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
22static 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 */
32int 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
41int 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
65static 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 rsa->dirty_cnt++;
112
113 /* We need the RSA components non-NULL */
114 if (!rsa->n && ((rsa->n = BN_new()) == NULL))
115 goto err;
116 if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
117 goto err;
118 if (!rsa->e && ((rsa->e = BN_new()) == NULL))
119 goto err;
120 if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
121 goto err;
122 if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
123 goto err;
124 if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
125 goto err;
126 if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
127 goto err;
128 if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
129 goto err;
130
131 /* initialize multi-prime components */
132 if (primes > RSA_DEFAULT_PRIME_NUM) {
133 rsa->version = RSA_ASN1_VERSION_MULTI;
134 prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
135 if (prime_infos == NULL)
136 goto err;
137 if (rsa->prime_infos != NULL) {
138 /* could this happen? */
139 sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
140 }
141 rsa->prime_infos = prime_infos;
142
143 /* prime_info from 2 to |primes| -1 */
144 for (i = 2; i < primes; i++) {
145 pinfo = rsa_multip_info_new();
146 if (pinfo == NULL)
147 goto err;
148 (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
149 }
150 }
151
152 if (BN_copy(rsa->e, e_value) == NULL)
153 goto err;
154
155 /* generate p, q and other primes (if any) */
156 for (i = 0; i < primes; i++) {
157 adj = 0;
158 retries = 0;
159
160 if (i == 0) {
161 prime = rsa->p;
162 } else if (i == 1) {
163 prime = rsa->q;
164 } else {
165 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
166 prime = pinfo->r;
167 }
168 BN_set_flags(prime, BN_FLG_CONSTTIME);
169
170 for (;;) {
171 redo:
172 if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
173 goto err;
174 /*
175 * prime should not be equal to p, q, r_3...
176 * (those primes prior to this one)
177 */
178 {
179 int j;
180
181 for (j = 0; j < i; j++) {
182 BIGNUM *prev_prime;
183
184 if (j == 0)
185 prev_prime = rsa->p;
186 else if (j == 1)
187 prev_prime = rsa->q;
188 else
189 prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
190 j - 2)->r;
191
192 if (!BN_cmp(prime, prev_prime)) {
193 goto redo;
194 }
195 }
196 }
197 if (!BN_sub(r2, prime, BN_value_one()))
198 goto err;
199 ERR_set_mark();
200 BN_set_flags(r2, BN_FLG_CONSTTIME);
201 if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
202 /* GCD == 1 since inverse exists */
203 break;
204 }
205 error = ERR_peek_last_error();
206 if (ERR_GET_LIB(error) == ERR_LIB_BN
207 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
208 /* GCD != 1 */
209 ERR_pop_to_mark();
210 } else {
211 goto err;
212 }
213 if (!BN_GENCB_call(cb, 2, n++))
214 goto err;
215 }
216
217 bitse += bitsr[i];
218
219 /* calculate n immediately to see if it's sufficient */
220 if (i == 1) {
221 /* we get at least 2 primes */
222 if (!BN_mul(r1, rsa->p, rsa->q, ctx))
223 goto err;
224 } else if (i != 0) {
225 /* modulus n = p * q * r_3 * r_4 ... */
226 if (!BN_mul(r1, rsa->n, prime, ctx))
227 goto err;
228 } else {
229 /* i == 0, do nothing */
230 if (!BN_GENCB_call(cb, 3, i))
231 goto err;
232 continue;
233 }
234 /*
235 * if |r1|, product of factors so far, is not as long as expected
236 * (by checking the first 4 bits are less than 0x9 or greater than
237 * 0xF). If so, re-generate the last prime.
238 *
239 * NOTE: This actually can't happen in two-prime case, because of
240 * the way factors are generated.
241 *
242 * Besides, another consideration is, for multi-prime case, even the
243 * length modulus is as long as expected, the modulus could start at
244 * 0x8, which could be utilized to distinguish a multi-prime private
245 * key by using the modulus in a certificate. This is also covered
246 * by checking the length should not be less than 0x9.
247 */
248 if (!BN_rshift(r2, r1, bitse - 4))
249 goto err;
250 bitst = BN_get_word(r2);
251
252 if (bitst < 0x9 || bitst > 0xF) {
253 /*
254 * For keys with more than 4 primes, we attempt longer factor to
255 * meet length requirement.
256 *
257 * Otherwise, we just re-generate the prime with the same length.
258 *
259 * This strategy has the following goals:
260 *
261 * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
262 * 2. stay the same logic with normal 2-prime key
263 */
264 bitse -= bitsr[i];
265 if (!BN_GENCB_call(cb, 2, n++))
266 goto err;
267 if (primes > 4) {
268 if (bitst < 0x9)
269 adj++;
270 else
271 adj--;
272 } else if (retries == 4) {
273 /*
274 * re-generate all primes from scratch, mainly used
275 * in 4 prime case to avoid long loop. Max retry times
276 * is set to 4.
277 */
278 i = -1;
279 bitse = 0;
280 continue;
281 }
282 retries++;
283 goto redo;
284 }
285 /* save product of primes for further use, for multi-prime only */
286 if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
287 goto err;
288 if (BN_copy(rsa->n, r1) == NULL)
289 goto err;
290 if (!BN_GENCB_call(cb, 3, i))
291 goto err;
292 }
293
294 if (BN_cmp(rsa->p, rsa->q) < 0) {
295 tmp = rsa->p;
296 rsa->p = rsa->q;
297 rsa->q = tmp;
298 }
299
300 /* calculate d */
301
302 /* p - 1 */
303 if (!BN_sub(r1, rsa->p, BN_value_one()))
304 goto err;
305 /* q - 1 */
306 if (!BN_sub(r2, rsa->q, BN_value_one()))
307 goto err;
308 /* (p - 1)(q - 1) */
309 if (!BN_mul(r0, r1, r2, ctx))
310 goto err;
311 /* multi-prime */
312 for (i = 2; i < primes; i++) {
313 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
314 /* save r_i - 1 to pinfo->d temporarily */
315 if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
316 goto err;
317 if (!BN_mul(r0, r0, pinfo->d, ctx))
318 goto err;
319 }
320
321 {
322 BIGNUM *pr0 = BN_new();
323
324 if (pr0 == NULL)
325 goto err;
326
327 BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
328 if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
329 BN_free(pr0);
330 goto err; /* d */
331 }
332 /* We MUST free pr0 before any further use of r0 */
333 BN_free(pr0);
334 }
335
336 {
337 BIGNUM *d = BN_new();
338
339 if (d == NULL)
340 goto err;
341
342 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
343
344 /* calculate d mod (p-1) and d mod (q - 1) */
345 if (!BN_mod(rsa->dmp1, d, r1, ctx)
346 || !BN_mod(rsa->dmq1, d, r2, ctx)) {
347 BN_free(d);
348 goto err;
349 }
350
351 /* calculate CRT exponents */
352 for (i = 2; i < primes; i++) {
353 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
354 /* pinfo->d == r_i - 1 */
355 if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
356 BN_free(d);
357 goto err;
358 }
359 }
360
361 /* We MUST free d before any further use of rsa->d */
362 BN_free(d);
363 }
364
365 {
366 BIGNUM *p = BN_new();
367
368 if (p == NULL)
369 goto err;
370 BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
371
372 /* calculate inverse of q mod p */
373 if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
374 BN_free(p);
375 goto err;
376 }
377
378 /* calculate CRT coefficient for other primes */
379 for (i = 2; i < primes; i++) {
380 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
381 BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
382 if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
383 BN_free(p);
384 goto err;
385 }
386 }
387
388 /* We MUST free p before any further use of rsa->p */
389 BN_free(p);
390 }
391
392 ok = 1;
393 err:
394 if (ok == -1) {
395 RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, ERR_LIB_BN);
396 ok = 0;
397 }
398 BN_CTX_end(ctx);
399 BN_CTX_free(ctx);
400 return ok;
401#endif /* FIPS_MODE */
402}
403