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
31bool curve25519_selftest(void);
32
33static inline
34bool __must_check curve25519(u8 mypublic[CURVE25519_KEY_SIZE],
35			     const u8 secret[CURVE25519_KEY_SIZE],
36			     const u8 basepoint[CURVE25519_KEY_SIZE])
37{
38	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
39		curve25519_arch(mypublic, secret, basepoint);
40	else
41		curve25519_generic(mypublic, secret, basepoint);
42	return crypto_memneq(mypublic, curve25519_null_point,
43			     CURVE25519_KEY_SIZE);
44}
45
46static inline bool
47__must_check curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],
48					const u8 secret[CURVE25519_KEY_SIZE])
49{
50	if (unlikely(!crypto_memneq(secret, curve25519_null_point,
51				    CURVE25519_KEY_SIZE)))
52		return false;
53
54	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
55		curve25519_base_arch(pub, secret);
56	else
57		curve25519_generic(pub, secret, curve25519_base_point);
58	return crypto_memneq(pub, curve25519_null_point, CURVE25519_KEY_SIZE);
59}
60
61static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
62{
63	secret[0] &= 248;
64	secret[31] = (secret[31] & 127) | 64;
65}
66
67static inline void curve25519_generate_secret(u8 secret[CURVE25519_KEY_SIZE])
68{
69	get_random_bytes_wait(secret, CURVE25519_KEY_SIZE);
70	curve25519_clamp_secret(secret);
71}
72
73#endif /* CURVE25519_H */
74