1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 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 #ifdef SHA512_DIGEST_LENGTH 36 # undef SHA512_DIGEST_LENGTH 37 #endif 38 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 39 40 #define MINIMUM(a,b) (((a) < (b)) ? (a) : (b)) 41 42 /* 43 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 44 * 45 * The bcrypt hash function is derived from the bcrypt password hashing 46 * function with the following modifications: 47 * 1. The input password and salt are preprocessed with SHA512. 48 * 2. The output length is expanded to 256 bits. 49 * 3. Subsequently the magic string to be encrypted is lengthened and modified 50 * to "OxychromaticBlowfishSwatDynamite" 51 * 4. The hash function is defined to perform 64 rounds of initial state 52 * expansion. (More rounds are performed by iterating the hash.) 53 * 54 * Note that this implementation pulls the SHA512 operations into the caller 55 * as a performance optimization. 56 * 57 * One modification from official pbkdf2. Instead of outputting key material 58 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 59 * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an 60 * attacker can merely run once through the outer loop, but the user 61 * always runs it twice. Shuffling output bytes requires computing the 62 * entirety of the key material to assemble any subkey. This is something a 63 * wise caller could do; we just do it for you. 64 */ 65 66 #define BCRYPT_WORDS 8 67 #define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4) 68 69 static void 70 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 71 { 72 blf_ctx state; 73 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 74 "OxychromaticBlowfishSwatDynamite"; 75 uint32_t cdata[BCRYPT_WORDS]; 76 int i; 77 uint16_t j; 78 size_t shalen = SHA512_DIGEST_LENGTH; 79 80 /* key expansion */ 81 Blowfish_initstate(&state); 82 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 83 for (i = 0; i < 64; i++) { 84 Blowfish_expand0state(&state, sha2salt, shalen); 85 Blowfish_expand0state(&state, sha2pass, shalen); 86 } 87 88 /* encryption */ 89 j = 0; 90 for (i = 0; i < BCRYPT_WORDS; i++) 91 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 92 &j); 93 for (i = 0; i < 64; i++) 94 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 95 96 /* copy out */ 97 for (i = 0; i < BCRYPT_WORDS; i++) { 98 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 99 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 100 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 101 out[4 * i + 0] = cdata[i] & 0xff; 102 } 103 104 /* zap */ 105 explicit_bzero(ciphertext, sizeof(ciphertext)); 106 explicit_bzero(cdata, sizeof(cdata)); 107 explicit_bzero(&state, sizeof(state)); 108 } 109 110 int 111 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 112 u_int8_t *key, size_t keylen, unsigned int rounds) 113 { 114 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 115 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 116 u_int8_t out[BCRYPT_HASHSIZE]; 117 u_int8_t tmpout[BCRYPT_HASHSIZE]; 118 u_int8_t *countsalt; 119 size_t i, j, amt, stride; 120 uint32_t count; 121 size_t origkeylen = keylen; 122 123 /* nothing crazy */ 124 if (rounds < 1) 125 return -1; 126 if (passlen == 0 || saltlen == 0 || keylen == 0 || 127 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 128 return -1; 129 if ((countsalt = calloc(1, saltlen + 4)) == NULL) 130 return -1; 131 stride = (keylen + sizeof(out) - 1) / sizeof(out); 132 amt = (keylen + stride - 1) / stride; 133 134 memcpy(countsalt, salt, saltlen); 135 136 /* collapse password */ 137 crypto_hash_sha512(sha2pass, pass, passlen); 138 139 /* generate key, sizeof(out) at a time */ 140 for (count = 1; keylen > 0; count++) { 141 countsalt[saltlen + 0] = (count >> 24) & 0xff; 142 countsalt[saltlen + 1] = (count >> 16) & 0xff; 143 countsalt[saltlen + 2] = (count >> 8) & 0xff; 144 countsalt[saltlen + 3] = count & 0xff; 145 146 /* first round, salt is salt */ 147 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 148 149 bcrypt_hash(sha2pass, sha2salt, tmpout); 150 memcpy(out, tmpout, sizeof(out)); 151 152 for (i = 1; i < rounds; i++) { 153 /* subsequent rounds, salt is previous output */ 154 crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 155 bcrypt_hash(sha2pass, sha2salt, tmpout); 156 for (j = 0; j < sizeof(out); j++) 157 out[j] ^= tmpout[j]; 158 } 159 160 /* 161 * pbkdf2 deviation: output the key material non-linearly. 162 */ 163 amt = MINIMUM(amt, keylen); 164 for (i = 0; i < amt; i++) { 165 size_t dest = i * stride + (count - 1); 166 if (dest >= origkeylen) 167 break; 168 key[dest] = out[i]; 169 } 170 keylen -= i; 171 } 172 173 /* zap */ 174 explicit_bzero(out, sizeof(out)); 175 free(countsalt); 176 177 return 0; 178 } 179 #endif /* HAVE_BCRYPT_PBKDF */ 180