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
13 enum curve25519_lengths {
14 CURVE25519_KEY_SIZE = 32
15 };
16
17 extern const u8 curve25519_null_point[];
18 extern const u8 curve25519_base_point[];
19
20 void curve25519_generic(u8 out[CURVE25519_KEY_SIZE],
21 const u8 scalar[CURVE25519_KEY_SIZE],
22 const u8 point[CURVE25519_KEY_SIZE]);
23
24 void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
25 const u8 scalar[CURVE25519_KEY_SIZE],
26 const u8 point[CURVE25519_KEY_SIZE]);
27
28 void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
29 const u8 secret[CURVE25519_KEY_SIZE]);
30
31 static inline
curve25519(u8 mypublic[CURVE25519_KEY_SIZE],const u8 secret[CURVE25519_KEY_SIZE],const u8 basepoint[CURVE25519_KEY_SIZE])32 bool __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
44 static inline bool
curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],const u8 secret[CURVE25519_KEY_SIZE])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
curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])59 static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
60 {
61 secret[0] &= 248;
62 secret[31] = (secret[31] & 127) | 64;
63 }
64
curve25519_generate_secret(u8 secret[CURVE25519_KEY_SIZE])65 static 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