xref: /openbmc/linux/crypto/rsa.c (revision c0605cd6)
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   */
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   */
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  
88  static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm)
89  {
90  	return akcipher_tfm_ctx(tfm);
91  }
92  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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