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
27/*
28 * RSAEP function [RFC3447 sec 5.1.1]
29 * c = m^e mod n;
30 */
31static 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(u: m, v: 0) < 0 || mpi_cmp(u: m, v: key->n) >= 0)
35 return -EINVAL;
36
37 /* (2) c = m^e mod n */
38 return mpi_powm(res: c, base: m, exp: key->e, mod: 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 */
48static 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(u: c, v: 0) < 0 || mpi_cmp(u: c, v: key->n) >= 0)
55 return -EINVAL;
56
57 m2 = mpi_alloc(nlimbs: 0);
58 m12_or_qh = mpi_alloc(nlimbs: 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(res: m_or_m1_or_h, base: c, exp: key->dp, mod: key->p);
64 if (ret)
65 goto err_free_mpi;
66
67 /* (2i) m_2 = c^dQ mod q */
68 ret = mpi_powm(res: m2, base: c, exp: key->dq, mod: key->q);
69 if (ret)
70 goto err_free_mpi;
71
72 /* (2iii) h = (m_1 - m_2) * qInv mod p */
73 mpi_sub(w: m12_or_qh, u: m_or_m1_or_h, v: m2);
74 mpi_mulm(w: m_or_m1_or_h, u: m12_or_qh, v: key->qinv, m: key->p);
75
76 /* (2iv) m = m_2 + q * h */
77 mpi_mul(w: m12_or_qh, u: key->q, v: m_or_m1_or_h);
78 mpi_addm(w: m_or_m1_or_h, u: m2, v: m12_or_qh, m: key->n);
79
80 ret = 0;
81
82err_free_mpi:
83 mpi_free(a: m12_or_qh);
84 mpi_free(a: m2);
85 return ret;
86}
87
88static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
89{
90 return akcipher_tfm_ctx(tfm);
91}
92
93static 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(nlimbs: 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(sgl: req->src, len: req->src_len);
111 if (!m)
112 goto err_free_c;
113
114 ret = _rsa_enc(key: pkey, c, m);
115 if (ret)
116 goto err_free_m;
117
118 ret = mpi_write_to_sgl(a: c, sg: req->dst, nbytes: req->dst_len, sign: &sign);
119 if (ret)
120 goto err_free_m;
121
122 if (sign < 0)
123 ret = -EBADMSG;
124
125err_free_m:
126 mpi_free(a: m);
127err_free_c:
128 mpi_free(a: c);
129 return ret;
130}
131
132static 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(nlimbs: 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(sgl: req->src, len: req->src_len);
150 if (!c)
151 goto err_free_m;
152
153 ret = _rsa_dec_crt(key: pkey, m_or_m1_or_h: m, c);
154 if (ret)
155 goto err_free_c;
156
157 ret = mpi_write_to_sgl(a: m, sg: req->dst, nbytes: req->dst_len, sign: &sign);
158 if (ret)
159 goto err_free_c;
160
161 if (sign < 0)
162 ret = -EBADMSG;
163err_free_c:
164 mpi_free(a: c);
165err_free_m:
166 mpi_free(a: m);
167 return ret;
168}
169
170static void rsa_free_mpi_key(struct rsa_mpi_key *key)
171{
172 mpi_free(a: key->d);
173 mpi_free(a: key->e);
174 mpi_free(a: key->n);
175 mpi_free(a: key->p);
176 mpi_free(a: key->q);
177 mpi_free(a: key->dp);
178 mpi_free(a: key->dq);
179 mpi_free(a: 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
190static 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
208static int rsa_check_exponent_fips(MPI e)
209{
210 MPI e_max = NULL;
211
212 /* check if odd */
213 if (!mpi_test_bit(a: e, n: 0)) {
214 return -EINVAL;
215 }
216
217 /* check if 2^16 < e < 2^256. */
218 if (mpi_cmp_ui(u: e, v: 65536) <= 0) {
219 return -EINVAL;
220 }
221
222 e_max = mpi_alloc(nlimbs: 0);
223 mpi_set_bit(a: e_max, n: 256);
224
225 if (mpi_cmp(u: e, v: e_max) >= 0) {
226 mpi_free(a: e_max);
227 return -EINVAL;
228 }
229
230 mpi_free(a: e_max);
231 return 0;
232}
233
234static 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(key: mpi_key);
243
244 ret = rsa_parse_pub_key(rsa_key: &raw_key, key, key_len: keylen);
245 if (ret)
246 return ret;
247
248 mpi_key->e = mpi_read_raw_data(xbuffer: raw_key.e, nbytes: raw_key.e_sz);
249 if (!mpi_key->e)
250 goto err;
251
252 mpi_key->n = mpi_read_raw_data(xbuffer: raw_key.n, nbytes: raw_key.n_sz);
253 if (!mpi_key->n)
254 goto err;
255
256 if (rsa_check_key_length(len: mpi_get_size(a: mpi_key->n) << 3)) {
257 rsa_free_mpi_key(key: mpi_key);
258 return -EINVAL;
259 }
260
261 if (fips_enabled && rsa_check_exponent_fips(e: mpi_key->e)) {
262 rsa_free_mpi_key(key: mpi_key);
263 return -EINVAL;
264 }
265
266 return 0;
267
268err:
269 rsa_free_mpi_key(key: mpi_key);
270 return -ENOMEM;
271}
272
273static 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(key: mpi_key);
282
283 ret = rsa_parse_priv_key(rsa_key: &raw_key, key, key_len: keylen);
284 if (ret)
285 return ret;
286
287 mpi_key->d = mpi_read_raw_data(xbuffer: raw_key.d, nbytes: raw_key.d_sz);
288 if (!mpi_key->d)
289 goto err;
290
291 mpi_key->e = mpi_read_raw_data(xbuffer: raw_key.e, nbytes: raw_key.e_sz);
292 if (!mpi_key->e)
293 goto err;
294
295 mpi_key->n = mpi_read_raw_data(xbuffer: raw_key.n, nbytes: raw_key.n_sz);
296 if (!mpi_key->n)
297 goto err;
298
299 mpi_key->p = mpi_read_raw_data(xbuffer: raw_key.p, nbytes: raw_key.p_sz);
300 if (!mpi_key->p)
301 goto err;
302
303 mpi_key->q = mpi_read_raw_data(xbuffer: raw_key.q, nbytes: raw_key.q_sz);
304 if (!mpi_key->q)
305 goto err;
306
307 mpi_key->dp = mpi_read_raw_data(xbuffer: raw_key.dp, nbytes: raw_key.dp_sz);
308 if (!mpi_key->dp)
309 goto err;
310
311 mpi_key->dq = mpi_read_raw_data(xbuffer: raw_key.dq, nbytes: raw_key.dq_sz);
312 if (!mpi_key->dq)
313 goto err;
314
315 mpi_key->qinv = mpi_read_raw_data(xbuffer: raw_key.qinv, nbytes: raw_key.qinv_sz);
316 if (!mpi_key->qinv)
317 goto err;
318
319 if (rsa_check_key_length(len: mpi_get_size(a: mpi_key->n) << 3)) {
320 rsa_free_mpi_key(key: mpi_key);
321 return -EINVAL;
322 }
323
324 if (fips_enabled && rsa_check_exponent_fips(e: mpi_key->e)) {
325 rsa_free_mpi_key(key: mpi_key);
326 return -EINVAL;
327 }
328
329 return 0;
330
331err:
332 rsa_free_mpi_key(key: mpi_key);
333 return -ENOMEM;
334}
335
336static 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(a: pkey->n);
341}
342
343static 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(key: pkey);
348}
349
350static 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
366static int __init rsa_init(void)
367{
368 int err;
369
370 err = crypto_register_akcipher(alg: &rsa);
371 if (err)
372 return err;
373
374 err = crypto_register_template(tmpl: &rsa_pkcs1pad_tmpl);
375 if (err) {
376 crypto_unregister_akcipher(alg: &rsa);
377 return err;
378 }
379
380 return 0;
381}
382
383static void __exit rsa_exit(void)
384{
385 crypto_unregister_template(tmpl: &rsa_pkcs1pad_tmpl);
386 crypto_unregister_akcipher(alg: &rsa);
387}
388
389subsys_initcall(rsa_init);
390module_exit(rsa_exit);
391MODULE_ALIAS_CRYPTO("rsa");
392MODULE_LICENSE("GPL");
393MODULE_DESCRIPTION("RSA generic algorithm");
394

source code of linux/crypto/rsa.c