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/module.h>
9 #include <linux/mpi.h>
10 #include <crypto/internal/rsa.h>
11 #include <crypto/internal/akcipher.h>
12 #include <crypto/akcipher.h>
13 #include <crypto/algapi.h>
14
15 struct rsa_mpi_key {
16 MPI n;
17 MPI e;
18 MPI d;
19 };
20
21 /*
22 * RSAEP function [RFC3447 sec 5.1.1]
23 * c = m^e mod n;
24 */
_rsa_enc(const struct rsa_mpi_key * key,MPI c,MPI m)25 static int _rsa_enc(const struct rsa_mpi_key *key, MPI c, MPI m)
26 {
27 /* (1) Validate 0 <= m < n */
28 if (mpi_cmp_ui(m, 0) < 0 || mpi_cmp(m, key->n) >= 0)
29 return -EINVAL;
30
31 /* (2) c = m^e mod n */
32 return mpi_powm(c, m, key->e, key->n);
33 }
34
35 /*
36 * RSADP function [RFC3447 sec 5.1.2]
37 * m = c^d mod n;
38 */
_rsa_dec(const struct rsa_mpi_key * key,MPI m,MPI c)39 static int _rsa_dec(const struct rsa_mpi_key *key, MPI m, MPI c)
40 {
41 /* (1) Validate 0 <= c < n */
42 if (mpi_cmp_ui(c, 0) < 0 || mpi_cmp(c, key->n) >= 0)
43 return -EINVAL;
44
45 /* (2) m = c^d mod n */
46 return mpi_powm(m, c, key->d, key->n);
47 }
48
rsa_get_key(struct crypto_akcipher * tfm)49 static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
50 {
51 return akcipher_tfm_ctx(tfm);
52 }
53
rsa_enc(struct akcipher_request * req)54 static int rsa_enc(struct akcipher_request *req)
55 {
56 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
57 const struct rsa_mpi_key *pkey = rsa_get_key(tfm);
58 MPI m, c = mpi_alloc(0);
59 int ret = 0;
60 int sign;
61
62 if (!c)
63 return -ENOMEM;
64
65 if (unlikely(!pkey->n || !pkey->e)) {
66 ret = -EINVAL;
67 goto err_free_c;
68 }
69
70 ret = -ENOMEM;
71 m = mpi_read_raw_from_sgl(req->src, req->src_len);
72 if (!m)
73 goto err_free_c;
74
75 ret = _rsa_enc(pkey, c, m);
76 if (ret)
77 goto err_free_m;
78
79 ret = mpi_write_to_sgl(c, req->dst, req->dst_len, &sign);
80 if (ret)
81 goto err_free_m;
82
83 if (sign < 0)
84 ret = -EBADMSG;
85
86 err_free_m:
87 mpi_free(m);
88 err_free_c:
89 mpi_free(c);
90 return ret;
91 }
92
rsa_dec(struct akcipher_request * req)93 static int rsa_dec(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 c, m = mpi_alloc(0);
98 int ret = 0;
99 int sign;
100
101 if (!m)
102 return -ENOMEM;
103
104 if (unlikely(!pkey->n || !pkey->d)) {
105 ret = -EINVAL;
106 goto err_free_m;
107 }
108
109 ret = -ENOMEM;
110 c = mpi_read_raw_from_sgl(req->src, req->src_len);
111 if (!c)
112 goto err_free_m;
113
114 ret = _rsa_dec(pkey, m, c);
115 if (ret)
116 goto err_free_c;
117
118 ret = mpi_write_to_sgl(m, req->dst, req->dst_len, &sign);
119 if (ret)
120 goto err_free_c;
121
122 if (sign < 0)
123 ret = -EBADMSG;
124 err_free_c:
125 mpi_free(c);
126 err_free_m:
127 mpi_free(m);
128 return ret;
129 }
130
rsa_free_mpi_key(struct rsa_mpi_key * key)131 static void rsa_free_mpi_key(struct rsa_mpi_key *key)
132 {
133 mpi_free(key->d);
134 mpi_free(key->e);
135 mpi_free(key->n);
136 key->d = NULL;
137 key->e = NULL;
138 key->n = NULL;
139 }
140
rsa_check_key_length(unsigned int len)141 static int rsa_check_key_length(unsigned int len)
142 {
143 switch (len) {
144 case 512:
145 case 1024:
146 case 1536:
147 case 2048:
148 case 3072:
149 case 4096:
150 return 0;
151 }
152
153 return -EINVAL;
154 }
155
rsa_set_pub_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)156 static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
157 unsigned int keylen)
158 {
159 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
160 struct rsa_key raw_key = {0};
161 int ret;
162
163 /* Free the old MPI key if any */
164 rsa_free_mpi_key(mpi_key);
165
166 ret = rsa_parse_pub_key(&raw_key, key, keylen);
167 if (ret)
168 return ret;
169
170 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
171 if (!mpi_key->e)
172 goto err;
173
174 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
175 if (!mpi_key->n)
176 goto err;
177
178 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
179 rsa_free_mpi_key(mpi_key);
180 return -EINVAL;
181 }
182
183 return 0;
184
185 err:
186 rsa_free_mpi_key(mpi_key);
187 return -ENOMEM;
188 }
189
rsa_set_priv_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)190 static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
191 unsigned int keylen)
192 {
193 struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
194 struct rsa_key raw_key = {0};
195 int ret;
196
197 /* Free the old MPI key if any */
198 rsa_free_mpi_key(mpi_key);
199
200 ret = rsa_parse_priv_key(&raw_key, key, keylen);
201 if (ret)
202 return ret;
203
204 mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
205 if (!mpi_key->d)
206 goto err;
207
208 mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
209 if (!mpi_key->e)
210 goto err;
211
212 mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
213 if (!mpi_key->n)
214 goto err;
215
216 if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
217 rsa_free_mpi_key(mpi_key);
218 return -EINVAL;
219 }
220
221 return 0;
222
223 err:
224 rsa_free_mpi_key(mpi_key);
225 return -ENOMEM;
226 }
227
rsa_max_size(struct crypto_akcipher * tfm)228 static unsigned int rsa_max_size(struct crypto_akcipher *tfm)
229 {
230 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
231
232 return mpi_get_size(pkey->n);
233 }
234
rsa_exit_tfm(struct crypto_akcipher * tfm)235 static void rsa_exit_tfm(struct crypto_akcipher *tfm)
236 {
237 struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
238
239 rsa_free_mpi_key(pkey);
240 }
241
242 static struct akcipher_alg rsa = {
243 .encrypt = rsa_enc,
244 .decrypt = rsa_dec,
245 .set_priv_key = rsa_set_priv_key,
246 .set_pub_key = rsa_set_pub_key,
247 .max_size = rsa_max_size,
248 .exit = rsa_exit_tfm,
249 .base = {
250 .cra_name = "rsa",
251 .cra_driver_name = "rsa-generic",
252 .cra_priority = 100,
253 .cra_module = THIS_MODULE,
254 .cra_ctxsize = sizeof(struct rsa_mpi_key),
255 },
256 };
257
rsa_init(void)258 static int rsa_init(void)
259 {
260 int err;
261
262 err = crypto_register_akcipher(&rsa);
263 if (err)
264 return err;
265
266 err = crypto_register_template(&rsa_pkcs1pad_tmpl);
267 if (err) {
268 crypto_unregister_akcipher(&rsa);
269 return err;
270 }
271
272 return 0;
273 }
274
rsa_exit(void)275 static void rsa_exit(void)
276 {
277 crypto_unregister_template(&rsa_pkcs1pad_tmpl);
278 crypto_unregister_akcipher(&rsa);
279 }
280
281 subsys_initcall(rsa_init);
282 module_exit(rsa_exit);
283 MODULE_ALIAS_CRYPTO("rsa");
284 MODULE_LICENSE("GPL");
285 MODULE_DESCRIPTION("RSA generic algorithm");
286