include/crypto/curve25519.h

   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 */