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