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 	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 
ecdh_compute_value(struct kpp_request * req)55 static 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 */
116 free_all:
117 	kfree_sensitive(shared_secret);
118 free_pubkey:
119 	kfree(public_key);
120 	return ret;
121 }
122 
ecdh_max_size(struct crypto_kpp * tfm)123 static 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 
ecdh_nist_p192_init_tfm(struct crypto_kpp * tfm)131 static 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 
141 static 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 
ecdh_nist_p256_init_tfm(struct crypto_kpp * tfm)156 static 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 
166 static 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 
ecdh_nist_p384_init_tfm(struct crypto_kpp * tfm)181 static 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 
191 static 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 
206 static bool ecdh_nist_p192_registered;
207 
ecdh_init(void)208 static 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 
226 nist_p384_error:
227 	crypto_unregister_kpp(&ecdh_nist_p256);
228 
229 nist_p256_error:
230 	if (ecdh_nist_p192_registered)
231 		crypto_unregister_kpp(&ecdh_nist_p192);
232 	return ret;
233 }
234 
ecdh_exit(void)235 static 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 
243 subsys_initcall(ecdh_init);
244 module_exit(ecdh_exit);
245 MODULE_ALIAS_CRYPTO("ecdh");
246 MODULE_LICENSE("GPL");
247 MODULE_DESCRIPTION("ECDH generic algorithm");
248