LXR linux/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
  13enum curve25519_lengths {
  14        CURVE25519_KEY_SIZE = 32
  15};
  16
  17extern const u8 curve25519_null_point[];
  18extern const u8 curve25519_base_point[];
  19
  20void curve25519_generic(u8 out[CURVE25519_KEY_SIZE],
  21                        const u8 scalar[CURVE25519_KEY_SIZE],
  22                        const u8 point[CURVE25519_KEY_SIZE]);
  23
  24void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
  25                     const u8 scalar[CURVE25519_KEY_SIZE],
  26                     const u8 point[CURVE25519_KEY_SIZE]);
  27
  28void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
  29                          const u8 secret[CURVE25519_KEY_SIZE]);
  30
  31static inline
  32bool __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
  44static 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
  59static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
  60{
  61        secret[0] &= 248;
  62        secret[31] = (secret[31] & 127) | 64;
  63}
  64
  65static 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