1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.16 2020/08/02 18:35:48 tb 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 /* This version has been modified to use SHA512 from SUPERCOP */ 21 22 #include "includes.h" 23 24 #ifndef HAVE_BCRYPT_PBKDF 25 26 #include <sys/types.h> 27 28 #ifdef HAVE_STDLIB_H 29 # include <stdlib.h> 30 #endif 31 #include <string.h> 32 33 #ifdef HAVE_BLF_H 34 # include <blf.h> 35 #endif 36 37 #include "crypto_api.h" 38 #ifdef SHA512_DIGEST_LENGTH 39 # undef SHA512_DIGEST_LENGTH 40 #endif 41 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 42 43 #define MINIMUM(a,b) (((a) < (b)) ? (a) : (b)) 44 45 /* 46 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 47 * 48 * The bcrypt hash function is derived from the bcrypt password hashing 49 * function with the following modifications: 50 * 1. The input password and salt are preprocessed with SHA512. 51 * 2. The output length is expanded to 256 bits. 52 * 3. Subsequently the magic string to be encrypted is lengthened and modifed 53 * to "OxychromaticBlowfishSwatDynamite" 54 * 4. The hash function is defined to perform 64 rounds of initial state 55 * expansion. (More rounds are performed by iterating the hash.) 56 * 57 * Note that this implementation pulls the SHA512 operations into the caller 58 * as a performance optimization. 59 * 60 * One modification from official pbkdf2. Instead of outputting key material 61 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 62 * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an 63 * attacker can merely run once through the outer loop, but the user 64 * always runs it twice. Shuffling output bytes requires computing the 65 * entirety of the key material to assemble any subkey. This is something a 66 * wise caller could do; we just do it for you. 67 */ 68 69 #define BCRYPT_WORDS 8 70 #define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4) 71 72 static void 73 bcrypt_hash(uint8_t *sha2pass, uint8_t *sha2salt, uint8_t *out) 74 { 75 blf_ctx state; 76 uint8_t ciphertext[BCRYPT_HASHSIZE] = 77 "OxychromaticBlowfishSwatDynamite"; 78 uint32_t cdata[BCRYPT_WORDS]; 79 int i; 80 uint16_t j; 81 size_t shalen = SHA512_DIGEST_LENGTH; 82 83 /* key expansion */ 84 Blowfish_initstate(&state); 85 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 86 for (i = 0; i < 64; i++) { 87 Blowfish_expand0state(&state, sha2salt, shalen); 88 Blowfish_expand0state(&state, sha2pass, shalen); 89 } 90 91 /* encryption */ 92 j = 0; 93 for (i = 0; i < BCRYPT_WORDS; i++) 94 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 95 &j); 96 for (i = 0; i < 64; i++) 97 blf_enc(&state, cdata, BCRYPT_WORDS / 2); 98 99 /* copy out */ 100 for (i = 0; i < BCRYPT_WORDS; i++) { 101 out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 102 out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 103 out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 104 out[4 * i + 0] = cdata[i] & 0xff; 105 } 106 107 /* zap */ 108 explicit_bzero(ciphertext, sizeof(ciphertext)); 109 explicit_bzero(cdata, sizeof(cdata)); 110 explicit_bzero(&state, sizeof(state)); 111 } 112 113 int 114 bcrypt_pbkdf(const char *pass, size_t passlen, const uint8_t *salt, size_t saltlen, 115 uint8_t *key, size_t keylen, unsigned int rounds) 116 { 117 uint8_t sha2pass[SHA512_DIGEST_LENGTH]; 118 uint8_t sha2salt[SHA512_DIGEST_LENGTH]; 119 uint8_t out[BCRYPT_HASHSIZE]; 120 uint8_t tmpout[BCRYPT_HASHSIZE]; 121 uint8_t *countsalt; 122 size_t i, j, amt, stride; 123 uint32_t count; 124 size_t origkeylen = keylen; 125 126 /* nothing crazy */ 127 if (rounds < 1) 128 goto bad; 129 if (passlen == 0 || saltlen == 0 || keylen == 0 || 130 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 131 goto bad; 132 if ((countsalt = calloc(1, saltlen + 4)) == NULL) 133 goto bad; 134 stride = (keylen + sizeof(out) - 1) / sizeof(out); 135 amt = (keylen + stride - 1) / stride; 136 137 memcpy(countsalt, salt, saltlen); 138 139 /* collapse password */ 140 crypto_hash_sha512(sha2pass, pass, passlen); 141 142 /* generate key, sizeof(out) at a time */ 143 for (count = 1; keylen > 0; count++) { 144 countsalt[saltlen + 0] = (count >> 24) & 0xff; 145 countsalt[saltlen + 1] = (count >> 16) & 0xff; 146 countsalt[saltlen + 2] = (count >> 8) & 0xff; 147 countsalt[saltlen + 3] = count & 0xff; 148 149 /* first round, salt is salt */ 150 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 151 152 bcrypt_hash(sha2pass, sha2salt, tmpout); 153 memcpy(out, tmpout, sizeof(out)); 154 155 for (i = 1; i < rounds; i++) { 156 /* subsequent rounds, salt is previous output */ 157 crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 158 bcrypt_hash(sha2pass, sha2salt, tmpout); 159 for (j = 0; j < sizeof(out); j++) 160 out[j] ^= tmpout[j]; 161 } 162 163 /* 164 * pbkdf2 deviation: output the key material non-linearly. 165 */ 166 amt = MINIMUM(amt, keylen); 167 for (i = 0; i < amt; i++) { 168 size_t dest = i * stride + (count - 1); 169 if (dest >= origkeylen) 170 break; 171 key[dest] = out[i]; 172 } 173 keylen -= i; 174 } 175 176 /* zap */ 177 freezero(countsalt, saltlen + 4); 178 explicit_bzero(out, sizeof(out)); 179 explicit_bzero(tmpout, sizeof(tmpout)); 180 181 return 0; 182 183 bad: 184 /* overwrite with random in case caller doesn't check return code */ 185 arc4random_buf(key, keylen); 186 return -1; 187 } 188 #endif /* HAVE_BCRYPT_PBKDF */ 189