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 pr_err("alg: kpp: Failed to allocate %d bytes for buf\n", 94 buf_len); 95 goto free_req; 96 } 97 crypto_ecdh_encode_key(buf, buf_len, &p); 98 99 /* Set A private Key */ 100 err = crypto_kpp_set_secret(tfm, (void *)buf, buf_len); 101 if (err) 102 goto free_all; 103 104 swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */ 105 swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */ 106 107 sg_init_one(&src, tmp, 64); 108 sg_init_one(&dst, secret, 32); 109 kpp_request_set_input(req, &src, 64); 110 kpp_request_set_output(req, &dst, 32); 111 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, 112 ecdh_complete, &result); 113 err = crypto_kpp_compute_shared_secret(req); 114 if (err == -EINPROGRESS) { 115 wait_for_completion(&result.completion); 116 err = result.err; 117 } 118 if (err < 0) { 119 pr_err("alg: ecdh: compute shared secret failed. err %d\n", 120 err); 121 goto free_all; 122 } 123 124 swap_digits((u64 *)secret, (u64 *)tmp, 4); 125 memcpy(secret, tmp, 32); 126 127 free_all: 128 kzfree(buf); 129 free_req: 130 kpp_request_free(req); 131 free_kpp: 132 crypto_free_kpp(tfm); 133 free_tmp: 134 kfree(tmp); 135 return (err == 0); 136 } 137 138 bool generate_ecdh_keys(u8 public_key[64], u8 private_key[32]) 139 { 140 struct crypto_kpp *tfm; 141 struct kpp_request *req; 142 struct ecdh p; 143 struct ecdh_completion result; 144 struct scatterlist dst; 145 u8 *tmp, *buf; 146 unsigned int buf_len; 147 int err = -ENOMEM; 148 const unsigned short max_tries = 16; 149 unsigned short tries = 0; 150 151 tmp = kmalloc(64, GFP_KERNEL); 152 if (!tmp) 153 return false; 154 155 tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0); 156 if (IS_ERR(tfm)) { 157 pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n", 158 PTR_ERR(tfm)); 159 goto free_tmp; 160 } 161 162 req = kpp_request_alloc(tfm, GFP_KERNEL); 163 if (!req) 164 goto free_kpp; 165 166 init_completion(&result.completion); 167 168 /* Set curve_id */ 169 p.curve_id = ECC_CURVE_NIST_P256; 170 p.key_size = 32; 171 buf_len = crypto_ecdh_key_len(&p); 172 buf = kmalloc(buf_len, GFP_KERNEL); 173 if (!buf) { 174 pr_err("alg: kpp: Failed to allocate %d bytes for buf\n", 175 buf_len); 176 goto free_req; 177 } 178 179 do { 180 if (tries++ >= max_tries) 181 goto free_all; 182 183 /* Set private Key */ 184 p.key = (char *)private_key; 185 crypto_ecdh_encode_key(buf, buf_len, &p); 186 err = crypto_kpp_set_secret(tfm, buf, buf_len); 187 if (err) 188 goto free_all; 189 190 sg_init_one(&dst, tmp, 64); 191 kpp_request_set_input(req, NULL, 0); 192 kpp_request_set_output(req, &dst, 64); 193 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, 194 ecdh_complete, &result); 195 196 err = crypto_kpp_generate_public_key(req); 197 198 if (err == -EINPROGRESS) { 199 wait_for_completion(&result.completion); 200 err = result.err; 201 } 202 203 /* Private key is not valid. Regenerate */ 204 if (err == -EINVAL) 205 continue; 206 207 if (err < 0) 208 goto free_all; 209 else 210 break; 211 212 } while (true); 213 214 /* Keys are handed back in little endian as expected by Security 215 * Manager Protocol 216 */ 217 swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */ 218 swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */ 219 swap_digits((u64 *)private_key, (u64 *)tmp, 4); 220 memcpy(private_key, tmp, 32); 221 222 free_all: 223 kzfree(buf); 224 free_req: 225 kpp_request_free(req); 226 free_kpp: 227 crypto_free_kpp(tfm); 228 free_tmp: 229 kfree(tmp); 230 return (err == 0); 231 } 232