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 /*
28 * RSAEP function [RFC3447 sec 5.1.1]
29 * c = m^e mod n;
30 */
_rsa_enc(const struct rsa_mpi_key * key,MPI c,MPI m)31 static int _rsa_enc(const struct rsa_mpi_key *key, MPI c, MPI m)
32 {
33 /* (1) Validate 0 <= m < n */
34 if (mpi_cmp_ui(m, 0) < 0 || mpi_cmp(m, key->n) >= 0)
35 return -EINVAL;
36
37 /* (2) c = m^e mod n */
38 return mpi_powm(c, m, key->e, key->n);
39 }
40
41 /*
42 * RSADP function [RFC3447 sec 5.1.2]
43 * m_1 = c^dP mod p;
44 * m_2 = c^dQ mod q;
45 * h = (m_1 - m_2) * qInv mod p;
46 * m = m_2 + q * h;
47 */
_rsa_dec_crt(const struct rsa_mpi_key * key,MPI m_or_m1_or_h,MPI c)48 static int _rsa_dec_crt(const struct rsa_mpi_key *key, MPI m_or_m1_or_h, MPI c)
49 {
50 MPI m2, m12_or_qh;
51 int ret = -ENOMEM;
52
53 /* (1) Validate 0 <= c < n */
54 if (mpi_cmp_ui(c, 0) < 0 || mpi_cmp(c, key->n) >= 0)
55 return -EINVAL;
56
57 m2 = mpi_alloc(0);
58 m12_or_qh = mpi_alloc(0);
59 if (!m2 || !m12_or_qh)
60 goto err_free_mpi;
61
62 /* (2i) m_1 = c^dP mod p */
63 ret = mpi_powm(m_or_m1_or_h, c, key->dp, key->p);
64 if (ret)
65 goto err_free_mpi;
66
67 /* (2i) m_2 = c^dQ mod q */
68 ret = mpi_powm(m2, c, key->dq, key->q);
69 if (ret)
70 goto err_free_mpi;
71
72 /* (2iii) h = (m_1 - m_2) * qInv mod p */
73 mpi_sub(m12_or_qh, m_or_m1_or_h, m2);
74 mpi_mulm(m_or_m1_or_h, m12_or_qh, key->qinv, key->p);
75
76 /* (2iv) m = m_2 + q * h */
77 mpi_mul(m12_or_qh, key->q, m_or_m1_or_h);
78 mpi_addm(m_or_m1_or_h, m2, m12_or_qh, key->n);
79
80 ret = 0;
81
82 err_free_mpi:
83 mpi_free(m12_or_qh);
84 mpi_free(m2);
85 return ret;
86 }
87
rsa_get_key(struct crypto_akcipher * tfm)88 static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
89 {
90 return akcipher_tfm_ctx(tfm);
91 }
92
rsa_enc(struct akcipher_request * req)93 static int rsa_enc(struct akcipher_request *req)
94 {
95 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
96 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
97 MPI m, c = mpi_alloc(0);
98 int ret = 0;
99 int sign;
100
101 if (!c)
102 return -ENOMEM;
103
104 if (unlikely(!pkey->n || !pkey->e)) {
105 ret = -EINVAL;
106 goto err_free_c;
107 }
108
109 ret = -ENOMEM;
110 m = mpi_read_raw_from_sgl(req->src, req->src_len);
111 if (!m)
112 goto err_free_c;
113
114 ret = _rsa_enc(pkey, c, m);
115 if (ret)
116 goto err_free_m;
117
118 ret = mpi_write_to_sgl(c, req->dst, req->dst_len, &sign);
119 if (ret)
120 goto err_free_m;
121
122 if (sign < 0)
123 ret = -EBADMSG;
124
125 err_free_m:
126 mpi_free(m);
127 err_free_c:
128 mpi_free(c);
129 return ret;
130 }
131
rsa_dec(struct akcipher_request * req)132 static int rsa_dec(struct akcipher_request *req)
133 {
134 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
135 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
136 MPI c, m = mpi_alloc(0);
137 int ret = 0;
138 int sign;
139
140 if (!m)
141 return -ENOMEM;
142
143 if (unlikely(!pkey->n || !pkey->d)) {
144 ret = -EINVAL;
145 goto err_free_m;
146 }
147
148 ret = -ENOMEM;
149 c = mpi_read_raw_from_sgl(req->src, req->src_len);
150 if (!c)
151 goto err_free_m;
152
153 ret = _rsa_dec_crt(pkey, m, c);
154 if (ret)
155 goto err_free_c;
156
157 ret = mpi_write_to_sgl(m, req->dst, req->dst_len, &sign);
158 if (ret)
159 goto err_free_c;
160
161 if (sign < 0)
162 ret = -EBADMSG;
163 err_free_c:
164 mpi_free(c);
165 err_free_m:
166 mpi_free(m);
167 return ret;
168 }
169
rsa_free_mpi_key(struct rsa_mpi_key * key)170 static void rsa_free_mpi_key(struct rsa_mpi_key *key)
171 {
172 mpi_free(key->d);
173 mpi_free(key->e);
174 mpi_free(key->n);
175 mpi_free(key->p);
176 mpi_free(key->q);
177 mpi_free(key->dp);
178 mpi_free(key->dq);
179 mpi_free(key->qinv);
180 key->d = NULL;
181 key->e = NULL;
182 key->n = NULL;
183 key->p = NULL;
184 key->q = NULL;
185 key->dp = NULL;
186 key->dq = NULL;
187 key->qinv = NULL;
188 }
189
rsa_check_key_length(unsigned int len)190 static int rsa_check_key_length(unsigned int len)
191 {
192 switch (len) {
193 case 512:
194 case 1024:
195 case 1536:
196 if (fips_enabled)
197 return -EINVAL;
198 fallthrough;
199 case 2048:
200 case 3072:
201 case 4096:
202 return 0;
203 }
204
205 return -EINVAL;
206 }
207
rsa_check_exponent_fips(MPI e)208 static int rsa_check_exponent_fips(MPI e)
209 {
210 MPI e_max = NULL;
211
212 /* check if odd */
213 if (!mpi_test_bit(e, 0)) {
214 return -EINVAL;
215 }
216
217 /* check if 2^16 < e < 2^256. */
218 if (mpi_cmp_ui(e, 65536) <= 0) {
219 return -EINVAL;
220 }
221
222 e_max = mpi_alloc(0);
223 mpi_set_bit(e_max, 256);
224
225 if (mpi_cmp(e, e_max) >= 0) {
226 mpi_free(e_max);
227 return -EINVAL;
228 }
229
230 mpi_free(e_max);
231 return 0;
232 }
233
rsa_set_pub_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)234 static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
235 unsigned int keylen)
236 {
237 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
238 struct rsa_key raw_key = {0};
239 int ret;
240
241 /* Free the old MPI key if any */
242 rsa_free_mpi_key(mpi_key);
243
244 ret = rsa_parse_pub_key(&raw_key, key, keylen);
245 if (ret)
246 return ret;
247
248 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
249 if (!mpi_key->e)
250 goto err;
251
252 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
253 if (!mpi_key->n)
254 goto err;
255
256 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
257 rsa_free_mpi_key(mpi_key);
258 return -EINVAL;
259 }
260
261 if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
262 rsa_free_mpi_key(mpi_key);
263 return -EINVAL;
264 }
265
266 return 0;
267
268 err:
269 rsa_free_mpi_key(mpi_key);
270 return -ENOMEM;
271 }
272
rsa_set_priv_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)273 static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
274 unsigned int keylen)
275 {
276 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
277 struct rsa_key raw_key = {0};
278 int ret;
279
280 /* Free the old MPI key if any */
281 rsa_free_mpi_key(mpi_key);
282
283 ret = rsa_parse_priv_key(&raw_key, key, keylen);
284 if (ret)
285 return ret;
286
287 mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
288 if (!mpi_key->d)
289 goto err;
290
291 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
292 if (!mpi_key->e)
293 goto err;
294
295 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
296 if (!mpi_key->n)
297 goto err;
298
299 mpi_key->p = mpi_read_raw_data(raw_key.p, raw_key.p_sz);
300 if (!mpi_key->p)
301 goto err;
302
303 mpi_key->q = mpi_read_raw_data(raw_key.q, raw_key.q_sz);
304 if (!mpi_key->q)
305 goto err;
306
307 mpi_key->dp = mpi_read_raw_data(raw_key.dp, raw_key.dp_sz);
308 if (!mpi_key->dp)
309 goto err;
310
311 mpi_key->dq = mpi_read_raw_data(raw_key.dq, raw_key.dq_sz);
312 if (!mpi_key->dq)
313 goto err;
314
315 mpi_key->qinv = mpi_read_raw_data(raw_key.qinv, raw_key.qinv_sz);
316 if (!mpi_key->qinv)
317 goto err;
318
319 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
320 rsa_free_mpi_key(mpi_key);
321 return -EINVAL;
322 }
323
324 if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {
325 rsa_free_mpi_key(mpi_key);
326 return -EINVAL;
327 }
328
329 return 0;
330
331 err:
332 rsa_free_mpi_key(mpi_key);
333 return -ENOMEM;
334 }
335
rsa_max_size(struct crypto_akcipher * tfm)336 static unsigned int rsa_max_size(struct crypto_akcipher *tfm)
337 {
338 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
339
340 return mpi_get_size(pkey->n);
341 }
342
rsa_exit_tfm(struct crypto_akcipher * tfm)343 static void rsa_exit_tfm(struct crypto_akcipher *tfm)
344 {
345 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
346
347 rsa_free_mpi_key(pkey);
348 }
349
350 static struct akcipher_alg rsa = {
351 .encrypt = rsa_enc,
352 .decrypt = rsa_dec,
353 .set_priv_key = rsa_set_priv_key,
354 .set_pub_key = rsa_set_pub_key,
355 .max_size = rsa_max_size,
356 .exit = rsa_exit_tfm,
357 .base = {
358 .cra_name = "rsa",
359 .cra_driver_name = "rsa-generic",
360 .cra_priority = 100,
361 .cra_module = THIS_MODULE,
362 .cra_ctxsize = sizeof(struct rsa_mpi_key),
363 },
364 };
365
rsa_init(void)366 static int __init rsa_init(void)
367 {
368 int err;
369
370 err = crypto_register_akcipher(&rsa);
371 if (err)
372 return err;
373
374 err = crypto_register_template(&rsa_pkcs1pad_tmpl);
375 if (err) {
376 crypto_unregister_akcipher(&rsa);
377 return err;
378 }
379
380 return 0;
381 }
382
rsa_exit(void)383 static void __exit rsa_exit(void)
384 {
385 crypto_unregister_template(&rsa_pkcs1pad_tmpl);
386 crypto_unregister_akcipher(&rsa);
387 }
388
389 subsys_initcall(rsa_init);
390 module_exit(rsa_exit);
391 MODULE_ALIAS_CRYPTO("rsa");
392 MODULE_LICENSE("GPL");
393 MODULE_DESCRIPTION("RSA generic algorithm");
394
