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 bool curve25519_selftest(void);
32
33 static inline
34 bool __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
46 static 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
61 static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
62 {
63 secret[0] &= 248;
64 secret[31] = (secret[31] & 127) | 64;
65 }
66
67 static 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
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