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(out: mypublic, scalar: secret, point: basepoint);
40 else
41 curve25519_generic(out: mypublic, scalar: secret, point: basepoint);
42 return crypto_memneq(a: mypublic, b: curve25519_null_point,
43 size: 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(out: pub, scalar: secret, point: curve25519_base_point);
58 return crypto_memneq(a: pub, b: curve25519_null_point, size: 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(buf: secret, nbytes: CURVE25519_KEY_SIZE);
70 curve25519_clamp_secret(secret);
71}
72
73#endif /* CURVE25519_H */
74

source code of linux/include/crypto/curve25519.h