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_MODULE */
  70     return rsa_keygen(NULL, 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     if (!rsa->e && ((rsa->e = BN_new()) == NULL))
 130         goto err;
 131     if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
 132         goto err;
 133     if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
 134         goto err;
 135     if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
 136         goto err;
 137     if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
 138         goto err;
 139     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
 140         goto err;
 141
 142     /* initialize multi-prime components */
 143     if (primes > RSA_DEFAULT_PRIME_NUM) {
 144         rsa->version = RSA_ASN1_VERSION_MULTI;
 145         prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
 146         if (prime_infos == NULL)
 147             goto err;
 148         if (rsa->prime_infos != NULL) {
 149             /* could this happen? */
 150             sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
 151         }
 152         rsa->prime_infos = prime_infos;
 153
 154         /* prime_info from 2 to |primes| -1 */
 155         for (i = 2; i < primes; i++) {
 156             pinfo = rsa_multip_info_new();
 157             if (pinfo == NULL)
 158                 goto err;
 159             (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
 160         }
 161     }
 162
 163     if (BN_copy(rsa->e, e_value) == NULL)
 164         goto err;
 165
 166     /* generate p, q and other primes (if any) */
 167     for (i = 0; i < primes; i++) {
 168         adj = 0;
 169         retries = 0;
 170
 171         if (i == 0) {
 172             prime = rsa->p;
 173         } else if (i == 1) {
 174             prime = rsa->q;
 175         } else {
 176             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 177             prime = pinfo->r;
 178         }
 179         BN_set_flags(prime, BN_FLG_CONSTTIME);
 180
 181         for (;;) {
 182  redo:
 183             if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
 184                 goto err;
 185             /*
 186              * prime should not be equal to p, q, r_3...
 187              * (those primes prior to this one)
 188              */
 189             {
 190                 int j;
 191
 192                 for (j = 0; j < i; j++) {
 193                     BIGNUM *prev_prime;
 194
 195                     if (j == 0)
 196                         prev_prime = rsa->p;
 197                     else if (j == 1)
 198                         prev_prime = rsa->q;
 199                     else
 200                         prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
 201                                                              j - 2)->r;
 202
 203                     if (!BN_cmp(prime, prev_prime)) {
 204                         goto redo;
 205                     }
 206                 }
 207             }
 208             if (!BN_sub(r2, prime, BN_value_one()))
 209                 goto err;
 210             ERR_set_mark();
 211             BN_set_flags(r2, BN_FLG_CONSTTIME);
 212             if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
 213                /* GCD == 1 since inverse exists */
 214                 break;
 215             }
 216             error = ERR_peek_last_error();
 217             if (ERR_GET_LIB(error) == ERR_LIB_BN
 218                 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
 219                 /* GCD != 1 */
 220                 ERR_pop_to_mark();
 221             } else {
 222                 goto err;
 223             }
 224             if (!BN_GENCB_call(cb, 2, n++))
 225                 goto err;
 226         }
 227
 228         bitse += bitsr[i];
 229
 230         /* calculate n immediately to see if it's sufficient */
 231         if (i == 1) {
 232             /* we get at least 2 primes */
 233             if (!BN_mul(r1, rsa->p, rsa->q, ctx))
 234                 goto err;
 235         } else if (i != 0) {
 236             /* modulus n = p * q * r_3 * r_4 ... */
 237             if (!BN_mul(r1, rsa->n, prime, ctx))
 238                 goto err;
 239         } else {
 240             /* i == 0, do nothing */
 241             if (!BN_GENCB_call(cb, 3, i))
 242                 goto err;
 243             continue;
 244         }
 245         /*
 246          * if |r1|, product of factors so far, is not as long as expected
 247          * (by checking the first 4 bits are less than 0x9 or greater than
 248          * 0xF). If so, re-generate the last prime.
 249          *
 250          * NOTE: This actually can't happen in two-prime case, because of
 251          * the way factors are generated.
 252          *
 253          * Besides, another consideration is, for multi-prime case, even the
 254          * length modulus is as long as expected, the modulus could start at
 255          * 0x8, which could be utilized to distinguish a multi-prime private
 256          * key by using the modulus in a certificate. This is also covered
 257          * by checking the length should not be less than 0x9.
 258          */
 259         if (!BN_rshift(r2, r1, bitse - 4))
 260             goto err;
 261         bitst = BN_get_word(r2);
 262
 263         if (bitst < 0x9 || bitst > 0xF) {
 264             /*
 265              * For keys with more than 4 primes, we attempt longer factor to
 266              * meet length requirement.
 267              *
 268              * Otherwise, we just re-generate the prime with the same length.
 269              *
 270              * This strategy has the following goals:
 271              *
 272              * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
 273              * 2. stay the same logic with normal 2-prime key
 274              */
 275             bitse -= bitsr[i];
 276             if (!BN_GENCB_call(cb, 2, n++))
 277                 goto err;
 278             if (primes > 4) {
 279                 if (bitst < 0x9)
 280                     adj++;
 281                 else
 282                     adj--;
 283             } else if (retries == 4) {
 284                 /*
 285                  * re-generate all primes from scratch, mainly used
 286                  * in 4 prime case to avoid long loop. Max retry times
 287                  * is set to 4.
 288                  */
 289                 i = -1;
 290                 bitse = 0;
 291                 continue;
 292             }
 293             retries++;
 294             goto redo;
 295         }
 296         /* save product of primes for further use, for multi-prime only */
 297         if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
 298             goto err;
 299         if (BN_copy(rsa->n, r1) == NULL)
 300             goto err;
 301         if (!BN_GENCB_call(cb, 3, i))
 302             goto err;
 303     }
 304
 305     if (BN_cmp(rsa->p, rsa->q) < 0) {
 306         tmp = rsa->p;
 307         rsa->p = rsa->q;
 308         rsa->q = tmp;
 309     }
 310
 311     /* calculate d */
 312
 313     /* p - 1 */
 314     if (!BN_sub(r1, rsa->p, BN_value_one()))
 315         goto err;
 316     /* q - 1 */
 317     if (!BN_sub(r2, rsa->q, BN_value_one()))
 318         goto err;
 319     /* (p - 1)(q - 1) */
 320     if (!BN_mul(r0, r1, r2, ctx))
 321         goto err;
 322     /* multi-prime */
 323     for (i = 2; i < primes; i++) {
 324         pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 325         /* save r_i - 1 to pinfo->d temporarily */
 326         if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
 327             goto err;
 328         if (!BN_mul(r0, r0, pinfo->d, ctx))
 329             goto err;
 330     }
 331
 332     {
 333         BIGNUM *pr0 = BN_new();
 334
 335         if (pr0 == NULL)
 336             goto err;
 337
 338         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
 339         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
 340             BN_free(pr0);
 341             goto err;               /* d */
 342         }
 343         /* We MUST free pr0 before any further use of r0 */
 344         BN_free(pr0);
 345     }
 346
 347     {
 348         BIGNUM *d = BN_new();
 349
 350         if (d == NULL)
 351             goto err;
 352
 353         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 354
 355         /* calculate d mod (p-1) and d mod (q - 1) */
 356         if (!BN_mod(rsa->dmp1, d, r1, ctx)
 357             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
 358             BN_free(d);
 359             goto err;
 360         }
 361
 362         /* calculate CRT exponents */
 363         for (i = 2; i < primes; i++) {
 364             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 365             /* pinfo->d == r_i - 1 */
 366             if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
 367                 BN_free(d);
 368                 goto err;
 369             }
 370         }
 371
 372         /* We MUST free d before any further use of rsa->d */
 373         BN_free(d);
 374     }
 375
 376     {
 377         BIGNUM *p = BN_new();
 378
 379         if (p == NULL)
 380             goto err;
 381         BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 382
 383         /* calculate inverse of q mod p */
 384         if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
 385             BN_free(p);
 386             goto err;
 387         }
 388
 389         /* calculate CRT coefficient for other primes */
 390         for (i = 2; i < primes; i++) {
 391             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 392             BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
 393             if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
 394                 BN_free(p);
 395                 goto err;
 396             }
 397         }
 398
 399         /* We MUST free p before any further use of rsa->p */
 400         BN_free(p);
 401     }
 402
 403     ok = 1;
 404  err:
 405     if (ok == -1) {
 406         RSAerr(0, ERR_LIB_BN);
 407         ok = 0;
 408     }
 409     BN_CTX_end(ctx);
 410     BN_CTX_free(ctx);
 411     return ok;
 412 }
 413 #endif /* FIPS_MODULE */
 414
 415 static int rsa_keygen(OPENSSL_CTX *libctx, RSA *rsa, int bits, int primes,
 416                       BIGNUM *e_value, BN_GENCB *cb, int pairwise_test)
 417 {
 418     int ok = 0;
 419
 420     /*
 421      * Only multi-prime keys or insecure keys with a small key length will use
 422      * the older rsa_multiprime_keygen().
 423      */
 424     if (primes == 2 && bits >= 2048)
 425         ok = rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
 426 #ifndef FIPS_MODULE
 427     else
 428         ok = rsa_multiprime_keygen(rsa, bits, primes, e_value, cb);
 429 #endif /* FIPS_MODULE */
 430
 431 #ifdef FIPS_MODULE
 432     pairwise_test = 1; /* FIPS MODE needs to always run the pairwise test */
 433 #endif
 434     if (pairwise_test && ok > 0) {
 435         OSSL_CALLBACK *stcb = NULL;
 436         void *stcbarg = NULL;
 437
 438         OSSL_SELF_TEST_get_callback(libctx, &stcb, &stcbarg);
 439         ok = rsa_keygen_pairwise_test(rsa, stcb, stcbarg);
 440         if (!ok) {
 441             /* Clear intermediate results */
 442             BN_clear_free(rsa->d);
 443             BN_clear_free(rsa->p);
 444             BN_clear_free(rsa->q);
 445             BN_clear_free(rsa->dmp1);
 446             BN_clear_free(rsa->dmq1);
 447             BN_clear_free(rsa->iqmp);
 448         }
 449     }
 450     return ok;
 451 }
 452
 453 /*
 454  * For RSA key generation it is not known whether the key pair will be used
 455  * for key transport or signatures. FIPS 140-2 IG 9.9 states that in this case
 456  * either a signature verification OR an encryption operation may be used to
 457  * perform the pairwise consistency check. The simpler encrypt/decrypt operation
 458  * has been chosen for this case.
 459  */
 460 static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg)
 461 {
 462     int ret = 0;
 463     unsigned int ciphertxt_len;
 464     unsigned char *ciphertxt = NULL;
 465     const unsigned char plaintxt[16] = {0};
 466     unsigned char decoded[256];
 467     unsigned int decoded_len;
 468     unsigned int plaintxt_len = (unsigned int)sizeof(plaintxt_len);
 469     int padding = RSA_PKCS1_PADDING;
 470     OSSL_SELF_TEST *st = NULL;
 471
 472     st = OSSL_SELF_TEST_new(cb, cbarg);
 473     if (st == NULL)
 474         goto err;
 475     OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,
 476                            OSSL_SELF_TEST_DESC_PCT_RSA_PKCS1);
 477
 478     ciphertxt_len = RSA_size(rsa);
 479     ciphertxt = OPENSSL_zalloc(ciphertxt_len);
 480     if (ciphertxt == NULL)
 481         goto err;
 482
 483     ciphertxt_len = RSA_public_encrypt(plaintxt_len, plaintxt, ciphertxt, rsa,
 484                                        padding);
 485     if (ciphertxt_len <= 0)
 486         goto err;
 487     if (ciphertxt_len == plaintxt_len
 488         && memcmp(ciphertxt, plaintxt, plaintxt_len) == 0)
 489         goto err;
 490
 491     OSSL_SELF_TEST_oncorrupt_byte(st, ciphertxt);
 492
 493     decoded_len = RSA_private_decrypt(ciphertxt_len, ciphertxt, decoded, rsa,
 494                                       padding);
 495     if (decoded_len != plaintxt_len
 496         || memcmp(decoded, plaintxt,  decoded_len) != 0)
 497         goto err;
 498
 499     ret = 1;
 500 err:
 501     OSSL_SELF_TEST_onend(st, ret);
 502     OSSL_SELF_TEST_free(st);
 503     OPENSSL_free(ciphertxt);
 504
 505     return ret;
 506 }