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 memset(ctx->private_key, 0, sizeof(ctx->private_key));
53
54 if (!params.key || !params.key_size)
55 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
56 ctx->private_key);
57
58 memcpy(ctx->private_key, params.key, params.key_size);
59
60 if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
61 ctx->private_key, params.key_size) < 0) {
62 memzero_explicit(ctx->private_key, params.key_size);
63 return -EINVAL;
64 }
65 return 0;
66 }
67
ecdh_compute_value(struct kpp_request * req)68 static int ecdh_compute_value(struct kpp_request *req)
69 {
70 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
71 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
72 u64 *public_key;
73 u64 *shared_secret = NULL;
74 void *buf;
75 size_t copied, nbytes, public_key_sz;
76 int ret = -ENOMEM;
77
78 nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
79 /* Public part is a point thus it has both coordinates */
80 public_key_sz = 2 * nbytes;
81
82 public_key = kmalloc(public_key_sz, GFP_KERNEL);
83 if (!public_key)
84 return -ENOMEM;
85
86 if (req->src) {
87 shared_secret = kmalloc(nbytes, GFP_KERNEL);
88 if (!shared_secret)
89 goto free_pubkey;
90
91 /* from here on it's invalid parameters */
92 ret = -EINVAL;
93
94 /* must have exactly two points to be on the curve */
95 if (public_key_sz != req->src_len)
96 goto free_all;
97
98 copied = sg_copy_to_buffer(req->src,
99 sg_nents_for_len(req->src,
100 public_key_sz),
101 public_key, public_key_sz);
102 if (copied != public_key_sz)
103 goto free_all;
104
105 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
106 ctx->private_key, public_key,
107 shared_secret);
108
109 buf = shared_secret;
110 } else {
111 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
112 ctx->private_key, public_key);
113 buf = public_key;
114 nbytes = public_key_sz;
115 }
116
117 if (ret < 0)
118 goto free_all;
119
120 /* might want less than we've got */
121 nbytes = min_t(size_t, nbytes, req->dst_len);
122 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
123 nbytes),
124 buf, nbytes);
125 if (copied != nbytes)
126 ret = -EINVAL;
127
128 /* fall through */
129 free_all:
130 kfree_sensitive(shared_secret);
131 free_pubkey:
132 kfree(public_key);
133 return ret;
134 }
135
ecdh_max_size(struct crypto_kpp * tfm)136 static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
137 {
138 struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
139
140 /* Public key is made of two coordinates, add one to the left shift */
141 return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
142 }
143
144 static struct kpp_alg ecdh = {
145 .set_secret = ecdh_set_secret,
146 .generate_public_key = ecdh_compute_value,
147 .compute_shared_secret = ecdh_compute_value,
148 .max_size = ecdh_max_size,
149 .base = {
150 .cra_name = "ecdh",
151 .cra_driver_name = "ecdh-generic",
152 .cra_priority = 100,
153 .cra_module = THIS_MODULE,
154 .cra_ctxsize = sizeof(struct ecdh_ctx),
155 },
156 };
157
ecdh_init(void)158 static int ecdh_init(void)
159 {
160 return crypto_register_kpp(&ecdh);
161 }
162
ecdh_exit(void)163 static void ecdh_exit(void)
164 {
165 crypto_unregister_kpp(&ecdh);
166 }
167
168 subsys_initcall(ecdh_init);
169 module_exit(ecdh_exit);
170 MODULE_ALIAS_CRYPTO("ecdh");
171 MODULE_LICENSE("GPL");
172 MODULE_DESCRIPTION("ECDH generic algorithm");
173