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_set_pub_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)208 static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
209 			   unsigned int keylen)
210 {
211 	struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
212 	struct rsa_key raw_key = {0};
213 	int ret;
214 
215 	/* Free the old MPI key if any */
216 	rsa_free_mpi_key(mpi_key);
217 
218 	ret = rsa_parse_pub_key(&raw_key, key, keylen);
219 	if (ret)
220 		return ret;
221 
222 	mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
223 	if (!mpi_key->e)
224 		goto err;
225 
226 	mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
227 	if (!mpi_key->n)
228 		goto err;
229 
230 	if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
231 		rsa_free_mpi_key(mpi_key);
232 		return -EINVAL;
233 	}
234 
235 	return 0;
236 
237 err:
238 	rsa_free_mpi_key(mpi_key);
239 	return -ENOMEM;
240 }
241 
rsa_set_priv_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)242 static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
243 			    unsigned int keylen)
244 {
245 	struct rsa_mpi_key *mpi_key = akcipher_tfm_ctx(tfm);
246 	struct rsa_key raw_key = {0};
247 	int ret;
248 
249 	/* Free the old MPI key if any */
250 	rsa_free_mpi_key(mpi_key);
251 
252 	ret = rsa_parse_priv_key(&raw_key, key, keylen);
253 	if (ret)
254 		return ret;
255 
256 	mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
257 	if (!mpi_key->d)
258 		goto err;
259 
260 	mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
261 	if (!mpi_key->e)
262 		goto err;
263 
264 	mpi_key->n = mpi_read_raw_data(raw_key.n, raw_key.n_sz);
265 	if (!mpi_key->n)
266 		goto err;
267 
268 	mpi_key->p = mpi_read_raw_data(raw_key.p, raw_key.p_sz);
269 	if (!mpi_key->p)
270 		goto err;
271 
272 	mpi_key->q = mpi_read_raw_data(raw_key.q, raw_key.q_sz);
273 	if (!mpi_key->q)
274 		goto err;
275 
276 	mpi_key->dp = mpi_read_raw_data(raw_key.dp, raw_key.dp_sz);
277 	if (!mpi_key->dp)
278 		goto err;
279 
280 	mpi_key->dq = mpi_read_raw_data(raw_key.dq, raw_key.dq_sz);
281 	if (!mpi_key->dq)
282 		goto err;
283 
284 	mpi_key->qinv = mpi_read_raw_data(raw_key.qinv, raw_key.qinv_sz);
285 	if (!mpi_key->qinv)
286 		goto err;
287 
288 	if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) {
289 		rsa_free_mpi_key(mpi_key);
290 		return -EINVAL;
291 	}
292 
293 	return 0;
294 
295 err:
296 	rsa_free_mpi_key(mpi_key);
297 	return -ENOMEM;
298 }
299 
rsa_max_size(struct crypto_akcipher * tfm)300 static unsigned int rsa_max_size(struct crypto_akcipher *tfm)
301 {
302 	struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
303 
304 	return mpi_get_size(pkey->n);
305 }
306 
rsa_exit_tfm(struct crypto_akcipher * tfm)307 static void rsa_exit_tfm(struct crypto_akcipher *tfm)
308 {
309 	struct rsa_mpi_key *pkey = akcipher_tfm_ctx(tfm);
310 
311 	rsa_free_mpi_key(pkey);
312 }
313 
314 static struct akcipher_alg rsa = {
315 	.encrypt = rsa_enc,
316 	.decrypt = rsa_dec,
317 	.set_priv_key = rsa_set_priv_key,
318 	.set_pub_key = rsa_set_pub_key,
319 	.max_size = rsa_max_size,
320 	.exit = rsa_exit_tfm,
321 	.base = {
322 		.cra_name = "rsa",
323 		.cra_driver_name = "rsa-generic",
324 		.cra_priority = 100,
325 		.cra_module = THIS_MODULE,
326 		.cra_ctxsize = sizeof(struct rsa_mpi_key),
327 	},
328 };
329 
rsa_init(void)330 static int __init rsa_init(void)
331 {
332 	int err;
333 
334 	err = crypto_register_akcipher(&rsa);
335 	if (err)
336 		return err;
337 
338 	err = crypto_register_template(&rsa_pkcs1pad_tmpl);
339 	if (err) {
340 		crypto_unregister_akcipher(&rsa);
341 		return err;
342 	}
343 
344 	return 0;
345 }
346 
rsa_exit(void)347 static void __exit rsa_exit(void)
348 {
349 	crypto_unregister_template(&rsa_pkcs1pad_tmpl);
350 	crypto_unregister_akcipher(&rsa);
351 }
352 
353 subsys_initcall(rsa_init);
354 module_exit(rsa_exit);
355 MODULE_ALIAS_CRYPTO("rsa");
356 MODULE_LICENSE("GPL");
357 MODULE_DESCRIPTION("RSA generic algorithm");
358