mbedtls/library/ecp_invasive.h
Gilles Peskine 7967ec5d25 mbedtls_ecp_gen_privkey_sw: generalize to mbedtls_mpi_random
Rename mbedtls_ecp_gen_privkey_sw to mbedtls_mpi_random since it has
no particular connection to elliptic curves beyond the fact that its
operation is defined by the deterministic ECDSA specification. This is
a generic function that generates a random MPI between 1 inclusive and
N exclusive.

Slightly generalize the function to accept a different lower bound,
which adds a negligible amount of complexity.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2021-06-02 21:31:24 +02:00

115 lines
4.4 KiB
C

/**
* \file ecp_invasive.h
*
* \brief ECP module: interfaces for invasive testing only.
*
* The interfaces in this file are intended for testing purposes only.
* They SHOULD NOT be made available in library integrations except when
* building the library for testing.
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef MBEDTLS_ECP_INVASIVE_H
#define MBEDTLS_ECP_INVASIVE_H
#include "common.h"
#include "mbedtls/bignum.h"
#include "mbedtls/ecp.h"
#if defined(MBEDTLS_TEST_HOOKS) && defined(MBEDTLS_ECP_C)
#if defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED) || \
defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED) || \
defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
/* Preconditions:
* - bits is a multiple of 64 or is 224
* - c is -1 or -2
* - 0 <= N < 2^bits
* - N has room for bits plus one limb
*
* Behavior:
* Set N to c * 2^bits + old_value_of_N.
*/
void mbedtls_ecp_fix_negative( mbedtls_mpi *N, signed char c, size_t bits );
#endif
#if defined(MBEDTLS_ECP_MONTGOMERY_ENABLED)
/** Generate a private key on a Montgomery curve (Curve25519 or Curve448).
*
* This function implements key generation for the set of secret keys
* specified in [Curve25519] p. 5 and in [Curve448]. The resulting value
* has the lower bits masked but is not necessarily canonical.
*
* \note - [Curve25519] http://cr.yp.to/ecdh/curve25519-20060209.pdf
* - [RFC7748] https://tools.ietf.org/html/rfc7748
*
* \p high_bit The position of the high-order bit of the key to generate.
* This is the bit-size of the key minus 1:
* 254 for Curve25519 or 447 for Curve448.
* \param d The randomly generated key. This is a number of size
* exactly \p n_bits + 1 bits, with the least significant bits
* masked as specified in [Curve25519] and in [RFC7748] §5.
* \param f_rng The RNG function.
* \param p_rng The RNG context to be passed to \p f_rng.
*
* \return \c 0 on success.
* \return \c MBEDTLS_ERR_ECP_xxx or MBEDTLS_ERR_MPI_xxx on failure.
*/
int mbedtls_ecp_gen_privkey_mx( size_t n_bits,
mbedtls_mpi *d,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
#endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
#if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
/** Generate a random number uniformly in a range.
*
* This function generates a random number between \p min inclusive and
* \p N exclusive.
*
* The procedure complies with RFC 6979 §3.3 (deterministic ECDSA)
* when the RNG is a suitably parametrized instance of HMAC_DRBG
* and \p min is \c 1.
*
* \note There are `N - min` possible outputs. The lower bound
* \p min can be reached, but the upper bound \p N cannot.
*
* \param X The destination MPI. This must point to an initialized MPI.
* \param min The minimum value to return.
* It must be nonnegative.
* \param N The upper bound of the range, exclusive.
* In other words, this is one plus the maximum value to return.
* \p N must be strictly larger than \p min.
* \param f_rng The RNG function to use. This must not be \c NULL.
* \param p_rng The RNG parameter to be passed to \p f_rng.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if a memory allocation failed.
* \return Another negative error code on failure.
*/
int mbedtls_mpi_random( mbedtls_mpi *X,
mbedtls_mpi_sint min,
const mbedtls_mpi *N,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
#endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
#endif /* MBEDTLS_TEST_HOOKS && MBEDTLS_ECP_C */
#endif /* MBEDTLS_ECP_INVASIVE_H */