crypto_backend.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) 2002-2026 OpenVPN Inc <sales@openvpn.net>
 *  Copyright (C) 2010-2026 Sentyron B.V. <openvpn@sentyron.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, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef CRYPTO_BACKEND_H_
#define CRYPTO_BACKEND_H_
 
#ifdef ENABLE_CRYPTO_OPENSSL
#include "crypto_openssl.h"
#endif
 
#ifdef ENABLE_CRYPTO_MBEDTLS
#include <mbedtls/version.h>
#if MBEDTLS_VERSION_NUMBER < 0x04000000
#include "crypto_mbedtls_legacy.h"
#else
#include "crypto_mbedtls.h"
#endif
#endif
 
#include "basic.h"
#include "buffer.h"
 
/* TLS uses a tag of 128 bits, let's do the same for OpenVPN */
#define OPENVPN_AEAD_TAG_LENGTH 16
 
/* Maximum cipher block size (bytes) */
#define OPENVPN_MAX_CIPHER_BLOCK_SIZE 32
 
/* Maximum HMAC digest size (bytes) */
#define OPENVPN_MAX_HMAC_SIZE 64
 
typedef enum
{
    MD_SHA1,
    MD_SHA256
} hash_algo_type;
 
typedef struct
{
    const char *openvpn_name; 
    const char *lib_name;     
} cipher_name_pair;
 
extern const cipher_name_pair cipher_name_translation_table[];
extern const size_t cipher_name_translation_table_count;
 
/*
 * This routine should have additional OpenSSL crypto library initialisations
 * used by both crypto and ssl components of OpenVPN.
 */
void crypto_init_lib(void);
 
void crypto_uninit_lib(void);
 
void crypto_clear_error(void);
 
/*
 * Initialise the given named crypto engine.
 */
void crypto_init_lib_engine(const char *engine_name);
 
 
provider_t *crypto_load_provider(const char *provider);
 
void crypto_unload_provider(const char *provname, provider_t *provider);
 
void show_available_ciphers(void);
 
void show_available_digests(void);
 
void show_available_engines(void);
 
bool crypto_pem_encode(const char *name, struct buffer *dst, const struct buffer *src,
                       struct gc_arena *gc);
 
bool crypto_pem_decode(const char *name, struct buffer *dst, const struct buffer *src);
 
/*
 *
 * Random number functions, used in cases where we want
 * reasonably strong cryptographic random number generation
 * without depleting our entropy pool.  Used for random
 * IV values and a number of other miscellaneous tasks.
 *
 */
 
int rand_bytes(uint8_t *output, int len);
 
/*
 *
 * Generic cipher key type functions
 *
 */
/*
 * Max size in bytes of any cipher key that might conceivably be used.
 *
 * This value is checked at compile time in crypto.c to make sure
 * it is always at least EVP_MAX_KEY_LENGTH.
 *
 * We define our own value, since this parameter
 * is used to control the size of static key files.
 * If the OpenSSL library increases EVP_MAX_KEY_LENGTH,
 * we don't want our key files to be suddenly rendered
 * unusable.
 */
#define MAX_CIPHER_KEY_LENGTH 64
 
bool cipher_valid_reason(const char *ciphername, const char **reason);
 
static inline bool
cipher_valid(const char *ciphername)
{
    const char *reason;
    return cipher_valid_reason(ciphername, &reason);
}
 
static inline bool
cipher_defined(const char *ciphername)
{
    ASSERT(ciphername);
    return strcmp(ciphername, "none") != 0;
}
 
const char *cipher_kt_name(const char *ciphername);
 
unsigned int cipher_kt_key_size(const char *ciphername);
 
unsigned int cipher_kt_iv_size(const char *ciphername);
 
unsigned int cipher_kt_block_size(const char *ciphername);
 
unsigned int cipher_kt_tag_size(const char *ciphername);
 
bool cipher_kt_insecure(const char *ciphername);
 
 
bool cipher_kt_mode_cbc(const char *ciphername);
 
bool cipher_kt_mode_ofb_cfb(const char *ciphername);
 
bool cipher_kt_mode_aead(const char *ciphername);
 
 
cipher_ctx_t *cipher_ctx_new(void);
 
void cipher_ctx_free(cipher_ctx_t *ctx);
 
void cipher_ctx_init(cipher_ctx_t *ctx, const uint8_t *key, const char *ciphername,
                     crypto_operation_t enc);
 
unsigned int cipher_ctx_iv_length(const cipher_ctx_t *ctx);
 
int cipher_ctx_get_tag(cipher_ctx_t *ctx, uint8_t *tag, int tag_len);
 
unsigned int cipher_ctx_block_size(const cipher_ctx_t *ctx);
 
int cipher_ctx_mode(const cipher_ctx_t *ctx);
 
bool cipher_ctx_mode_cbc(const cipher_ctx_t *ctx);
 
bool cipher_ctx_mode_ofb_cfb(const cipher_ctx_t *ctx);
 
bool cipher_ctx_mode_aead(const cipher_ctx_t *ctx);
 
int cipher_ctx_reset(cipher_ctx_t *ctx, const uint8_t *iv_buf);
 
int cipher_ctx_update_ad(cipher_ctx_t *ctx, const uint8_t *src, int src_len);
 
int cipher_ctx_update(cipher_ctx_t *ctx, uint8_t *dst, int *dst_len, uint8_t *src, int src_len);
 
int cipher_ctx_final(cipher_ctx_t *ctx, uint8_t *dst, int *dst_len);
 
int cipher_ctx_final_check_tag(cipher_ctx_t *ctx, uint8_t *dst, int *dst_len, uint8_t *tag,
                               size_t tag_len);
 
 
/*
 *
 * Generic message digest information functions
 *
 */
 
/*
 * Max size in bytes of any HMAC key that might conceivably be used.
 *
 * This value is checked at compile time in crypto.c to make sure
 * it is always at least EVP_MAX_MD_SIZE.  We define our own value
 * for the same reason as above.
 */
#define MAX_HMAC_KEY_LENGTH 64
 
static inline bool
md_defined(const char *mdname)
{
    return strcmp(mdname, "none") != 0;
}
 
 
bool md_valid(const char *digest);
 
const char *md_kt_name(const char *mdname);
 
unsigned char md_kt_size(const char *mdname);
 
 
/*
 *
 * Generic message digest functions
 *
 */
 
/*
 * Allocate a new message digest context
 *
 * @return              a new zeroed MD context
 */
md_ctx_t *md_ctx_new(void);
 
/*
 * Free an existing, non-null message digest context
 *
 * @param ctx           Message digest context
 */
void md_ctx_free(md_ctx_t *ctx);
 
void md_ctx_init(md_ctx_t *ctx, const char *mdname);
 
/*
 * Free the given message digest context.
 *
 * @param ctx           Message digest context
 */
void md_ctx_cleanup(md_ctx_t *ctx);
 
/*
 * Returns the size of the message digest output by the given context
 *
 * @param ctx           Message digest context.
 *
 * @return              Size of the message digest, or \0 if ctx is NULL.
 */
int md_ctx_size(const md_ctx_t *ctx);
 
/*
 * Process the given data for use in the message digest.
 *
 * @param ctx           Message digest context. May not be NULL.
 * @param src           Buffer to digest. May not be NULL.
 * @param src_len       The length of the incoming buffer.
 */
void md_ctx_update(md_ctx_t *ctx, const uint8_t *src, size_t src_len);
 
/*
 * Output the message digest to the given buffer.
 *
 * @param ctx           Message digest context. May not be NULL.
 * @param dst           Buffer to write the message digest to. May not be NULL.
 */
void md_ctx_final(md_ctx_t *ctx, uint8_t *dst);
 
 
/*
 *
 * Generic HMAC functions
 *
 */
 
/*
 * Create a new HMAC context
 *
 * @return              A new HMAC context
 */
hmac_ctx_t *hmac_ctx_new(void);
 
/*
 * Free an existing HMAC context
 *
 * @param  ctx           HMAC context to free
 */
void hmac_ctx_free(hmac_ctx_t *ctx);
 
/*
 * Initialises the given HMAC context, using the given digest
 * and key.
 *
 * @param ctx           HMAC context to initialise
 * @param key           The key to use for the HMAC
 * @param mdname        message digest name
 *
 */
void hmac_ctx_init(hmac_ctx_t *ctx, const uint8_t *key, const char *mdname);
 
 
/*
 * Free the given HMAC context.
 *
 * @param ctx           HMAC context
 */
void hmac_ctx_cleanup(hmac_ctx_t *ctx);
 
/*
 * Returns the size of the HMAC output by the given HMAC Context
 *
 * @param ctx           HMAC context.
 *
 * @return              Size of the HMAC, or \0 if ctx is NULL.
 */
int hmac_ctx_size(hmac_ctx_t *ctx);
 
/*
 * Resets the given HMAC context, preserving the associated key information
 *
 * @param ctx           HMAC context. May not be NULL.
 */
void hmac_ctx_reset(hmac_ctx_t *ctx);
 
/*
 * Process the given data for use in the HMAC.
 *
 * @param ctx           HMAC context. May not be NULL.
 * @param src           The buffer to HMAC. May not be NULL.
 * @param src_len       The length of the incoming buffer.
 */
void hmac_ctx_update(hmac_ctx_t *ctx, const uint8_t *src, int src_len);
 
/*
 * Output the HMAC to the given buffer.
 *
 * @param ctx           HMAC context. May not be NULL.
 * @param dst           buffer to write the HMAC to. May not be NULL.
 */
void hmac_ctx_final(hmac_ctx_t *ctx, uint8_t *dst);
 
const char *translate_cipher_name_from_openvpn(const char *cipher_name);
 
const char *translate_cipher_name_to_openvpn(const char *cipher_name);
 
 
bool ssl_tls1_PRF(const uint8_t *seed, size_t seed_len, const uint8_t *secret, size_t secret_len,
                  uint8_t *output, size_t output_len);
 
#endif /* CRYPTO_BACKEND_H_ */