1295367Sdes/* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 tedu Exp $ */ 2261287Sdes/* 3261287Sdes * Copyright (c) 2013 Ted Unangst <tedu@openbsd.org> 4261287Sdes * 5261287Sdes * Permission to use, copy, modify, and distribute this software for any 6261287Sdes * purpose with or without fee is hereby granted, provided that the above 7261287Sdes * copyright notice and this permission notice appear in all copies. 8261287Sdes * 9261287Sdes * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10261287Sdes * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11261287Sdes * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12261287Sdes * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13261287Sdes * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14261287Sdes * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15261287Sdes * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16261287Sdes */ 17261287Sdes 18261287Sdes#include "includes.h" 19261287Sdes 20261287Sdes#ifndef HAVE_BCRYPT_PBKDF 21261287Sdes 22261287Sdes#include <sys/types.h> 23261287Sdes#include <sys/param.h> 24261287Sdes 25261287Sdes#ifdef HAVE_STDLIB_H 26261287Sdes# include <stdlib.h> 27261287Sdes#endif 28261287Sdes#include <string.h> 29261287Sdes 30261287Sdes#ifdef HAVE_BLF_H 31261287Sdes# include <blf.h> 32261287Sdes#endif 33261287Sdes 34261287Sdes#include "crypto_api.h" 35295367Sdes#ifdef SHA512_DIGEST_LENGTH 36295367Sdes# undef SHA512_DIGEST_LENGTH 37295367Sdes#endif 38261287Sdes#define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES 39261287Sdes 40295367Sdes#define MINIMUM(a,b) (((a) < (b)) ? (a) : (b)) 41295367Sdes 42261287Sdes/* 43261287Sdes * pkcs #5 pbkdf2 implementation using the "bcrypt" hash 44261287Sdes * 45261287Sdes * The bcrypt hash function is derived from the bcrypt password hashing 46261287Sdes * function with the following modifications: 47261287Sdes * 1. The input password and salt are preprocessed with SHA512. 48261287Sdes * 2. The output length is expanded to 256 bits. 49261287Sdes * 3. Subsequently the magic string to be encrypted is lengthened and modifed 50261287Sdes * to "OxychromaticBlowfishSwatDynamite" 51261287Sdes * 4. The hash function is defined to perform 64 rounds of initial state 52261287Sdes * expansion. (More rounds are performed by iterating the hash.) 53261287Sdes * 54261287Sdes * Note that this implementation pulls the SHA512 operations into the caller 55261287Sdes * as a performance optimization. 56261287Sdes * 57261287Sdes * One modification from official pbkdf2. Instead of outputting key material 58261287Sdes * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to 59295367Sdes * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an 60295367Sdes * attacker can merely run once through the outer loop, but the user 61261287Sdes * always runs it twice. Shuffling output bytes requires computing the 62261287Sdes * entirety of the key material to assemble any subkey. This is something a 63261287Sdes * wise caller could do; we just do it for you. 64261287Sdes */ 65261287Sdes 66295367Sdes#define BCRYPT_WORDS 8 67295367Sdes#define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4) 68261287Sdes 69261287Sdesstatic void 70261287Sdesbcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out) 71261287Sdes{ 72261287Sdes blf_ctx state; 73261287Sdes u_int8_t ciphertext[BCRYPT_HASHSIZE] = 74261287Sdes "OxychromaticBlowfishSwatDynamite"; 75295367Sdes uint32_t cdata[BCRYPT_WORDS]; 76261287Sdes int i; 77261287Sdes uint16_t j; 78261287Sdes size_t shalen = SHA512_DIGEST_LENGTH; 79261287Sdes 80261287Sdes /* key expansion */ 81261287Sdes Blowfish_initstate(&state); 82261287Sdes Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); 83261287Sdes for (i = 0; i < 64; i++) { 84261287Sdes Blowfish_expand0state(&state, sha2salt, shalen); 85261287Sdes Blowfish_expand0state(&state, sha2pass, shalen); 86261287Sdes } 87261287Sdes 88261287Sdes /* encryption */ 89261287Sdes j = 0; 90295367Sdes for (i = 0; i < BCRYPT_WORDS; i++) 91261287Sdes cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), 92261287Sdes &j); 93261287Sdes for (i = 0; i < 64; i++) 94261287Sdes blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); 95261287Sdes 96261287Sdes /* copy out */ 97295367Sdes for (i = 0; i < BCRYPT_WORDS; i++) { 98261287Sdes out[4 * i + 3] = (cdata[i] >> 24) & 0xff; 99261287Sdes out[4 * i + 2] = (cdata[i] >> 16) & 0xff; 100261287Sdes out[4 * i + 1] = (cdata[i] >> 8) & 0xff; 101261287Sdes out[4 * i + 0] = cdata[i] & 0xff; 102261287Sdes } 103261287Sdes 104261287Sdes /* zap */ 105295367Sdes explicit_bzero(ciphertext, sizeof(ciphertext)); 106295367Sdes explicit_bzero(cdata, sizeof(cdata)); 107295367Sdes explicit_bzero(&state, sizeof(state)); 108261287Sdes} 109261287Sdes 110261287Sdesint 111261287Sdesbcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen, 112261287Sdes u_int8_t *key, size_t keylen, unsigned int rounds) 113261287Sdes{ 114261287Sdes u_int8_t sha2pass[SHA512_DIGEST_LENGTH]; 115261287Sdes u_int8_t sha2salt[SHA512_DIGEST_LENGTH]; 116261287Sdes u_int8_t out[BCRYPT_HASHSIZE]; 117261287Sdes u_int8_t tmpout[BCRYPT_HASHSIZE]; 118261287Sdes u_int8_t *countsalt; 119261287Sdes size_t i, j, amt, stride; 120261287Sdes uint32_t count; 121295367Sdes size_t origkeylen = keylen; 122261287Sdes 123261287Sdes /* nothing crazy */ 124261287Sdes if (rounds < 1) 125261287Sdes return -1; 126261287Sdes if (passlen == 0 || saltlen == 0 || keylen == 0 || 127261287Sdes keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20) 128261287Sdes return -1; 129261287Sdes if ((countsalt = calloc(1, saltlen + 4)) == NULL) 130261287Sdes return -1; 131261287Sdes stride = (keylen + sizeof(out) - 1) / sizeof(out); 132261287Sdes amt = (keylen + stride - 1) / stride; 133261287Sdes 134261287Sdes memcpy(countsalt, salt, saltlen); 135261287Sdes 136261287Sdes /* collapse password */ 137261287Sdes crypto_hash_sha512(sha2pass, pass, passlen); 138261287Sdes 139261287Sdes /* generate key, sizeof(out) at a time */ 140261287Sdes for (count = 1; keylen > 0; count++) { 141261287Sdes countsalt[saltlen + 0] = (count >> 24) & 0xff; 142261287Sdes countsalt[saltlen + 1] = (count >> 16) & 0xff; 143261287Sdes countsalt[saltlen + 2] = (count >> 8) & 0xff; 144261287Sdes countsalt[saltlen + 3] = count & 0xff; 145261287Sdes 146261287Sdes /* first round, salt is salt */ 147261287Sdes crypto_hash_sha512(sha2salt, countsalt, saltlen + 4); 148261287Sdes 149261287Sdes bcrypt_hash(sha2pass, sha2salt, tmpout); 150261287Sdes memcpy(out, tmpout, sizeof(out)); 151261287Sdes 152261287Sdes for (i = 1; i < rounds; i++) { 153261287Sdes /* subsequent rounds, salt is previous output */ 154261287Sdes crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout)); 155261287Sdes bcrypt_hash(sha2pass, sha2salt, tmpout); 156261287Sdes for (j = 0; j < sizeof(out); j++) 157261287Sdes out[j] ^= tmpout[j]; 158261287Sdes } 159261287Sdes 160261287Sdes /* 161295367Sdes * pbkdf2 deviation: output the key material non-linearly. 162261287Sdes */ 163295367Sdes amt = MINIMUM(amt, keylen); 164295367Sdes for (i = 0; i < amt; i++) { 165295367Sdes size_t dest = i * stride + (count - 1); 166295367Sdes if (dest >= origkeylen) 167295367Sdes break; 168295367Sdes key[dest] = out[i]; 169295367Sdes } 170295367Sdes keylen -= i; 171261287Sdes } 172261287Sdes 173261287Sdes /* zap */ 174295367Sdes explicit_bzero(out, sizeof(out)); 175261287Sdes free(countsalt); 176261287Sdes 177261287Sdes return 0; 178261287Sdes} 179261287Sdes#endif /* HAVE_BCRYPT_PBKDF */ 180