1// SPDX-License-Identifier: GPL-2.0-or-later
2/* ECDH key-agreement protocol
3 *
4 * Copyright (c) 2016, Intel Corporation
5 * Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
6 */
7
8#include <linux/module.h>
9#include <crypto/internal/ecc.h>
10#include <crypto/internal/kpp.h>
11#include <crypto/kpp.h>
12#include <crypto/ecdh.h>
13#include <linux/scatterlist.h>
14
15struct ecdh_ctx {
16	unsigned int curve_id;
17	unsigned int ndigits;
18	u64 private_key[ECC_MAX_DIGITS];
19};
20
21static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
22{
23	return kpp_tfm_ctx(tfm);
24}
25
26static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
27			   unsigned int len)
28{
29	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
30	struct ecdh params;
31	int ret = 0;
32
33	if (crypto_ecdh_decode_key(buf, len, &params) < 0 ||
34	    params.key_size > sizeof(u64) * ctx->ndigits)
35		return -EINVAL;
36
37	memset(ctx->private_key, 0, sizeof(ctx->private_key));
38
39	if (!params.key || !params.key_size)
40		return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
41				       ctx->private_key);
42
43	ecc_digits_from_bytes(params.key, params.key_size,
44			      ctx->private_key, ctx->ndigits);
45
46	if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
47			     ctx->private_key, params.key_size) < 0) {
48		memzero_explicit(ctx->private_key, params.key_size);
49		ret = -EINVAL;
50	}
51
52	return ret;
53}
54
55static int ecdh_compute_value(struct kpp_request *req)
56{
57	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
58	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
59	u64 *public_key;
60	u64 *shared_secret = NULL;
61	void *buf;
62	size_t copied, nbytes, public_key_sz;
63	int ret = -ENOMEM;
64
65	nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
66	/* Public part is a point thus it has both coordinates */
67	public_key_sz = 2 * nbytes;
68
69	public_key = kmalloc(public_key_sz, GFP_KERNEL);
70	if (!public_key)
71		return -ENOMEM;
72
73	if (req->src) {
74		shared_secret = kmalloc(nbytes, GFP_KERNEL);
75		if (!shared_secret)
76			goto free_pubkey;
77
78		/* from here on it's invalid parameters */
79		ret = -EINVAL;
80
81		/* must have exactly two points to be on the curve */
82		if (public_key_sz != req->src_len)
83			goto free_all;
84
85		copied = sg_copy_to_buffer(req->src,
86					   sg_nents_for_len(req->src,
87							    public_key_sz),
88					   public_key, public_key_sz);
89		if (copied != public_key_sz)
90			goto free_all;
91
92		ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
93						ctx->private_key, public_key,
94						shared_secret);
95
96		buf = shared_secret;
97	} else {
98		ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
99				       ctx->private_key, public_key);
100		buf = public_key;
101		nbytes = public_key_sz;
102	}
103
104	if (ret < 0)
105		goto free_all;
106
107	/* might want less than we've got */
108	nbytes = min_t(size_t, nbytes, req->dst_len);
109	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
110								nbytes),
111				     buf, nbytes);
112	if (copied != nbytes)
113		ret = -EINVAL;
114
115	/* fall through */
116free_all:
117	kfree_sensitive(shared_secret);
118free_pubkey:
119	kfree(public_key);
120	return ret;
121}
122
123static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
124{
125	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
126
127	/* Public key is made of two coordinates, add one to the left shift */
128	return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
129}
130
131static int ecdh_nist_p192_init_tfm(struct crypto_kpp *tfm)
132{
133	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
134
135	ctx->curve_id = ECC_CURVE_NIST_P192;
136	ctx->ndigits = ECC_CURVE_NIST_P192_DIGITS;
137
138	return 0;
139}
140
141static struct kpp_alg ecdh_nist_p192 = {
142	.set_secret = ecdh_set_secret,
143	.generate_public_key = ecdh_compute_value,
144	.compute_shared_secret = ecdh_compute_value,
145	.max_size = ecdh_max_size,
146	.init = ecdh_nist_p192_init_tfm,
147	.base = {
148		.cra_name = "ecdh-nist-p192",
149		.cra_driver_name = "ecdh-nist-p192-generic",
150		.cra_priority = 100,
151		.cra_module = THIS_MODULE,
152		.cra_ctxsize = sizeof(struct ecdh_ctx),
153	},
154};
155
156static int ecdh_nist_p256_init_tfm(struct crypto_kpp *tfm)
157{
158	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
159
160	ctx->curve_id = ECC_CURVE_NIST_P256;
161	ctx->ndigits = ECC_CURVE_NIST_P256_DIGITS;
162
163	return 0;
164}
165
166static struct kpp_alg ecdh_nist_p256 = {
167	.set_secret = ecdh_set_secret,
168	.generate_public_key = ecdh_compute_value,
169	.compute_shared_secret = ecdh_compute_value,
170	.max_size = ecdh_max_size,
171	.init = ecdh_nist_p256_init_tfm,
172	.base = {
173		.cra_name = "ecdh-nist-p256",
174		.cra_driver_name = "ecdh-nist-p256-generic",
175		.cra_priority = 100,
176		.cra_module = THIS_MODULE,
177		.cra_ctxsize = sizeof(struct ecdh_ctx),
178	},
179};
180
181static int ecdh_nist_p384_init_tfm(struct crypto_kpp *tfm)
182{
183	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
184
185	ctx->curve_id = ECC_CURVE_NIST_P384;
186	ctx->ndigits = ECC_CURVE_NIST_P384_DIGITS;
187
188	return 0;
189}
190
191static struct kpp_alg ecdh_nist_p384 = {
192	.set_secret = ecdh_set_secret,
193	.generate_public_key = ecdh_compute_value,
194	.compute_shared_secret = ecdh_compute_value,
195	.max_size = ecdh_max_size,
196	.init = ecdh_nist_p384_init_tfm,
197	.base = {
198		.cra_name = "ecdh-nist-p384",
199		.cra_driver_name = "ecdh-nist-p384-generic",
200		.cra_priority = 100,
201		.cra_module = THIS_MODULE,
202		.cra_ctxsize = sizeof(struct ecdh_ctx),
203	},
204};
205
206static bool ecdh_nist_p192_registered;
207
208static int __init ecdh_init(void)
209{
210	int ret;
211
212	/* NIST p192 will fail to register in FIPS mode */
213	ret = crypto_register_kpp(&ecdh_nist_p192);
214	ecdh_nist_p192_registered = ret == 0;
215
216	ret = crypto_register_kpp(&ecdh_nist_p256);
217	if (ret)
218		goto nist_p256_error;
219
220	ret = crypto_register_kpp(&ecdh_nist_p384);
221	if (ret)
222		goto nist_p384_error;
223
224	return 0;
225
226nist_p384_error:
227	crypto_unregister_kpp(&ecdh_nist_p256);
228
229nist_p256_error:
230	if (ecdh_nist_p192_registered)
231		crypto_unregister_kpp(&ecdh_nist_p192);
232	return ret;
233}
234
235static void __exit ecdh_exit(void)
236{
237	if (ecdh_nist_p192_registered)
238		crypto_unregister_kpp(&ecdh_nist_p192);
239	crypto_unregister_kpp(&ecdh_nist_p256);
240	crypto_unregister_kpp(&ecdh_nist_p384);
241}
242
243subsys_initcall(ecdh_init);
244module_exit(ecdh_exit);
245MODULE_ALIAS_CRYPTO("ecdh");
246MODULE_LICENSE("GPL");
247MODULE_DESCRIPTION("ECDH generic algorithm");
248