bcrypt_pbkdf.c revision 1.5
1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.4 2013/07/29 00:55:53 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 __RCSID("$NetBSD: bcrypt_pbkdf.c,v 1.5 2026/04/09 06:36:39 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 #ifndef SHA512_DIGEST_LENGTH 40 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 41 #endif 42 43 /* 44 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 45 * 46 * The bcrypt hash function is derived from the bcrypt password hashing 47 * function with the following modifications: 48 * 1. The input password and salt are preprocessed with SHA512. 49 * 2. The output length is expanded to 256 bits. 50 * 3. Subsequently the magic string to be encrypted is lengthened and modifed 51 * to "OxychromaticBlowfishSwatDynamite" 52 * 4. The hash function is defined to perform 64 rounds of initial state 53 * expansion. (More rounds are performed by iterating the hash.) 54 * 55 * Note that this implementation pulls the SHA512 operations into the caller 56 * as a performance optimization. 57 * 58 * One modification from official pbkdf2. Instead of outputting key material 59 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 60 * generate (i.e.) 512 bits of key material for use as two 256 bit keys, an 61 * attacker can merely run once through the outer loop below, but the user 62 * always runs it twice. Shuffling output bytes requires computing the 63 * entirety of the key material to assemble any subkey. This is something a 64 * wise caller could do; we just do it for you. 65 */ 66 67 #define BCRYPT_BLOCKS 8 68 #define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4) 69 70 static void 71 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 72 { 73 blf_ctx state; 74 u_int8_t ciphertext[BCRYPT_HASHSIZE] = 75 "OxychromaticBlowfishSwatDynamite"; 76 uint32_t cdata[BCRYPT_BLOCKS]; 77 int i; 78 uint16_t j; 79 size_t shalen = SHA512_DIGEST_LENGTH; 80 81 /* key expansion */ 82 Blowfish_initstate(&state); 83 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 84 for (i = 0; i < 64; i++) { 85 Blowfish_expand0state(&state, sha2salt, shalen); 86 Blowfish_expand0state(&state, sha2pass, shalen); 87 } 88 89 /* encryption */ 90 j = 0; 91 for (i = 0; i < BCRYPT_BLOCKS; i++) 92 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 93 &j); 94 for (i = 0; i < 64; i++) 95 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 96 97 /* copy out */ 98 for (i = 0; i < BCRYPT_BLOCKS; i++) { 99 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 100 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 101 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 102 out[4 * i + 0] = cdata[i] & 0xff; 103 } 104 105 /* zap */ 106 memset(ciphertext, 0, sizeof(ciphertext)); 107 memset(cdata, 0, sizeof(cdata)); 108 memset(&state, 0, sizeof(state)); 109 } 110 111 int 112 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 113 u_int8_t *key, size_t keylen, unsigned int rounds) 114 { 115 u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 116 u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 117 u_int8_t out[BCRYPT_HASHSIZE]; 118 u_int8_t tmpout[BCRYPT_HASHSIZE]; 119 u_int8_t *countsalt; 120 size_t i, j, amt, stride; 121 uint32_t count; 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, (const u_char *)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: ouput the key material non-linearly. 162 */ 163 amt = MIN(amt, keylen); 164 for (i = 0; i < amt; i++) 165 key[i * stride + (count - 1)] = out[i]; 166 keylen -= amt; 167 } 168 169 /* zap */ 170 memset(out, 0, sizeof(out)); 171 memset(countsalt, 0, saltlen + 4); 172 free(countsalt); 173 174 return 0; 175 } 176 #endif /* HAVE_BCRYPT_PBKDF */ 177
Indexes created Tue Oct 27 00:25:24 UTC 2026