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
curve25519(u8 mypublic[CURVE25519_KEY_SIZE],const u8 secret[CURVE25519_KEY_SIZE],const u8 basepoint[CURVE25519_KEY_SIZE])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
curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],const u8 secret[CURVE25519_KEY_SIZE])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 
curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])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 
curve25519_generate_secret(u8 secret[CURVE25519_KEY_SIZE])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