *cipher; /**< Generic cipher %context. */
+ hmac_ctx_t *hmac; /**< Generic HMAC %context. */
+};
+
+#define KEY_DIRECTION_BIDIRECTIONAL 0 /* same keys for both directions */
+#define KEY_DIRECTION_NORMAL 1 /* encrypt with keys[0], decrypt with keys[1] */
+#define KEY_DIRECTION_INVERSE 2 /* encrypt with keys[1], decrypt with keys[0] */
+
+/**
+ * Container for bidirectional cipher and HMAC %key material.
+ * @ingroup control_processor
+ */
+struct key2
+{
+ int n; /**< The number of \c key objects stored
+ * in the \c key2.keys array. */
+ struct key keys[2]; /**< Two unidirectional sets of %key
+ * material. */
+};
+
+/**
+ * %Key ordering of the \c key2.keys array.
+ * @ingroup control_processor
+ *
+ * This structure takes care of correct ordering when using unidirectional
+ * or bidirectional %key material, and allows the same shared secret %key
+ * file to be loaded in the same way by client and server by having one of
+ * the hosts use an reversed ordering.
+ */
+struct key_direction_state
+{
+ int out_key; /**< Index into the \c key2.keys array for
+ * the sending direction. */
+ int in_key; /**< Index into the \c key2.keys array for
+ * the receiving direction. */
+ int need_keys; /**< The number of key objects necessary
+ * to support both sending and
+ * receiving.
+ *
+ * This will be 1 if the same keys are
+ * used in both directions, or 2 if
+ * there are two sets of unidirectional
+ * keys. */
+};
+
+/**
+ * Container for two sets of OpenSSL cipher and/or HMAC contexts for both
+ * sending and receiving directions.
+ * @ingroup control_processor
+ */
+struct key_ctx_bi
+{
+ struct key_ctx encrypt; /**< OpenSSL cipher and/or HMAC contexts
+ * for sending direction. */
+ struct key_ctx decrypt; /**< OpenSSL cipher and/or HMAC contexts
+ * for receiving direction. */
+};
+
+/**
+ * Security parameter state for processing data channel packets.
+ * @ingroup data_crypto
+ */
+struct crypto_options
+{
+ struct key_ctx_bi *key_ctx_bi;
+ /**< OpenSSL cipher and HMAC contexts for
+ * both sending and receiving
+ * directions. */
+ struct packet_id *packet_id; /**< Current packet ID state for both
+ * sending and receiving directions. */
+ struct packet_id_persist *pid_persist;
+ /**< Persistent packet ID state for
+ * keeping state between successive
+ * OpenVPN process startups. */
+
+# define CO_PACKET_ID_LONG_FORM (1<<0)
+ /**< Bit-flag indicating whether to use
+ * OpenVPN's long packet ID format. */
+# define CO_USE_IV (1<<1)
+ /**< Bit-flag indicating whether to
+ * generate a pseudo-random IV for each
+ * packet being encrypted. */
+# define CO_IGNORE_PACKET_ID (1<<2)
+ /**< Bit-flag indicating whether to ignore
+ * the packet ID of a received packet.
+ * This flag is used during processing
+ * of the first packet received from a
+ * client. */
+# define CO_MUTE_REPLAY_WARNINGS (1<<3)
+ /**< Bit-flag indicating not to display
+ * replay warnings. */
+ unsigned int flags; /**< Bit-flags determining behavior of
+ * security operation functions. */
+};
+
+#define RKF_MUST_SUCCEED (1<<0)
+#define RKF_INLINE (1<<1)
+void read_key_file (struct key2 *key2, const char *file, const unsigned int flags);
+
+int write_key_file (const int nkeys, const char *filename);
+
+int read_passphrase_hash (const char *passphrase_file,
+ const md_kt_t *digest,
+ uint8_t *output,
+ int len);
+
+void generate_key_random (struct key *key, const struct key_type *kt);
+
+void check_replay_iv_consistency(const struct key_type *kt, bool packet_id, bool use_iv);
+
+bool check_key (struct key *key, const struct key_type *kt);
+
+void fixup_key (struct key *key, const struct key_type *kt);
+
+bool write_key (const struct key *key, const struct key_type *kt,
+ struct buffer *buf);
+
+int read_key (struct key *key, const struct key_type *kt, struct buffer *buf);
+
+bool cfb_ofb_mode (const struct key_type* kt);
+
+void init_key_type (struct key_type *kt, const char *ciphername,
+ bool ciphername_defined, const char *authname, bool authname_defined,
+ int keysize, bool cfb_ofb_allowed, bool warn);
+
+/*
+ * Key context functions
+ */
+
+void init_key_ctx (struct key_ctx *ctx, struct key *key,
+ const struct key_type *kt, int enc,
+ const char *prefix);
+
+void free_key_ctx (struct key_ctx *ctx);
+
+void free_key_ctx_bi (struct key_ctx_bi *ctx);
+
+
+/**************************************************************************/
+/** @name Functions for performing security operations on data channel packets
+ * @{ */
+
+/**
+ * Encrypt and HMAC sign a packet so that it can be sent as a data channel
+ * VPN tunnel packet to a remote OpenVPN peer.
+ * @ingroup data_crypto
+ *
+ * This function handles encryption and HMAC signing of a data channel
+ * packet before it is sent to its remote OpenVPN peer. It receives the
+ * necessary security parameters in the \a opt argument, which should have
+ * been set to the correct values by the \c tls_pre_encrypt() function.
+ *
+ * This function calls the \c EVP_Cipher* and \c HMAC_* functions of the
+ * OpenSSL library to perform the actual security operations.
+ *
+ * If an error occurs during processing, then the \a buf %buffer is set to
+ * empty.
+ *
+ * @param buf - The %buffer containing the packet on which to
+ * perform security operations.
+ * @param work - A working %buffer.
+ * @param opt - The security parameter state for this VPN tunnel.
+ * @param frame - The packet geometry parameters for this VPN
+ * tunnel.
+ * @return This function returns void.\n On return, the \a buf argument
+ * will point to the resulting %buffer. This %buffer will either
+ * contain the processed packet ready for sending, or be empty if an
+ * error occurred.
+ */
+void openvpn_encrypt (struct buffer *buf, struct buffer work,
+ const struct crypto_options *opt,
+ const struct frame* frame);
+
+
+/**
+ * HMAC verify and decrypt a data channel packet received from a remote
+ * OpenVPN peer.
+ * @ingroup data_crypto
+ *
+ * This function handles authenticating and decrypting a data channel
+ * packet received from a remote OpenVPN peer. It receives the necessary
+ * security parameters in the \a opt argument, which should have been set
+ * to the correct values by the \c tls_pre_decrypt() function.
+ *
+ * This function calls the \c EVP_Cipher* and \c HMAC_* functions of the
+ * OpenSSL library to perform the actual security operations.
+ *
+ * If an error occurs during processing, then the \a buf %buffer is set to
+ * empty.
+ *
+ * @param buf - The %buffer containing the packet received from a
+ * remote OpenVPN peer on which to perform security
+ * operations.
+ * @param work - A working %buffer.
+ * @param opt - The security parameter state for this VPN tunnel.
+ * @param frame - The packet geometry parameters for this VPN
+ * tunnel.
+ *
+ * @return
+ * @li True, if the packet was authenticated and decrypted successfully.
+ * @li False, if an error occurred. \n On return, the \a buf argument will
+ * point to the resulting %buffer. This %buffer will either contain
+ * the plaintext packet ready for further processing, or be empty if
+ * an error occurred.
+ */
+bool openvpn_decrypt (struct buffer *buf, struct buffer work,
+ const struct crypto_options *opt,
+ const struct frame* frame);
+
+/** @} name Functions for performing security operations on data channel packets */
+
+void crypto_adjust_frame_parameters(struct frame *frame,
+ const struct key_type* kt,
+ bool cipher_defined,
+ bool use_iv,
+ bool packet_id,
+ bool packet_id_long_form);
+
+
+/* Minimum length of the nonce used by the PRNG */
+#define NONCE_SECRET_LEN_MIN 16
+
+/* Maximum length of the nonce used by the PRNG */
+#define NONCE_SECRET_LEN_MAX 64
+
+/** Number of bytes of random to allow before resetting the nonce */
+#define PRNG_NONCE_RESET_BYTES 1024
+
+/**
+ * Pseudo-random number generator initialisation.
+ * (see \c prng_rand_bytes())
+ *
+ * @param md_name Name of the message digest to use
+ * @param nonce_secret_len_param Length of the nonce to use
+ */
+void prng_init (const char *md_name, const int nonce_secret_len_parm);
+
+/*
+ * Message digest-based pseudo random number generator.
+ *
+ * If the PRNG was initialised with a certain message digest, uses the digest
+ * to calculate the next random number, and prevent depletion of the entropy
+ * pool.
+ *
+ * This PRNG is aimed at IV generation and similar miscellaneous tasks. Use
+ * \c rand_bytes() for higher-assurance functionality.
+ *
+ * Retrieves len bytes of pseudo random data, and places it in output.
+ *
+ * @param output Output buffer
+ * @param len Length of the output buffer
+ */
+void prng_bytes (uint8_t *output, int len);
+
+void prng_uninit ();
+
+void test_crypto (const struct crypto_options *co, struct frame* f);
+
+
+/* key direction functions */
+
+void key_direction_state_init (struct key_direction_state *kds, int key_direction);
+
+void verify_fix_key2 (struct key2 *key2, const struct key_type *kt, const char *shared_secret_file);
+
+void must_have_n_keys (const char *filename, const char *option, const struct key2 *key2, int n);
+
+int ascii2keydirection (int msglevel, const char *str);
+
+const char *keydirection2ascii (int kd, bool remote);
+
+/* print keys */
+void key2_print (const struct key2* k,
+ const struct key_type *kt,
+ const char* prefix0,
+ const char* prefix1);
+
+#ifdef ENABLE_SSL
+
+#define GHK_INLINE (1<<0)
+void get_tls_handshake_key (const struct key_type *key_type,
+ struct key_ctx_bi *ctx,
+ const char *passphrase_file,
+ const int key_direction,
+ const unsigned int flags);
+
+#else
+
+void init_ssl_lib (void);
+void free_ssl_lib (void);
+
+#endif /* ENABLE_SSL */
+
+/*
+ * md5 functions
+ */
+
+struct md5_state {
+ md_ctx_t ctx;
+};
+
+struct md5_digest {
+ uint8_t digest [MD5_DIGEST_LENGTH];
+};
+
+const char *md5sum(uint8_t *buf, int len, int n_print_chars, struct gc_arena *gc);
+void md5_state_init (struct md5_state *s);
+void md5_state_update (struct md5_state *s, void *data, size_t len);
+void md5_state_final (struct md5_state *s, struct md5_digest *out);
+void md5_digest_clear (struct md5_digest *digest);
+bool md5_digest_defined (const struct md5_digest *digest);
+bool md5_digest_equal (const struct md5_digest *d1, const struct md5_digest *d2);
+
+/*
+ * Inline functions
+ */
+
+static inline bool
+key_ctx_bi_defined(const struct key_ctx_bi* key)
+{
+ return key->encrypt.cipher || key->encrypt.hmac || key->decrypt.cipher || key->decrypt.hmac;
+}
+
+
+#endif /* ENABLE_CRYPTO */
+#endif /* CRYPTO_H */