// SPDX-License-Identifier: GPL-2.0-or-later
/* ECDH key-agreement protocol
 *
 * Copyright (c) 2016, Intel Corporation
 * Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
 */

#include <linux/module.h>
#include <crypto/internal/kpp.h>
#include <crypto/kpp.h>
#include <crypto/ecdh.h>
#include <linux/scatterlist.h>
#include "ecc.h"

struct ecdh_ctx {
        unsigned int curve_id;
        unsigned int ndigits;
        u64 private_key[ECC_MAX_DIGITS];
};

static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
{
        return kpp_tfm_ctx(tfm);
}

static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
                           unsigned int len)
{
        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
        struct ecdh params;

        if (crypto_ecdh_decode_key(buf, len, &params) < 0 ||
            params.key_size > sizeof(u64) * ctx->ndigits)
                return -EINVAL;

        if (!params.key || !params.key_size)
                return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
                                       ctx->private_key);

        memcpy(ctx->private_key, params.key, params.key_size);

        if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
                             ctx->private_key, params.key_size) < 0) {
                memzero_explicit(ctx->private_key, params.key_size);
                return -EINVAL;
        }
        return 0;
}

static int ecdh_compute_value(struct kpp_request *req)
{
        struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
        u64 *public_key;
        u64 *shared_secret = NULL;
        void *buf;
        size_t copied, nbytes, public_key_sz;
        int ret = -ENOMEM;

        nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
        /* Public part is a point thus it has both coordinates */
        public_key_sz = 2 * nbytes;

        public_key = kmalloc(public_key_sz, GFP_KERNEL);
        if (!public_key)
                return -ENOMEM;

        if (req->src) {
                shared_secret = kmalloc(nbytes, GFP_KERNEL);
                if (!shared_secret)
                        goto free_pubkey;

                /* from here on it's invalid parameters */
                ret = -EINVAL;

                /* must have exactly two points to be on the curve */
                if (public_key_sz != req->src_len)
                        goto free_all;

                copied = sg_copy_to_buffer(req->src,
                                           sg_nents_for_len(req->src,
                                                            public_key_sz),
                                           public_key, public_key_sz);
                if (copied != public_key_sz)
                        goto free_all;

                ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
                                                ctx->private_key, public_key,
                                                shared_secret);

                buf = shared_secret;
        } else {
                ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
                                       ctx->private_key, public_key);
                buf = public_key;
                nbytes = public_key_sz;
        }

        if (ret < 0)
                goto free_all;

        /* might want less than we've got */
        nbytes = min_t(size_t, nbytes, req->dst_len);
        copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
                                                                nbytes),
                                     buf, nbytes);
        if (copied != nbytes)
                ret = -EINVAL;

        /* fall through */
free_all:
        kfree_sensitive(shared_secret);
free_pubkey:
        kfree(public_key);
        return ret;
}

static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
{
        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);

        /* Public key is made of two coordinates, add one to the left shift */
        return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
}

static int ecdh_nist_p192_init_tfm(struct crypto_kpp *tfm)
{
        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);

        ctx->curve_id = ECC_CURVE_NIST_P192;
        ctx->ndigits = ECC_CURVE_NIST_P192_DIGITS;

        return 0;
}

static struct kpp_alg ecdh_nist_p192 = {
        .set_secret = ecdh_set_secret,
        .generate_public_key = ecdh_compute_value,
        .compute_shared_secret = ecdh_compute_value,
        .max_size = ecdh_max_size,
        .init = ecdh_nist_p192_init_tfm,
        .base = {
                .cra_name = "ecdh-nist-p192",
                .cra_driver_name = "ecdh-generic",
                .cra_priority = 100,
                .cra_module = THIS_MODULE,
                .cra_ctxsize = sizeof(struct ecdh_ctx),
        },
};

static int ecdh_nist_p256_init_tfm(struct crypto_kpp *tfm)
{
        struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);

        ctx->curve_id = ECC_CURVE_NIST_P256;
        ctx->ndigits = ECC_CURVE_NIST_P256_DIGITS;

        return 0;
}

static struct kpp_alg ecdh_nist_p256 = {
        .set_secret = ecdh_set_secret,
        .generate_public_key = ecdh_compute_value,
        .compute_shared_secret = ecdh_compute_value,
        .max_size = ecdh_max_size,
        .init = ecdh_nist_p256_init_tfm,
        .base = {
                .cra_name = "ecdh-nist-p256",
                .cra_driver_name = "ecdh-generic",
                .cra_priority = 100,
                .cra_module = THIS_MODULE,
                .cra_ctxsize = sizeof(struct ecdh_ctx),
        },
};

static bool ecdh_nist_p192_registered;

static int ecdh_init(void)
{
        int ret;

        ret = crypto_register_kpp(&ecdh_nist_p192);
        ecdh_nist_p192_registered = ret == 0;

        return crypto_register_kpp(&ecdh_nist_p256);
}

static void ecdh_exit(void)
{
        if (ecdh_nist_p192_registered)
                crypto_unregister_kpp(&ecdh_nist_p192);
        crypto_unregister_kpp(&ecdh_nist_p256);
}

subsys_initcall(ecdh_init);
module_exit(ecdh_exit);
MODULE_ALIAS_CRYPTO("ecdh");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ECDH generic algorithm");