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 <crypto/curve25519.h>
  20
  21 asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
  22                                 const u8 secret[CURVE25519_KEY_SIZE],
  23                                 const u8 basepoint[CURVE25519_KEY_SIZE]);
  24
  25 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
  26
  27 void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
  28                      const u8 scalar[CURVE25519_KEY_SIZE],
  29                      const u8 point[CURVE25519_KEY_SIZE])
  30 {
  31         if (static_branch_likely(&have_neon) && crypto_simd_usable()) {
  32                 kernel_neon_begin();
  33                 curve25519_neon(out, scalar, point);
  34                 kernel_neon_end();
  35         } else {
  36                 curve25519_generic(out, scalar, point);
  37         }
  38 }
  39 EXPORT_SYMBOL(curve25519_arch);
  40
  41 static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
  42                                  unsigned int len)
  43 {
  44         u8 *secret = kpp_tfm_ctx(tfm);
  45
  46         if (!len)
  47                 curve25519_generate_secret(secret);
  48         else if (len == CURVE25519_KEY_SIZE &&
  49                  crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
  50                 memcpy(secret, buf, CURVE25519_KEY_SIZE);
  51         else
  52                 return -EINVAL;
  53         return 0;
  54 }
  55
  56 static int curve25519_compute_value(struct kpp_request *req)
  57 {
  58         struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  59         const u8 *secret = kpp_tfm_ctx(tfm);
  60         u8 public_key[CURVE25519_KEY_SIZE];
  61         u8 buf[CURVE25519_KEY_SIZE];
  62         int copied, nbytes;
  63         u8 const *bp;
  64
  65         if (req->src) {
  66                 copied = sg_copy_to_buffer(req->src,
  67                                            sg_nents_for_len(req->src,
  68                                                             CURVE25519_KEY_SIZE),
  69                                            public_key, CURVE25519_KEY_SIZE);
  70                 if (copied != CURVE25519_KEY_SIZE)
  71                         return -EINVAL;
  72                 bp = public_key;
  73         } else {
  74                 bp = curve25519_base_point;
  75         }
  76
  77         curve25519_arch(buf, secret, bp);
  78
  79         /* might want less than we've got */
  80         nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
  81         copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
  82                                                                 nbytes),
  83                                      buf, nbytes);
  84         if (copied != nbytes)
  85                 return -EINVAL;
  86         return 0;
  87 }
  88
  89 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
  90 {
  91         return CURVE25519_KEY_SIZE;
  92 }
  93
  94 static struct kpp_alg curve25519_alg = {
  95         .base.cra_name          = "curve25519",
  96         .base.cra_driver_name   = "curve25519-neon",
  97         .base.cra_priority      = 200,
  98         .base.cra_module        = THIS_MODULE,
  99         .base.cra_ctxsize       = CURVE25519_KEY_SIZE,
 100
 101         .set_secret             = curve25519_set_secret,
 102         .generate_public_key    = curve25519_compute_value,
 103         .compute_shared_secret  = curve25519_compute_value,
 104         .max_size               = curve25519_max_size,
 105 };
 106
 107 static int __init mod_init(void)
 108 {
 109         if (elf_hwcap & HWCAP_NEON) {
 110                 static_branch_enable(&have_neon);
 111                 return crypto_register_kpp(&curve25519_alg);
 112         }
 113         return 0;
 114 }
 115
 116 static void __exit mod_exit(void)
 117 {
 118         if (elf_hwcap & HWCAP_NEON)
 119                 crypto_unregister_kpp(&curve25519_alg);
 120 }
 121
 122 module_init(mod_init);
 123 module_exit(mod_exit);
 124
 125 MODULE_ALIAS_CRYPTO("curve25519");
 126 MODULE_ALIAS_CRYPTO("curve25519-neon");
 127 MODULE_LICENSE("GPL v2");