lc_cshake_crypt.h

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/*
 * Copyright (C) 2022 - 2024, Stephan Mueller <smueller@chronox.de>
 *
 * License: see LICENSE file in root directory
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */
 
#ifndef LC_CSHAKE_CRYPT_H
#define LC_CSHAKE_CRYPT_H
 
#include "lc_aead.h"
#include "lc_memory_support.h"
 
/*
 * This is the CSHAKE crypt cipher operation using the CSHAKE output as
 * keystream
 */
#include "lc_cshake.h"
#include "lc_memset_secure.h"
 
#ifdef __cplusplus
extern "C" {
#endif
 
struct lc_cc_cryptor {
        struct lc_hash_ctx cshake;
        struct lc_cshake_ctx auth_ctx;
        size_t keystream_ptr;
        uint8_t *keystream;
};
 
/*
 * The block size of the algorithm for generating the key stream. It must be
 * a multiple of the cSHAKE block size.
 */
#define LC_CC_KEYSTREAM_BLOCK LC_SHA3_256_SIZE_BLOCK
 
#define LC_CSHAKE_CRYPT_ALIGNMENT LC_XOR_ALIGNMENT(LC_HASH_COMMON_ALIGNMENT)
 
#define LC_ALIGN_CSHAKE_CRYPT_MASK(p)                                          \
        LC_ALIGN_PTR_8(p, LC_ALIGNMENT_MASK(LC_CSHAKE_CRYPT_ALIGNMENT))
 
/*
 * One block LC_CSHAKE_CRYPT_ALIGNMENT is required to ensure the
 * ->keystream pointer is aligned
 */
#define LC_CC_STATE_SIZE(x)                                                    \
        (LC_HASH_STATE_SIZE(x) + LC_CSHAKE_STATE_SIZE_REINIT(x) +              \
         LC_CC_KEYSTREAM_BLOCK + LC_CSHAKE_CRYPT_ALIGNMENT)
#define LC_CC_CTX_SIZE(x)                                                      \
        (sizeof(struct lc_aead) + sizeof(struct lc_cc_cryptor) +               \
         LC_CC_STATE_SIZE(x))
 
/* CSHAKE-based AEAD-algorithm */
extern const struct lc_aead *lc_cshake_aead;
 
/* Ensure that ->keystream is aligned to XOR alignment requirement */
#define _LC_CC_SET_CTX(name, hashname)                                         \
        _LC_HASH_SET_CTX((&name->cshake), hashname, name,                      \
                         (sizeof(struct lc_cc_cryptor)));                      \
        _LC_CSHAKE_SET_CTX_REINIT((&name->auth_ctx), hashname, name,           \
                                  (sizeof(struct lc_cc_cryptor) +              \
                                   LC_HASH_STATE_SIZE(hashname)));             \
        name->keystream = LC_ALIGN_CSHAKE_CRYPT_MASK(                          \
                (uint8_t *)((uint8_t *)name +                                  \
                            (sizeof(struct lc_cc_cryptor) +                    \
                             LC_HASH_STATE_SIZE(hashname) +                    \
                             LC_CSHAKE_STATE_SIZE_REINIT(hashname))))
 
#define LC_CC_SET_CTX(name, hashname)                                          \
        LC_AEAD_CTX(name, lc_cshake_aead);                                     \
        _LC_CC_SET_CTX(((struct lc_cc_cryptor *)name->aead_state), hashname)
 
int lc_cc_alloc(const struct lc_hash *hash, struct lc_aead_ctx **ctx);
 
#define LC_CC_CTX_ON_STACK(name, hash)                                              \
        _Pragma("GCC diagnostic push")                                              \
                _Pragma("GCC diagnostic ignored \"-Wvla\"") _Pragma(                \
                        "GCC diagnostic ignored \"-Wdeclaration-after-statement\"") \
                        LC_ALIGNED_BUFFER(name##_ctx_buf,                           \
                                          LC_CC_CTX_SIZE(hash),                     \
                                          LC_CSHAKE_CRYPT_ALIGNMENT);               \
        struct lc_aead_ctx *name = (struct lc_aead_ctx *)name##_ctx_buf;            \
        LC_CC_SET_CTX(name, hash);                                                  \
        _Pragma("GCC diagnostic pop")
/* invocation of lc_cc_zero_free(name); not needed */
 
#ifdef __cplusplus
}
#endif
 
#endif /* LC_CSHAKE_CRYPT_H */