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