1 /*
2 * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (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 */
RSA_generate_key_ex(RSA * rsa,int bits,BIGNUM * e_value,BN_GENCB * cb)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
RSA_generate_multi_prime_key(RSA * rsa,int bits,int primes,BIGNUM * e_value,BN_GENCB * cb)41 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
42 BIGNUM *e_value, BN_GENCB *cb)
43 {
44 /* multi-prime is only supported with the builtin key generation */
45 if (rsa->meth->rsa_multi_prime_keygen != NULL) {
46 return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
47 e_value, cb);
48 } else if (rsa->meth->rsa_keygen != NULL) {
49 /*
50 * However, if rsa->meth implements only rsa_keygen, then we
51 * have to honour it in 2-prime case and assume that it wouldn't
52 * know what to do with multi-prime key generated by builtin
53 * subroutine...
54 */
55 if (primes == 2)
56 return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
57 else
58 return 0;
59 }
60
61 return rsa_builtin_keygen(rsa, bits, primes, e_value, cb);
62 }
63
rsa_builtin_keygen(RSA * rsa,int bits,int primes,BIGNUM * e_value,BN_GENCB * cb)64 static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
65 BN_GENCB *cb)
66 {
67 BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
68 int ok = -1, n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
69 int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
70 RSA_PRIME_INFO *pinfo = NULL;
71 STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
72 BN_CTX *ctx = NULL;
73 BN_ULONG bitst = 0;
74 unsigned long error = 0;
75
76 if (bits < RSA_MIN_MODULUS_BITS) {
77 ok = 0; /* we set our own err */
78 RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_SIZE_TOO_SMALL);
79 goto err;
80 }
81
82 if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
83 ok = 0; /* we set our own err */
84 RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_PRIME_NUM_INVALID);
85 goto err;
86 }
87
88 ctx = BN_CTX_new();
89 if (ctx == NULL)
90 goto err;
91 BN_CTX_start(ctx);
92 r0 = BN_CTX_get(ctx);
93 r1 = BN_CTX_get(ctx);
94 r2 = BN_CTX_get(ctx);
95 if (r2 == NULL)
96 goto err;
97
98 /* divide bits into 'primes' pieces evenly */
99 quo = bits / primes;
100 rmd = bits % primes;
101
102 for (i = 0; i < primes; i++)
103 bitsr[i] = (i < rmd) ? quo + 1 : quo;
104
105 /* We need the RSA components non-NULL */
106 if (!rsa->n && ((rsa->n = BN_new()) == NULL))
107 goto err;
108 if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))
109 goto err;
110 if (!rsa->e && ((rsa->e = BN_new()) == NULL))
111 goto err;
112 if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))
113 goto err;
114 if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))
115 goto err;
116 if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))
117 goto err;
118 if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))
119 goto err;
120 if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
121 goto err;
122
123 /* initialize multi-prime components */
124 if (primes > RSA_DEFAULT_PRIME_NUM) {
125 rsa->version = RSA_ASN1_VERSION_MULTI;
126 prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
127 if (prime_infos == NULL)
128 goto err;
129 if (rsa->prime_infos != NULL) {
130 /* could this happen? */
131 sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
132 }
133 rsa->prime_infos = prime_infos;
134
135 /* prime_info from 2 to |primes| -1 */
136 for (i = 2; i < primes; i++) {
137 pinfo = rsa_multip_info_new();
138 if (pinfo == NULL)
139 goto err;
140 (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
141 }
142 }
143
144 if (BN_copy(rsa->e, e_value) == NULL)
145 goto err;
146
147 /* generate p, q and other primes (if any) */
148 for (i = 0; i < primes; i++) {
149 adj = 0;
150 retries = 0;
151
152 if (i == 0) {
153 prime = rsa->p;
154 } else if (i == 1) {
155 prime = rsa->q;
156 } else {
157 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
158 prime = pinfo->r;
159 }
160 BN_set_flags(prime, BN_FLG_CONSTTIME);
161
162 for (;;) {
163 redo:
164 if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
165 goto err;
166 /*
167 * prime should not be equal to p, q, r_3...
168 * (those primes prior to this one)
169 */
170 {
171 int j;
172
173 for (j = 0; j < i; j++) {
174 BIGNUM *prev_prime;
175
176 if (j == 0)
177 prev_prime = rsa->p;
178 else if (j == 1)
179 prev_prime = rsa->q;
180 else
181 prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
182 j - 2)->r;
183
184 if (!BN_cmp(prime, prev_prime)) {
185 goto redo;
186 }
187 }
188 }
189 if (!BN_sub(r2, prime, BN_value_one()))
190 goto err;
191 ERR_set_mark();
192 BN_set_flags(r2, BN_FLG_CONSTTIME);
193 if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
194 /* GCD == 1 since inverse exists */
195 break;
196 }
197 error = ERR_peek_last_error();
198 if (ERR_GET_LIB(error) == ERR_LIB_BN
199 && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
200 /* GCD != 1 */
201 ERR_pop_to_mark();
202 } else {
203 goto err;
204 }
205 if (!BN_GENCB_call(cb, 2, n++))
206 goto err;
207 }
208
209 bitse += bitsr[i];
210
211 /* calculate n immediately to see if it's sufficient */
212 if (i == 1) {
213 /* we get at least 2 primes */
214 if (!BN_mul(r1, rsa->p, rsa->q, ctx))
215 goto err;
216 } else if (i != 0) {
217 /* modulus n = p * q * r_3 * r_4 ... */
218 if (!BN_mul(r1, rsa->n, prime, ctx))
219 goto err;
220 } else {
221 /* i == 0, do nothing */
222 if (!BN_GENCB_call(cb, 3, i))
223 goto err;
224 continue;
225 }
226 /*
227 * if |r1|, product of factors so far, is not as long as expected
228 * (by checking the first 4 bits are less than 0x9 or greater than
229 * 0xF). If so, re-generate the last prime.
230 *
231 * NOTE: This actually can't happen in two-prime case, because of
232 * the way factors are generated.
233 *
234 * Besides, another consideration is, for multi-prime case, even the
235 * length modulus is as long as expected, the modulus could start at
236 * 0x8, which could be utilized to distinguish a multi-prime private
237 * key by using the modulus in a certificate. This is also covered
238 * by checking the length should not be less than 0x9.
239 */
240 if (!BN_rshift(r2, r1, bitse - 4))
241 goto err;
242 bitst = BN_get_word(r2);
243
244 if (bitst < 0x9 || bitst > 0xF) {
245 /*
246 * For keys with more than 4 primes, we attempt longer factor to
247 * meet length requirement.
248 *
249 * Otherwise, we just re-generate the prime with the same length.
250 *
251 * This strategy has the following goals:
252 *
253 * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key
254 * 2. stay the same logic with normal 2-prime key
255 */
256 bitse -= bitsr[i];
257 if (!BN_GENCB_call(cb, 2, n++))
258 goto err;
259 if (primes > 4) {
260 if (bitst < 0x9)
261 adj++;
262 else
263 adj--;
264 } else if (retries == 4) {
265 /*
266 * re-generate all primes from scratch, mainly used
267 * in 4 prime case to avoid long loop. Max retry times
268 * is set to 4.
269 */
270 i = -1;
271 bitse = 0;
272 continue;
273 }
274 retries++;
275 goto redo;
276 }
277 /* save product of primes for further use, for multi-prime only */
278 if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
279 goto err;
280 if (BN_copy(rsa->n, r1) == NULL)
281 goto err;
282 if (!BN_GENCB_call(cb, 3, i))
283 goto err;
284 }
285
286 if (BN_cmp(rsa->p, rsa->q) < 0) {
287 tmp = rsa->p;
288 rsa->p = rsa->q;
289 rsa->q = tmp;
290 }
291
292 /* calculate d */
293
294 /* p - 1 */
295 if (!BN_sub(r1, rsa->p, BN_value_one()))
296 goto err;
297 /* q - 1 */
298 if (!BN_sub(r2, rsa->q, BN_value_one()))
299 goto err;
300 /* (p - 1)(q - 1) */
301 if (!BN_mul(r0, r1, r2, ctx))
302 goto err;
303 /* multi-prime */
304 for (i = 2; i < primes; i++) {
305 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
306 /* save r_i - 1 to pinfo->d temporarily */
307 if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
308 goto err;
309 if (!BN_mul(r0, r0, pinfo->d, ctx))
310 goto err;
311 }
312
313 {
314 BIGNUM *pr0 = BN_new();
315
316 if (pr0 == NULL)
317 goto err;
318
319 BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
320 if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
321 BN_free(pr0);
322 goto err; /* d */
323 }
324 /* We MUST free pr0 before any further use of r0 */
325 BN_free(pr0);
326 }
327
328 {
329 BIGNUM *d = BN_new();
330
331 if (d == NULL)
332 goto err;
333
334 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
335
336 /* calculate d mod (p-1) and d mod (q - 1) */
337 if (!BN_mod(rsa->dmp1, d, r1, ctx)
338 || !BN_mod(rsa->dmq1, d, r2, ctx)) {
339 BN_free(d);
340 goto err;
341 }
342
343 /* calculate CRT exponents */
344 for (i = 2; i < primes; i++) {
345 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
346 /* pinfo->d == r_i - 1 */
347 if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
348 BN_free(d);
349 goto err;
350 }
351 }
352
353 /* We MUST free d before any further use of rsa->d */
354 BN_free(d);
355 }
356
357 {
358 BIGNUM *p = BN_new();
359
360 if (p == NULL)
361 goto err;
362 BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
363
364 /* calculate inverse of q mod p */
365 if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {
366 BN_free(p);
367 goto err;
368 }
369
370 /* calculate CRT coefficient for other primes */
371 for (i = 2; i < primes; i++) {
372 pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
373 BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
374 if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
375 BN_free(p);
376 goto err;
377 }
378 }
379
380 /* We MUST free p before any further use of rsa->p */
381 BN_free(p);
382 }
383
384 ok = 1;
385 err:
386 if (ok == -1) {
387 RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, ERR_LIB_BN);
388 ok = 0;
389 }
390 BN_CTX_end(ctx);
391 BN_CTX_free(ctx);
392 return ok;
393 }
394