1// SPDX-License-Identifier: GPL-2.0-or-later
2
3#include <crypto/curve25519.h>
4#include <crypto/internal/kpp.h>
5#include <crypto/kpp.h>
6#include <linux/module.h>
7#include <linux/scatterlist.h>
8
9static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
10				 unsigned int len)
11{
12	u8 *secret = kpp_tfm_ctx(tfm);
13
14	if (!len)
15		curve25519_generate_secret(secret);
16	else if (len == CURVE25519_KEY_SIZE &&
17		 crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
18		memcpy(secret, buf, CURVE25519_KEY_SIZE);
19	else
20		return -EINVAL;
21	return 0;
22}
23
24static int curve25519_compute_value(struct kpp_request *req)
25{
26	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
27	const u8 *secret = kpp_tfm_ctx(tfm);
28	u8 public_key[CURVE25519_KEY_SIZE];
29	u8 buf[CURVE25519_KEY_SIZE];
30	int copied, nbytes;
31	u8 const *bp;
32
33	if (req->src) {
34		copied = sg_copy_to_buffer(req->src,
35					   sg_nents_for_len(req->src,
36							    CURVE25519_KEY_SIZE),
37					   public_key, CURVE25519_KEY_SIZE);
38		if (copied != CURVE25519_KEY_SIZE)
39			return -EINVAL;
40		bp = public_key;
41	} else {
42		bp = curve25519_base_point;
43	}
44
45	curve25519_generic(buf, secret, bp);
46
47	/* might want less than we've got */
48	nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
49	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
50								nbytes),
51				     buf, nbytes);
52	if (copied != nbytes)
53		return -EINVAL;
54	return 0;
55}
56
57static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
58{
59	return CURVE25519_KEY_SIZE;
60}
61
62static struct kpp_alg curve25519_alg = {
63	.base.cra_name		= "curve25519",
64	.base.cra_driver_name	= "curve25519-generic",
65	.base.cra_priority	= 100,
66	.base.cra_module	= THIS_MODULE,
67	.base.cra_ctxsize	= CURVE25519_KEY_SIZE,
68
69	.set_secret		= curve25519_set_secret,
70	.generate_public_key	= curve25519_compute_value,
71	.compute_shared_secret	= curve25519_compute_value,
72	.max_size		= curve25519_max_size,
73};
74
75static int __init curve25519_init(void)
76{
77	return crypto_register_kpp(&curve25519_alg);
78}
79
80static void __exit curve25519_exit(void)
81{
82	crypto_unregister_kpp(&curve25519_alg);
83}
84
85subsys_initcall(curve25519_init);
86module_exit(curve25519_exit);
87
88MODULE_ALIAS_CRYPTO("curve25519");
89MODULE_ALIAS_CRYPTO("curve25519-generic");
90MODULE_LICENSE("GPL");
91