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
27static 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 */
51static 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 */
72static 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
110err_free_mpi:
111	mpi_free(m12_or_qh);
112	mpi_free(m2);
113	return ret;
114}
115
116static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
117{
118	return akcipher_tfm_ctx(tfm);
119}
120
121static 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
153err_free_m:
154	mpi_free(m);
155err_free_c:
156	mpi_free(c);
157	return ret;
158}
159
160static 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;
191err_free_c:
192	mpi_free(c);
193err_free_m:
194	mpi_free(m);
195	return ret;
196}
197
198static 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
218static 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
236static 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
264static 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
298err:
299	rsa_free_mpi_key(mpi_key);
300	return -ENOMEM;
301}
302
303static 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
361err:
362	rsa_free_mpi_key(mpi_key);
363	return -ENOMEM;
364}
365
366static 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
373static 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
380static 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
396static 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
413static void __exit rsa_exit(void)
414{
415	crypto_unregister_template(&rsa_pkcs1pad_tmpl);
416	crypto_unregister_akcipher(&rsa);
417}
418
419subsys_initcall(rsa_init);
420module_exit(rsa_exit);
421MODULE_ALIAS_CRYPTO("rsa");
422MODULE_LICENSE("GPL");
423MODULE_DESCRIPTION("RSA generic algorithm");
424