xref: /openbmc/linux/include/crypto/curve25519.h (revision dc6a81c3)
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
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
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 
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 
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