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
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
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
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
75 static int __init curve25519_init(void)
76 {
77 return crypto_register_kpp(&curve25519_alg);
78 }
79
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_DESCRIPTION("Curve25519 elliptic curve (RFC7748)");
91 MODULE_LICENSE("GPL");
92
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