crypto/rsa/rsa_sp800_56b_gen.c

   1 /*
   2  * Copyright 2018-2024 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright (c) 2018-2019, Oracle and/or its affiliates.  All rights reserved.
   4  *
   5  * Licensed under the Apache License 2.0 (the "License").  You may not use
   6  * this file except in compliance with the License.  You can obtain a copy
   7  * in the file LICENSE in the source distribution or at
   8  * https://www.openssl.org/source/license.html
   9  */
  10
  11 #include <openssl/err.h>
  12 #include <openssl/bn.h>
  13 #include <openssl/core.h>
  14 #include <openssl/evp.h>
  15 #include <openssl/rand.h>
  16 #include "crypto/bn.h"
  17 #include "crypto/security_bits.h"
  18 #include "rsa_local.h"
  19
  20 #define RSA_FIPS1864_MIN_KEYGEN_KEYSIZE 2048
  21 #define RSA_FIPS1864_MIN_KEYGEN_STRENGTH 112
  22
  23 /*
  24  * Generate probable primes 'p' & 'q'. See FIPS 186-4 Section B.3.6
  25  * "Generation of Probable Primes with Conditions Based on Auxiliary Probable
  26  * Primes".
  27  *
  28  * Params:
  29  *     rsa  Object used to store primes p & q.
  30  *     test Object used for CAVS testing only.that contains..
  31  *       p1, p2 The returned auxiliary primes for p.
  32  *              If NULL they are not returned.
  33  *       Xp An optional passed in value (that is random number used during
  34  *          generation of p).
  35  *       Xp1, Xp2 Optionally passed in randomly generated numbers from which
  36  *                auxiliary primes p1 & p2 are calculated. If NULL these values
  37  *                are generated internally.
  38  *       q1, q2 The returned auxiliary primes for q.
  39  *              If NULL they are not returned.
  40  *       Xq An optional passed in value (that is random number used during
  41  *          generation of q).
  42  *       Xq1, Xq2 Optionally passed in randomly generated numbers from which
  43  *                auxiliary primes q1 & q2 are calculated. If NULL these values
  44  *                are generated internally.
  45  *     nbits The key size in bits (The size of the modulus n).
  46  *     e The public exponent.
  47  *     ctx A BN_CTX object.
  48  *     cb An optional BIGNUM callback.
  49  * Returns: 1 if successful, or  0 otherwise.
  50  * Notes:
  51  *     p1, p2, q1, q2 are returned if they are not NULL.
  52  *     Xp, Xp1, Xp2, Xq, Xq1, Xq2 are optionally passed in.
  53  *     (Required for CAVS testing).
  54  */
  55 int ossl_rsa_fips186_4_gen_prob_primes(RSA *rsa, RSA_ACVP_TEST *test,
  56                                        int nbits, const BIGNUM *e, BN_CTX *ctx,
  57                                        BN_GENCB *cb)
  58 {
  59     int ret = 0, ok;
  60     /* Temp allocated BIGNUMS */
  61     BIGNUM *Xpo = NULL, *Xqo = NULL, *tmp = NULL;
  62     /* Intermediate BIGNUMS that can be returned for testing */
  63     BIGNUM *p1 = NULL, *p2 = NULL;
  64     BIGNUM *q1 = NULL, *q2 = NULL;
  65     /* Intermediate BIGNUMS that can be input for testing */
  66     BIGNUM *Xp = NULL, *Xp1 = NULL, *Xp2 = NULL;
  67     BIGNUM *Xq = NULL, *Xq1 = NULL, *Xq2 = NULL;
  68
  69 #if defined(FIPS_MODULE) && !defined(OPENSSL_NO_ACVP_TESTS)
  70     if (test != NULL) {
  71         Xp1 = test->Xp1;
  72         Xp2 = test->Xp2;
  73         Xq1 = test->Xq1;
  74         Xq2 = test->Xq2;
  75         Xp = test->Xp;
  76         Xq = test->Xq;
  77         p1 = test->p1;
  78         p2 = test->p2;
  79         q1 = test->q1;
  80         q2 = test->q2;
  81     }
  82 #endif
  83
  84     /* (Step 1) Check key length
  85      * NOTE: SP800-131A Rev1 Disallows key lengths of < 2048 bits for RSA
  86      * Signature Generation and Key Agree/Transport.
  87      */
  88     if (nbits < RSA_FIPS1864_MIN_KEYGEN_KEYSIZE) {
  89         ERR_raise(ERR_LIB_RSA, RSA_R_KEY_SIZE_TOO_SMALL);
  90         return 0;
  91     }
  92
  93     if (!ossl_rsa_check_public_exponent(e)) {
  94         ERR_raise(ERR_LIB_RSA, RSA_R_PUB_EXPONENT_OUT_OF_RANGE);
  95         return 0;
  96     }
  97
  98     /* (Step 3) Determine strength and check rand generator strength is ok -
  99      * this step is redundant because the generator always returns a higher
 100      * strength than is required.
 101      */
 102
 103     BN_CTX_start(ctx);
 104     tmp = BN_CTX_get(ctx);
 105     Xpo = BN_CTX_get(ctx);
 106     Xqo = BN_CTX_get(ctx);
 107     if (tmp == NULL || Xpo == NULL || Xqo == NULL)
 108         goto err;
 109     BN_set_flags(Xpo, BN_FLG_CONSTTIME);
 110     BN_set_flags(Xqo, BN_FLG_CONSTTIME);
 111
 112     if (rsa->p == NULL)
 113         rsa->p = BN_secure_new();
 114     if (rsa->q == NULL)
 115         rsa->q = BN_secure_new();
 116     if (rsa->p == NULL || rsa->q == NULL)
 117         goto err;
 118     BN_set_flags(rsa->p, BN_FLG_CONSTTIME);
 119     BN_set_flags(rsa->q, BN_FLG_CONSTTIME);
 120
 121     /* (Step 4) Generate p, Xp */
 122     if (!ossl_bn_rsa_fips186_4_gen_prob_primes(rsa->p, Xpo, p1, p2, Xp, Xp1, Xp2,
 123                                                nbits, e, ctx, cb))
 124         goto err;
 125     for (;;) {
 126         /* (Step 5) Generate q, Xq*/
 127         if (!ossl_bn_rsa_fips186_4_gen_prob_primes(rsa->q, Xqo, q1, q2, Xq, Xq1,
 128                                                    Xq2, nbits, e, ctx, cb))
 129             goto err;
 130
 131         /* (Step 6) |Xp - Xq| > 2^(nbitlen/2 - 100) */
 132         ok = ossl_rsa_check_pminusq_diff(tmp, Xpo, Xqo, nbits);
 133         if (ok < 0)
 134             goto err;
 135         if (ok == 0)
 136             continue;
 137
 138         /* (Step 6) |p - q| > 2^(nbitlen/2 - 100) */
 139         ok = ossl_rsa_check_pminusq_diff(tmp, rsa->p, rsa->q, nbits);
 140         if (ok < 0)
 141             goto err;
 142         if (ok == 0)
 143             continue;
 144         break; /* successfully finished */
 145     }
 146     rsa->dirty_cnt++;
 147     ret = 1;
 148 err:
 149     /* Zeroize any internally generated values that are not returned */
 150     if (Xpo != NULL)
 151         BN_clear(Xpo);
 152     if (Xqo != NULL)
 153         BN_clear(Xqo);
 154     BN_clear(tmp);
 155
 156     BN_CTX_end(ctx);
 157     return ret;
 158 }
 159
 160 /*
 161  * Validates the RSA key size based on the target strength.
 162  * See SP800-56Br1 6.3.1.1 (Steps 1a-1b)
 163  *
 164  * Params:
 165  *     nbits The key size in bits.
 166  *     strength The target strength in bits. -1 means the target
 167  *              strength is unknown.
 168  * Returns: 1 if the key size matches the target strength, or 0 otherwise.
 169  */
 170 int ossl_rsa_sp800_56b_validate_strength(int nbits, int strength)
 171 {
 172     int s = (int)ossl_ifc_ffc_compute_security_bits(nbits);
 173
 174 #ifdef FIPS_MODULE
 175     if (s < RSA_FIPS1864_MIN_KEYGEN_STRENGTH) {
 176         ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_MODULUS);
 177         return 0;
 178     }
 179 #endif
 180     if (strength != -1 && s != strength) {
 181         ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_STRENGTH);
 182         return 0;
 183     }
 184     return 1;
 185 }
 186
 187 /*
 188  * Validate that the random bit generator is of sufficient strength to generate
 189  * a key of the specified length.
 190  */
 191 static int rsa_validate_rng_strength(EVP_RAND_CTX *rng, int nbits)
 192 {
 193     if (rng == NULL)
 194         return 0;
 195 #ifdef FIPS_MODULE
 196     /*
 197      * This should become mainstream once similar tests are added to the other
 198      * key generations and once there is a way to disable these checks.
 199      */
 200     if (EVP_RAND_get_strength(rng) < ossl_ifc_ffc_compute_security_bits(nbits)) {
 201         ERR_raise(ERR_LIB_RSA,
 202                   RSA_R_RANDOMNESS_SOURCE_STRENGTH_INSUFFICIENT);
 203         return 0;
 204     }
 205 #endif
 206     return 1;
 207 }
 208
 209 /*
 210  *
 211  * Using p & q, calculate other required parameters such as n, d.
 212  * as well as the CRT parameters dP, dQ, qInv.
 213  *
 214  * See SP800-56Br1
 215  *   6.3.1.1 rsakpg1 - basic (Steps 3-4)
 216  *   6.3.1.3 rsakpg1 - crt   (Step 5)
 217  *
 218  * Params:
 219  *     rsa An rsa object.
 220  *     nbits The key size.
 221  *     e The public exponent.
 222  *     ctx A BN_CTX object.
 223  * Notes:
 224  *   There is a small chance that the generated d will be too small.
 225  * Returns: -1 = error,
 226  *           0 = d is too small,
 227  *           1 = success.
 228  *
 229  * SP800-56b key generation always passes a non NULL value for e.
 230  * For other purposes, if e is NULL then it is assumed that e, n and d are
 231  * already set in the RSA key and do not need to be recalculated.
 232  */
 233 int ossl_rsa_sp800_56b_derive_params_from_pq(RSA *rsa, int nbits,
 234                                              const BIGNUM *e, BN_CTX *ctx)
 235 {
 236     int ret = -1;
 237     BIGNUM *p1, *q1, *lcm, *p1q1, *gcd;
 238     BN_CTX_start(ctx);
 239     p1 = BN_CTX_get(ctx);
 240     q1 = BN_CTX_get(ctx);
 241     lcm = BN_CTX_get(ctx);
 242     p1q1 = BN_CTX_get(ctx);
 243     gcd = BN_CTX_get(ctx);
 244     if (gcd == NULL)
 245         goto err;
 246
 247     BN_set_flags(p1, BN_FLG_CONSTTIME);
 248     BN_set_flags(q1, BN_FLG_CONSTTIME);
 249     BN_set_flags(lcm, BN_FLG_CONSTTIME);
 250     BN_set_flags(p1q1, BN_FLG_CONSTTIME);
 251     BN_set_flags(gcd, BN_FLG_CONSTTIME);
 252
 253     /* LCM((p-1, q-1)) */
 254     if (ossl_rsa_get_lcm(ctx, rsa->p, rsa->q, lcm, gcd, p1, q1, p1q1) != 1)
 255         goto err;
 256
 257     /*
 258      * if e is provided as a parameter, don't recompute e, d or n
 259      */
 260     if (e != NULL) {
 261         /* copy e */
 262         BN_free(rsa->e);
 263         rsa->e = BN_dup(e);
 264         if (rsa->e == NULL)
 265             goto err;
 266
 267         BN_clear_free(rsa->d);
 268         /* (Step 3) d = (e^-1) mod (LCM(p-1, q-1)) */
 269         rsa->d = BN_secure_new();
 270         if (rsa->d == NULL)
 271             goto err;
 272         BN_set_flags(rsa->d, BN_FLG_CONSTTIME);
 273         if (BN_mod_inverse(rsa->d, e, lcm, ctx) == NULL)
 274             goto err;
 275
 276         /* (Step 3) return an error if d is too small */
 277         if (BN_num_bits(rsa->d) <= (nbits >> 1)) {
 278             ret = 0;
 279             goto err;
 280         }
 281
 282         /* (Step 4) n = pq */
 283         if (rsa->n == NULL)
 284             rsa->n = BN_new();
 285         if (rsa->n == NULL || !BN_mul(rsa->n, rsa->p, rsa->q, ctx))
 286             goto err;
 287     }
 288
 289     /* (Step 5a) dP = d mod (p-1) */
 290     if (rsa->dmp1 == NULL)
 291         rsa->dmp1 = BN_secure_new();
 292     if (rsa->dmp1 == NULL)
 293         goto err;
 294     BN_set_flags(rsa->dmp1, BN_FLG_CONSTTIME);
 295     if (!BN_mod(rsa->dmp1, rsa->d, p1, ctx))
 296         goto err;
 297
 298     /* (Step 5b) dQ = d mod (q-1) */
 299     if (rsa->dmq1 == NULL)
 300         rsa->dmq1 = BN_secure_new();
 301     if (rsa->dmq1 == NULL)
 302         goto err;
 303     BN_set_flags(rsa->dmq1, BN_FLG_CONSTTIME);
 304     if (!BN_mod(rsa->dmq1, rsa->d, q1, ctx))
 305         goto err;
 306
 307     /* (Step 5c) qInv = (inverse of q) mod p */
 308     BN_free(rsa->iqmp);
 309     rsa->iqmp = BN_secure_new();
 310     if (rsa->iqmp == NULL)
 311         goto err;
 312     BN_set_flags(rsa->iqmp, BN_FLG_CONSTTIME);
 313     if (BN_mod_inverse(rsa->iqmp, rsa->q, rsa->p, ctx) == NULL)
 314         goto err;
 315
 316     rsa->dirty_cnt++;
 317     ret = 1;
 318 err:
 319     if (ret != 1) {
 320         BN_free(rsa->e);
 321         rsa->e = NULL;
 322         BN_free(rsa->d);
 323         rsa->d = NULL;
 324         BN_free(rsa->n);
 325         rsa->n = NULL;
 326         BN_free(rsa->iqmp);
 327         rsa->iqmp = NULL;
 328         BN_free(rsa->dmq1);
 329         rsa->dmq1 = NULL;
 330         BN_free(rsa->dmp1);
 331         rsa->dmp1 = NULL;
 332     }
 333     BN_clear(p1);
 334     BN_clear(q1);
 335     BN_clear(lcm);
 336     BN_clear(p1q1);
 337     BN_clear(gcd);
 338
 339     BN_CTX_end(ctx);
 340     return ret;
 341 }
 342
 343 /*
 344  * Generate a SP800-56B RSA key.
 345  *
 346  * See SP800-56Br1 6.3.1 "RSA Key-Pair Generation with a Fixed Public Exponent"
 347  *    6.3.1.1 rsakpg1 - basic
 348  *    6.3.1.3 rsakpg1 - crt
 349  *
 350  * See also FIPS 186-4 Section B.3.6
 351  * "Generation of Probable Primes with Conditions Based on Auxiliary
 352  * Probable Primes."
 353  *
 354  * Params:
 355  *     rsa The rsa object.
 356  *     nbits The intended key size in bits.
 357  *     efixed The public exponent. If NULL a default of 65537 is used.
 358  *     cb An optional BIGNUM callback.
 359  * Returns: 1 if successfully generated otherwise it returns 0.
 360  */
 361 int ossl_rsa_sp800_56b_generate_key(RSA *rsa, int nbits, const BIGNUM *efixed,
 362                                     BN_GENCB *cb)
 363 {
 364     int ret = 0;
 365     int ok;
 366     BN_CTX *ctx = NULL;
 367     BIGNUM *e = NULL;
 368     RSA_ACVP_TEST *info = NULL;
 369     BIGNUM *tmp;
 370
 371 #if defined(FIPS_MODULE) && !defined(OPENSSL_NO_ACVP_TESTS)
 372     info = rsa->acvp_test;
 373 #endif
 374
 375     /* (Steps 1a-1b) : Currently ignores the strength check */
 376     if (!ossl_rsa_sp800_56b_validate_strength(nbits, -1))
 377         return 0;
 378
 379     /* Check that the RNG is capable of generating a key this large */
 380    if (!rsa_validate_rng_strength(RAND_get0_private(rsa->libctx), nbits))
 381         return 0;
 382
 383     ctx = BN_CTX_new_ex(rsa->libctx);
 384     if (ctx == NULL)
 385         return 0;
 386
 387     /* Set default if e is not passed in */
 388     if (efixed == NULL) {
 389         e = BN_new();
 390         if (e == NULL || !BN_set_word(e, 65537))
 391             goto err;
 392     } else {
 393         e = (BIGNUM *)efixed;
 394     }
 395     /* (Step 1c) fixed exponent is checked later .*/
 396
 397     for (;;) {
 398         /* (Step 2) Generate prime factors */
 399         if (!ossl_rsa_fips186_4_gen_prob_primes(rsa, info, nbits, e, ctx, cb))
 400             goto err;
 401
 402         /* p>q check and skipping in case of acvp test */
 403         if (info == NULL && BN_cmp(rsa->p, rsa->q) < 0) {
 404             tmp = rsa->p;
 405             rsa->p = rsa->q;
 406             rsa->q = tmp;
 407         }
 408
 409         /* (Steps 3-5) Compute params d, n, dP, dQ, qInv */
 410         ok = ossl_rsa_sp800_56b_derive_params_from_pq(rsa, nbits, e, ctx);
 411         if (ok < 0)
 412             goto err;
 413         if (ok > 0)
 414             break;
 415         /* Gets here if computed d is too small - so try again */
 416     }
 417
 418     /* (Step 6) Do pairwise test - optional validity test has been omitted */
 419     ret = ossl_rsa_sp800_56b_pairwise_test(rsa, ctx);
 420 err:
 421     if (efixed == NULL)
 422         BN_free(e);
 423     BN_CTX_free(ctx);
 424     return ret;
 425 }
 426
 427 /*
 428  * See SP800-56Br1 6.3.1.3 (Step 6) Perform a pair-wise consistency test by
 429  * verifying that: k = (k^e)^d mod n for some integer k where 1 < k < n-1.
 430  *
 431  * Returns 1 if the RSA key passes the pairwise test or 0 if it fails.
 432  */
 433 int ossl_rsa_sp800_56b_pairwise_test(RSA *rsa, BN_CTX *ctx)
 434 {
 435     int ret = 0;
 436     BIGNUM *k, *tmp;
 437
 438     BN_CTX_start(ctx);
 439     tmp = BN_CTX_get(ctx);
 440     k = BN_CTX_get(ctx);
 441     if (k == NULL)
 442         goto err;
 443     BN_set_flags(k, BN_FLG_CONSTTIME);
 444
 445     ret = (BN_set_word(k, 2)
 446            && BN_mod_exp(tmp, k, rsa->e, rsa->n, ctx)
 447            && BN_mod_exp(tmp, tmp, rsa->d, rsa->n, ctx)
 448            && BN_cmp(k, tmp) == 0);
 449     if (ret == 0)
 450         ERR_raise(ERR_LIB_RSA, RSA_R_PAIRWISE_TEST_FAILURE);
 451 err:
 452     BN_CTX_end(ctx);
 453     return ret;
 454 }