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 "rsa_local.h"
  28
  29 static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg);
  30 static int rsa_keygen(OPENSSL_CTX *libctx, RSA *rsa, int bits, int primes,
  31                       BIGNUM *e_value, BN_GENCB *cb, int pairwise_test);
  32
  33 /*
  34  * NB: this wrapper would normally be placed in rsa_lib.c and the static
  35  * implementation would probably be in rsa_eay.c. Nonetheless, is kept here
  36  * so that we don't introduce a new linker dependency. Eg. any application
  37  * that wasn't previously linking object code related to key-generation won't
  38  * have to now just because key-generation is part of RSA_METHOD.
  39  */
  40 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
  41 {
  42     if (rsa->meth->rsa_keygen != NULL)
  43         return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  44
  45     return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,
  46                                         e_value, cb);
  47 }
  48
  49 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
  50                                  BIGNUM *e_value, BN_GENCB *cb)
  51 {
  52 #ifndef FIPS_MODULE
  53     /* multi-prime is only supported with the builtin key generation */
  54     if (rsa->meth->rsa_multi_prime_keygen != NULL) {
  55         return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
  56                                                  e_value, cb);
  57     } else if (rsa->meth->rsa_keygen != NULL) {
  58         /*
  59          * However, if rsa->meth implements only rsa_keygen, then we
  60          * have to honour it in 2-prime case and assume that it wouldn't
  61          * know what to do with multi-prime key generated by builtin
  62          * subroutine...
  63          */
  64         if (primes == 2)
  65             return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  66         else
  67             return 0;
  68     }
  69 #endif /* FIPS_MODUKE */
  70     return rsa_keygen(rsa->libctx, rsa, bits, primes, e_value, cb, 0);
  71 }
  72
  73 #ifndef FIPS_MODULE
  74 static int rsa_multiprime_keygen(RSA *rsa, int bits, int primes,
  75                                  BIGNUM *e_value, BN_GENCB *cb)
  76 {
  77     BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
  78     int n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
  79     int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
  80     RSA_PRIME_INFO *pinfo = NULL;
  81     STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
  82     BN_CTX *ctx = NULL;
  83     BN_ULONG bitst = 0;
  84     unsigned long error = 0;
  85     int ok = -1;
  86
  87     if (bits < RSA_MIN_MODULUS_BITS) {
  88         ok = 0;             /* we set our own err */
  89         RSAerr(0, RSA_R_KEY_SIZE_TOO_SMALL);
  90         goto err;
  91     }
  92
  93     /* A bad value for e can cause infinite loops */
  94     if (e_value != NULL && !rsa_check_public_exponent(e_value)) {
  95         RSAerr(0, RSA_R_PUB_EXPONENT_OUT_OF_RANGE);
  96         return 0;
  97     }
  98
  99     if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
 100         ok = 0;             /* we set our own err */
 101         RSAerr(0, RSA_R_KEY_PRIME_NUM_INVALID);
 102         goto err;
 103     }
 104
 105     ctx = BN_CTX_new();
 106     if (ctx == NULL)
 107         goto err;
 108     BN_CTX_start(ctx);
 109     r0 = BN_CTX_get(ctx);
 110     r1 = BN_CTX_get(ctx);
 111     r2 = BN_CTX_get(ctx);
 112     if (r2 == NULL)
 113         goto err;
 114
 115     /* divide bits into 'primes' pieces evenly */
 116     quo = bits / primes;
 117     rmd = bits % primes;
 118
 119     for (i = 0; i < primes; i++)
 120         bitsr[i] = (i < rmd) ? quo + 1 : quo;
 121
 122     rsa->dirty_cnt++;
 123
 124     /* We need the RSA components non-NULL */
 125     if (!rsa->n && ((rsa->n = BN_new()) == NULL))
 126         goto err;
 127     if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
 128         goto err;
 129     BN_set_flags(rsa->d, BN_FLG_CONSTTIME);
 130     if (!rsa->e && ((rsa->e = BN_new()) == NULL))
 131         goto err;
 132     if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
 133         goto err;
 134     BN_set_flags(rsa->p, BN_FLG_CONSTTIME);
 135     if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
 136         goto err;
 137     BN_set_flags(rsa->q, BN_FLG_CONSTTIME);
 138     if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
 139         goto err;
 140     BN_set_flags(rsa->dmp1, BN_FLG_CONSTTIME);
 141     if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
 142         goto err;
 143     BN_set_flags(rsa->dmq1, BN_FLG_CONSTTIME);
 144     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
 145         goto err;
 146     BN_set_flags(rsa->iqmp, BN_FLG_CONSTTIME);
 147
 148     /* initialize multi-prime components */
 149     if (primes > RSA_DEFAULT_PRIME_NUM) {
 150         rsa->version = RSA_ASN1_VERSION_MULTI;
 151         prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
 152         if (prime_infos == NULL)
 153             goto err;
 154         if (rsa->prime_infos != NULL) {
 155             /* could this happen? */
 156             sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
 157         }
 158         rsa->prime_infos = prime_infos;
 159
 160         /* prime_info from 2 to |primes| -1 */
 161         for (i = 2; i < primes; i++) {
 162             pinfo = rsa_multip_info_new();
 163             if (pinfo == NULL)
 164                 goto err;
 165             (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
 166         }
 167     }
 168
 169     if (BN_copy(rsa->e, e_value) == NULL)
 170         goto err;
 171
 172     /* generate p, q and other primes (if any) */
 173     for (i = 0; i < primes; i++) {
 174         adj = 0;
 175         retries = 0;
 176
 177         if (i == 0) {
 178             prime = rsa->p;
 179         } else if (i == 1) {
 180             prime = rsa->q;
 181         } else {
 182             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 183             prime = pinfo->r;
 184         }
 185         BN_set_flags(prime, BN_FLG_CONSTTIME);
 186
 187         for (;;) {
 188  redo:
 189             if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
 190                 goto err;
 191             /*
 192              * prime should not be equal to p, q, r_3...
 193              * (those primes prior to this one)
 194              */
 195             {
 196                 int j;
 197
 198                 for (j = 0; j < i; j++) {
 199                     BIGNUM *prev_prime;
 200
 201                     if (j == 0)
 202                         prev_prime = rsa->p;
 203                     else if (j == 1)
 204                         prev_prime = rsa->q;
 205                     else
 206                         prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
 207                                                              j - 2)->r;
 208
 209                     if (!BN_cmp(prime, prev_prime)) {
 210                         goto redo;
 211                     }
 212                 }
 213             }
 214             if (!BN_sub(r2, prime, BN_value_one()))
 215                 goto err;
 216             ERR_set_mark();
 217             BN_set_flags(r2, BN_FLG_CONSTTIME);
 218             if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
 219                /* GCD == 1 since inverse exists */
 220                 break;
 221             }
 222             error = ERR_peek_last_error();
 223             if (ERR_GET_LIB(error) == ERR_LIB_BN
 224                 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
 225                 /* GCD != 1 */
 226                 ERR_pop_to_mark();
 227             } else {
 228                 goto err;
 229             }
 230             if (!BN_GENCB_call(cb, 2, n++))
 231                 goto err;
 232         }
 233
 234         bitse += bitsr[i];
 235
 236         /* calculate n immediately to see if it's sufficient */
 237         if (i == 1) {
 238             /* we get at least 2 primes */
 239             if (!BN_mul(r1, rsa->p, rsa->q, ctx))
 240                 goto err;
 241         } else if (i != 0) {
 242             /* modulus n = p * q * r_3 * r_4 ... */
 243             if (!BN_mul(r1, rsa->n, prime, ctx))
 244                 goto err;
 245         } else {
 246             /* i == 0, do nothing */
 247             if (!BN_GENCB_call(cb, 3, i))
 248                 goto err;
 249             continue;
 250         }
 251         /*
 252          * if |r1|, product of factors so far, is not as long as expected
 253          * (by checking the first 4 bits are less than 0x9 or greater than
 254          * 0xF). If so, re-generate the last prime.
 255          *
 256          * NOTE: This actually can't happen in two-prime case, because of
 257          * the way factors are generated.
 258          *
 259          * Besides, another consideration is, for multi-prime case, even the
 260          * length modulus is as long as expected, the modulus could start at
 261          * 0x8, which could be utilized to distinguish a multi-prime private
 262          * key by using the modulus in a certificate. This is also covered
 263          * by checking the length should not be less than 0x9.
 264          */
 265         if (!BN_rshift(r2, r1, bitse - 4))
 266             goto err;
 267         bitst = BN_get_word(r2);
 268
 269         if (bitst < 0x9 || bitst > 0xF) {
 270             /*
 271              * For keys with more than 4 primes, we attempt longer factor to
 272              * meet length requirement.
 273              *
 274              * Otherwise, we just re-generate the prime with the same length.
 275              *
 276              * This strategy has the following goals:
 277              *
 278              * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
 279              * 2. stay the same logic with normal 2-prime key
 280              */
 281             bitse -= bitsr[i];
 282             if (!BN_GENCB_call(cb, 2, n++))
 283                 goto err;
 284             if (primes > 4) {
 285                 if (bitst < 0x9)
 286                     adj++;
 287                 else
 288                     adj--;
 289             } else if (retries == 4) {
 290                 /*
 291                  * re-generate all primes from scratch, mainly used
 292                  * in 4 prime case to avoid long loop. Max retry times
 293                  * is set to 4.
 294                  */
 295                 i = -1;
 296                 bitse = 0;
 297                 continue;
 298             }
 299             retries++;
 300             goto redo;
 301         }
 302         /* save product of primes for further use, for multi-prime only */
 303         if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
 304             goto err;
 305         if (BN_copy(rsa->n, r1) == NULL)
 306             goto err;
 307         if (!BN_GENCB_call(cb, 3, i))
 308             goto err;
 309     }
 310
 311     if (BN_cmp(rsa->p, rsa->q) < 0) {
 312         tmp = rsa->p;
 313         rsa->p = rsa->q;
 314         rsa->q = tmp;
 315     }
 316
 317     /* calculate d */
 318
 319     /* p - 1 */
 320     if (!BN_sub(r1, rsa->p, BN_value_one()))
 321         goto err;
 322     /* q - 1 */
 323     if (!BN_sub(r2, rsa->q, BN_value_one()))
 324         goto err;
 325     /* (p - 1)(q - 1) */
 326     if (!BN_mul(r0, r1, r2, ctx))
 327         goto err;
 328     /* multi-prime */
 329     for (i = 2; i < primes; i++) {
 330         pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 331         /* save r_i - 1 to pinfo->d temporarily */
 332         if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
 333             goto err;
 334         if (!BN_mul(r0, r0, pinfo->d, ctx))
 335             goto err;
 336     }
 337
 338     {
 339         BIGNUM *pr0 = BN_new();
 340
 341         if (pr0 == NULL)
 342             goto err;
 343
 344         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
 345         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
 346             BN_free(pr0);
 347             goto err;               /* d */
 348         }
 349         /* We MUST free pr0 before any further use of r0 */
 350         BN_free(pr0);
 351     }
 352
 353     {
 354         BIGNUM *d = BN_new();
 355
 356         if (d == NULL)
 357             goto err;
 358
 359         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 360
 361         /* calculate d mod (p-1) and d mod (q - 1) */
 362         if (!BN_mod(rsa->dmp1, d, r1, ctx)
 363             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
 364             BN_free(d);
 365             goto err;
 366         }
 367
 368         /* calculate CRT exponents */
 369         for (i = 2; i < primes; i++) {
 370             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 371             /* pinfo->d == r_i - 1 */
 372             if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
 373                 BN_free(d);
 374                 goto err;
 375             }
 376         }
 377
 378         /* We MUST free d before any further use of rsa->d */
 379         BN_free(d);
 380     }
 381
 382     {
 383         BIGNUM *p = BN_new();
 384
 385         if (p == NULL)
 386             goto err;
 387         BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 388
 389         /* calculate inverse of q mod p */
 390         if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
 391             BN_free(p);
 392             goto err;
 393         }
 394
 395         /* calculate CRT coefficient for other primes */
 396         for (i = 2; i < primes; i++) {
 397             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 398             BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
 399             if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
 400                 BN_free(p);
 401                 goto err;
 402             }
 403         }
 404
 405         /* We MUST free p before any further use of rsa->p */
 406         BN_free(p);
 407     }
 408
 409     ok = 1;
 410  err:
 411     if (ok == -1) {
 412         RSAerr(0, ERR_LIB_BN);
 413         ok = 0;
 414     }
 415     BN_CTX_end(ctx);
 416     BN_CTX_free(ctx);
 417     return ok;
 418 }
 419 #endif /* FIPS_MODULE */
 420
 421 static int rsa_keygen(OPENSSL_CTX *libctx, RSA *rsa, int bits, int primes,
 422                       BIGNUM *e_value, BN_GENCB *cb, int pairwise_test)
 423 {
 424     int ok = 0;
 425
 426     /*
 427      * Only multi-prime keys or insecure keys with a small key length will use
 428      * the older rsa_multiprime_keygen().
 429      */
 430     if (primes == 2 && bits >= 2048)
 431         ok = rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
 432 #ifndef FIPS_MODULE
 433     else
 434         ok = rsa_multiprime_keygen(rsa, bits, primes, e_value, cb);
 435 #endif /* FIPS_MODULE */
 436
 437 #ifdef FIPS_MODULE
 438     pairwise_test = 1; /* FIPS MODE needs to always run the pairwise test */
 439 #endif
 440     if (pairwise_test && ok > 0) {
 441         OSSL_CALLBACK *stcb = NULL;
 442         void *stcbarg = NULL;
 443
 444         OSSL_SELF_TEST_get_callback(libctx, &stcb, &stcbarg);
 445         ok = rsa_keygen_pairwise_test(rsa, stcb, stcbarg);
 446         if (!ok) {
 447             /* Clear intermediate results */
 448             BN_clear_free(rsa->d);
 449             BN_clear_free(rsa->p);
 450             BN_clear_free(rsa->q);
 451             BN_clear_free(rsa->dmp1);
 452             BN_clear_free(rsa->dmq1);
 453             BN_clear_free(rsa->iqmp);
 454             rsa->d = NULL;
 455             rsa->p = NULL;
 456             rsa->q = NULL;
 457             rsa->dmp1 = NULL;
 458             rsa->dmq1 = NULL;
 459             rsa->iqmp = NULL;
 460         }
 461     }
 462     return ok;
 463 }
 464
 465 /*
 466  * For RSA key generation it is not known whether the key pair will be used
 467  * for key transport or signatures. FIPS 140-2 IG 9.9 states that in this case
 468  * either a signature verification OR an encryption operation may be used to
 469  * perform the pairwise consistency check. The simpler encrypt/decrypt operation
 470  * has been chosen for this case.
 471  */
 472 static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg)
 473 {
 474     int ret = 0;
 475     unsigned int ciphertxt_len;
 476     unsigned char *ciphertxt = NULL;
 477     const unsigned char plaintxt[16] = {0};
 478     unsigned char decoded[256];
 479     unsigned int decoded_len;
 480     unsigned int plaintxt_len = (unsigned int)sizeof(plaintxt_len);
 481     int padding = RSA_PKCS1_PADDING;
 482     OSSL_SELF_TEST *st = NULL;
 483
 484     st = OSSL_SELF_TEST_new(cb, cbarg);
 485     if (st == NULL)
 486         goto err;
 487     OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,
 488                            OSSL_SELF_TEST_DESC_PCT_RSA_PKCS1);
 489
 490     ciphertxt_len = RSA_size(rsa);
 491     ciphertxt = OPENSSL_zalloc(ciphertxt_len);
 492     if (ciphertxt == NULL)
 493         goto err;
 494
 495     ciphertxt_len = RSA_public_encrypt(plaintxt_len, plaintxt, ciphertxt, rsa,
 496                                        padding);
 497     if (ciphertxt_len <= 0)
 498         goto err;
 499     if (ciphertxt_len == plaintxt_len
 500         && memcmp(ciphertxt, plaintxt, plaintxt_len) == 0)
 501         goto err;
 502
 503     OSSL_SELF_TEST_oncorrupt_byte(st, ciphertxt);
 504
 505     decoded_len = RSA_private_decrypt(ciphertxt_len, ciphertxt, decoded, rsa,
 506                                       padding);
 507     if (decoded_len != plaintxt_len
 508         || memcmp(decoded, plaintxt,  decoded_len) != 0)
 509         goto err;
 510
 511     ret = 1;
 512 err:
 513     OSSL_SELF_TEST_onend(st, ret);
 514     OSSL_SELF_TEST_free(st);
 515     OPENSSL_free(ciphertxt);
 516
 517     return ret;
 518 }