1// SPDX-License-Identifier: GPL-2.0 OR MIT
2/*
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 *
5 * Based on public domain code from Daniel J. Bernstein and Peter Schwabe. This
6 * began from SUPERCOP's curve25519/neon2/scalarmult.s, but has subsequently been
7 * manually reworked for use in kernel space.
8 */
9
10#include <asm/hwcap.h>
11#include <asm/neon.h>
12#include <asm/simd.h>
13#include <crypto/internal/kpp.h>
14#include <crypto/internal/simd.h>
15#include <linux/types.h>
16#include <linux/module.h>
17#include <linux/init.h>
18#include <linux/jump_label.h>
19#include <linux/scatterlist.h>
20#include <crypto/curve25519.h>
21
22asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
23				const u8 secret[CURVE25519_KEY_SIZE],
24				const u8 basepoint[CURVE25519_KEY_SIZE]);
25
26static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
27
28void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
29		     const u8 scalar[CURVE25519_KEY_SIZE],
30		     const u8 point[CURVE25519_KEY_SIZE])
31{
32	if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
33		kernel_neon_begin();
34		curve25519_neon(out, scalar, point);
35		kernel_neon_end();
36	} else {
37		curve25519_generic(out, scalar, point);
38	}
39}
40EXPORT_SYMBOL(curve25519_arch);
41
42void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
43			  const u8 secret[CURVE25519_KEY_SIZE])
44{
45	return curve25519_arch(pub, secret, curve25519_base_point);
46}
47EXPORT_SYMBOL(curve25519_base_arch);
48
49static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
50				 unsigned int len)
51{
52	u8 *secret = kpp_tfm_ctx(tfm);
53
54	if (!len)
55		curve25519_generate_secret(secret);
56	else if (len == CURVE25519_KEY_SIZE &&
57		 crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
58		memcpy(secret, buf, CURVE25519_KEY_SIZE);
59	else
60		return -EINVAL;
61	return 0;
62}
63
64static int curve25519_compute_value(struct kpp_request *req)
65{
66	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
67	const u8 *secret = kpp_tfm_ctx(tfm);
68	u8 public_key[CURVE25519_KEY_SIZE];
69	u8 buf[CURVE25519_KEY_SIZE];
70	int copied, nbytes;
71	u8 const *bp;
72
73	if (req->src) {
74		copied = sg_copy_to_buffer(req->src,
75					   sg_nents_for_len(req->src,
76							    CURVE25519_KEY_SIZE),
77					   public_key, CURVE25519_KEY_SIZE);
78		if (copied != CURVE25519_KEY_SIZE)
79			return -EINVAL;
80		bp = public_key;
81	} else {
82		bp = curve25519_base_point;
83	}
84
85	curve25519_arch(buf, secret, bp);
86
87	/* might want less than we've got */
88	nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
89	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
90								nbytes),
91				     buf, nbytes);
92	if (copied != nbytes)
93		return -EINVAL;
94	return 0;
95}
96
97static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
98{
99	return CURVE25519_KEY_SIZE;
100}
101
102static struct kpp_alg curve25519_alg = {
103	.base.cra_name		= "curve25519",
104	.base.cra_driver_name	= "curve25519-neon",
105	.base.cra_priority	= 200,
106	.base.cra_module	= THIS_MODULE,
107	.base.cra_ctxsize	= CURVE25519_KEY_SIZE,
108
109	.set_secret		= curve25519_set_secret,
110	.generate_public_key	= curve25519_compute_value,
111	.compute_shared_secret	= curve25519_compute_value,
112	.max_size		= curve25519_max_size,
113};
114
115static int __init arm_curve25519_init(void)
116{
117	if (elf_hwcap & HWCAP_NEON) {
118		static_branch_enable(&have_neon);
119		return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
120			crypto_register_kpp(&curve25519_alg) : 0;
121	}
122	return 0;
123}
124
125static void __exit arm_curve25519_exit(void)
126{
127	if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
128		crypto_unregister_kpp(&curve25519_alg);
129}
130
131module_init(arm_curve25519_init);
132module_exit(arm_curve25519_exit);
133
134MODULE_ALIAS_CRYPTO("curve25519");
135MODULE_ALIAS_CRYPTO("curve25519-neon");
136MODULE_LICENSE("GPL v2");
137