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 void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
  42                           const u8 secret[CURVE25519_KEY_SIZE])
  43 {
  44         return curve25519_arch(pub, secret, curve25519_base_point);
  45 }
  46 EXPORT_SYMBOL(curve25519_base_arch);
  47
  48 static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
  49                                  unsigned int len)
  50 {
  51         u8 *secret = kpp_tfm_ctx(tfm);
  52
  53         if (!len)
  54                 curve25519_generate_secret(secret);
  55         else if (len == CURVE25519_KEY_SIZE &&
  56                  crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
  57                 memcpy(secret, buf, CURVE25519_KEY_SIZE);
  58         else
  59                 return -EINVAL;
  60         return 0;
  61 }
  62
  63 static int curve25519_compute_value(struct kpp_request *req)
  64 {
  65         struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  66         const u8 *secret = kpp_tfm_ctx(tfm);
  67         u8 public_key[CURVE25519_KEY_SIZE];
  68         u8 buf[CURVE25519_KEY_SIZE];
  69         int copied, nbytes;
  70         u8 const *bp;
  71
  72         if (req->src) {
  73                 copied = sg_copy_to_buffer(req->src,
  74                                            sg_nents_for_len(req->src,
  75                                                             CURVE25519_KEY_SIZE),
  76                                            public_key, CURVE25519_KEY_SIZE);
  77                 if (copied != CURVE25519_KEY_SIZE)
  78                         return -EINVAL;
  79                 bp = public_key;
  80         } else {
  81                 bp = curve25519_base_point;
  82         }
  83
  84         curve25519_arch(buf, secret, bp);
  85
  86         /* might want less than we've got */
  87         nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
  88         copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
  89                                                                 nbytes),
  90                                      buf, nbytes);
  91         if (copied != nbytes)
  92                 return -EINVAL;
  93         return 0;
  94 }
  95
  96 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
  97 {
  98         return CURVE25519_KEY_SIZE;
  99 }
 100
 101 static struct kpp_alg curve25519_alg = {
 102         .base.cra_name          = "curve25519",
 103         .base.cra_driver_name   = "curve25519-neon",
 104         .base.cra_priority      = 200,
 105         .base.cra_module        = THIS_MODULE,
 106         .base.cra_ctxsize       = CURVE25519_KEY_SIZE,
 107
 108         .set_secret             = curve25519_set_secret,
 109         .generate_public_key    = curve25519_compute_value,
 110         .compute_shared_secret  = curve25519_compute_value,
 111         .max_size               = curve25519_max_size,
 112 };
 113
 114 static int __init mod_init(void)
 115 {
 116         if (elf_hwcap & HWCAP_NEON) {
 117                 static_branch_enable(&have_neon);
 118                 return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
 119                         crypto_register_kpp(&curve25519_alg) : 0;
 120         }
 121         return 0;
 122 }
 123
 124 static void __exit mod_exit(void)
 125 {
 126         if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
 127                 crypto_unregister_kpp(&curve25519_alg);
 128 }
 129
 130 module_init(mod_init);
 131 module_exit(mod_exit);
 132
 133 MODULE_ALIAS_CRYPTO("curve25519");
 134 MODULE_ALIAS_CRYPTO("curve25519-neon");
 135 MODULE_LICENSE("GPL v2");