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 /* OPENBSD ORIGINAL: lib/libutil/bcrypt_pbkdf.c */ 19 20 #include "includes.h" 21 22 #ifndef HAVE_BCRYPT_PBKDF 23 24 #include <sys/types.h> 25 #include <sys/param.h> 26 27 #ifdef HAVE_STDLIB_H 28 # include <stdlib.h> 29 #endif 30 #include <string.h> 31 32 #ifdef HAVE_BLF_H 33 # include <blf.h> 34 #endif 35 36 #include "crypto_api.h" 37 #ifdef SHA512_DIGEST_LENGTH 38 # undef SHA512_DIGEST_LENGTH 39 #endif 40 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 41 42 #define MINIMUM(a,b) (((a) < (b)) ? (a) : (b)) 43 44 /* 45 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 46 * 47 * The bcrypt hash function is derived from the bcrypt password hashing 48 * function with the following modifications: 49 * 1. The input password and salt are preprocessed with SHA512. 50 * 2. The output length is expanded to 256 bits. 51 * 3. Subsequently the magic string to be encrypted is lengthened and modified 52 * to "OxychromaticBlowfishSwatDynamite" 53 * 4. The hash function is defined to perform 64 rounds of initial state 54 * expansion. (More rounds are performed by iterating the hash.) 55 * 56 * Note that this implementation pulls the SHA512 operations into the caller 57 * as a performance optimization. 58 * 59 * One modification from official pbkdf2. Instead of outputting key material 60 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 61 * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an 62 * attacker can merely run once through the outer loop, but the user 63 * always runs it twice. Shuffling output bytes requires computing the 64 * entirety of the key material to assemble any subkey. This is something a 65 * wise caller could do; we just do it for you. 66 */ 67 68 #define BCRYPT_WORDS 8 69 #define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4) 70 71 static void 72 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 73 { 74 blf_ctx state; 75 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 76 "OxychromaticBlowfishSwatDynamite"; 77 uint32_t cdata[BCRYPT_WORDS]; 78 int i; 79 uint16_t j; 80 size_t shalen = SHA512_DIGEST_LENGTH; 81 82 /* key expansion */ 83 Blowfish_initstate(&state); 84 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 85 for (i = 0; i < 64; i++) { 86 Blowfish_expand0state(&state, sha2salt, shalen); 87 Blowfish_expand0state(&state, sha2pass, shalen); 88 } 89 90 /* encryption */ 91 j = 0; 92 for (i = 0; i < BCRYPT_WORDS; i++) 93 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 94 &j); 95 for (i = 0; i < 64; i++) 96 blf_enc(&state, cdata, sizeof(cdata) / (sizeof(uint64_t))); 97 98 /* copy out */ 99 for (i = 0; i < BCRYPT_WORDS; i++) { 100 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 101 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 102 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 103 out[4 * i + 0] = cdata[i] & 0xff; 104 } 105 106 /* zap */ 107 explicit_bzero(ciphertext, sizeof(ciphertext)); 108 explicit_bzero(cdata, sizeof(cdata)); 109 explicit_bzero(&state, sizeof(state)); 110 } 111 112 int 113 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 114 u_int8_t *key, size_t keylen, unsigned int rounds) 115 { 116 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 117 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 118 u_int8_t out[BCRYPT_HASHSIZE]; 119 u_int8_t tmpout[BCRYPT_HASHSIZE]; 120 u_int8_t *countsalt; 121 size_t i, j, amt, stride; 122 uint32_t count; 123 size_t origkeylen = keylen; 124 125 /* nothing crazy */ 126 if (rounds < 1) 127 return -1; 128 if (passlen == 0 || saltlen == 0 || keylen == 0 || 129 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 130 return -1; 131 if ((countsalt = calloc(1, saltlen + 4)) == NULL) 132 return -1; 133 stride = (keylen + sizeof(out) - 1) / sizeof(out); 134 amt = (keylen + stride - 1) / stride; 135 136 memcpy(countsalt, salt, saltlen); 137 138 /* collapse password */ 139 crypto_hash_sha512(sha2pass, pass, passlen); 140 141 /* generate key, sizeof(out) at a time */ 142 for (count = 1; keylen > 0; count++) { 143 countsalt[saltlen + 0] = (count >> 24) & 0xff; 144 countsalt[saltlen + 1] = (count >> 16) & 0xff; 145 countsalt[saltlen + 2] = (count >> 8) & 0xff; 146 countsalt[saltlen + 3] = count & 0xff; 147 148 /* first round, salt is salt */ 149 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 150 151 bcrypt_hash(sha2pass, sha2salt, tmpout); 152 memcpy(out, tmpout, sizeof(out)); 153 154 for (i = 1; i < rounds; i++) { 155 /* subsequent rounds, salt is previous output */ 156 crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 157 bcrypt_hash(sha2pass, sha2salt, tmpout); 158 for (j = 0; j < sizeof(out); j++) 159 out[j] ^= tmpout[j]; 160 } 161 162 /* 163 * pbkdf2 deviation: output the key material non-linearly. 164 */ 165 amt = MINIMUM(amt, keylen); 166 for (i = 0; i < amt; i++) { 167 size_t dest = i * stride + (count - 1); 168 if (dest >= origkeylen) 169 break; 170 key[dest] = out[i]; 171 } 172 keylen -= i; 173 } 174 175 /* zap */ 176 explicit_bzero(out, sizeof(out)); 177 free(countsalt); 178 179 return 0; 180 } 181 #endif /* HAVE_BCRYPT_PBKDF */ 182