crypto/ecdh.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* ECDH key-agreement protocol
   3  *
   4  * Copyright (c) 2016, Intel Corporation
   5  * Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <crypto/internal/ecc.h>
  10 #include <crypto/internal/kpp.h>
  11 #include <crypto/kpp.h>
  12 #include <crypto/ecdh.h>
  13 #include <linux/scatterlist.h>
  14
  15 struct ecdh_ctx {
  16         unsigned int curve_id;
  17         unsigned int ndigits;
  18         u64 private_key[ECC_MAX_DIGITS];
  19 };
  20
  21 static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
  22 {
  23         return kpp_tfm_ctx(tfm);
  24 }
  25
  26 static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
  27                            unsigned int len)
  28 {
  29         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
  30         struct ecdh params;
  31         int ret = 0;
  32
  33         if (crypto_ecdh_decode_key(buf, len, &params) < 0 ||
  34             params.key_size > sizeof(u64) * ctx->ndigits)
  35                 return -EINVAL;
  36
  37         memset(ctx->private_key, 0, sizeof(ctx->private_key));
  38
  39         if (!params.key || !params.key_size)
  40                 return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
  41                                        ctx->private_key);
  42
  43         ecc_digits_from_bytes(params.key, params.key_size,
  44                               ctx->private_key, ctx->ndigits);
  45
  46         if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
  47                              ctx->private_key, params.key_size) < 0) {
  48                 memzero_explicit(ctx->private_key, params.key_size);
  49                 ret = -EINVAL;
  50         }
  51
  52         return ret;
  53 }
  54
  55 static int ecdh_compute_value(struct kpp_request *req)
  56 {
  57         struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  58         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
  59         u64 *public_key;
  60         u64 *shared_secret = NULL;
  61         void *buf;
  62         size_t copied, nbytes, public_key_sz;
  63         int ret = -ENOMEM;
  64
  65         nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
  66         /* Public part is a point thus it has both coordinates */
  67         public_key_sz = 2 * nbytes;
  68
  69         public_key = kmalloc(public_key_sz, GFP_KERNEL);
  70         if (!public_key)
  71                 return -ENOMEM;
  72
  73         if (req->src) {
  74                 shared_secret = kmalloc(nbytes, GFP_KERNEL);
  75                 if (!shared_secret)
  76                         goto free_pubkey;
  77
  78                 /* from here on it's invalid parameters */
  79                 ret = -EINVAL;
  80
  81                 /* must have exactly two points to be on the curve */
  82                 if (public_key_sz != req->src_len)
  83                         goto free_all;
  84
  85                 copied = sg_copy_to_buffer(req->src,
  86                                            sg_nents_for_len(req->src,
  87                                                             public_key_sz),
  88                                            public_key, public_key_sz);
  89                 if (copied != public_key_sz)
  90                         goto free_all;
  91
  92                 ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
  93                                                 ctx->private_key, public_key,
  94                                                 shared_secret);
  95
  96                 buf = shared_secret;
  97         } else {
  98                 ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
  99                                        ctx->private_key, public_key);
 100                 buf = public_key;
 101                 nbytes = public_key_sz;
 102         }
 103
 104         if (ret < 0)
 105                 goto free_all;
 106
 107         /* might want less than we've got */
 108         nbytes = min_t(size_t, nbytes, req->dst_len);
 109         copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
 110                                                                 nbytes),
 111                                      buf, nbytes);
 112         if (copied != nbytes)
 113                 ret = -EINVAL;
 114
 115         /* fall through */
 116 free_all:
 117         kfree_sensitive(shared_secret);
 118 free_pubkey:
 119         kfree(public_key);
 120         return ret;
 121 }
 122
 123 static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
 124 {
 125         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
 126
 127         /* Public key is made of two coordinates, add one to the left shift */
 128         return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
 129 }
 130
 131 static int ecdh_nist_p192_init_tfm(struct crypto_kpp *tfm)
 132 {
 133         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
 134
 135         ctx->curve_id = ECC_CURVE_NIST_P192;
 136         ctx->ndigits = ECC_CURVE_NIST_P192_DIGITS;
 137
 138         return 0;
 139 }
 140
 141 static struct kpp_alg ecdh_nist_p192 = {
 142         .set_secret = ecdh_set_secret,
 143         .generate_public_key = ecdh_compute_value,
 144         .compute_shared_secret = ecdh_compute_value,
 145         .max_size = ecdh_max_size,
 146         .init = ecdh_nist_p192_init_tfm,
 147         .base = {
 148                 .cra_name = "ecdh-nist-p192",
 149                 .cra_driver_name = "ecdh-nist-p192-generic",
 150                 .cra_priority = 100,
 151                 .cra_module = THIS_MODULE,
 152                 .cra_ctxsize = sizeof(struct ecdh_ctx),
 153         },
 154 };
 155
 156 static int ecdh_nist_p256_init_tfm(struct crypto_kpp *tfm)
 157 {
 158         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
 159
 160         ctx->curve_id = ECC_CURVE_NIST_P256;
 161         ctx->ndigits = ECC_CURVE_NIST_P256_DIGITS;
 162
 163         return 0;
 164 }
 165
 166 static struct kpp_alg ecdh_nist_p256 = {
 167         .set_secret = ecdh_set_secret,
 168         .generate_public_key = ecdh_compute_value,
 169         .compute_shared_secret = ecdh_compute_value,
 170         .max_size = ecdh_max_size,
 171         .init = ecdh_nist_p256_init_tfm,
 172         .base = {
 173                 .cra_name = "ecdh-nist-p256",
 174                 .cra_driver_name = "ecdh-nist-p256-generic",
 175                 .cra_priority = 100,
 176                 .cra_module = THIS_MODULE,
 177                 .cra_ctxsize = sizeof(struct ecdh_ctx),
 178         },
 179 };
 180
 181 static int ecdh_nist_p384_init_tfm(struct crypto_kpp *tfm)
 182 {
 183         struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
 184
 185         ctx->curve_id = ECC_CURVE_NIST_P384;
 186         ctx->ndigits = ECC_CURVE_NIST_P384_DIGITS;
 187
 188         return 0;
 189 }
 190
 191 static struct kpp_alg ecdh_nist_p384 = {
 192         .set_secret = ecdh_set_secret,
 193         .generate_public_key = ecdh_compute_value,
 194         .compute_shared_secret = ecdh_compute_value,
 195         .max_size = ecdh_max_size,
 196         .init = ecdh_nist_p384_init_tfm,
 197         .base = {
 198                 .cra_name = "ecdh-nist-p384",
 199                 .cra_driver_name = "ecdh-nist-p384-generic",
 200                 .cra_priority = 100,
 201                 .cra_module = THIS_MODULE,
 202                 .cra_ctxsize = sizeof(struct ecdh_ctx),
 203         },
 204 };
 205
 206 static bool ecdh_nist_p192_registered;
 207
 208 static int __init ecdh_init(void)
 209 {
 210         int ret;
 211
 212         /* NIST p192 will fail to register in FIPS mode */
 213         ret = crypto_register_kpp(&ecdh_nist_p192);
 214         ecdh_nist_p192_registered = ret == 0;
 215
 216         ret = crypto_register_kpp(&ecdh_nist_p256);
 217         if (ret)
 218                 goto nist_p256_error;
 219
 220         ret = crypto_register_kpp(&ecdh_nist_p384);
 221         if (ret)
 222                 goto nist_p384_error;
 223
 224         return 0;
 225
 226 nist_p384_error:
 227         crypto_unregister_kpp(&ecdh_nist_p256);
 228
 229 nist_p256_error:
 230         if (ecdh_nist_p192_registered)
 231                 crypto_unregister_kpp(&ecdh_nist_p192);
 232         return ret;
 233 }
 234
 235 static void __exit ecdh_exit(void)
 236 {
 237         if (ecdh_nist_p192_registered)
 238                 crypto_unregister_kpp(&ecdh_nist_p192);
 239         crypto_unregister_kpp(&ecdh_nist_p256);
 240         crypto_unregister_kpp(&ecdh_nist_p384);
 241 }
 242
 243 subsys_initcall(ecdh_init);
 244 module_exit(ecdh_exit);
 245 MODULE_ALIAS_CRYPTO("ecdh");
 246 MODULE_LICENSE("GPL");
 247 MODULE_DESCRIPTION("ECDH generic algorithm");