crypto/rsa/rsa_gen.c

   1 /*
   2  * Copyright 1995-2018 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 "rsa_local.h"
  27
  28 static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
  29                               BN_GENCB *cb);
  30
  31 /*
  32  * NB: this wrapper would normally be placed in rsa_lib.c and the static
  33  * implementation would probably be in rsa_eay.c. Nonetheless, is kept here
  34  * so that we don't introduce a new linker dependency. Eg. any application
  35  * that wasn't previously linking object code related to key-generation won't
  36  * have to now just because key-generation is part of RSA_METHOD.
  37  */
  38 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
  39 {
  40     if (rsa->meth->rsa_keygen != NULL)
  41         return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  42
  43     return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,
  44                                         e_value, cb);
  45 }
  46
  47 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
  48                                  BIGNUM *e_value, BN_GENCB *cb)
  49 {
  50 #ifndef FIPS_MODE
  51     /* multi-prime is only supported with the builtin key generation */
  52     if (rsa->meth->rsa_multi_prime_keygen != NULL) {
  53         return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
  54                                                  e_value, cb);
  55     } else if (rsa->meth->rsa_keygen != NULL) {
  56         /*
  57          * However, if rsa->meth implements only rsa_keygen, then we
  58          * have to honour it in 2-prime case and assume that it wouldn't
  59          * know what to do with multi-prime key generated by builtin
  60          * subroutine...
  61          */
  62         if (primes == 2)
  63             return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  64         else
  65             return 0;
  66     }
  67 #endif /* FIPS_MODE */
  68     return rsa_builtin_keygen(rsa, bits, primes, e_value, cb);
  69 }
  70
  71 static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
  72                               BN_GENCB *cb)
  73 {
  74 #ifdef FIPS_MODE
  75     if (primes != 2)
  76         return 0;
  77     return rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
  78 #else
  79     BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
  80     int ok = -1, n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
  81     int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
  82     RSA_PRIME_INFO *pinfo = NULL;
  83     STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
  84     BN_CTX *ctx = NULL;
  85     BN_ULONG bitst = 0;
  86     unsigned long error = 0;
  87
  88     if (bits < RSA_MIN_MODULUS_BITS) {
  89         ok = 0;             /* we set our own err */
  90         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_SIZE_TOO_SMALL);
  91         goto err;
  92     }
  93
  94     if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
  95         ok = 0;             /* we set our own err */
  96         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_PRIME_NUM_INVALID);
  97         goto err;
  98     }
  99
 100     ctx = BN_CTX_new();
 101     if (ctx == NULL)
 102         goto err;
 103     BN_CTX_start(ctx);
 104     r0 = BN_CTX_get(ctx);
 105     r1 = BN_CTX_get(ctx);
 106     r2 = BN_CTX_get(ctx);
 107     if (r2 == NULL)
 108         goto err;
 109
 110     /* divide bits into 'primes' pieces evenly */
 111     quo = bits / primes;
 112     rmd = bits % primes;
 113
 114     for (i = 0; i < primes; i++)
 115         bitsr[i] = (i < rmd) ? quo + 1 : quo;
 116
 117     rsa->dirty_cnt++;
 118
 119     /* We need the RSA components non-NULL */
 120     if (!rsa->n && ((rsa->n = BN_new()) == NULL))
 121         goto err;
 122     if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
 123         goto err;
 124     if (!rsa->e && ((rsa->e = BN_new()) == NULL))
 125         goto err;
 126     if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
 127         goto err;
 128     if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
 129         goto err;
 130     if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
 131         goto err;
 132     if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
 133         goto err;
 134     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
 135         goto err;
 136
 137     /* initialize multi-prime components */
 138     if (primes > RSA_DEFAULT_PRIME_NUM) {
 139         rsa->version = RSA_ASN1_VERSION_MULTI;
 140         prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
 141         if (prime_infos == NULL)
 142             goto err;
 143         if (rsa->prime_infos != NULL) {
 144             /* could this happen? */
 145             sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
 146         }
 147         rsa->prime_infos = prime_infos;
 148
 149         /* prime_info from 2 to |primes| -1 */
 150         for (i = 2; i < primes; i++) {
 151             pinfo = rsa_multip_info_new();
 152             if (pinfo == NULL)
 153                 goto err;
 154             (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
 155         }
 156     }
 157
 158     if (BN_copy(rsa->e, e_value) == NULL)
 159         goto err;
 160
 161     /* generate p, q and other primes (if any) */
 162     for (i = 0; i < primes; i++) {
 163         adj = 0;
 164         retries = 0;
 165
 166         if (i == 0) {
 167             prime = rsa->p;
 168         } else if (i == 1) {
 169             prime = rsa->q;
 170         } else {
 171             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 172             prime = pinfo->r;
 173         }
 174         BN_set_flags(prime, BN_FLG_CONSTTIME);
 175
 176         for (;;) {
 177  redo:
 178             if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
 179                 goto err;
 180             /*
 181              * prime should not be equal to p, q, r_3...
 182              * (those primes prior to this one)
 183              */
 184             {
 185                 int j;
 186
 187                 for (j = 0; j < i; j++) {
 188                     BIGNUM *prev_prime;
 189
 190                     if (j == 0)
 191                         prev_prime = rsa->p;
 192                     else if (j == 1)
 193                         prev_prime = rsa->q;
 194                     else
 195                         prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
 196                                                              j - 2)->r;
 197
 198                     if (!BN_cmp(prime, prev_prime)) {
 199                         goto redo;
 200                     }
 201                 }
 202             }
 203             if (!BN_sub(r2, prime, BN_value_one()))
 204                 goto err;
 205             ERR_set_mark();
 206             BN_set_flags(r2, BN_FLG_CONSTTIME);
 207             if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
 208                /* GCD == 1 since inverse exists */
 209                 break;
 210             }
 211             error = ERR_peek_last_error();
 212             if (ERR_GET_LIB(error) == ERR_LIB_BN
 213                 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
 214                 /* GCD != 1 */
 215                 ERR_pop_to_mark();
 216             } else {
 217                 goto err;
 218             }
 219             if (!BN_GENCB_call(cb, 2, n++))
 220                 goto err;
 221         }
 222
 223         bitse += bitsr[i];
 224
 225         /* calculate n immediately to see if it's sufficient */
 226         if (i == 1) {
 227             /* we get at least 2 primes */
 228             if (!BN_mul(r1, rsa->p, rsa->q, ctx))
 229                 goto err;
 230         } else if (i != 0) {
 231             /* modulus n = p * q * r_3 * r_4 ... */
 232             if (!BN_mul(r1, rsa->n, prime, ctx))
 233                 goto err;
 234         } else {
 235             /* i == 0, do nothing */
 236             if (!BN_GENCB_call(cb, 3, i))
 237                 goto err;
 238             continue;
 239         }
 240         /*
 241          * if |r1|, product of factors so far, is not as long as expected
 242          * (by checking the first 4 bits are less than 0x9 or greater than
 243          * 0xF). If so, re-generate the last prime.
 244          *
 245          * NOTE: This actually can't happen in two-prime case, because of
 246          * the way factors are generated.
 247          *
 248          * Besides, another consideration is, for multi-prime case, even the
 249          * length modulus is as long as expected, the modulus could start at
 250          * 0x8, which could be utilized to distinguish a multi-prime private
 251          * key by using the modulus in a certificate. This is also covered
 252          * by checking the length should not be less than 0x9.
 253          */
 254         if (!BN_rshift(r2, r1, bitse - 4))
 255             goto err;
 256         bitst = BN_get_word(r2);
 257
 258         if (bitst < 0x9 || bitst > 0xF) {
 259             /*
 260              * For keys with more than 4 primes, we attempt longer factor to
 261              * meet length requirement.
 262              *
 263              * Otherwise, we just re-generate the prime with the same length.
 264              *
 265              * This strategy has the following goals:
 266              *
 267              * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
 268              * 2. stay the same logic with normal 2-prime key
 269              */
 270             bitse -= bitsr[i];
 271             if (!BN_GENCB_call(cb, 2, n++))
 272                 goto err;
 273             if (primes > 4) {
 274                 if (bitst < 0x9)
 275                     adj++;
 276                 else
 277                     adj--;
 278             } else if (retries == 4) {
 279                 /*
 280                  * re-generate all primes from scratch, mainly used
 281                  * in 4 prime case to avoid long loop. Max retry times
 282                  * is set to 4.
 283                  */
 284                 i = -1;
 285                 bitse = 0;
 286                 continue;
 287             }
 288             retries++;
 289             goto redo;
 290         }
 291         /* save product of primes for further use, for multi-prime only */
 292         if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
 293             goto err;
 294         if (BN_copy(rsa->n, r1) == NULL)
 295             goto err;
 296         if (!BN_GENCB_call(cb, 3, i))
 297             goto err;
 298     }
 299
 300     if (BN_cmp(rsa->p, rsa->q) < 0) {
 301         tmp = rsa->p;
 302         rsa->p = rsa->q;
 303         rsa->q = tmp;
 304     }
 305
 306     /* calculate d */
 307
 308     /* p - 1 */
 309     if (!BN_sub(r1, rsa->p, BN_value_one()))
 310         goto err;
 311     /* q - 1 */
 312     if (!BN_sub(r2, rsa->q, BN_value_one()))
 313         goto err;
 314     /* (p - 1)(q - 1) */
 315     if (!BN_mul(r0, r1, r2, ctx))
 316         goto err;
 317     /* multi-prime */
 318     for (i = 2; i < primes; i++) {
 319         pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 320         /* save r_i - 1 to pinfo->d temporarily */
 321         if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
 322             goto err;
 323         if (!BN_mul(r0, r0, pinfo->d, ctx))
 324             goto err;
 325     }
 326
 327     {
 328         BIGNUM *pr0 = BN_new();
 329
 330         if (pr0 == NULL)
 331             goto err;
 332
 333         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
 334         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
 335             BN_free(pr0);
 336             goto err;               /* d */
 337         }
 338         /* We MUST free pr0 before any further use of r0 */
 339         BN_free(pr0);
 340     }
 341
 342     {
 343         BIGNUM *d = BN_new();
 344
 345         if (d == NULL)
 346             goto err;
 347
 348         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 349
 350         /* calculate d mod (p-1) and d mod (q - 1) */
 351         if (!BN_mod(rsa->dmp1, d, r1, ctx)
 352             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
 353             BN_free(d);
 354             goto err;
 355         }
 356
 357         /* calculate CRT exponents */
 358         for (i = 2; i < primes; i++) {
 359             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 360             /* pinfo->d == r_i - 1 */
 361             if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
 362                 BN_free(d);
 363                 goto err;
 364             }
 365         }
 366
 367         /* We MUST free d before any further use of rsa->d */
 368         BN_free(d);
 369     }
 370
 371     {
 372         BIGNUM *p = BN_new();
 373
 374         if (p == NULL)
 375             goto err;
 376         BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 377
 378         /* calculate inverse of q mod p */
 379         if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
 380             BN_free(p);
 381             goto err;
 382         }
 383
 384         /* calculate CRT coefficient for other primes */
 385         for (i = 2; i < primes; i++) {
 386             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 387             BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
 388             if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
 389                 BN_free(p);
 390                 goto err;
 391             }
 392         }
 393
 394         /* We MUST free p before any further use of rsa->p */
 395         BN_free(p);
 396     }
 397
 398     ok = 1;
 399  err:
 400     if (ok == -1) {
 401         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, ERR_LIB_BN);
 402         ok = 0;
 403     }
 404     BN_CTX_end(ctx);
 405     BN_CTX_free(ctx);
 406     return ok;
 407 #endif /* FIPS_MODE */
 408 }