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/**
* \file rsa_alt_helpers.h
*
* \brief Context-independent RSA helper functions
*
* This module declares some RSA-related helper functions useful when
* implementing the RSA interface. These functions are provided in a separate
* compilation unit in order to make it easy for designers of alternative RSA
* implementations to use them in their own code, as it is conceived that the
* functionality they provide will be necessary for most complete
* implementations.
*
* End-users of Mbed TLS who are not providing their own alternative RSA
* implementations should not use these functions directly, and should instead
* use only the functions declared in rsa.h.
*
* The interface provided by this module will be maintained through LTS (Long
* Term Support) branches of Mbed TLS, but may otherwise be subject to change,
* and must be considered an internal interface of the library.
*
* There are two classes of helper functions:
*
* (1) Parameter-generating helpers. These are:
* - mbedtls_rsa_deduce_primes
* - mbedtls_rsa_deduce_private_exponent
* - mbedtls_rsa_deduce_crt
* Each of these functions takes a set of core RSA parameters and
* generates some other, or CRT related parameters.
*
* (2) Parameter-checking helpers. These are:
* - mbedtls_rsa_validate_params
* - mbedtls_rsa_validate_crt
* They take a set of core or CRT related RSA parameters and check their
* validity.
*
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#ifndef MBEDTLS_RSA_ALT_HELPERS_H
#define MBEDTLS_RSA_ALT_HELPERS_H
#include "mbedtls/build_info.h"
#include "mbedtls/bignum.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief Compute RSA prime moduli P, Q from public modulus N=PQ
* and a pair of private and public key.
*
* \note This is a 'static' helper function not operating on
* an RSA context. Alternative implementations need not
* overwrite it.
*
* \param N RSA modulus N = PQ, with P, Q to be found
* \param E RSA public exponent
* \param D RSA private exponent
* \param P Pointer to MPI holding first prime factor of N on success
* \param Q Pointer to MPI holding second prime factor of N on success
*
* \return
* - 0 if successful. In this case, P and Q constitute a
* factorization of N.
* - A non-zero error code otherwise.
*
* \note It is neither checked that P, Q are prime nor that
* D, E are modular inverses wrt. P-1 and Q-1. For that,
* use the helper function \c mbedtls_rsa_validate_params.
*
*/
int mbedtls_rsa_deduce_primes(mbedtls_mpi const *N, mbedtls_mpi const *E,
mbedtls_mpi const *D,
mbedtls_mpi *P, mbedtls_mpi *Q);
/**
* \brief Compute RSA private exponent from
* prime moduli and public key.
*
* \note This is a 'static' helper function not operating on
* an RSA context. Alternative implementations need not
* overwrite it.
*
* \param P First prime factor of RSA modulus
* \param Q Second prime factor of RSA modulus
* \param E RSA public exponent
* \param D Pointer to MPI holding the private exponent on success.
*
* \return
* - 0 if successful. In this case, D is set to a simultaneous
* modular inverse of E modulo both P-1 and Q-1.
* - A non-zero error code otherwise.
*
* \note This function does not check whether P and Q are primes.
*
*/
int mbedtls_rsa_deduce_private_exponent(mbedtls_mpi const *P,
mbedtls_mpi const *Q,
mbedtls_mpi const *E,
mbedtls_mpi *D);
/**
* \brief Generate RSA-CRT parameters
*
* \note This is a 'static' helper function not operating on
* an RSA context. Alternative implementations need not
* overwrite it.
*
* \param P First prime factor of N
* \param Q Second prime factor of N
* \param D RSA private exponent
* \param DP Output variable for D modulo P-1
* \param DQ Output variable for D modulo Q-1
* \param QP Output variable for the modular inverse of Q modulo P.
*
* \return 0 on success, non-zero error code otherwise.
*
* \note This function does not check whether P, Q are
* prime and whether D is a valid private exponent.
*
*/
int mbedtls_rsa_deduce_crt(const mbedtls_mpi *P, const mbedtls_mpi *Q,
const mbedtls_mpi *D, mbedtls_mpi *DP,
mbedtls_mpi *DQ, mbedtls_mpi *QP);
/**
* \brief Check validity of core RSA parameters
*
* \note This is a 'static' helper function not operating on
* an RSA context. Alternative implementations need not
* overwrite it.
*
* \param N RSA modulus N = PQ
* \param P First prime factor of N
* \param Q Second prime factor of N
* \param D RSA private exponent
* \param E RSA public exponent
* \param f_rng PRNG to be used for primality check, or NULL
* \param p_rng PRNG context for f_rng, or NULL
*
* \return
* - 0 if the following conditions are satisfied
* if all relevant parameters are provided:
* - P prime if f_rng != NULL (%)
* - Q prime if f_rng != NULL (%)
* - 1 < N = P * Q
* - 1 < D, E < N
* - D and E are modular inverses modulo P-1 and Q-1
* (%) This is only done if MBEDTLS_GENPRIME is defined.
* - A non-zero error code otherwise.
*
* \note The function can be used with a restricted set of arguments
* to perform specific checks only. E.g., calling it with
* (-,P,-,-,-) and a PRNG amounts to a primality check for P.
*/
int mbedtls_rsa_validate_params(const mbedtls_mpi *N, const mbedtls_mpi *P,
const mbedtls_mpi *Q, const mbedtls_mpi *D,
const mbedtls_mpi *E,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng);
/**
* \brief Check validity of RSA CRT parameters
*
* \note This is a 'static' helper function not operating on
* an RSA context. Alternative implementations need not
* overwrite it.
*
* \param P First prime factor of RSA modulus
* \param Q Second prime factor of RSA modulus
* \param D RSA private exponent
* \param DP MPI to check for D modulo P-1
* \param DQ MPI to check for D modulo P-1
* \param QP MPI to check for the modular inverse of Q modulo P.
*
* \return
* - 0 if the following conditions are satisfied:
* - D = DP mod P-1 if P, D, DP != NULL
* - Q = DQ mod P-1 if P, D, DQ != NULL
* - QP = Q^-1 mod P if P, Q, QP != NULL
* - \c MBEDTLS_ERR_RSA_KEY_CHECK_FAILED if check failed,
* potentially including \c MBEDTLS_ERR_MPI_XXX if some
* MPI calculations failed.
* - \c MBEDTLS_ERR_RSA_BAD_INPUT_DATA if insufficient
* data was provided to check DP, DQ or QP.
*
* \note The function can be used with a restricted set of arguments
* to perform specific checks only. E.g., calling it with the
* parameters (P, -, D, DP, -, -) will check DP = D mod P-1.
*/
int mbedtls_rsa_validate_crt(const mbedtls_mpi *P, const mbedtls_mpi *Q,
const mbedtls_mpi *D, const mbedtls_mpi *DP,
const mbedtls_mpi *DQ, const mbedtls_mpi *QP);
#ifdef __cplusplus
}
#endif
#endif /* rsa_alt_helpers.h */
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