1/* $OpenBSD: bcrypt_pbkdf.c,v 1.4 2013/07/29 00:55:53 tedu Exp $ */ 2/* 3 * Copyright (c) 2013 Ted Unangst <tedu@openbsd.org> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18#include "includes.h" 19__RCSID("$NetBSD: bcrypt_pbkdf.c,v 1.4 2017/04/18 18:41:46 christos Exp $"); 20 21#ifndef HAVE_BCRYPT_PBKDF 22 23#include <sys/types.h> 24#include <sys/param.h> 25 26#ifdef HAVE_STDLIB_H 27# include <stdlib.h> 28#endif 29#include <string.h> 30 31#ifdef HAVE_BLF_H 32# include <blf.h> 33#endif 34 35#include "crypto_api.h" 36#include <stdio.h> 37#include <time.h> 38#include "misc.h" 39#define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 40 41/* 42 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 43 * 44 * The bcrypt hash function is derived from the bcrypt password hashing 45 * function with the following modifications: 46 * 1. The input password and salt are preprocessed with SHA512. 47 * 2. The output length is expanded to 256 bits. 48 * 3. Subsequently the magic string to be encrypted is lengthened and modifed 49 * to "OxychromaticBlowfishSwatDynamite" 50 * 4. The hash function is defined to perform 64 rounds of initial state 51 * expansion. (More rounds are performed by iterating the hash.) 52 * 53 * Note that this implementation pulls the SHA512 operations into the caller 54 * as a performance optimization. 55 * 56 * One modification from official pbkdf2. Instead of outputting key material 57 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 58 * generate (i.e.) 512 bits of key material for use as two 256 bit keys, an 59 * attacker can merely run once through the outer loop below, but the user 60 * always runs it twice. Shuffling output bytes requires computing the 61 * entirety of the key material to assemble any subkey. This is something a 62 * wise caller could do; we just do it for you. 63 */ 64 65#define BCRYPT_BLOCKS 8 66#define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4) 67 68static void 69bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 70{ 71 blf_ctx state; 72 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 73 "OxychromaticBlowfishSwatDynamite"; 74 uint32_t cdata[BCRYPT_BLOCKS]; 75 int i; 76 uint16_t j; 77 size_t shalen = SHA512_DIGEST_LENGTH; 78 79 /* key expansion */ 80 Blowfish_initstate(&state); 81 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 82 for (i = 0; i < 64; i++) { 83 Blowfish_expand0state(&state, sha2salt, shalen); 84 Blowfish_expand0state(&state, sha2pass, shalen); 85 } 86 87 /* encryption */ 88 j = 0; 89 for (i = 0; i < BCRYPT_BLOCKS; i++) 90 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 91 &j); 92 for (i = 0; i < 64; i++) 93 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 94 95 /* copy out */ 96 for (i = 0; i < BCRYPT_BLOCKS; i++) { 97 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 98 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 99 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 100 out[4 * i + 0] = cdata[i] & 0xff; 101 } 102 103 /* zap */ 104 memset(ciphertext, 0, sizeof(ciphertext)); 105 memset(cdata, 0, sizeof(cdata)); 106 memset(&state, 0, sizeof(state)); 107} 108 109int 110bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 111 u_int8_t *key, size_t keylen, unsigned int rounds) 112{ 113 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 114 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 115 u_int8_t out[BCRYPT_HASHSIZE]; 116 u_int8_t tmpout[BCRYPT_HASHSIZE]; 117 u_int8_t *countsalt; 118 size_t i, j, amt, stride; 119 uint32_t count; 120 121 /* nothing crazy */ 122 if (rounds < 1) 123 return -1; 124 if (passlen == 0 || saltlen == 0 || keylen == 0 || 125 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 126 return -1; 127 if ((countsalt = calloc(1, saltlen + 4)) == NULL) 128 return -1; 129 stride = (keylen + sizeof(out) - 1) / sizeof(out); 130 amt = (keylen + stride - 1) / stride; 131 132 memcpy(countsalt, salt, saltlen); 133 134 /* collapse password */ 135 crypto_hash_sha512(sha2pass, (const u_char *)pass, passlen); 136 137 /* generate key, sizeof(out) at a time */ 138 for (count = 1; keylen > 0; count++) { 139 countsalt[saltlen + 0] = (count >> 24) & 0xff; 140 countsalt[saltlen + 1] = (count >> 16) & 0xff; 141 countsalt[saltlen + 2] = (count >> 8) & 0xff; 142 countsalt[saltlen + 3] = count & 0xff; 143 144 /* first round, salt is salt */ 145 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 146 147 bcrypt_hash(sha2pass, sha2salt, tmpout); 148 memcpy(out, tmpout, sizeof(out)); 149 150 for (i = 1; i < rounds; i++) { 151 /* subsequent rounds, salt is previous output */ 152 crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 153 bcrypt_hash(sha2pass, sha2salt, tmpout); 154 for (j = 0; j < sizeof(out); j++) 155 out[j] ^= tmpout[j]; 156 } 157 158 /* 159 * pbkdf2 deviation: ouput the key material non-linearly. 160 */ 161 amt = MIN(amt, keylen); 162 for (i = 0; i < amt; i++) 163 key[i * stride + (count - 1)] = out[i]; 164 keylen -= amt; 165 } 166 167 /* zap */ 168 memset(out, 0, sizeof(out)); 169 memset(countsalt, 0, saltlen + 4); 170 free(countsalt); 171 172 return 0; 173} 174#endif /* HAVE_BCRYPT_PBKDF */ 175