1// SPDX-License-Identifier: GPL-2.0-or-later
2/* RSA asymmetric public-key algorithm [RFC3447]
3 *
4 * Copyright (c) 2015, Intel Corporation
5 * Authors: Tadeusz Struk <tadeusz.struk@intel.com>
6 */
7
8#include <linux/fips.h>
9#include <linux/module.h>
10#include <linux/mpi.h>
11#include <crypto/internal/rsa.h>
12#include <crypto/internal/akcipher.h>
13#include <crypto/akcipher.h>
14#include <crypto/algapi.h>
15
16struct rsa_mpi_key {
17 MPI n;
18 MPI e;
19 MPI d;
20 MPI p;
21 MPI q;
22 MPI dp;
23 MPI dq;
24 MPI qinv;
25};
26
27static int rsa_check_payload(MPI x, MPI n)
28{
29 MPI n1;
30
31 if (mpi_cmp_ui(u: x, v: 1) <= 0)
32 return -EINVAL;
33
34 n1 = mpi_alloc(nlimbs: 0);
35 if (!n1)
36 return -ENOMEM;
37
38 if (mpi_sub_ui(w: n1, u: n, vval: 1) || mpi_cmp(u: x, v: n1) >= 0) {
39 mpi_free(a: n1);
40 return -EINVAL;
41 }
42
43 mpi_free(a: n1);
44 return 0;
45}
46
47/*
48 * RSAEP function [RFC3447 sec 5.1.1]
49 * c = m^e mod n;
50 */
51static int _rsa_enc(const struct rsa_mpi_key *key, MPI c, MPI m)
52{
53 /*
54 * Even though (1) in RFC3447 only requires 0 <= m <= n - 1, we are
55 * slightly more conservative and require 1 < m < n - 1. This is in line
56 * with SP 800-56Br2, Section 7.1.1.
57 */
58 if (rsa_check_payload(x: m, n: key->n))
59 return -EINVAL;
60
61 /* (2) c = m^e mod n */
62 return mpi_powm(res: c, base: m, exp: key->e, mod: key->n);
63}
64
65/*
66 * RSADP function [RFC3447 sec 5.1.2]
67 * m_1 = c^dP mod p;
68 * m_2 = c^dQ mod q;
69 * h = (m_1 - m_2) * qInv mod p;
70 * m = m_2 + q * h;
71 */
72static int _rsa_dec_crt(const struct rsa_mpi_key *key, MPI m_or_m1_or_h, MPI c)
73{
74 MPI m2, m12_or_qh;
75 int ret = -ENOMEM;
76
77 /*
78 * Even though (1) in RFC3447 only requires 0 <= c <= n - 1, we are
79 * slightly more conservative and require 1 < c < n - 1. This is in line
80 * with SP 800-56Br2, Section 7.1.2.
81 */
82 if (rsa_check_payload(x: c, n: key->n))
83 return -EINVAL;
84
85 m2 = mpi_alloc(nlimbs: 0);
86 m12_or_qh = mpi_alloc(nlimbs: 0);
87 if (!m2 || !m12_or_qh)
88 goto err_free_mpi;
89
90 /* (2i) m_1 = c^dP mod p */
91 ret = mpi_powm(res: m_or_m1_or_h, base: c, exp: key->dp, mod: key->p);
92 if (ret)
93 goto err_free_mpi;
94
95 /* (2i) m_2 = c^dQ mod q */
96 ret = mpi_powm(res: m2, base: c, exp: key->dq, mod: key->q);
97 if (ret)
98 goto err_free_mpi;
99
100 /* (2iii) h = (m_1 - m_2) * qInv mod p */
101 ret = mpi_sub(w: m12_or_qh, u: m_or_m1_or_h, v: m2) ?:
102 mpi_mulm(w: m_or_m1_or_h, u: m12_or_qh, v: key->qinv, m: key->p);
103
104 /* (2iv) m = m_2 + q * h */
105 ret = ret ?:
106 mpi_mul(w: m12_or_qh, u: key->q, v: m_or_m1_or_h) ?:
107 mpi_addm(w: m_or_m1_or_h, u: m2, v: m12_or_qh, m: key->n);
108
109err_free_mpi:
110 mpi_free(a: m12_or_qh);
111 mpi_free(a: m2);
112 return ret;
113}
114
115static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
116{
117 return akcipher_tfm_ctx(tfm);
118}
119
120static int rsa_enc(struct akcipher_request *req)
121{
122 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
123 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
124 MPI m, c = mpi_alloc(nlimbs: 0);
125 int ret = 0;
126 int sign;
127
128 if (!c)
129 return -ENOMEM;
130
131 if (unlikely(!pkey->n || !pkey->e)) {
132 ret = -EINVAL;
133 goto err_free_c;
134 }
135
136 ret = -ENOMEM;
137 m = mpi_read_raw_from_sgl(sgl: req->src, len: req->src_len);
138 if (!m)
139 goto err_free_c;
140
141 ret = _rsa_enc(key: pkey, c, m);
142 if (ret)
143 goto err_free_m;
144
145 ret = mpi_write_to_sgl(a: c, sg: req->dst, nbytes: req->dst_len, sign: &sign);
146 if (ret)
147 goto err_free_m;
148
149 if (sign < 0)
150 ret = -EBADMSG;
151
152err_free_m:
153 mpi_free(a: m);
154err_free_c:
155 mpi_free(a: c);
156 return ret;
157}
158
159static int rsa_dec(struct akcipher_request *req)
160{
161 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
162 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
163 MPI c, m = mpi_alloc(nlimbs: 0);
164 int ret = 0;
165 int sign;
166
167 if (!m)
168 return -ENOMEM;
169
170 if (unlikely(!pkey->n || !pkey->d)) {
171 ret = -EINVAL;
172 goto err_free_m;
173 }
174
175 ret = -ENOMEM;
176 c = mpi_read_raw_from_sgl(sgl: req->src, len: req->src_len);
177 if (!c)
178 goto err_free_m;
179
180 ret = _rsa_dec_crt(key: pkey, m_or_m1_or_h: m, c);
181 if (ret)
182 goto err_free_c;
183
184 ret = mpi_write_to_sgl(a: m, sg: req->dst, nbytes: req->dst_len, sign: &sign);
185 if (ret)
186 goto err_free_c;
187
188 if (sign < 0)
189 ret = -EBADMSG;
190err_free_c:
191 mpi_free(a: c);
192err_free_m:
193 mpi_free(a: m);
194 return ret;
195}
196
197static void rsa_free_mpi_key(struct rsa_mpi_key *key)
198{
199 mpi_free(a: key->d);
200 mpi_free(a: key->e);
201 mpi_free(a: key->n);
202 mpi_free(a: key->p);
203 mpi_free(a: key->q);
204 mpi_free(a: key->dp);
205 mpi_free(a: key->dq);
206 mpi_free(a: key->qinv);
207 key->d = NULL;
208 key->e = NULL;
209 key->n = NULL;
210 key->p = NULL;
211 key->q = NULL;
212 key->dp = NULL;
213 key->dq = NULL;
214 key->qinv = NULL;
215}
216
217static int rsa_check_key_length(unsigned int len)
218{
219 switch (len) {
220 case 512:
221 case 1024:
222 case 1536:
223 if (fips_enabled)
224 return -EINVAL;
225 fallthrough;
226 case 2048:
227 case 3072:
228 case 4096:
229 return 0;
230 }
231
232 return -EINVAL;
233}
234
235static int rsa_check_exponent_fips(MPI e)
236{
237 MPI e_max = NULL;
238 int err;
239
240 /* check if odd */
241 if (!mpi_test_bit(a: e, n: 0)) {
242 return -EINVAL;
243 }
244
245 /* check if 2^16 < e < 2^256. */
246 if (mpi_cmp_ui(u: e, v: 65536) <= 0) {
247 return -EINVAL;
248 }
249
250 e_max = mpi_alloc(nlimbs: 0);
251 if (!e_max)
252 return -ENOMEM;
253
254 err = mpi_set_bit(a: e_max, n: 256);
255 if (err) {
256 mpi_free(a: e_max);
257 return err;
258 }
259
260 if (mpi_cmp(u: e, v: e_max) >= 0) {
261 mpi_free(a: e_max);
262 return -EINVAL;
263 }
264
265 mpi_free(a: e_max);
266 return 0;
267}
268
269static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
270 unsigned int keylen)
271{
272 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
273 struct rsa_key raw_key = {0};
274 int ret;
275
276 /* Free the old MPI key if any */
277 rsa_free_mpi_key(key: mpi_key);
278
279 ret = rsa_parse_pub_key(rsa_key: &raw_key, key, key_len: keylen);
280 if (ret)
281 return ret;
282
283 mpi_key->e = mpi_read_raw_data(xbuffer: raw_key.e, nbytes: raw_key.e_sz);
284 if (!mpi_key->e)
285 goto err;
286
287 mpi_key->n = mpi_read_raw_data(xbuffer: raw_key.n, nbytes: raw_key.n_sz);
288 if (!mpi_key->n)
289 goto err;
290
291 if (rsa_check_key_length(len: mpi_get_size(a: mpi_key->n) << 3)) {
292 rsa_free_mpi_key(key: mpi_key);
293 return -EINVAL;
294 }
295
296 if (fips_enabled && rsa_check_exponent_fips(e: mpi_key->e)) {
297 rsa_free_mpi_key(key: mpi_key);
298 return -EINVAL;
299 }
300
301 return 0;
302
303err:
304 rsa_free_mpi_key(key: mpi_key);
305 return -ENOMEM;
306}
307
308static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
309 unsigned int keylen)
310{
311 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
312 struct rsa_key raw_key = {0};
313 int ret;
314
315 /* Free the old MPI key if any */
316 rsa_free_mpi_key(key: mpi_key);
317
318 ret = rsa_parse_priv_key(rsa_key: &raw_key, key, key_len: keylen);
319 if (ret)
320 return ret;
321
322 mpi_key->d = mpi_read_raw_data(xbuffer: raw_key.d, nbytes: raw_key.d_sz);
323 if (!mpi_key->d)
324 goto err;
325
326 mpi_key->e = mpi_read_raw_data(xbuffer: raw_key.e, nbytes: raw_key.e_sz);
327 if (!mpi_key->e)
328 goto err;
329
330 mpi_key->n = mpi_read_raw_data(xbuffer: raw_key.n, nbytes: raw_key.n_sz);
331 if (!mpi_key->n)
332 goto err;
333
334 mpi_key->p = mpi_read_raw_data(xbuffer: raw_key.p, nbytes: raw_key.p_sz);
335 if (!mpi_key->p)
336 goto err;
337
338 mpi_key->q = mpi_read_raw_data(xbuffer: raw_key.q, nbytes: raw_key.q_sz);
339 if (!mpi_key->q)
340 goto err;
341
342 mpi_key->dp = mpi_read_raw_data(xbuffer: raw_key.dp, nbytes: raw_key.dp_sz);
343 if (!mpi_key->dp)
344 goto err;
345
346 mpi_key->dq = mpi_read_raw_data(xbuffer: raw_key.dq, nbytes: raw_key.dq_sz);
347 if (!mpi_key->dq)
348 goto err;
349
350 mpi_key->qinv = mpi_read_raw_data(xbuffer: raw_key.qinv, nbytes: raw_key.qinv_sz);
351 if (!mpi_key->qinv)
352 goto err;
353
354 if (rsa_check_key_length(len: mpi_get_size(a: mpi_key->n) << 3)) {
355 rsa_free_mpi_key(key: mpi_key);
356 return -EINVAL;
357 }
358
359 if (fips_enabled && rsa_check_exponent_fips(e: mpi_key->e)) {
360 rsa_free_mpi_key(key: mpi_key);
361 return -EINVAL;
362 }
363
364 return 0;
365
366err:
367 rsa_free_mpi_key(key: mpi_key);
368 return -ENOMEM;
369}
370
371static unsigned int rsa_max_size(struct crypto_akcipher *tfm)
372{
373 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
374
375 return mpi_get_size(a: pkey->n);
376}
377
378static void rsa_exit_tfm(struct crypto_akcipher *tfm)
379{
380 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
381
382 rsa_free_mpi_key(key: pkey);
383}
384
385static struct akcipher_alg rsa = {
386 .encrypt = rsa_enc,
387 .decrypt = rsa_dec,
388 .set_priv_key = rsa_set_priv_key,
389 .set_pub_key = rsa_set_pub_key,
390 .max_size = rsa_max_size,
391 .exit = rsa_exit_tfm,
392 .base = {
393 .cra_name = "rsa",
394 .cra_driver_name = "rsa-generic",
395 .cra_priority = 100,
396 .cra_module = THIS_MODULE,
397 .cra_ctxsize = sizeof(struct rsa_mpi_key),
398 },
399};
400
401static int __init rsa_init(void)
402{
403 int err;
404
405 err = crypto_register_akcipher(alg: &rsa);
406 if (err)
407 return err;
408
409 err = crypto_register_template(tmpl: &rsa_pkcs1pad_tmpl);
410 if (err)
411 goto err_unregister_rsa;
412
413 err = crypto_register_template(tmpl: &rsassa_pkcs1_tmpl);
414 if (err)
415 goto err_unregister_rsa_pkcs1pad;
416
417 return 0;
418
419err_unregister_rsa_pkcs1pad:
420 crypto_unregister_template(tmpl: &rsa_pkcs1pad_tmpl);
421err_unregister_rsa:
422 crypto_unregister_akcipher(alg: &rsa);
423 return err;
424}
425
426static void __exit rsa_exit(void)
427{
428 crypto_unregister_template(tmpl: &rsassa_pkcs1_tmpl);
429 crypto_unregister_template(tmpl: &rsa_pkcs1pad_tmpl);
430 crypto_unregister_akcipher(alg: &rsa);
431}
432
433module_init(rsa_init);
434module_exit(rsa_exit);
435MODULE_ALIAS_CRYPTO("rsa");
436MODULE_LICENSE("GPL");
437MODULE_DESCRIPTION("RSA generic algorithm");
438

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source code of linux/crypto/rsa.c