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
6#ifndef CURVE25519_H
7#define CURVE25519_H
8
9#include <crypto/algapi.h> // For crypto_memneq.
10#include <linux/types.h>
11#include <linux/random.h>
12
13enum curve25519_lengths {
14	CURVE25519_KEY_SIZE = 32
15};
16
17extern const u8 curve25519_null_point[];
18extern const u8 curve25519_base_point[];
19
20void curve25519_generic(u8 out[CURVE25519_KEY_SIZE],
21			const u8 scalar[CURVE25519_KEY_SIZE],
22			const u8 point[CURVE25519_KEY_SIZE]);
23
24void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
25		     const u8 scalar[CURVE25519_KEY_SIZE],
26		     const u8 point[CURVE25519_KEY_SIZE]);
27
28void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
29			  const u8 secret[CURVE25519_KEY_SIZE]);
30
31static inline
32bool __must_check curve25519(u8 mypublic[CURVE25519_KEY_SIZE],
33			     const u8 secret[CURVE25519_KEY_SIZE],
34			     const u8 basepoint[CURVE25519_KEY_SIZE])
35{
36	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
37		curve25519_arch(mypublic, secret, basepoint);
38	else
39		curve25519_generic(mypublic, secret, basepoint);
40	return crypto_memneq(mypublic, curve25519_null_point,
41			     CURVE25519_KEY_SIZE);
42}
43
44static inline bool
45__must_check curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],
46					const u8 secret[CURVE25519_KEY_SIZE])
47{
48	if (unlikely(!crypto_memneq(secret, curve25519_null_point,
49				    CURVE25519_KEY_SIZE)))
50		return false;
51
52	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
53		curve25519_base_arch(pub, secret);
54	else
55		curve25519_generic(pub, secret, curve25519_base_point);
56	return crypto_memneq(pub, curve25519_null_point, CURVE25519_KEY_SIZE);
57}
58
59static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
60{
61	secret[0] &= 248;
62	secret[31] = (secret[31] & 127) | 64;
63}
64
65static inline void curve25519_generate_secret(u8 secret[CURVE25519_KEY_SIZE])
66{
67	get_random_bytes_wait(secret, CURVE25519_KEY_SIZE);
68	curve25519_clamp_secret(secret);
69}
70
71#endif /* CURVE25519_H */
72