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/kpp.h> 27 #include <crypto/ecdh.h> 28 29 struct ecdh_completion { 30 struct completion completion; 31 int err; 32 }; 33 34 static void ecdh_complete(struct crypto_async_request *req, int err) 35 { 36 struct ecdh_completion *res = req->data; 37 38 if (err == -EINPROGRESS) 39 return; 40 41 res->err = err; 42 complete(&res->completion); 43 } 44 45 static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits) 46 { 47 int i; 48 49 for (i = 0; i < ndigits; i++) 50 out[i] = __swab64(in[ndigits - 1 - i]); 51 } 52 53 bool compute_ecdh_secret(const u8 public_key[64], const u8 private_key[32], 54 u8 secret[32]) 55 { 56 struct crypto_kpp *tfm; 57 struct kpp_request *req; 58 struct ecdh p; 59 struct ecdh_completion result; 60 struct scatterlist src, dst; 61 u8 *tmp, *buf; 62 unsigned int buf_len; 63 int err = -ENOMEM; 64 65 tmp = kmalloc(64, GFP_KERNEL); 66 if (!tmp) 67 return false; 68 69 tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0); 70 if (IS_ERR(tfm)) { 71 pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n", 72 PTR_ERR(tfm)); 73 goto free_tmp; 74 } 75 76 req = kpp_request_alloc(tfm, GFP_KERNEL); 77 if (!req) 78 goto free_kpp; 79 80 init_completion(&result.completion); 81 82 /* Security Manager Protocol holds digits in litte-endian order 83 * while ECC API expect big-endian data 84 */ 85 swap_digits((u64 *)private_key, (u64 *)tmp, 4); 86 p.key = (char *)tmp; 87 p.key_size = 32; 88 /* Set curve_id */ 89 p.curve_id = ECC_CURVE_NIST_P256; 90 buf_len = crypto_ecdh_key_len(&p); 91 buf = kmalloc(buf_len, GFP_KERNEL); 92 if (!buf) 93 goto free_req; 94 95 crypto_ecdh_encode_key(buf, buf_len, &p); 96 97 /* Set A private Key */ 98 err = crypto_kpp_set_secret(tfm, (void *)buf, buf_len); 99 if (err) 100 goto free_all; 101 102 swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */ 103 swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */ 104 105 sg_init_one(&src, tmp, 64); 106 sg_init_one(&dst, secret, 32); 107 kpp_request_set_input(req, &src, 64); 108 kpp_request_set_output(req, &dst, 32); 109 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, 110 ecdh_complete, &result); 111 err = crypto_kpp_compute_shared_secret(req); 112 if (err == -EINPROGRESS) { 113 wait_for_completion(&result.completion); 114 err = result.err; 115 } 116 if (err < 0) { 117 pr_err("alg: ecdh: compute shared secret failed. err %d\n", 118 err); 119 goto free_all; 120 } 121 122 swap_digits((u64 *)secret, (u64 *)tmp, 4); 123 memcpy(secret, tmp, 32); 124 125 free_all: 126 kzfree(buf); 127 free_req: 128 kpp_request_free(req); 129 free_kpp: 130 crypto_free_kpp(tfm); 131 free_tmp: 132 kfree(tmp); 133 return (err == 0); 134 } 135 136 bool generate_ecdh_keys(u8 public_key[64], u8 private_key[32]) 137 { 138 struct crypto_kpp *tfm; 139 struct kpp_request *req; 140 struct ecdh p; 141 struct ecdh_completion result; 142 struct scatterlist dst; 143 u8 *tmp, *buf; 144 unsigned int buf_len; 145 int err = -ENOMEM; 146 const unsigned short max_tries = 16; 147 unsigned short tries = 0; 148 149 tmp = kmalloc(64, GFP_KERNEL); 150 if (!tmp) 151 return false; 152 153 tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0); 154 if (IS_ERR(tfm)) { 155 pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n", 156 PTR_ERR(tfm)); 157 goto free_tmp; 158 } 159 160 req = kpp_request_alloc(tfm, GFP_KERNEL); 161 if (!req) 162 goto free_kpp; 163 164 init_completion(&result.completion); 165 166 /* Set curve_id */ 167 p.curve_id = ECC_CURVE_NIST_P256; 168 p.key_size = 32; 169 buf_len = crypto_ecdh_key_len(&p); 170 buf = kmalloc(buf_len, GFP_KERNEL); 171 if (!buf) 172 goto free_req; 173 174 do { 175 if (tries++ >= max_tries) 176 goto free_all; 177 178 /* Set private Key */ 179 p.key = (char *)private_key; 180 crypto_ecdh_encode_key(buf, buf_len, &p); 181 err = crypto_kpp_set_secret(tfm, buf, buf_len); 182 if (err) 183 goto free_all; 184 185 sg_init_one(&dst, tmp, 64); 186 kpp_request_set_input(req, NULL, 0); 187 kpp_request_set_output(req, &dst, 64); 188 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, 189 ecdh_complete, &result); 190 191 err = crypto_kpp_generate_public_key(req); 192 193 if (err == -EINPROGRESS) { 194 wait_for_completion(&result.completion); 195 err = result.err; 196 } 197 198 /* Private key is not valid. Regenerate */ 199 if (err == -EINVAL) 200 continue; 201 202 if (err < 0) 203 goto free_all; 204 else 205 break; 206 207 } while (true); 208 209 /* Keys are handed back in little endian as expected by Security 210 * Manager Protocol 211 */ 212 swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */ 213 swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */ 214 swap_digits((u64 *)private_key, (u64 *)tmp, 4); 215 memcpy(private_key, tmp, 32); 216 217 free_all: 218 kzfree(buf); 219 free_req: 220 kpp_request_free(req); 221 free_kpp: 222 crypto_free_kpp(tfm); 223 free_tmp: 224 kfree(tmp); 225 return (err == 0); 226 } 227