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
  31bool curve25519_selftest(void);
  32
  33static inline
  34bool __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
  46static 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
  61static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
  62{
  63        secret[0] &= 248;
  64        secret[31] = (secret[31] & 127) | 64;
  65}
  66
  67static 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