LXR linux/arch/arm/crypto/curve25519-glue.c

   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 * Based on public domain code from Daniel J. Bernstein and Peter Schwabe. This
   6 * began from SUPERCOP's curve25519/neon2/scalarmult.s, but has subsequently been
   7 * manually reworked for use in kernel space.
   8 */
   9
  10#include <asm/hwcap.h>
  11#include <asm/neon.h>
  12#include <asm/simd.h>
  13#include <crypto/internal/kpp.h>
  14#include <crypto/internal/simd.h>
  15#include <linux/types.h>
  16#include <linux/module.h>
  17#include <linux/init.h>
  18#include <linux/jump_label.h>
  19#include <linux/scatterlist.h>
  20#include <crypto/curve25519.h>
  21
  22asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
  23                                const u8 secret[CURVE25519_KEY_SIZE],
  24                                const u8 basepoint[CURVE25519_KEY_SIZE]);
  25
  26static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
  27
  28void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
  29                     const u8 scalar[CURVE25519_KEY_SIZE],
  30                     const u8 point[CURVE25519_KEY_SIZE])
  31{
  32        if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
  33                kernel_neon_begin();
  34                curve25519_neon(out, scalar, point);
  35                kernel_neon_end();
  36        } else {
  37                curve25519_generic(out, scalar, point);
  38        }
  39}
  40EXPORT_SYMBOL(curve25519_arch);
  41
  42void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
  43                          const u8 secret[CURVE25519_KEY_SIZE])
  44{
  45        return curve25519_arch(pub, secret, curve25519_base_point);
  46}
  47EXPORT_SYMBOL(curve25519_base_arch);
  48
  49static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
  50                                 unsigned int len)
  51{
  52        u8 *secret = kpp_tfm_ctx(tfm);
  53
  54        if (!len)
  55                curve25519_generate_secret(secret);
  56        else if (len == CURVE25519_KEY_SIZE &&
  57                 crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
  58                memcpy(secret, buf, CURVE25519_KEY_SIZE);
  59        else
  60                return -EINVAL;
  61        return 0;
  62}
  63
  64static int curve25519_compute_value(struct kpp_request *req)
  65{
  66        struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  67        const u8 *secret = kpp_tfm_ctx(tfm);
  68        u8 public_key[CURVE25519_KEY_SIZE];
  69        u8 buf[CURVE25519_KEY_SIZE];
  70        int copied, nbytes;
  71        u8 const *bp;
  72
  73        if (req->src) {
  74                copied = sg_copy_to_buffer(req->src,
  75                                           sg_nents_for_len(req->src,
  76                                                            CURVE25519_KEY_SIZE),
  77                                           public_key, CURVE25519_KEY_SIZE);
  78                if (copied != CURVE25519_KEY_SIZE)
  79                        return -EINVAL;
  80                bp = public_key;
  81        } else {
  82                bp = curve25519_base_point;
  83        }
  84
  85        curve25519_arch(buf, secret, bp);
  86
  87        /* might want less than we've got */
  88        nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
  89        copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
  90                                                                nbytes),
  91                                     buf, nbytes);
  92        if (copied != nbytes)
  93                return -EINVAL;
  94        return 0;
  95}
  96
  97static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
  98{
  99        return CURVE25519_KEY_SIZE;
 100}
 101
 102static struct kpp_alg curve25519_alg = {
 103        .base.cra_name          = "curve25519",
 104        .base.cra_driver_name   = "curve25519-neon",
 105        .base.cra_priority      = 200,
 106        .base.cra_module        = THIS_MODULE,
 107        .base.cra_ctxsize       = CURVE25519_KEY_SIZE,
 108
 109        .set_secret             = curve25519_set_secret,
 110        .generate_public_key    = curve25519_compute_value,
 111        .compute_shared_secret  = curve25519_compute_value,
 112        .max_size               = curve25519_max_size,
 113};
 114
 115static int __init arm_curve25519_init(void)
 116{
 117        if (elf_hwcap & HWCAP_NEON) {
 118                static_branch_enable(&have_neon);
 119                return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
 120                        crypto_register_kpp(&curve25519_alg) : 0;
 121        }
 122        return 0;
 123}
 124
 125static void __exit arm_curve25519_exit(void)
 126{
 127        if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
 128                crypto_unregister_kpp(&curve25519_alg);
 129}
 130
 131module_init(arm_curve25519_init);
 132module_exit(arm_curve25519_exit);
 133
 134MODULE_ALIAS_CRYPTO("curve25519");
 135MODULE_ALIAS_CRYPTO("curve25519-neon");
 136MODULE_LICENSE("GPL v2");
 137