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
16 struct 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
27 static int rsa_check_payload(MPI x, MPI n)
28 {
29 MPI n1;
30
31 if (mpi_cmp_ui(x, 1) <= 0)
32 return -EINVAL;
33
34 n1 = mpi_alloc(0);
35 if (!n1)
36 return -ENOMEM;
37
38 if (mpi_sub_ui(n1, n, 1) || mpi_cmp(x, n1) >= 0) {
39 mpi_free(n1);
40 return -EINVAL;
41 }
42
43 mpi_free(n1);
44 return 0;
45 }
46
47 /*
48 * RSAEP function [RFC3447 sec 5.1.1]
49 * c = m^e mod n;
50 */
51 static 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(m, key->n))
59 return -EINVAL;
60
61 /* (2) c = m^e mod n */
62 return mpi_powm(c, m, key->e, 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 */
72 static 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(c, key->n))
83 return -EINVAL;
84
85 m2 = mpi_alloc(0);
86 m12_or_qh = mpi_alloc(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(m_or_m1_or_h, c, key->dp, key->p);
92 if (ret)
93 goto err_free_mpi;
94
95 /* (2i) m_2 = c^dQ mod q */
96 ret = mpi_powm(m2, c, key->dq, key->q);
97 if (ret)
98 goto err_free_mpi;
99
100 /* (2iii) h = (m_1 - m_2) * qInv mod p */
101 mpi_sub(m12_or_qh, m_or_m1_or_h, m2);
102 mpi_mulm(m_or_m1_or_h, m12_or_qh, key->qinv, key->p);
103
104 /* (2iv) m = m_2 + q * h */
105 mpi_mul(m12_or_qh, key->q, m_or_m1_or_h);
106 mpi_addm(m_or_m1_or_h, m2, m12_or_qh, key->n);
107
108 ret = 0;
109
110 err_free_mpi:
111 mpi_free(m12_or_qh);
112 mpi_free(m2);
113 return ret;
114 }
115
116 static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
117 {
118 return akcipher_tfm_ctx(tfm);
119 }
120
121 static int rsa_enc(struct akcipher_request *req)
122 {
123 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
124 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
125 MPI m, c = mpi_alloc(0);
126 int ret = 0;
127 int sign;
128
129 if (!c)
130 return -ENOMEM;
131
132 if (unlikely(!pkey->n || !pkey->e)) {
133 ret = -EINVAL;
134 goto err_free_c;
135 }
136
137 ret = -ENOMEM;
138 m = mpi_read_raw_from_sgl(req->src, req->src_len);
139 if (!m)
140 goto err_free_c;
141
142 ret = _rsa_enc(pkey, c, m);
143 if (ret)
144 goto err_free_m;
145
146 ret = mpi_write_to_sgl(c, req->dst, req->dst_len, &sign);
147 if (ret)
148 goto err_free_m;
149
150 if (sign < 0)
151 ret = -EBADMSG;
152
153 err_free_m:
154 mpi_free(m);
155 err_free_c:
156 mpi_free(c);
157 return ret;
158 }
159
160 static int rsa_dec(struct akcipher_request *req)
161 {
162 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
163 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
164 MPI c, m = mpi_alloc(0);
165 int ret = 0;
166 int sign;
167
168 if (!m)
169 return -ENOMEM;
170
171 if (unlikely(!pkey->n || !pkey->d)) {
172 ret = -EINVAL;
173 goto err_free_m;
174 }
175
176 ret = -ENOMEM;
177 c = mpi_read_raw_from_sgl(req->src, req->src_len);
178 if (!c)
179 goto err_free_m;
180
181 ret = _rsa_dec_crt(pkey, m, c);
182 if (ret)
183 goto err_free_c;
184
185 ret = mpi_write_to_sgl(m, req->dst, req->dst_len, &sign);
186 if (ret)
187 goto err_free_c;
188
189 if (sign < 0)
190 ret = -EBADMSG;
191 err_free_c:
192 mpi_free(c);
193 err_free_m:
194 mpi_free(m);
195 return ret;
196 }
197
198 static void rsa_free_mpi_key(struct rsa_mpi_key *key)
199 {
200 mpi_free(key->d);
201 mpi_free(key->e);
202 mpi_free(key->n);
203 mpi_free(key->p);
204 mpi_free(key->q);
205 mpi_free(key->dp);
206 mpi_free(key->dq);
207 mpi_free(key->qinv);
208 key->d = NULL;
209 key->e = NULL;
210 key->n = NULL;
211 key->p = NULL;
212 key->q = NULL;
213 key->dp = NULL;
214 key->dq = NULL;
215 key->qinv = NULL;
216 }
217
218 static int rsa_check_key_length(unsigned int len)
219 {
220 switch (len) {
221 case 512:
222 case 1024:
223 case 1536:
224 if (fips_enabled)
225 return -EINVAL;
226 fallthrough;
227 case 2048:
228 case 3072:
229 case 4096:
230 return 0;
231 }
232
233 return -EINVAL;
234 }
235
236 static int rsa_check_exponent_fips(MPI e)
237 {
238 MPI e_max = NULL;
239
240 /* check if odd */
241 if (!mpi_test_bit(e, 0)) {
242 return -EINVAL;
243 }
244
245 /* check if 2^16 < e < 2^256. */
246 if (mpi_cmp_ui(e, 65536) <= 0) {
247 return -EINVAL;
248 }
249
250 e_max = mpi_alloc(0);
251 if (!e_max)
252 return -ENOMEM;
253 mpi_set_bit(e_max, 256);
254
255 if (mpi_cmp(e, e_max) >= 0) {
256 mpi_free(e_max);
257 return -EINVAL;
258 }
259
260 mpi_free(e_max);
261 return 0;
262 }
263
264 static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
265 unsigned int keylen)
266 {
267 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
268 struct rsa_key raw_key = {0};
269 int ret;
270
271 /* Free the old MPI key if any */
272 rsa_free_mpi_key(mpi_key);
273
274 ret = rsa_parse_pub_key(&raw_key, key, keylen);
275 if (ret)
276 return ret;
277
278 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
279 if (!mpi_key->e)
280 goto err;
281
282 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
283 if (!mpi_key->n)
284 goto err;
285
286 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
287 rsa_free_mpi_key(mpi_key);
288 return -EINVAL;
289 }
290
291 if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
292 rsa_free_mpi_key(mpi_key);
293 return -EINVAL;
294 }
295
296 return 0;
297
298 err:
299 rsa_free_mpi_key(mpi_key);
300 return -ENOMEM;
301 }
302
303 static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
304 unsigned int keylen)
305 {
306 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
307 struct rsa_key raw_key = {0};
308 int ret;
309
310 /* Free the old MPI key if any */
311 rsa_free_mpi_key(mpi_key);
312
313 ret = rsa_parse_priv_key(&raw_key, key, keylen);
314 if (ret)
315 return ret;
316
317 mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
318 if (!mpi_key->d)
319 goto err;
320
321 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
322 if (!mpi_key->e)
323 goto err;
324
325 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
326 if (!mpi_key->n)
327 goto err;
328
329 mpi_key->p = mpi_read_raw_data(raw_key.p, raw_key.p_sz);
330 if (!mpi_key->p)
331 goto err;
332
333 mpi_key->q = mpi_read_raw_data(raw_key.q, raw_key.q_sz);
334 if (!mpi_key->q)
335 goto err;
336
337 mpi_key->dp = mpi_read_raw_data(raw_key.dp, raw_key.dp_sz);
338 if (!mpi_key->dp)
339 goto err;
340
341 mpi_key->dq = mpi_read_raw_data(raw_key.dq, raw_key.dq_sz);
342 if (!mpi_key->dq)
343 goto err;
344
345 mpi_key->qinv = mpi_read_raw_data(raw_key.qinv, raw_key.qinv_sz);
346 if (!mpi_key->qinv)
347 goto err;
348
349 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
350 rsa_free_mpi_key(mpi_key);
351 return -EINVAL;
352 }
353
354 if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
355 rsa_free_mpi_key(mpi_key);
356 return -EINVAL;
357 }
358
359 return 0;
360
361 err:
362 rsa_free_mpi_key(mpi_key);
363 return -ENOMEM;
364 }
365
366 static unsigned int rsa_max_size(struct crypto_akcipher *tfm)
367 {
368 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
369
370 return mpi_get_size(pkey->n);
371 }
372
373 static void rsa_exit_tfm(struct crypto_akcipher *tfm)
374 {
375 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
376
377 rsa_free_mpi_key(pkey);
378 }
379
380 static struct akcipher_alg rsa = {
381 .encrypt = rsa_enc,
382 .decrypt = rsa_dec,
383 .set_priv_key = rsa_set_priv_key,
384 .set_pub_key = rsa_set_pub_key,
385 .max_size = rsa_max_size,
386 .exit = rsa_exit_tfm,
387 .base = {
388 .cra_name = "rsa",
389 .cra_driver_name = "rsa-generic",
390 .cra_priority = 100,
391 .cra_module = THIS_MODULE,
392 .cra_ctxsize = sizeof(struct rsa_mpi_key),
393 },
394 };
395
396 static int __init rsa_init(void)
397 {
398 int err;
399
400 err = crypto_register_akcipher(&rsa);
401 if (err)
402 return err;
403
404 err = crypto_register_template(&rsa_pkcs1pad_tmpl);
405 if (err) {
406 crypto_unregister_akcipher(&rsa);
407 return err;
408 }
409
410 return 0;
411 }
412
413 static void __exit rsa_exit(void)
414 {
415 crypto_unregister_template(&rsa_pkcs1pad_tmpl);
416 crypto_unregister_akcipher(&rsa);
417 }
418
419 subsys_initcall(rsa_init);
420 module_exit(rsa_exit);
421 MODULE_ALIAS_CRYPTO("rsa");
422 MODULE_LICENSE("GPL");
423 MODULE_DESCRIPTION("RSA generic algorithm");
424
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