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/kpp.h>
10 #include <crypto/kpp.h>
11 #include <crypto/ecdh.h>
12 #include <linux/scatterlist.h>
13 #include "ecc.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_supported_curve(unsigned int curve_id)26 static unsigned int ecdh_supported_curve(unsigned int curve_id)
27 {
28 switch (curve_id) {
29 case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS;
30 case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS;
31 default: return 0;
32 }
33 }
34
ecdh_set_secret(struct crypto_kpp * tfm,const void * buf,unsigned int len)35 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
36 unsigned int len)
37 {
38 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
39 struct ecdh params;
40 unsigned int ndigits;
41
42 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0 ||
43 params.key_size > sizeof(ctx->private_key))
44 return -EINVAL;
45
46 ndigits = ecdh_supported_curve(params.curve_id);
47 if (!ndigits)
48 return -EINVAL;
49
50 ctx->curve_id = params.curve_id;
51 ctx->ndigits = ndigits;
52
53 if (!params.key || !params.key_size)
54 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
55 ctx->private_key);
56
57 memcpy(ctx->private_key, params.key, params.key_size);
58
59 if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
60 ctx->private_key, params.key_size) < 0) {
61 memzero_explicit(ctx->private_key, params.key_size);
62 return -EINVAL;
63 }
64 return 0;
65 }
66
ecdh_compute_value(struct kpp_request * req)67 static int ecdh_compute_value(struct kpp_request *req)
68 {
69 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
70 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
71 u64 *public_key;
72 u64 *shared_secret = NULL;
73 void *buf;
74 size_t copied, nbytes, public_key_sz;
75 int ret = -ENOMEM;
76
77 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
78 /* Public part is a point thus it has both coordinates */
79 public_key_sz = 2 * nbytes;
80
81 public_key = kmalloc(public_key_sz, GFP_KERNEL);
82 if (!public_key)
83 return -ENOMEM;
84
85 if (req->src) {
86 shared_secret = kmalloc(nbytes, GFP_KERNEL);
87 if (!shared_secret)
88 goto free_pubkey;
89
90 /* from here on it's invalid parameters */
91 ret = -EINVAL;
92
93 /* must have exactly two points to be on the curve */
94 if (public_key_sz != req->src_len)
95 goto free_all;
96
97 copied = sg_copy_to_buffer(req->src,
98 sg_nents_for_len(req->src,
99 public_key_sz),
100 public_key, public_key_sz);
101 if (copied != public_key_sz)
102 goto free_all;
103
104 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
105 ctx->private_key, public_key,
106 shared_secret);
107
108 buf = shared_secret;
109 } else {
110 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
111 ctx->private_key, public_key);
112 buf = public_key;
113 nbytes = public_key_sz;
114 }
115
116 if (ret < 0)
117 goto free_all;
118
119 /* might want less than we've got */
120 nbytes = min_t(size_t, nbytes, req->dst_len);
121 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
122 nbytes),
123 buf, nbytes);
124 if (copied != nbytes)
125 ret = -EINVAL;
126
127 /* fall through */
128 free_all:
129 kfree_sensitive(shared_secret);
130 free_pubkey:
131 kfree(public_key);
132 return ret;
133 }
134
ecdh_max_size(struct crypto_kpp * tfm)135 static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
136 {
137 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
138
139 /* Public key is made of two coordinates, add one to the left shift */
140 return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
141 }
142
143 static struct kpp_alg ecdh = {
144 .set_secret = ecdh_set_secret,
145 .generate_public_key = ecdh_compute_value,
146 .compute_shared_secret = ecdh_compute_value,
147 .max_size = ecdh_max_size,
148 .base = {
149 .cra_name = "ecdh",
150 .cra_driver_name = "ecdh-generic",
151 .cra_priority = 100,
152 .cra_module = THIS_MODULE,
153 .cra_ctxsize = sizeof(struct ecdh_ctx),
154 },
155 };
156
ecdh_init(void)157 static int ecdh_init(void)
158 {
159 return crypto_register_kpp(&ecdh);
160 }
161
ecdh_exit(void)162 static void ecdh_exit(void)
163 {
164 crypto_unregister_kpp(&ecdh);
165 }
166
167 subsys_initcall(ecdh_init);
168 module_exit(ecdh_exit);
169 MODULE_ALIAS_CRYPTO("ecdh");
170 MODULE_LICENSE("GPL");
171 MODULE_DESCRIPTION("ECDH generic algorithm");
172