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, &params) < 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