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![Tudor Ambarus](/assets/img/avatar_default.png)
That Bluetooth SMP knows about the private key is pointless, since the detection of debug key usage is actually via the public key portion. With this patch, the Bluetooth SMP will stop keeping a copy of the ecdh private key and will let the crypto subsystem to generate and handle the ecdh private key, potentially benefiting of hardware ecc private key generation and retention. The loop that tries to generate a correct private key is now removed and we trust the crypto subsystem to generate a correct private key. This backup logic should be done in crypto, if really needed. Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
230 lines
5.9 KiB
C
230 lines
5.9 KiB
C
/*
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* ECDH helper functions - KPP wrappings
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*
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* Copyright (C) 2017 Intel Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation;
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
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* CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
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* COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
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* SOFTWARE IS DISCLAIMED.
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*/
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#include "ecdh_helper.h"
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#include <linux/scatterlist.h>
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#include <crypto/ecdh.h>
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struct ecdh_completion {
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struct completion completion;
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int err;
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};
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static void ecdh_complete(struct crypto_async_request *req, int err)
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{
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struct ecdh_completion *res = req->data;
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if (err == -EINPROGRESS)
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return;
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res->err = err;
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complete(&res->completion);
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}
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static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits)
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{
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int i;
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for (i = 0; i < ndigits; i++)
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out[i] = __swab64(in[ndigits - 1 - i]);
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}
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/* compute_ecdh_secret() - function assumes that the private key was
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* already set.
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* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
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* @public_key: pair's ecc public key.
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* secret: memory where the ecdh computed shared secret will be saved.
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*
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* Return: zero on success; error code in case of error.
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*/
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int compute_ecdh_secret(struct crypto_kpp *tfm, const u8 public_key[64],
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u8 secret[32])
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{
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struct kpp_request *req;
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u8 *tmp;
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struct ecdh_completion result;
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struct scatterlist src, dst;
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int err;
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tmp = kmalloc(64, GFP_KERNEL);
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if (!tmp)
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return -ENOMEM;
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req = kpp_request_alloc(tfm, GFP_KERNEL);
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if (!req) {
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err = -ENOMEM;
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goto free_tmp;
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}
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init_completion(&result.completion);
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swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */
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swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */
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sg_init_one(&src, tmp, 64);
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sg_init_one(&dst, secret, 32);
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kpp_request_set_input(req, &src, 64);
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kpp_request_set_output(req, &dst, 32);
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kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
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ecdh_complete, &result);
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err = crypto_kpp_compute_shared_secret(req);
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if (err == -EINPROGRESS) {
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wait_for_completion(&result.completion);
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err = result.err;
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}
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if (err < 0) {
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pr_err("alg: ecdh: compute shared secret failed. err %d\n",
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err);
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goto free_all;
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}
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swap_digits((u64 *)secret, (u64 *)tmp, 4);
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memcpy(secret, tmp, 32);
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free_all:
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kpp_request_free(req);
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free_tmp:
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kzfree(tmp);
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return err;
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}
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/* set_ecdh_privkey() - set or generate ecc private key.
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*
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* Function generates an ecc private key in the crypto subsystem when receiving
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* a NULL private key or sets the received key when not NULL.
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*
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* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
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* @private_key: user's ecc private key. When not NULL, the key is expected
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* in little endian format.
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*
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* Return: zero on success; error code in case of error.
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*/
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int set_ecdh_privkey(struct crypto_kpp *tfm, const u8 private_key[32])
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{
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u8 *buf, *tmp = NULL;
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unsigned int buf_len;
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int err;
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struct ecdh p = {0};
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p.curve_id = ECC_CURVE_NIST_P256;
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if (private_key) {
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tmp = kmalloc(32, GFP_KERNEL);
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if (!tmp)
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return -ENOMEM;
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swap_digits((u64 *)private_key, (u64 *)tmp, 4);
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p.key = tmp;
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p.key_size = 32;
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}
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buf_len = crypto_ecdh_key_len(&p);
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buf = kmalloc(buf_len, GFP_KERNEL);
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if (!buf) {
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err = -ENOMEM;
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goto free_tmp;
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}
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err = crypto_ecdh_encode_key(buf, buf_len, &p);
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if (err)
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goto free_all;
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err = crypto_kpp_set_secret(tfm, buf, buf_len);
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/* fall through */
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free_all:
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kzfree(buf);
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free_tmp:
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kzfree(tmp);
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return err;
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}
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/* generate_ecdh_public_key() - function assumes that the private key was
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* already set.
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*
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* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
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* @public_key: memory where the computed ecc public key will be saved.
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*
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* Return: zero on success; error code in case of error.
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*/
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int generate_ecdh_public_key(struct crypto_kpp *tfm, u8 public_key[64])
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{
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struct kpp_request *req;
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u8 *tmp;
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struct ecdh_completion result;
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struct scatterlist dst;
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int err;
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tmp = kmalloc(64, GFP_KERNEL);
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if (!tmp)
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return -ENOMEM;
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req = kpp_request_alloc(tfm, GFP_KERNEL);
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if (!req) {
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err = -ENOMEM;
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goto free_tmp;
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}
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init_completion(&result.completion);
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sg_init_one(&dst, tmp, 64);
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kpp_request_set_input(req, NULL, 0);
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kpp_request_set_output(req, &dst, 64);
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kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
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ecdh_complete, &result);
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err = crypto_kpp_generate_public_key(req);
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if (err == -EINPROGRESS) {
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wait_for_completion(&result.completion);
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err = result.err;
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}
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if (err < 0)
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goto free_all;
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/* The public key is handed back in little endian as expected by
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* the Security Manager Protocol.
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*/
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swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */
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swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */
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free_all:
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kpp_request_free(req);
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free_tmp:
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kfree(tmp);
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return err;
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}
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/* generate_ecdh_keys() - generate ecc key pair.
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*
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* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
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* @public_key: memory where the computed ecc public key will be saved.
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*
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* Return: zero on success; error code in case of error.
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*/
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int generate_ecdh_keys(struct crypto_kpp *tfm, u8 public_key[64])
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{
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int err;
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err = set_ecdh_privkey(tfm, NULL);
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if (err)
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return err;
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return generate_ecdh_public_key(tfm, public_key);
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}
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