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 #include <stdio.h>
  17 #include <time.h>
  18 #include "internal/cryptlib.h"
  19 #include <openssl/bn.h>
  20 #include "rsa_local.h"
  21
  22 static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
  23                               BN_GENCB *cb);
  24
  25 /*
  26  * NB: this wrapper would normally be placed in rsa_lib.c and the static
  27  * implementation would probably be in rsa_eay.c. Nonetheless, is kept here
  28  * so that we don't introduce a new linker dependency. Eg. any application
  29  * that wasn't previously linking object code related to key-generation won't
  30  * have to now just because key-generation is part of RSA_METHOD.
  31  */
  32 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
  33 {
  34     if (rsa->meth->rsa_keygen != NULL)
  35         return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  36
  37     return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,
  38                                         e_value, cb);
  39 }
  40
  41 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
  42                                  BIGNUM *e_value, BN_GENCB *cb)
  43 {
  44 #ifndef FIPS_MODE
  45     /* multi-prime is only supported with the builtin key generation */
  46     if (rsa->meth->rsa_multi_prime_keygen != NULL) {
  47         return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
  48                                                  e_value, cb);
  49     } else if (rsa->meth->rsa_keygen != NULL) {
  50         /*
  51          * However, if rsa->meth implements only rsa_keygen, then we
  52          * have to honour it in 2-prime case and assume that it wouldn't
  53          * know what to do with multi-prime key generated by builtin
  54          * subroutine...
  55          */
  56         if (primes == 2)
  57             return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
  58         else
  59             return 0;
  60     }
  61 #endif /* FIPS_MODE */
  62     return rsa_builtin_keygen(rsa, bits, primes, e_value, cb);
  63 }
  64
  65 static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
  66                               BN_GENCB *cb)
  67 {
  68 #ifdef FIPS_MODE
  69     if (primes != 2)
  70         return 0;
  71     return rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
  72 #else
  73     BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
  74     int ok = -1, n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
  75     int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
  76     RSA_PRIME_INFO *pinfo = NULL;
  77     STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
  78     BN_CTX *ctx = NULL;
  79     BN_ULONG bitst = 0;
  80     unsigned long error = 0;
  81
  82     if (bits < RSA_MIN_MODULUS_BITS) {
  83         ok = 0;             /* we set our own err */
  84         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_SIZE_TOO_SMALL);
  85         goto err;
  86     }
  87
  88     if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
  89         ok = 0;             /* we set our own err */
  90         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_PRIME_NUM_INVALID);
  91         goto err;
  92     }
  93
  94     ctx = BN_CTX_new();
  95     if (ctx == NULL)
  96         goto err;
  97     BN_CTX_start(ctx);
  98     r0 = BN_CTX_get(ctx);
  99     r1 = BN_CTX_get(ctx);
 100     r2 = BN_CTX_get(ctx);
 101     if (r2 == NULL)
 102         goto err;
 103
 104     /* divide bits into 'primes' pieces evenly */
 105     quo = bits / primes;
 106     rmd = bits % primes;
 107
 108     for (i = 0; i < primes; i++)
 109         bitsr[i] = (i < rmd) ? quo + 1 : quo;
 110
 111     /* We need the RSA components non-NULL */
 112     if (!rsa->n && ((rsa->n = BN_new()) == NULL))
 113         goto err;
 114     if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
 115         goto err;
 116     if (!rsa->e && ((rsa->e = BN_new()) == NULL))
 117         goto err;
 118     if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
 119         goto err;
 120     if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
 121         goto err;
 122     if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
 123         goto err;
 124     if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
 125         goto err;
 126     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
 127         goto err;
 128
 129     /* initialize multi-prime components */
 130     if (primes > RSA_DEFAULT_PRIME_NUM) {
 131         rsa->version = RSA_ASN1_VERSION_MULTI;
 132         prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
 133         if (prime_infos == NULL)
 134             goto err;
 135         if (rsa->prime_infos != NULL) {
 136             /* could this happen? */
 137             sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
 138         }
 139         rsa->prime_infos = prime_infos;
 140
 141         /* prime_info from 2 to |primes| -1 */
 142         for (i = 2; i < primes; i++) {
 143             pinfo = rsa_multip_info_new();
 144             if (pinfo == NULL)
 145                 goto err;
 146             (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
 147         }
 148     }
 149
 150     if (BN_copy(rsa->e, e_value) == NULL)
 151         goto err;
 152
 153     /* generate p, q and other primes (if any) */
 154     for (i = 0; i < primes; i++) {
 155         adj = 0;
 156         retries = 0;
 157
 158         if (i == 0) {
 159             prime = rsa->p;
 160         } else if (i == 1) {
 161             prime = rsa->q;
 162         } else {
 163             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 164             prime = pinfo->r;
 165         }
 166         BN_set_flags(prime, BN_FLG_CONSTTIME);
 167
 168         for (;;) {
 169  redo:
 170             if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
 171                 goto err;
 172             /*
 173              * prime should not be equal to p, q, r_3...
 174              * (those primes prior to this one)
 175              */
 176             {
 177                 int j;
 178
 179                 for (j = 0; j < i; j++) {
 180                     BIGNUM *prev_prime;
 181
 182                     if (j == 0)
 183                         prev_prime = rsa->p;
 184                     else if (j == 1)
 185                         prev_prime = rsa->q;
 186                     else
 187                         prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
 188                                                              j - 2)->r;
 189
 190                     if (!BN_cmp(prime, prev_prime)) {
 191                         goto redo;
 192                     }
 193                 }
 194             }
 195             if (!BN_sub(r2, prime, BN_value_one()))
 196                 goto err;
 197             ERR_set_mark();
 198             BN_set_flags(r2, BN_FLG_CONSTTIME);
 199             if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
 200                /* GCD == 1 since inverse exists */
 201                 break;
 202             }
 203             error = ERR_peek_last_error();
 204             if (ERR_GET_LIB(error) == ERR_LIB_BN
 205                 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
 206                 /* GCD != 1 */
 207                 ERR_pop_to_mark();
 208             } else {
 209                 goto err;
 210             }
 211             if (!BN_GENCB_call(cb, 2, n++))
 212                 goto err;
 213         }
 214
 215         bitse += bitsr[i];
 216
 217         /* calculate n immediately to see if it's sufficient */
 218         if (i == 1) {
 219             /* we get at least 2 primes */
 220             if (!BN_mul(r1, rsa->p, rsa->q, ctx))
 221                 goto err;
 222         } else if (i != 0) {
 223             /* modulus n = p * q * r_3 * r_4 ... */
 224             if (!BN_mul(r1, rsa->n, prime, ctx))
 225                 goto err;
 226         } else {
 227             /* i == 0, do nothing */
 228             if (!BN_GENCB_call(cb, 3, i))
 229                 goto err;
 230             continue;
 231         }
 232         /*
 233          * if |r1|, product of factors so far, is not as long as expected
 234          * (by checking the first 4 bits are less than 0x9 or greater than
 235          * 0xF). If so, re-generate the last prime.
 236          *
 237          * NOTE: This actually can't happen in two-prime case, because of
 238          * the way factors are generated.
 239          *
 240          * Besides, another consideration is, for multi-prime case, even the
 241          * length modulus is as long as expected, the modulus could start at
 242          * 0x8, which could be utilized to distinguish a multi-prime private
 243          * key by using the modulus in a certificate. This is also covered
 244          * by checking the length should not be less than 0x9.
 245          */
 246         if (!BN_rshift(r2, r1, bitse - 4))
 247             goto err;
 248         bitst = BN_get_word(r2);
 249
 250         if (bitst < 0x9 || bitst > 0xF) {
 251             /*
 252              * For keys with more than 4 primes, we attempt longer factor to
 253              * meet length requirement.
 254              *
 255              * Otherwise, we just re-generate the prime with the same length.
 256              *
 257              * This strategy has the following goals:
 258              *
 259              * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
 260              * 2. stay the same logic with normal 2-prime key
 261              */
 262             bitse -= bitsr[i];
 263             if (!BN_GENCB_call(cb, 2, n++))
 264                 goto err;
 265             if (primes > 4) {
 266                 if (bitst < 0x9)
 267                     adj++;
 268                 else
 269                     adj--;
 270             } else if (retries == 4) {
 271                 /*
 272                  * re-generate all primes from scratch, mainly used
 273                  * in 4 prime case to avoid long loop. Max retry times
 274                  * is set to 4.
 275                  */
 276                 i = -1;
 277                 bitse = 0;
 278                 continue;
 279             }
 280             retries++;
 281             goto redo;
 282         }
 283         /* save product of primes for further use, for multi-prime only */
 284         if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
 285             goto err;
 286         if (BN_copy(rsa->n, r1) == NULL)
 287             goto err;
 288         if (!BN_GENCB_call(cb, 3, i))
 289             goto err;
 290     }
 291
 292     if (BN_cmp(rsa->p, rsa->q) < 0) {
 293         tmp = rsa->p;
 294         rsa->p = rsa->q;
 295         rsa->q = tmp;
 296     }
 297
 298     /* calculate d */
 299
 300     /* p - 1 */
 301     if (!BN_sub(r1, rsa->p, BN_value_one()))
 302         goto err;
 303     /* q - 1 */
 304     if (!BN_sub(r2, rsa->q, BN_value_one()))
 305         goto err;
 306     /* (p - 1)(q - 1) */
 307     if (!BN_mul(r0, r1, r2, ctx))
 308         goto err;
 309     /* multi-prime */
 310     for (i = 2; i < primes; i++) {
 311         pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 312         /* save r_i - 1 to pinfo->d temporarily */
 313         if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
 314             goto err;
 315         if (!BN_mul(r0, r0, pinfo->d, ctx))
 316             goto err;
 317     }
 318
 319     {
 320         BIGNUM *pr0 = BN_new();
 321
 322         if (pr0 == NULL)
 323             goto err;
 324
 325         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
 326         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
 327             BN_free(pr0);
 328             goto err;               /* d */
 329         }
 330         /* We MUST free pr0 before any further use of r0 */
 331         BN_free(pr0);
 332     }
 333
 334     {
 335         BIGNUM *d = BN_new();
 336
 337         if (d == NULL)
 338             goto err;
 339
 340         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 341
 342         /* calculate d mod (p-1) and d mod (q - 1) */
 343         if (!BN_mod(rsa->dmp1, d, r1, ctx)
 344             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
 345             BN_free(d);
 346             goto err;
 347         }
 348
 349         /* calculate CRT exponents */
 350         for (i = 2; i < primes; i++) {
 351             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 352             /* pinfo->d == r_i - 1 */
 353             if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
 354                 BN_free(d);
 355                 goto err;
 356             }
 357         }
 358
 359         /* We MUST free d before any further use of rsa->d */
 360         BN_free(d);
 361     }
 362
 363     {
 364         BIGNUM *p = BN_new();
 365
 366         if (p == NULL)
 367             goto err;
 368         BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 369
 370         /* calculate inverse of q mod p */
 371         if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
 372             BN_free(p);
 373             goto err;
 374         }
 375
 376         /* calculate CRT coefficient for other primes */
 377         for (i = 2; i < primes; i++) {
 378             pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
 379             BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
 380             if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
 381                 BN_free(p);
 382                 goto err;
 383             }
 384         }
 385
 386         /* We MUST free p before any further use of rsa->p */
 387         BN_free(p);
 388     }
 389
 390     ok = 1;
 391  err:
 392     if (ok == -1) {
 393         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, ERR_LIB_BN);
 394         ok = 0;
 395     }
 396     BN_CTX_end(ctx);
 397     BN_CTX_free(ctx);
 398     return ok;
 399 #endif /* FIPS_MODE */
 400 }