LXR linux/net/bluetooth/ecdh

   1/*
   2 * ECDH helper functions - KPP wrappings
   3 *
   4 * Copyright (C) 2017 Intel Corporation
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation;
   9 *
  10 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  11 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  12 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
  13 * IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
  14 * CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
  15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18 *
  19 * ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
  20 * COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
  21 * SOFTWARE IS DISCLAIMED.
  22 */
  23#include "ecdh_helper.h"
  24
  25#include <linux/scatterlist.h>
  26#include <crypto/ecdh.h>
  27
  28struct ecdh_completion {
  29        struct completion completion;
  30        int err;
  31};
  32
  33static void ecdh_complete(struct crypto_async_request *req, int err)
  34{
  35        struct ecdh_completion *res = req->data;
  36
  37        if (err == -EINPROGRESS)
  38                return;
  39
  40        res->err = err;
  41        complete(&res->completion);
  42}
  43
  44static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits)
  45{
  46        int i;
  47
  48        for (i = 0; i < ndigits; i++)
  49                out[i] = __swab64(in[ndigits - 1 - i]);
  50}
  51
  52/* compute_ecdh_secret() - function assumes that the private key was
  53 *                         already set.
  54 * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
  55 * @public_key:   pair's ecc public key.
  56 * secret:        memory where the ecdh computed shared secret will be saved.
  57 *
  58 * Return: zero on success; error code in case of error.
  59 */
  60int compute_ecdh_secret(struct crypto_kpp *tfm, const u8 public_key[64],
  61                        u8 secret[32])
  62{
  63        struct kpp_request *req;
  64        u8 *tmp;
  65        struct ecdh_completion result;
  66        struct scatterlist src, dst;
  67        int err;
  68
  69        tmp = kmalloc(64, GFP_KERNEL);
  70        if (!tmp)
  71                return -ENOMEM;
  72
  73        req = kpp_request_alloc(tfm, GFP_KERNEL);
  74        if (!req) {
  75                err = -ENOMEM;
  76                goto free_tmp;
  77        }
  78
  79        init_completion(&result.completion);
  80
  81        swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */
  82        swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */
  83
  84        sg_init_one(&src, tmp, 64);
  85        sg_init_one(&dst, secret, 32);
  86        kpp_request_set_input(req, &src, 64);
  87        kpp_request_set_output(req, &dst, 32);
  88        kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
  89                                 ecdh_complete, &result);
  90        err = crypto_kpp_compute_shared_secret(req);
  91        if (err == -EINPROGRESS) {
  92                wait_for_completion(&result.completion);
  93                err = result.err;
  94        }
  95        if (err < 0) {
  96                pr_err("alg: ecdh: compute shared secret failed. err %d\n",
  97                       err);
  98                goto free_all;
  99        }
 100
 101        swap_digits((u64 *)secret, (u64 *)tmp, 4);
 102        memcpy(secret, tmp, 32);
 103
 104free_all:
 105        kpp_request_free(req);
 106free_tmp:
 107        kzfree(tmp);
 108        return err;
 109}
 110
 111/* set_ecdh_privkey() - set or generate ecc private key.
 112 *
 113 * Function generates an ecc private key in the crypto subsystem when receiving
 114 * a NULL private key or sets the received key when not NULL.
 115 *
 116 * @tfm:           KPP tfm handle allocated with crypto_alloc_kpp().
 117 * @private_key:   user's ecc private key. When not NULL, the key is expected
 118 *                 in little endian format.
 119 *
 120 * Return: zero on success; error code in case of error.
 121 */
 122int set_ecdh_privkey(struct crypto_kpp *tfm, const u8 private_key[32])
 123{
 124        u8 *buf, *tmp = NULL;
 125        unsigned int buf_len;
 126        int err;
 127        struct ecdh p = {0};
 128
 129        p.curve_id = ECC_CURVE_NIST_P256;
 130
 131        if (private_key) {
 132                tmp = kmalloc(32, GFP_KERNEL);
 133                if (!tmp)
 134                        return -ENOMEM;
 135                swap_digits((u64 *)private_key, (u64 *)tmp, 4);
 136                p.key = tmp;
 137                p.key_size = 32;
 138        }
 139
 140        buf_len = crypto_ecdh_key_len(&p);
 141        buf = kmalloc(buf_len, GFP_KERNEL);
 142        if (!buf) {
 143                err = -ENOMEM;
 144                goto free_tmp;
 145        }
 146
 147        err = crypto_ecdh_encode_key(buf, buf_len, &p);
 148        if (err)
 149                goto free_all;
 150
 151        err = crypto_kpp_set_secret(tfm, buf, buf_len);
 152        /* fall through */
 153free_all:
 154        kzfree(buf);
 155free_tmp:
 156        kzfree(tmp);
 157        return err;
 158}
 159
 160/* generate_ecdh_public_key() - function assumes that the private key was
 161 *                              already set.
 162 *
 163 * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
 164 * @public_key:   memory where the computed ecc public key will be saved.
 165 *
 166 * Return: zero on success; error code in case of error.
 167 */
 168int generate_ecdh_public_key(struct crypto_kpp *tfm, u8 public_key[64])
 169{
 170        struct kpp_request *req;
 171        u8 *tmp;
 172        struct ecdh_completion result;
 173        struct scatterlist dst;
 174        int err;
 175
 176        tmp = kmalloc(64, GFP_KERNEL);
 177        if (!tmp)
 178                return -ENOMEM;
 179
 180        req = kpp_request_alloc(tfm, GFP_KERNEL);
 181        if (!req) {
 182                err = -ENOMEM;
 183                goto free_tmp;
 184        }
 185
 186        init_completion(&result.completion);
 187        sg_init_one(&dst, tmp, 64);
 188        kpp_request_set_input(req, NULL, 0);
 189        kpp_request_set_output(req, &dst, 64);
 190        kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
 191                                 ecdh_complete, &result);
 192
 193        err = crypto_kpp_generate_public_key(req);
 194        if (err == -EINPROGRESS) {
 195                wait_for_completion(&result.completion);
 196                err = result.err;
 197        }
 198        if (err < 0)
 199                goto free_all;
 200
 201        /* The public key is handed back in little endian as expected by
 202         * the Security Manager Protocol.
 203         */
 204        swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */
 205        swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */
 206
 207free_all:
 208        kpp_request_free(req);
 209free_tmp:
 210        kfree(tmp);
 211        return err;
 212}
 213
 214/* generate_ecdh_keys() - generate ecc key pair.
 215 *
 216 * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
 217 * @public_key:   memory where the computed ecc public key will be saved.
 218 *
 219 * Return: zero on success; error code in case of error.
 220 */
 221int generate_ecdh_keys(struct crypto_kpp *tfm, u8 public_key[64])
 222{
 223        int err;
 224
 225        err = set_ecdh_privkey(tfm, NULL);
 226        if (err)
 227                return err;
 228
 229        return generate_ecdh_public_key(tfm, public_key);
 230}
 231