crypto/rsa/rsa_gen.c

   1 /*
   2  * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /*
  11  * NB: these functions have been "upgraded", the deprecated versions (which
  12  * are compatibility wrappers using these functions) are in rsa_depr.c. -
  13  * Geoff
  14  */
  15
  16 /*
  17  * RSA low level APIs are deprecated for public use, but still ok for
  18  * internal use.
  19  */
  20 #include "internal/deprecated.h"
  21
  22 #include <stdio.h>
  23 #include <time.h>
  24 #include "internal/cryptlib.h"
  25 #include <openssl/bn.h>
  26 #include <openssl/self_test.h>
  27 #include "prov/providercommon.h"
  28 #include "rsa_local.h"
  29
  30 static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg);
  31 static int rsa_keygen(OPENSSL_CTX *libctx, RSA *rsa, int bits, int primes,
  32                       BIGNUM *e_value, BN_GENCB *cb, int pairwise_test);
  33
  34 /*
  35  * NB: this wrapper would normally be placed in rsa_lib.c and the static
  36  * implementation would probably be in rsa_eay.c. Nonetheless, is kept here
  37  * so that we don't introduce a new linker dependency. Eg. any application
  38  * that wasn't previously linking object code related to key-generation won't
  39  * have to now just because key-generation is part of RSA_METHOD.
  40  */
  41 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
  42 {
  43     if (rsa->meth->rsa_keygen != NULL)
  44         return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  45
  46     return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,
  47                                         e_value, cb);
  48 }
  49
  50 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
  51                                  BIGNUM *e_value, BN_GENCB *cb)
  52 {
  53 #ifndef FIPS_MODULE
  54     /* multi-prime is only supported with the builtin key generation */
  55     if (rsa->meth->rsa_multi_prime_keygen != NULL) {
  56         return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
  57                                                  e_value, cb);
  58     } else if (rsa->meth->rsa_keygen != NULL) {
  59         /*
  60          * However, if rsa->meth implements only rsa_keygen, then we
  61          * have to honour it in 2-prime case and assume that it wouldn't
  62          * know what to do with multi-prime key generated by builtin
  63          * subroutine...
  64          */
  65         if (primes == 2)
  66             return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  67         else
  68             return 0;
  69     }
  70 #endif /* FIPS_MODULE */
  71     return rsa_keygen(rsa->libctx, rsa, bits, primes, e_value, cb, 0);
  72 }
  73
  74 #ifndef FIPS_MODULE
  75 static int rsa_multiprime_keygen(RSA *rsa, int bits, int primes,
  76                                  BIGNUM *e_value, BN_GENCB *cb)
  77 {
  78     BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
  79     int n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
  80     int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
  81     RSA_PRIME_INFO *pinfo = NULL;
  82     STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
  83     BN_CTX *ctx = NULL;
  84     BN_ULONG bitst = 0;
  85     unsigned long error = 0;
  86     int ok = -1;
  87
  88     if (bits < RSA_MIN_MODULUS_BITS) {
  89         ok = 0;             /* we set our own err */
  90         RSAerr(0, RSA_R_KEY_SIZE_TOO_SMALL);
  91         goto err;
  92     }
  93
  94     /* A bad value for e can cause infinite loops */
  95     if (e_value != NULL && !ossl_rsa_check_public_exponent(e_value)) {
  96         RSAerr(0, RSA_R_PUB_EXPONENT_OUT_OF_RANGE);
  97         return 0;
  98     }
  99
 100     if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
 101         ok = 0;             /* we set our own err */
 102         RSAerr(0, RSA_R_KEY_PRIME_NUM_INVALID);
 103         goto err;
 104     }
 105
 106     ctx = BN_CTX_new();
 107     if (ctx == NULL)
 108         goto err;
 109     BN_CTX_start(ctx);
 110     r0 = BN_CTX_get(ctx);
 111     r1 = BN_CTX_get(ctx);
 112     r2 = BN_CTX_get(ctx);
 113     if (r2 == NULL)
 114         goto err;
 115
 116     /* divide bits into 'primes' pieces evenly */
 117     quo = bits / primes;
 118     rmd = bits % primes;
 119
 120     for (i = 0; i < primes; i++)
 121         bitsr[i] = (i < rmd) ? quo + 1 : quo;
 122
 123     rsa->dirty_cnt++;
 124
 125     /* We need the RSA components non-NULL */
 126     if (!rsa->n && ((rsa->n = BN_new()) == NULL))
 127         goto err;
 128     if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
 129         goto err;
 130     BN_set_flags(rsa->d, BN_FLG_CONSTTIME);
 131     if (!rsa->e && ((rsa->e = BN_new()) == NULL))
 132         goto err;
 133     if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
 134         goto err;
 135     BN_set_flags(rsa->p, BN_FLG_CONSTTIME);
 136     if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
 137         goto err;
 138     BN_set_flags(rsa->q, BN_FLG_CONSTTIME);
 139     if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
 140         goto err;
 141     BN_set_flags(rsa->dmp1, BN_FLG_CONSTTIME);
 142     if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
 143         goto err;
 144     BN_set_flags(rsa->dmq1, BN_FLG_CONSTTIME);
 145     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
 146         goto err;
 147     BN_set_flags(rsa->iqmp, BN_FLG_CONSTTIME);
 148
 149     /* initialize multi-prime components */
 150     if (primes > RSA_DEFAULT_PRIME_NUM) {
 151         rsa->version = RSA_ASN1_VERSION_MULTI;
 152         prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
 153         if (prime_infos == NULL)
 154             goto err;
 155         if (rsa->prime_infos != NULL) {
 156             /* could this happen? */
 157             sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
 158         }
 159         rsa->prime_infos = prime_infos;
 160
 161         /* prime_info from 2 to |primes| -1 */
 162         for (i = 2; i < primes; i++) {
 163             pinfo = rsa_multip_info_new();
 164             if (pinfo == NULL)
 165                 goto err;
 166             (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
 167         }
 168     }
 169
 170     if (BN_copy(rsa->e, e_value) == NULL)
 171         goto err;
 172
 173     /* generate p, q and other primes (if any) */
 174     for (i = 0; i < primes; i++) {
 175         adj = 0;
 176         retries = 0;
 177
 178         if (i == 0) {
 179             prime = rsa->p;
 180         } else if (i == 1) {
 181             prime = rsa->q;
 182         } else {
 183             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 184             prime = pinfo->r;
 185         }
 186         BN_set_flags(prime, BN_FLG_CONSTTIME);
 187
 188         for (;;) {
 189  redo:
 190             if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
 191                 goto err;
 192             /*
 193              * prime should not be equal to p, q, r_3...
 194              * (those primes prior to this one)
 195              */
 196             {
 197                 int j;
 198
 199                 for (j = 0; j < i; j++) {
 200                     BIGNUM *prev_prime;
 201
 202                     if (j == 0)
 203                         prev_prime = rsa->p;
 204                     else if (j == 1)
 205                         prev_prime = rsa->q;
 206                     else
 207                         prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
 208                                                              j - 2)->r;
 209
 210                     if (!BN_cmp(prime, prev_prime)) {
 211                         goto redo;
 212                     }
 213                 }
 214             }
 215             if (!BN_sub(r2, prime, BN_value_one()))
 216                 goto err;
 217             ERR_set_mark();
 218             BN_set_flags(r2, BN_FLG_CONSTTIME);
 219             if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
 220                /* GCD == 1 since inverse exists */
 221                 break;
 222             }
 223             error = ERR_peek_last_error();
 224             if (ERR_GET_LIB(error) == ERR_LIB_BN
 225                 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
 226                 /* GCD != 1 */
 227                 ERR_pop_to_mark();
 228             } else {
 229                 goto err;
 230             }
 231             if (!BN_GENCB_call(cb, 2, n++))
 232                 goto err;
 233         }
 234
 235         bitse += bitsr[i];
 236
 237         /* calculate n immediately to see if it's sufficient */
 238         if (i == 1) {
 239             /* we get at least 2 primes */
 240             if (!BN_mul(r1, rsa->p, rsa->q, ctx))
 241                 goto err;
 242         } else if (i != 0) {
 243             /* modulus n = p * q * r_3 * r_4 ... */
 244             if (!BN_mul(r1, rsa->n, prime, ctx))
 245                 goto err;
 246         } else {
 247             /* i == 0, do nothing */
 248             if (!BN_GENCB_call(cb, 3, i))
 249                 goto err;
 250             continue;
 251         }
 252         /*
 253          * if |r1|, product of factors so far, is not as long as expected
 254          * (by checking the first 4 bits are less than 0x9 or greater than
 255          * 0xF). If so, re-generate the last prime.
 256          *
 257          * NOTE: This actually can't happen in two-prime case, because of
 258          * the way factors are generated.
 259          *
 260          * Besides, another consideration is, for multi-prime case, even the
 261          * length modulus is as long as expected, the modulus could start at
 262          * 0x8, which could be utilized to distinguish a multi-prime private
 263          * key by using the modulus in a certificate. This is also covered
 264          * by checking the length should not be less than 0x9.
 265          */
 266         if (!BN_rshift(r2, r1, bitse - 4))
 267             goto err;
 268         bitst = BN_get_word(r2);
 269
 270         if (bitst < 0x9 || bitst > 0xF) {
 271             /*
 272              * For keys with more than 4 primes, we attempt longer factor to
 273              * meet length requirement.
 274              *
 275              * Otherwise, we just re-generate the prime with the same length.
 276              *
 277              * This strategy has the following goals:
 278              *
 279              * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
 280              * 2. stay the same logic with normal 2-prime key
 281              */
 282             bitse -= bitsr[i];
 283             if (!BN_GENCB_call(cb, 2, n++))
 284                 goto err;
 285             if (primes > 4) {
 286                 if (bitst < 0x9)
 287                     adj++;
 288                 else
 289                     adj--;
 290             } else if (retries == 4) {
 291                 /*
 292                  * re-generate all primes from scratch, mainly used
 293                  * in 4 prime case to avoid long loop. Max retry times
 294                  * is set to 4.
 295                  */
 296                 i = -1;
 297                 bitse = 0;
 298                 continue;
 299             }
 300             retries++;
 301             goto redo;
 302         }
 303         /* save product of primes for further use, for multi-prime only */
 304         if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
 305             goto err;
 306         if (BN_copy(rsa->n, r1) == NULL)
 307             goto err;
 308         if (!BN_GENCB_call(cb, 3, i))
 309             goto err;
 310     }
 311
 312     if (BN_cmp(rsa->p, rsa->q) < 0) {
 313         tmp = rsa->p;
 314         rsa->p = rsa->q;
 315         rsa->q = tmp;
 316     }
 317
 318     /* calculate d */
 319
 320     /* p - 1 */
 321     if (!BN_sub(r1, rsa->p, BN_value_one()))
 322         goto err;
 323     /* q - 1 */
 324     if (!BN_sub(r2, rsa->q, BN_value_one()))
 325         goto err;
 326     /* (p - 1)(q - 1) */
 327     if (!BN_mul(r0, r1, r2, ctx))
 328         goto err;
 329     /* multi-prime */
 330     for (i = 2; i < primes; i++) {
 331         pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 332         /* save r_i - 1 to pinfo->d temporarily */
 333         if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
 334             goto err;
 335         if (!BN_mul(r0, r0, pinfo->d, ctx))
 336             goto err;
 337     }
 338
 339     {
 340         BIGNUM *pr0 = BN_new();
 341
 342         if (pr0 == NULL)
 343             goto err;
 344
 345         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
 346         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
 347             BN_free(pr0);
 348             goto err;               /* d */
 349         }
 350         /* We MUST free pr0 before any further use of r0 */
 351         BN_free(pr0);
 352     }
 353
 354     {
 355         BIGNUM *d = BN_new();
 356
 357         if (d == NULL)
 358             goto err;
 359
 360         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 361
 362         /* calculate d mod (p-1) and d mod (q - 1) */
 363         if (!BN_mod(rsa->dmp1, d, r1, ctx)
 364             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
 365             BN_free(d);
 366             goto err;
 367         }
 368
 369         /* calculate CRT exponents */
 370         for (i = 2; i < primes; i++) {
 371             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 372             /* pinfo->d == r_i - 1 */
 373             if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
 374                 BN_free(d);
 375                 goto err;
 376             }
 377         }
 378
 379         /* We MUST free d before any further use of rsa->d */
 380         BN_free(d);
 381     }
 382
 383     {
 384         BIGNUM *p = BN_new();
 385
 386         if (p == NULL)
 387             goto err;
 388         BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 389
 390         /* calculate inverse of q mod p */
 391         if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
 392             BN_free(p);
 393             goto err;
 394         }
 395
 396         /* calculate CRT coefficient for other primes */
 397         for (i = 2; i < primes; i++) {
 398             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 399             BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
 400             if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
 401                 BN_free(p);
 402                 goto err;
 403             }
 404         }
 405
 406         /* We MUST free p before any further use of rsa->p */
 407         BN_free(p);
 408     }
 409
 410     ok = 1;
 411  err:
 412     if (ok == -1) {
 413         RSAerr(0, ERR_LIB_BN);
 414         ok = 0;
 415     }
 416     BN_CTX_end(ctx);
 417     BN_CTX_free(ctx);
 418     return ok;
 419 }
 420 #endif /* FIPS_MODULE */
 421
 422 static int rsa_keygen(OPENSSL_CTX *libctx, RSA *rsa, int bits, int primes,
 423                       BIGNUM *e_value, BN_GENCB *cb, int pairwise_test)
 424 {
 425     int ok = 0;
 426
 427     /*
 428      * Only multi-prime keys or insecure keys with a small key length will use
 429      * the older rsa_multiprime_keygen().
 430      */
 431     if (primes == 2 && bits >= 2048)
 432         ok = ossl_rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
 433 #ifndef FIPS_MODULE
 434     else
 435         ok = rsa_multiprime_keygen(rsa, bits, primes, e_value, cb);
 436 #endif /* FIPS_MODULE */
 437
 438 #ifdef FIPS_MODULE
 439     pairwise_test = 1; /* FIPS MODE needs to always run the pairwise test */
 440 #endif
 441     if (pairwise_test && ok > 0) {
 442         OSSL_CALLBACK *stcb = NULL;
 443         void *stcbarg = NULL;
 444
 445         OSSL_SELF_TEST_get_callback(libctx, &stcb, &stcbarg);
 446         ok = rsa_keygen_pairwise_test(rsa, stcb, stcbarg);
 447         if (!ok) {
 448             ossl_set_error_state(OSSL_SELF_TEST_TYPE_PCT);
 449             /* Clear intermediate results */
 450             BN_clear_free(rsa->d);
 451             BN_clear_free(rsa->p);
 452             BN_clear_free(rsa->q);
 453             BN_clear_free(rsa->dmp1);
 454             BN_clear_free(rsa->dmq1);
 455             BN_clear_free(rsa->iqmp);
 456             rsa->d = NULL;
 457             rsa->p = NULL;
 458             rsa->q = NULL;
 459             rsa->dmp1 = NULL;
 460             rsa->dmq1 = NULL;
 461             rsa->iqmp = NULL;
 462         }
 463     }
 464     return ok;
 465 }
 466
 467 /*
 468  * For RSA key generation it is not known whether the key pair will be used
 469  * for key transport or signatures. FIPS 140-2 IG 9.9 states that in this case
 470  * either a signature verification OR an encryption operation may be used to
 471  * perform the pairwise consistency check. The simpler encrypt/decrypt operation
 472  * has been chosen for this case.
 473  */
 474 static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg)
 475 {
 476     int ret = 0;
 477     unsigned int ciphertxt_len;
 478     unsigned char *ciphertxt = NULL;
 479     const unsigned char plaintxt[16] = {0};
 480     unsigned char decoded[256];
 481     unsigned int decoded_len;
 482     unsigned int plaintxt_len = (unsigned int)sizeof(plaintxt_len);
 483     int padding = RSA_PKCS1_PADDING;
 484     OSSL_SELF_TEST *st = NULL;
 485
 486     st = OSSL_SELF_TEST_new(cb, cbarg);
 487     if (st == NULL)
 488         goto err;
 489     OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,
 490                            OSSL_SELF_TEST_DESC_PCT_RSA_PKCS1);
 491
 492     ciphertxt_len = RSA_size(rsa);
 493     ciphertxt = OPENSSL_zalloc(ciphertxt_len);
 494     if (ciphertxt == NULL)
 495         goto err;
 496
 497     ciphertxt_len = RSA_public_encrypt(plaintxt_len, plaintxt, ciphertxt, rsa,
 498                                        padding);
 499     if (ciphertxt_len <= 0)
 500         goto err;
 501     if (ciphertxt_len == plaintxt_len
 502         && memcmp(ciphertxt, plaintxt, plaintxt_len) == 0)
 503         goto err;
 504
 505     OSSL_SELF_TEST_oncorrupt_byte(st, ciphertxt);
 506
 507     decoded_len = RSA_private_decrypt(ciphertxt_len, ciphertxt, decoded, rsa,
 508                                       padding);
 509     if (decoded_len != plaintxt_len
 510         || memcmp(decoded, plaintxt,  decoded_len) != 0)
 511         goto err;
 512
 513     ret = 1;
 514 err:
 515     OSSL_SELF_TEST_onend(st, ret);
 516     OSSL_SELF_TEST_free(st);
 517     OPENSSL_free(ciphertxt);
 518
 519     return ret;
 520 }