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 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 */