1/* crypto/ecdh/ec_kdf.c */ 2/* 3 * Written by Stephen Henson for the OpenSSL project. 4 */ 5/* ==================================================================== 6 * Copyright (c) 2013 The OpenSSL Project. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in 17 * the documentation and/or other materials provided with the 18 * distribution. 19 * 20 * 3. All advertising materials mentioning features or use of this 21 * software must display the following acknowledgment: 22 * "This product includes software developed by the OpenSSL Project 23 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24 * 25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26 * endorse or promote products derived from this software without 27 * prior written permission. For written permission, please contact 28 * openssl-core@openssl.org. 29 * 30 * 5. Products derived from this software may not be called "OpenSSL" 31 * nor may "OpenSSL" appear in their names without prior written 32 * permission of the OpenSSL Project. 33 * 34 * 6. Redistributions of any form whatsoever must retain the following 35 * acknowledgment: 36 * "This product includes software developed by the OpenSSL Project 37 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38 * 39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50 * OF THE POSSIBILITY OF SUCH DAMAGE. 51 * ==================================================================== 52 */ 53 54#define OPENSSL_FIPSAPI 55 56#include <string.h> 57#include <openssl/ecdh.h> 58#include <openssl/evp.h> 59 60/* Key derivation function from X9.62/SECG */ 61/* Way more than we will ever need */ 62#define ECDH_KDF_MAX (1 << 30) 63 64int ECDH_KDF_X9_62(unsigned char *out, size_t outlen, 65 const unsigned char *Z, size_t Zlen, 66 const unsigned char *sinfo, size_t sinfolen, 67 const EVP_MD *md) 68{ 69 EVP_MD_CTX mctx; 70 int rv = 0; 71 unsigned int i; 72 size_t mdlen; 73 unsigned char ctr[4]; 74 if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX 75 || Zlen > ECDH_KDF_MAX) 76 return 0; 77 mdlen = EVP_MD_size(md); 78 EVP_MD_CTX_init(&mctx); 79 for (i = 1;; i++) { 80 unsigned char mtmp[EVP_MAX_MD_SIZE]; 81 EVP_DigestInit_ex(&mctx, md, NULL); 82 ctr[3] = i & 0xFF; 83 ctr[2] = (i >> 8) & 0xFF; 84 ctr[1] = (i >> 16) & 0xFF; 85 ctr[0] = (i >> 24) & 0xFF; 86 if (!EVP_DigestUpdate(&mctx, Z, Zlen)) 87 goto err; 88 if (!EVP_DigestUpdate(&mctx, ctr, sizeof(ctr))) 89 goto err; 90 if (!EVP_DigestUpdate(&mctx, sinfo, sinfolen)) 91 goto err; 92 if (outlen >= mdlen) { 93 if (!EVP_DigestFinal(&mctx, out, NULL)) 94 goto err; 95 outlen -= mdlen; 96 if (outlen == 0) 97 break; 98 out += mdlen; 99 } else { 100 if (!EVP_DigestFinal(&mctx, mtmp, NULL)) 101 goto err; 102 memcpy(out, mtmp, outlen); 103 OPENSSL_cleanse(mtmp, mdlen); 104 break; 105 } 106 } 107 rv = 1; 108 err: 109 EVP_MD_CTX_cleanup(&mctx); 110 return rv; 111} 112