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
  22 asmlinkage void curve25519_neon(u8 mypublic[CURVE25519_KEY_SIZE],
  23                                 const u8 secret[CURVE25519_KEY_SIZE],
  24                                 const u8 basepoint[CURVE25519_KEY_SIZE]);
  25
  26 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
  27
  28 void 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 }
  40 EXPORT_SYMBOL(curve25519_arch);
  41
  42 void 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 }
  47 EXPORT_SYMBOL(curve25519_base_arch);
  48
  49 static 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
  64 static 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
  97 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
  98 {
  99         return CURVE25519_KEY_SIZE;
 100 }
 101
 102 static 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
 115 static int __init mod_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
 125 static void __exit mod_exit(void)
 126 {
 127         if (IS_REACHABLE(CONFIG_CRYPTO_KPP) && elf_hwcap & HWCAP_NEON)
 128                 crypto_unregister_kpp(&curve25519_alg);
 129 }
 130
 131 module_init(mod_init);
 132 module_exit(mod_exit);
 133
 134 MODULE_ALIAS_CRYPTO("curve25519");
 135 MODULE_ALIAS_CRYPTO("curve25519-neon");
 136 MODULE_LICENSE("GPL v2");