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/*
* ECDH helper functions - KPP wrappings
*
* Copyright (C) 2017 Intel Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
* CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
* COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
* SOFTWARE IS DISCLAIMED.
*/
#include "ecdh_helper.h"
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <crypto/kpp.h>
#include <crypto/ecdh.h>
struct ecdh_completion {
struct completion completion;
int err;
};
static void ecdh_complete(struct crypto_async_request *req, int err)
{
struct ecdh_completion *res = req->data;
if (err == -EINPROGRESS)
return;
res->err = err;
complete(&res->completion);
}
static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits)
{
int i;
for (i = 0; i < ndigits; i++)
out[i] = __swab64(in[ndigits - 1 - i]);
}
bool compute_ecdh_secret(const u8 public_key[64], const u8 private_key[32],
u8 secret[32])
{
struct crypto_kpp *tfm;
struct kpp_request *req;
struct ecdh p;
struct ecdh_completion result;
struct scatterlist src, dst;
u8 tmp[64];
u8 *buf;
unsigned int buf_len;
int err = -ENOMEM;
tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0);
if (IS_ERR(tfm)) {
pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n",
PTR_ERR(tfm));
return false;
}
req = kpp_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto free_kpp;
init_completion(&result.completion);
/* Security Manager Protocol holds digits in litte-endian order
* while ECC API expect big-endian data
*/
swap_digits((u64 *)private_key, (u64 *)tmp, 4);
p.key = (char *)tmp;
p.key_size = 32;
/* Set curve_id */
p.curve_id = ECC_CURVE_NIST_P256;
buf_len = crypto_ecdh_key_len(&p);
buf = kmalloc(buf_len, GFP_KERNEL);
if (!buf) {
pr_err("alg: kpp: Failed to allocate %d bytes for buf\n",
buf_len);
goto free_req;
}
crypto_ecdh_encode_key(buf, buf_len, &p);
/* Set A private Key */
err = crypto_kpp_set_secret(tfm, (void *)buf, buf_len);
if (err)
goto free_all;
swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */
swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */
sg_init_one(&src, tmp, 64);
sg_init_one(&dst, secret, 32);
kpp_request_set_input(req, &src, 64);
kpp_request_set_output(req, &dst, 32);
kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
ecdh_complete, &result);
err = crypto_kpp_compute_shared_secret(req);
if (err == -EINPROGRESS) {
wait_for_completion(&result.completion);
err = result.err;
}
if (err < 0) {
pr_err("alg: ecdh: compute shared secret failed. err %d\n",
err);
goto free_all;
}
swap_digits((u64 *)secret, (u64 *)tmp, 4);
memcpy(secret, tmp, 32);
free_all:
kzfree(buf);
free_req:
kpp_request_free(req);
free_kpp:
crypto_free_kpp(tfm);
return (err == 0);
}
bool generate_ecdh_keys(u8 public_key[64], u8 private_key[32])
{
struct crypto_kpp *tfm;
struct kpp_request *req;
struct ecdh p;
struct ecdh_completion result;
struct scatterlist dst;
u8 tmp[64];
u8 *buf;
unsigned int buf_len;
int err = -ENOMEM;
const unsigned short max_tries = 16;
unsigned short tries = 0;
tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0);
if (IS_ERR(tfm)) {
pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n",
PTR_ERR(tfm));
return false;
}
req = kpp_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto free_kpp;
init_completion(&result.completion);
/* Set curve_id */
p.curve_id = ECC_CURVE_NIST_P256;
p.key_size = 32;
buf_len = crypto_ecdh_key_len(&p);
buf = kmalloc(buf_len, GFP_KERNEL);
if (!buf) {
pr_err("alg: kpp: Failed to allocate %d bytes for buf\n",
buf_len);
goto free_req;
}
do {
if (tries++ >= max_tries)
goto free_all;
get_random_bytes(private_key, 32);
/* Set private Key */
p.key = (char *)private_key;
crypto_ecdh_encode_key(buf, buf_len, &p);
err = crypto_kpp_set_secret(tfm, buf, buf_len);
if (err)
goto free_all;
sg_init_one(&dst, tmp, 64);
kpp_request_set_output(req, &dst, 64);
kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
ecdh_complete, &result);
err = crypto_kpp_generate_public_key(req);
if (err == -EINPROGRESS) {
wait_for_completion(&result.completion);
err = result.err;
}
/* Private key is not valid. Regenerate */
if (err == -EINVAL)
continue;
if (err < 0)
goto free_all;
else
break;
} while (true);
/* Keys are handed back in little endian as expected by Security
* Manager Protocol
*/
swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */
swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */
swap_digits((u64 *)private_key, (u64 *)tmp, 4);
memcpy(private_key, tmp, 32);
free_all:
kzfree(buf);
free_req:
kpp_request_free(req);
free_kpp:
crypto_free_kpp(tfm);
return (err == 0);
}
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