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 20 #ifndef HAVE_BCRYPT_PBKDF 21 22 #include <sys/types.h> 23 #include <sys/param.h> 24 25 #ifdef HAVE_STDLIB_H 26 # include <stdlib.h> 27 #endif 28 #include <string.h> 29 30 #ifdef HAVE_BLF_H 31 # include <blf.h> 32 #endif 33 34 #include "crypto_api.h" 35 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 36 37 /* 38 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 39 * 40 * The bcrypt hash function is derived from the bcrypt password hashing 41 * function with the following modifications: 42 * 1. The input password and salt are preprocessed with SHA512. 43 * 2. The output length is expanded to 256 bits. 44 * 3. Subsequently the magic string to be encrypted is lengthened and modifed 45 * to "OxychromaticBlowfishSwatDynamite" 46 * 4. The hash function is defined to perform 64 rounds of initial state 47 * expansion. (More rounds are performed by iterating the hash.) 48 * 49 * Note that this implementation pulls the SHA512 operations into the caller 50 * as a performance optimization. 51 * 52 * One modification from official pbkdf2. Instead of outputting key material 53 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 54 * generate (i.e.) 512 bits of key material for use as two 256 bit keys, an 55 * attacker can merely run once through the outer loop below, but the user 56 * always runs it twice. Shuffling output bytes requires computing the 57 * entirety of the key material to assemble any subkey. This is something a 58 * wise caller could do; we just do it for you. 59 */ 60 61 #define BCRYPT_BLOCKS 8 62 #define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4) 63 64 static void 65 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 66 { 67 blf_ctx state; 68 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 69 "OxychromaticBlowfishSwatDynamite"; 70 uint32_t cdata[BCRYPT_BLOCKS]; 71 int i; 72 uint16_t j; 73 size_t shalen = SHA512_DIGEST_LENGTH; 74 75 /* key expansion */ 76 Blowfish_initstate(&state); 77 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 78 for (i = 0; i < 64; i++) { 79 Blowfish_expand0state(&state, sha2salt, shalen); 80 Blowfish_expand0state(&state, sha2pass, shalen); 81 } 82 83 /* encryption */ 84 j = 0; 85 for (i = 0; i < BCRYPT_BLOCKS; i++) 86 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 87 &j); 88 for (i = 0; i < 64; i++) 89 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 90 91 /* copy out */ 92 for (i = 0; i < BCRYPT_BLOCKS; i++) { 93 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 94 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 95 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 96 out[4 * i + 0] = cdata[i] & 0xff; 97 } 98 99 /* zap */ 100 memset(ciphertext, 0, sizeof(ciphertext)); 101 memset(cdata, 0, sizeof(cdata)); 102 memset(&state, 0, sizeof(state)); 103 } 104 105 int 106 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 107 u_int8_t *key, size_t keylen, unsigned int rounds) 108 { 109 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 110 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 111 u_int8_t out[BCRYPT_HASHSIZE]; 112 u_int8_t tmpout[BCRYPT_HASHSIZE]; 113 u_int8_t *countsalt; 114 size_t i, j, amt, stride; 115 uint32_t count; 116 117 /* nothing crazy */ 118 if (rounds < 1) 119 return -1; 120 if (passlen == 0 || saltlen == 0 || keylen == 0 || 121 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 122 return -1; 123 if ((countsalt = calloc(1, saltlen + 4)) == NULL) 124 return -1; 125 stride = (keylen + sizeof(out) - 1) / sizeof(out); 126 amt = (keylen + stride - 1) / stride; 127 128 memcpy(countsalt, salt, saltlen); 129 130 /* collapse password */ 131 crypto_hash_sha512(sha2pass, pass, passlen); 132 133 /* generate key, sizeof(out) at a time */ 134 for (count = 1; keylen > 0; count++) { 135 countsalt[saltlen + 0] = (count >> 24) & 0xff; 136 countsalt[saltlen + 1] = (count >> 16) & 0xff; 137 countsalt[saltlen + 2] = (count >> 8) & 0xff; 138 countsalt[saltlen + 3] = count & 0xff; 139 140 /* first round, salt is salt */ 141 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 142 143 bcrypt_hash(sha2pass, sha2salt, tmpout); 144 memcpy(out, tmpout, sizeof(out)); 145 146 for (i = 1; i < rounds; i++) { 147 /* subsequent rounds, salt is previous output */ 148 crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 149 bcrypt_hash(sha2pass, sha2salt, tmpout); 150 for (j = 0; j < sizeof(out); j++) 151 out[j] ^= tmpout[j]; 152 } 153 154 /* 155 * pbkdf2 deviation: ouput the key material non-linearly. 156 */ 157 amt = MIN(amt, keylen); 158 for (i = 0; i < amt; i++) 159 key[i * stride + (count - 1)] = out[i]; 160 keylen -= amt; 161 } 162 163 /* zap */ 164 memset(out, 0, sizeof(out)); 165 memset(countsalt, 0, saltlen + 4); 166 free(countsalt); 167 168 return 0; 169 } 170 #endif /* HAVE_BCRYPT_PBKDF */ 171