163 lines
3.7 KiB
C
163 lines
3.7 KiB
C
/* ECDH key-agreement protocol
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*
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* Copyright (c) 2016, Intel Corporation
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* Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <crypto/internal/kpp.h>
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#include <crypto/kpp.h>
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#include <crypto/ecdh.h>
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#include <linux/scatterlist.h>
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#include "ecc.h"
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struct ecdh_ctx {
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unsigned int curve_id;
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unsigned int ndigits;
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u64 private_key[ECC_MAX_DIGITS];
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};
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static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
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{
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return kpp_tfm_ctx(tfm);
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}
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static unsigned int ecdh_supported_curve(unsigned int curve_id)
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{
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switch (curve_id) {
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case ECC_CURVE_NIST_P192: return 3;
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case ECC_CURVE_NIST_P256: return 4;
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default: return 0;
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}
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}
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static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
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unsigned int len)
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{
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struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
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struct ecdh params;
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unsigned int ndigits;
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if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0)
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return -EINVAL;
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ndigits = ecdh_supported_curve(params.curve_id);
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if (!ndigits)
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return -EINVAL;
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ctx->curve_id = params.curve_id;
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ctx->ndigits = ndigits;
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if (!params.key || !params.key_size)
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return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
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ctx->private_key);
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if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
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(const u64 *)params.key, params.key_size) < 0)
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return -EINVAL;
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memcpy(ctx->private_key, params.key, params.key_size);
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return 0;
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}
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static int ecdh_compute_value(struct kpp_request *req)
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{
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struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
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struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
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u64 *public_key;
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u64 *shared_secret = NULL;
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void *buf;
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size_t copied, nbytes, public_key_sz;
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int ret = -ENOMEM;
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nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
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/* Public part is a point thus it has both coordinates */
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public_key_sz = 2 * nbytes;
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public_key = kmalloc(public_key_sz, GFP_KERNEL);
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if (!public_key)
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return -ENOMEM;
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if (req->src) {
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shared_secret = kmalloc(nbytes, GFP_KERNEL);
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if (!shared_secret)
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goto free_pubkey;
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copied = sg_copy_to_buffer(req->src, 1, public_key,
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public_key_sz);
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if (copied != public_key_sz) {
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ret = -EINVAL;
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goto free_all;
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}
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ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
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ctx->private_key, public_key,
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shared_secret);
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buf = shared_secret;
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} else {
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ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits,
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ctx->private_key, public_key);
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buf = public_key;
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nbytes = public_key_sz;
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}
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if (ret < 0)
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goto free_all;
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copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes);
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if (copied != nbytes)
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ret = -EINVAL;
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/* fall through */
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free_all:
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kzfree(shared_secret);
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free_pubkey:
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kfree(public_key);
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return ret;
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}
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static unsigned int ecdh_max_size(struct crypto_kpp *tfm)
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{
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struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
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/* Public key is made of two coordinates, add one to the left shift */
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return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1);
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}
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static struct kpp_alg ecdh = {
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.set_secret = ecdh_set_secret,
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.generate_public_key = ecdh_compute_value,
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.compute_shared_secret = ecdh_compute_value,
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.max_size = ecdh_max_size,
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.base = {
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.cra_name = "ecdh",
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.cra_driver_name = "ecdh-generic",
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.cra_priority = 100,
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.cra_module = THIS_MODULE,
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.cra_ctxsize = sizeof(struct ecdh_ctx),
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},
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};
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static int ecdh_init(void)
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{
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return crypto_register_kpp(&ecdh);
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}
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static void ecdh_exit(void)
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{
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crypto_unregister_kpp(&ecdh);
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}
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module_init(ecdh_init);
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module_exit(ecdh_exit);
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MODULE_ALIAS_CRYPTO("ecdh");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("ECDH generic algorithm");
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