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