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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 <[email protected]>
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
243module_init(ecdh_init);
244module_exit(ecdh_exit);
245MODULE_ALIAS_CRYPTO("ecdh");
246MODULE_LICENSE("GPL");
247MODULE_DESCRIPTION("ECDH generic algorithm");