LXR linux/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/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 unsigned int ecdh_supported_curve(unsigned int curve_id)
  27{
  28        switch (curve_id) {
  29        case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS;
  30        case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS;
  31        default: return 0;
  32        }
  33}
  34
  35static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
  36                           unsigned int len)
  37{
  38        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
  39        struct ecdh params;
  40        unsigned int ndigits;
  41
  42        if (crypto_ecdh_decode_key(buf, len, &params) < 0)
  43                return -EINVAL;
  44
  45        ndigits = ecdh_supported_curve(params.curve_id);
  46        if (!ndigits)
  47                return -EINVAL;
  48
  49        ctx->curve_id = params.curve_id;
  50        ctx->ndigits = ndigits;
  51
  52        if (!params.key || !params.key_size)
  53                return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
  54                                       ctx->private_key);
  55
  56        if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
  57                             (const u64 *)params.key, params.key_size) < 0)
  58                return -EINVAL;
  59
  60        memcpy(ctx->private_key, params.key, params.key_size);
  61
  62        return 0;
  63}
  64
  65static int ecdh_compute_value(struct kpp_request *req)
  66{
  67        struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
  68        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
  69        u64 *public_key;
  70        u64 *shared_secret = NULL;
  71        void *buf;
  72        size_t copied, nbytes, public_key_sz;
  73        int ret = -ENOMEM;
  74
  75        nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
  76        /* Public part is a point thus it has both coordinates */
  77        public_key_sz = 2 * nbytes;
  78
  79        public_key = kmalloc(public_key_sz, GFP_KERNEL);
  80        if (!public_key)
  81                return -ENOMEM;
  82
  83        if (req->src) {
  84                shared_secret = kmalloc(nbytes, GFP_KERNEL);
  85                if (!shared_secret)
  86                        goto free_pubkey;
  87
  88                /* from here on it's invalid parameters */
  89                ret = -EINVAL;
  90
  91                /* must have exactly two points to be on the curve */
  92                if (public_key_sz != req->src_len)
  93                        goto free_all;
  94
  95                copied = sg_copy_to_buffer(req->src,
  96                                           sg_nents_for_len(req->src,
  97                                                            public_key_sz),
  98                                           public_key, public_key_sz);
  99                if (copied != public_key_sz)
 100                        goto free_all;
 101
 102                ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
 103                                                ctx->private_key, public_key,
 104                                                shared_secret);
 105
 106                buf = shared_secret;
 107        } else {
 108                ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
 109                                       ctx->private_key, public_key);
 110                buf = public_key;
 111                nbytes = public_key_sz;
 112        }
 113
 114        if (ret < 0)
 115                goto free_all;
 116
 117        /* might want less than we've got */
 118        nbytes = min_t(size_t, nbytes, req->dst_len);
 119        copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
 120                                                                nbytes),
 121                                     buf, nbytes);
 122        if (copied != nbytes)
 123                ret = -EINVAL;
 124
 125        /* fall through */
 126free_all:
 127        kzfree(shared_secret);
 128free_pubkey:
 129        kfree(public_key);
 130        return ret;
 131}
 132
 133static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
 134{
 135        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
 136
 137        /* Public key is made of two coordinates, add one to the left shift */
 138        return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
 139}
 140
 141static struct kpp_alg ecdh = {
 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        .base = {
 147                .cra_name = "ecdh",
 148                .cra_driver_name = "ecdh-generic",
 149                .cra_priority = 100,
 150                .cra_module = THIS_MODULE,
 151                .cra_ctxsize = sizeof(struct ecdh_ctx),
 152        },
 153};
 154
 155static int ecdh_init(void)
 156{
 157        return crypto_register_kpp(&ecdh);
 158}
 159
 160static void ecdh_exit(void)
 161{
 162        crypto_unregister_kpp(&ecdh);
 163}
 164
 165subsys_initcall(ecdh_init);
 166module_exit(ecdh_exit);
 167MODULE_ALIAS_CRYPTO("ecdh");
 168MODULE_LICENSE("GPL");
 169MODULE_DESCRIPTION("ECDH generic algorithm");
 170