net/bluetooth/ecdh_helper.c

   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
  28 struct ecdh_completion {
  29         struct completion completion;
  30         int err;
  31 };
  32
  33 static 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
  44 static 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  */
  60 int 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
 104 free_all:
 105         kpp_request_free(req);
 106 free_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  */
 122 int 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 */
 153 free_all:
 154         kzfree(buf);
 155 free_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  */
 168 int 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
 207 free_all:
 208         kpp_request_free(req);
 209 free_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  */
 221 int 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 }