1 /** 2 * \file rsa_alt_helpers.h 3 * 4 * \brief Context-independent RSA helper functions 5 * 6 * This module declares some RSA-related helper functions useful when 7 * implementing the RSA interface. These functions are provided in a separate 8 * compilation unit in order to make it easy for designers of alternative RSA 9 * implementations to use them in their own code, as it is conceived that the 10 * functionality they provide will be necessary for most complete 11 * implementations. 12 * 13 * End-users of Mbed TLS who are not providing their own alternative RSA 14 * implementations should not use these functions directly, and should instead 15 * use only the functions declared in rsa.h. 16 * 17 * The interface provided by this module will be maintained through LTS (Long 18 * Term Support) branches of Mbed TLS, but may otherwise be subject to change, 19 * and must be considered an internal interface of the library. 20 * 21 * There are two classes of helper functions: 22 * 23 * (1) Parameter-generating helpers. These are: 24 * - mbedtls_rsa_deduce_primes 25 * - mbedtls_rsa_deduce_private_exponent 26 * - mbedtls_rsa_deduce_crt 27 * Each of these functions takes a set of core RSA parameters and 28 * generates some other, or CRT related parameters. 29 * 30 * (2) Parameter-checking helpers. These are: 31 * - mbedtls_rsa_validate_params 32 * - mbedtls_rsa_validate_crt 33 * They take a set of core or CRT related RSA parameters and check their 34 * validity. 35 * 36 */ 37 /* 38 * Copyright The Mbed TLS Contributors 39 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 40 */ 41 #ifndef MBEDTLS_RSA_ALT_HELPERS_H 42 #define MBEDTLS_RSA_ALT_HELPERS_H 43 44 #include "mbedtls/build_info.h" 45 46 #include "mbedtls/bignum.h" 47 48 #ifdef __cplusplus 49 extern "C" { 50 #endif 51 52 53 /** 54 * \brief Compute RSA prime moduli P, Q from public modulus N=PQ 55 * and a pair of private and public key. 56 * 57 * \note This is a 'static' helper function not operating on 58 * an RSA context. Alternative implementations need not 59 * overwrite it. 60 * 61 * \param N RSA modulus N = PQ, with P, Q to be found 62 * \param E RSA public exponent 63 * \param D RSA private exponent 64 * \param P Pointer to MPI holding first prime factor of N on success 65 * \param Q Pointer to MPI holding second prime factor of N on success 66 * 67 * \return 68 * - 0 if successful. In this case, P and Q constitute a 69 * factorization of N. 70 * - A non-zero error code otherwise. 71 * 72 * \note It is neither checked that P, Q are prime nor that 73 * D, E are modular inverses wrt. P-1 and Q-1. For that, 74 * use the helper function \c mbedtls_rsa_validate_params. 75 * 76 */ 77 int mbedtls_rsa_deduce_primes(mbedtls_mpi const *N, mbedtls_mpi const *E, 78 mbedtls_mpi const *D, 79 mbedtls_mpi *P, mbedtls_mpi *Q); 80 81 /** 82 * \brief Compute RSA private exponent from 83 * prime moduli and public key. 84 * 85 * \note This is a 'static' helper function not operating on 86 * an RSA context. Alternative implementations need not 87 * overwrite it. 88 * 89 * \param P First prime factor of RSA modulus 90 * \param Q Second prime factor of RSA modulus 91 * \param E RSA public exponent 92 * \param D Pointer to MPI holding the private exponent on success, 93 * i.e. the modular inverse of E modulo LCM(P-1,Q-1). 94 * 95 * \return \c 0 if successful. 96 * \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if a memory allocation failed. 97 * \return #MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if E is not coprime to P-1 98 * and Q-1, that is, if GCD( E, (P-1)*(Q-1) ) != 1. 99 * \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if inputs are otherwise 100 * invalid. 101 * 102 * \note This function does not check whether P and Q are primes. 103 * 104 */ 105 int mbedtls_rsa_deduce_private_exponent(mbedtls_mpi const *P, 106 mbedtls_mpi const *Q, 107 mbedtls_mpi const *E, 108 mbedtls_mpi *D); 109 110 111 /** 112 * \brief Generate RSA-CRT parameters 113 * 114 * \note This is a 'static' helper function not operating on 115 * an RSA context. Alternative implementations need not 116 * overwrite it. 117 * 118 * \param P First prime factor of N 119 * \param Q Second prime factor of N 120 * \param D RSA private exponent 121 * \param DP Output variable for D modulo P-1 122 * \param DQ Output variable for D modulo Q-1 123 * \param QP Output variable for the modular inverse of Q modulo P. 124 * 125 * \return 0 on success, non-zero error code otherwise. 126 * 127 * \note This function does not check whether P, Q are 128 * prime and whether D is a valid private exponent. 129 * 130 */ 131 int mbedtls_rsa_deduce_crt(const mbedtls_mpi *P, const mbedtls_mpi *Q, 132 const mbedtls_mpi *D, mbedtls_mpi *DP, 133 mbedtls_mpi *DQ, mbedtls_mpi *QP); 134 135 136 /** 137 * \brief Check validity of core RSA parameters 138 * 139 * \note This is a 'static' helper function not operating on 140 * an RSA context. Alternative implementations need not 141 * overwrite it. 142 * 143 * \param N RSA modulus N = PQ 144 * \param P First prime factor of N 145 * \param Q Second prime factor of N 146 * \param D RSA private exponent 147 * \param E RSA public exponent 148 * \param f_rng PRNG to be used for primality check, or NULL 149 * \param p_rng PRNG context for f_rng, or NULL 150 * 151 * \return 152 * - 0 if the following conditions are satisfied 153 * if all relevant parameters are provided: 154 * - P prime if f_rng != NULL (%) 155 * - Q prime if f_rng != NULL (%) 156 * - 1 < N = P * Q 157 * - 1 < D, E < N 158 * - D and E are modular inverses modulo P-1 and Q-1 159 * (%) This is only done if MBEDTLS_GENPRIME is defined. 160 * - A non-zero error code otherwise. 161 * 162 * \note The function can be used with a restricted set of arguments 163 * to perform specific checks only. E.g., calling it with 164 * (-,P,-,-,-) and a PRNG amounts to a primality check for P. 165 */ 166 int mbedtls_rsa_validate_params(const mbedtls_mpi *N, const mbedtls_mpi *P, 167 const mbedtls_mpi *Q, const mbedtls_mpi *D, 168 const mbedtls_mpi *E, 169 int (*f_rng)(void *, unsigned char *, size_t), 170 void *p_rng); 171 172 /** 173 * \brief Check validity of RSA CRT parameters 174 * 175 * \note This is a 'static' helper function not operating on 176 * an RSA context. Alternative implementations need not 177 * overwrite it. 178 * 179 * \param P First prime factor of RSA modulus 180 * \param Q Second prime factor of RSA modulus 181 * \param D RSA private exponent 182 * \param DP MPI to check for D modulo P-1 183 * \param DQ MPI to check for D modulo P-1 184 * \param QP MPI to check for the modular inverse of Q modulo P. 185 * 186 * \return 187 * - 0 if the following conditions are satisfied: 188 * - D = DP mod P-1 if P, D, DP != NULL 189 * - Q = DQ mod P-1 if P, D, DQ != NULL 190 * - QP = Q^-1 mod P if P, Q, QP != NULL 191 * - \c MBEDTLS_ERR_RSA_KEY_CHECK_FAILED if check failed, 192 * potentially including \c MBEDTLS_ERR_MPI_XXX if some 193 * MPI calculations failed. 194 * - \c MBEDTLS_ERR_RSA_BAD_INPUT_DATA if insufficient 195 * data was provided to check DP, DQ or QP. 196 * 197 * \note The function can be used with a restricted set of arguments 198 * to perform specific checks only. E.g., calling it with the 199 * parameters (P, -, D, DP, -, -) will check DP = D mod P-1. 200 */ 201 int mbedtls_rsa_validate_crt(const mbedtls_mpi *P, const mbedtls_mpi *Q, 202 const mbedtls_mpi *D, const mbedtls_mpi *DP, 203 const mbedtls_mpi *DQ, const mbedtls_mpi *QP); 204 205 #ifdef __cplusplus 206 } 207 #endif 208 209 #endif /* rsa_alt_helpers.h */ 210