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 
curve25519_set_secret(struct crypto_kpp * tfm,const void * buf,unsigned int len)9 static 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 
curve25519_compute_value(struct kpp_request * req)24 static 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 
curve25519_max_size(struct crypto_kpp * tfm)57 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
58 {
59 	return CURVE25519_KEY_SIZE;
60 }
61 
62 static 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 
curve25519_init(void)75 static int __init curve25519_init(void)
76 {
77 	return crypto_register_kpp(&curve25519_alg);
78 }
79 
curve25519_exit(void)80 static void __exit curve25519_exit(void)
81 {
82 	crypto_unregister_kpp(&curve25519_alg);
83 }
84 
85 subsys_initcall(curve25519_init);
86 module_exit(curve25519_exit);
87 
88 MODULE_ALIAS_CRYPTO("curve25519");
89 MODULE_ALIAS_CRYPTO("curve25519-generic");
90 MODULE_LICENSE("GPL");
91