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