1 /* 2 * Written by Stephen Henson for the OpenSSL project. 3 */ 4 /* ==================================================================== 5 * Copyright (c) 2013 The OpenSSL Project. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in 16 * the documentation and/or other materials provided with the 17 * distribution. 18 * 19 * 3. All advertising materials mentioning features or use of this 20 * software must display the following acknowledgment: 21 * "This product includes software developed by the OpenSSL Project 22 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23 * 24 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25 * endorse or promote products derived from this software without 26 * prior written permission. For written permission, please contact 27 * openssl-core@openssl.org. 28 * 29 * 5. Products derived from this software may not be called "OpenSSL" 30 * nor may "OpenSSL" appear in their names without prior written 31 * permission of the OpenSSL Project. 32 * 33 * 6. Redistributions of any form whatsoever must retain the following 34 * acknowledgment: 35 * "This product includes software developed by the OpenSSL Project 36 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37 * 38 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49 * OF THE POSSIBILITY OF SUCH DAMAGE. 50 * ==================================================================== 51 */ 52 53 #include <string.h> 54 55 #include <openssl/ec.h> 56 #include <openssl/evp.h> 57 58 #include "ech_locl.h" 59 60 /* 61 * Key derivation function from X9.63/SECG. 62 */ 63 64 /* Way more than we will ever need */ 65 #define ECDH_KDF_MAX (1 << 30) 66 67 int 68 ecdh_KDF_X9_63(unsigned char *out, size_t outlen, const unsigned char *Z, 69 size_t Zlen, const unsigned char *sinfo, size_t sinfolen, const EVP_MD *md) 70 { 71 EVP_MD_CTX *mctx = NULL; 72 unsigned int i; 73 size_t mdlen; 74 unsigned char ctr[4]; 75 int rv = 0; 76 77 if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX || 78 Zlen > ECDH_KDF_MAX) 79 return 0; 80 mctx = EVP_MD_CTX_new(); 81 if (mctx == NULL) 82 return 0; 83 mdlen = EVP_MD_size(md); 84 for (i = 1;; i++) { 85 unsigned char mtmp[EVP_MAX_MD_SIZE]; 86 if (!EVP_DigestInit_ex(mctx, md, NULL)) 87 goto err; 88 ctr[3] = i & 0xFF; 89 ctr[2] = (i >> 8) & 0xFF; 90 ctr[1] = (i >> 16) & 0xFF; 91 ctr[0] = (i >> 24) & 0xFF; 92 if (!EVP_DigestUpdate(mctx, Z, Zlen)) 93 goto err; 94 if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr))) 95 goto err; 96 if (!EVP_DigestUpdate(mctx, sinfo, sinfolen)) 97 goto err; 98 if (outlen >= mdlen) { 99 if (!EVP_DigestFinal(mctx, out, NULL)) 100 goto err; 101 outlen -= mdlen; 102 if (outlen == 0) 103 break; 104 out += mdlen; 105 } else { 106 if (!EVP_DigestFinal(mctx, mtmp, NULL)) 107 goto err; 108 memcpy(out, mtmp, outlen); 109 explicit_bzero(mtmp, mdlen); 110 break; 111 } 112 } 113 rv = 1; 114 115 err: 116 EVP_MD_CTX_free(mctx); 117 118 return rv; 119 } 120