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 } 231