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 static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits)
  29 {
  30         int i;
  31
  32         for (i = 0; i < ndigits; i++)
  33                 out[i] = __swab64(in[ndigits - 1 - i]);
  34 }
  35
  36 /* compute_ecdh_secret() - function assumes that the private key was
  37  *                         already set.
  38  * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
  39  * @public_key:   pair's ecc public key.
  40  * secret:        memory where the ecdh computed shared secret will be saved.
  41  *
  42  * Return: zero on success; error code in case of error.
  43  */
  44 int compute_ecdh_secret(struct crypto_kpp *tfm, const u8 public_key[64],
  45                         u8 secret[32])
  46 {
  47         DECLARE_CRYPTO_WAIT(result);
  48         struct kpp_request *req;
  49         u8 *tmp;
  50         struct scatterlist src, dst;
  51         int err;
  52
  53         tmp = kmalloc(64, GFP_KERNEL);
  54         if (!tmp)
  55                 return -ENOMEM;
  56
  57         req = kpp_request_alloc(tfm, GFP_KERNEL);
  58         if (!req) {
  59                 err = -ENOMEM;
  60                 goto free_tmp;
  61         }
  62
  63         swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */
  64         swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */
  65
  66         sg_init_one(&src, tmp, 64);
  67         sg_init_one(&dst, secret, 32);
  68         kpp_request_set_input(req, &src, 64);
  69         kpp_request_set_output(req, &dst, 32);
  70         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
  71                                  crypto_req_done, &result);
  72         err = crypto_kpp_compute_shared_secret(req);
  73         err = crypto_wait_req(err, &result);
  74         if (err < 0) {
  75                 pr_err("alg: ecdh: compute shared secret failed. err %d\n",
  76                        err);
  77                 goto free_all;
  78         }
  79
  80         swap_digits((u64 *)secret, (u64 *)tmp, 4);
  81         memcpy(secret, tmp, 32);
  82
  83 free_all:
  84         kpp_request_free(req);
  85 free_tmp:
  86         kfree_sensitive(tmp);
  87         return err;
  88 }
  89
  90 /* set_ecdh_privkey() - set or generate ecc private key.
  91  *
  92  * Function generates an ecc private key in the crypto subsystem when receiving
  93  * a NULL private key or sets the received key when not NULL.
  94  *
  95  * @tfm:           KPP tfm handle allocated with crypto_alloc_kpp().
  96  * @private_key:   user's ecc private key. When not NULL, the key is expected
  97  *                 in little endian format.
  98  *
  99  * Return: zero on success; error code in case of error.
 100  */
 101 int set_ecdh_privkey(struct crypto_kpp *tfm, const u8 private_key[32])
 102 {
 103         u8 *buf, *tmp = NULL;
 104         unsigned int buf_len;
 105         int err;
 106         struct ecdh p = {0};
 107
 108         if (private_key) {
 109                 tmp = kmalloc(32, GFP_KERNEL);
 110                 if (!tmp)
 111                         return -ENOMEM;
 112                 swap_digits((u64 *)private_key, (u64 *)tmp, 4);
 113                 p.key = tmp;
 114                 p.key_size = 32;
 115         }
 116
 117         buf_len = crypto_ecdh_key_len(&p);
 118         buf = kmalloc(buf_len, GFP_KERNEL);
 119         if (!buf) {
 120                 err = -ENOMEM;
 121                 goto free_tmp;
 122         }
 123
 124         err = crypto_ecdh_encode_key(buf, buf_len, &p);
 125         if (err)
 126                 goto free_all;
 127
 128         err = crypto_kpp_set_secret(tfm, buf, buf_len);
 129         /* fall through */
 130 free_all:
 131         kfree_sensitive(buf);
 132 free_tmp:
 133         kfree_sensitive(tmp);
 134         return err;
 135 }
 136
 137 /* generate_ecdh_public_key() - function assumes that the private key was
 138  *                              already set.
 139  *
 140  * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
 141  * @public_key:   memory where the computed ecc public key will be saved.
 142  *
 143  * Return: zero on success; error code in case of error.
 144  */
 145 int generate_ecdh_public_key(struct crypto_kpp *tfm, u8 public_key[64])
 146 {
 147         DECLARE_CRYPTO_WAIT(result);
 148         struct kpp_request *req;
 149         u8 *tmp;
 150         struct scatterlist dst;
 151         int err;
 152
 153         tmp = kmalloc(64, GFP_KERNEL);
 154         if (!tmp)
 155                 return -ENOMEM;
 156
 157         req = kpp_request_alloc(tfm, GFP_KERNEL);
 158         if (!req) {
 159                 err = -ENOMEM;
 160                 goto free_tmp;
 161         }
 162
 163         sg_init_one(&dst, tmp, 64);
 164         kpp_request_set_input(req, NULL, 0);
 165         kpp_request_set_output(req, &dst, 64);
 166         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
 167                                  crypto_req_done, &result);
 168
 169         err = crypto_kpp_generate_public_key(req);
 170         err = crypto_wait_req(err, &result);
 171         if (err < 0)
 172                 goto free_all;
 173
 174         /* The public key is handed back in little endian as expected by
 175          * the Security Manager Protocol.
 176          */
 177         swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */
 178         swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */
 179
 180 free_all:
 181         kpp_request_free(req);
 182 free_tmp:
 183         kfree(tmp);
 184         return err;
 185 }
 186
 187 /* generate_ecdh_keys() - generate ecc key pair.
 188  *
 189  * @tfm:          KPP tfm handle allocated with crypto_alloc_kpp().
 190  * @public_key:   memory where the computed ecc public key will be saved.
 191  *
 192  * Return: zero on success; error code in case of error.
 193  */
 194 int generate_ecdh_keys(struct crypto_kpp *tfm, u8 public_key[64])
 195 {
 196         int err;
 197
 198         err = set_ecdh_privkey(tfm, NULL);
 199         if (err)
 200                 return err;
 201
 202         return generate_ecdh_public_key(tfm, public_key);
 203 }