1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.9 2014/07/13 21:21:25 tedu Exp $ */ 2 /* 3 * Copyright (c) 2013 Ted Unangst <tedu (at) 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 /* 41 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 42 * 43 * The bcrypt hash function is derived from the bcrypt password hashing 44 * function with the following modifications: 45 * 1. The input password and salt are preprocessed with SHA512. 46 * 2. The output length is expanded to 256 bits. 47 * 3. Subsequently the magic string to be encrypted is lengthened and modifed 48 * to "OxychromaticBlowfishSwatDynamite" 49 * 4. The hash function is defined to perform 64 rounds of initial state 50 * expansion. (More rounds are performed by iterating the hash.) 51 * 52 * Note that this implementation pulls the SHA512 operations into the caller 53 * as a performance optimization. 54 * 55 * One modification from official pbkdf2. Instead of outputting key material 56 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 57 * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an 58 * attacker can merely run once through the outer loop, but the user 59 * always runs it twice. Shuffling output bytes requires computing the 60 * entirety of the key material to assemble any subkey. This is something a 61 * wise caller could do; we just do it for you. 62 */ 63 64 #define BCRYPT_BLOCKS 8 65 #define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4) 66 67 static void 68 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 69 { 70 blf_ctx state; 71 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 72 "OxychromaticBlowfishSwatDynamite"; 73 uint32_t cdata[BCRYPT_BLOCKS]; 74 int i; 75 uint16_t j; 76 size_t shalen = SHA512_DIGEST_LENGTH; 77 78 /* key expansion */ 79 Blowfish_initstate(&state); 80 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 81 for (i = 0; i < 64; i++) { 82 Blowfish_expand0state(&state, sha2salt, shalen); 83 Blowfish_expand0state(&state, sha2pass, shalen); 84 } 85 86 /* encryption */ 87 j = 0; 88 for (i = 0; i < BCRYPT_BLOCKS; i++) 89 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 90 &j); 91 for (i = 0; i < 64; i++) 92 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 93 94 /* copy out */ 95 for (i = 0; i < BCRYPT_BLOCKS; i++) { 96 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 97 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 98 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 99 out[4 * i + 0] = cdata[i] & 0xff; 100 } 101 102 /* zap */ 103 explicit_bzero(ciphertext, sizeof(ciphertext)); 104 explicit_bzero(cdata, sizeof(cdata)); 105 explicit_bzero(&state, sizeof(state)); 106 } 107 108 int 109 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 110 u_int8_t *key, size_t keylen, unsigned int rounds) 111 { 112 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 113 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 114 u_int8_t out[BCRYPT_HASHSIZE]; 115 u_int8_t tmpout[BCRYPT_HASHSIZE]; 116 u_int8_t *countsalt; 117 size_t i, j, amt, stride; 118 uint32_t count; 119 size_t origkeylen = keylen; 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, 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 size_t dest = i * stride + (count - 1); 164 if (dest >= origkeylen) 165 break; 166 key[dest] = out[i]; 167 } 168 keylen -= i; 169 } 170 171 /* zap */ 172 explicit_bzero(out, sizeof(out)); 173 free(countsalt); 174 175 return 0; 176 } 177 #endif /* HAVE_BCRYPT_PBKDF */ 178
