crypto/curve25519-generic.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 #include <crypto/curve25519.h>
   4 #include <crypto/internal/kpp.h>
   5 #include <crypto/kpp.h>
   6 #include <linux/module.h>
   7 #include <linux/scatterlist.h>
   8
   9 static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
  10                                  unsigned int len)
  11 {
  12         u8 *secret = kpp_tfm_ctx(tfm);
  13
  14         if (!len)
  15                 curve25519_generate_secret(secret);
  16         else if (len == CURVE25519_KEY_SIZE &&
  17                  crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
  18                 memcpy(secret, buf, CURVE25519_KEY_SIZE);
  19         else
  20                 return -EINVAL;
  21         return 0;
  22 }
  23
  24 static int curve25519_compute_value(struct kpp_request *req)
  25 {
  26         struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  27         const u8 *secret = kpp_tfm_ctx(tfm);
  28         u8 public_key[CURVE25519_KEY_SIZE];
  29         u8 buf[CURVE25519_KEY_SIZE];
  30         int copied, nbytes;
  31         u8 const *bp;
  32
  33         if (req->src) {
  34                 copied = sg_copy_to_buffer(req->src,
  35                                            sg_nents_for_len(req->src,
  36                                                             CURVE25519_KEY_SIZE),
  37                                            public_key, CURVE25519_KEY_SIZE);
  38                 if (copied != CURVE25519_KEY_SIZE)
  39                         return -EINVAL;
  40                 bp = public_key;
  41         } else {
  42                 bp = curve25519_base_point;
  43         }
  44
  45         curve25519_generic(buf, secret, bp);
  46
  47         /* might want less than we've got */
  48         nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
  49         copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
  50                                                                 nbytes),
  51                                      buf, nbytes);
  52         if (copied != nbytes)
  53                 return -EINVAL;
  54         return 0;
  55 }
  56
  57 static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
  58 {
  59         return CURVE25519_KEY_SIZE;
  60 }
  61
  62 static struct kpp_alg curve25519_alg = {
  63         .base.cra_name          = "curve25519",
  64         .base.cra_driver_name   = "curve25519-generic",
  65         .base.cra_priority      = 100,
  66         .base.cra_module        = THIS_MODULE,
  67         .base.cra_ctxsize       = CURVE25519_KEY_SIZE,
  68
  69         .set_secret             = curve25519_set_secret,
  70         .generate_public_key    = curve25519_compute_value,
  71         .compute_shared_secret  = curve25519_compute_value,
  72         .max_size               = curve25519_max_size,
  73 };
  74
  75 static int __init curve25519_init(void)
  76 {
  77         return crypto_register_kpp(&curve25519_alg);
  78 }
  79
  80 static void __exit curve25519_exit(void)
  81 {
  82         crypto_unregister_kpp(&curve25519_alg);
  83 }
  84
  85 subsys_initcall(curve25519_init);
  86 module_exit(curve25519_exit);
  87
  88 MODULE_ALIAS_CRYPTO("curve25519");
  89 MODULE_ALIAS_CRYPTO("curve25519-generic");
  90 MODULE_LICENSE("GPL");