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/* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 tedu Exp $ */
/*
* Copyright (c) 2013 Ted Unangst <tedu@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <QtCore>
extern "C" {
#include "blf.h"
}
#define MINIMUM(a,b) (((a) < (b)) ? (a) : (b))
/*
* pkcs #5 pbkdf2 implementation using the "bcrypt" hash
*
* The bcrypt hash function is derived from the bcrypt password hashing
* function with the following modifications:
* 1. The input password and salt are preprocessed with SHA512.
* 2. The output length is expanded to 256 bits.
* 3. Subsequently the magic string to be encrypted is lengthened and modifed
* to "OxychromaticBlowfishSwatDynamite"
* 4. The hash function is defined to perform 64 rounds of initial state
* expansion. (More rounds are performed by iterating the hash.)
*
* Note that this implementation pulls the SHA512 operations into the caller
* as a performance optimization.
*
* One modification from official pbkdf2. Instead of outputting key material
* linearly, we mix it. pbkdf2 has a known weakness where if one uses it to
* generate (e.g.) 512 bits of key material for use as two 256 bit keys, an
* attacker can merely run once through the outer loop, but the user
* always runs it twice. Shuffling output bytes requires computing the
* entirety of the key material to assemble any subkey. This is something a
* wise caller could do; we just do it for you.
*/
#define BCRYPT_WORDS 8
#define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4)
#define SHA512_DIGEST_LENGTH 64
// FIXME: explicit_bzero exists to ensure bzero is not optimized out
#define explicit_bzero bzero
static void
bcrypt_hash(const quint8* sha2pass, const quint8* sha2salt, quint8* out)
{
blf_ctx state;
quint8 ciphertext[BCRYPT_HASHSIZE] = // "OxychromaticBlowfishSwatDynamite"
{ 0x4f, 0x78, 0x79, 0x63, 0x68, 0x72, 0x6f, 0x6d,
0x61, 0x74, 0x69, 0x63, 0x42, 0x6c, 0x6f, 0x77,
0x66, 0x69, 0x73, 0x68, 0x53, 0x77, 0x61, 0x74,
0x44, 0x79, 0x6e, 0x61, 0x6d, 0x69, 0x74, 0x65 };
quint32 cdata[BCRYPT_WORDS];
int i;
quint16 j;
size_t shalen = SHA512_DIGEST_LENGTH;
/* key expansion */
Blowfish_initstate(&state);
Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen);
for (i = 0; i < 64; i++) {
Blowfish_expand0state(&state, sha2salt, shalen);
Blowfish_expand0state(&state, sha2pass, shalen);
}
/* encryption */
j = 0;
for (i = 0; i < BCRYPT_WORDS; i++)
cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext),
&j);
for (i = 0; i < 64; i++)
blf_enc(&state, cdata, BCRYPT_WORDS / 2);
/* copy out */
for (i = 0; i < BCRYPT_WORDS; i++) {
out[4 * i + 3] = (cdata[i] >> 24) & 0xff;
out[4 * i + 2] = (cdata[i] >> 16) & 0xff;
out[4 * i + 1] = (cdata[i] >> 8) & 0xff;
out[4 * i + 0] = cdata[i] & 0xff;
}
/* zap */
explicit_bzero(ciphertext, sizeof(ciphertext));
explicit_bzero(cdata, sizeof(cdata));
explicit_bzero(&state, sizeof(state));
}
int bcrypt_pbkdf(const QByteArray& pass, const QByteArray& salt, QByteArray& key, quint32 rounds)
{
QCryptographicHash ctx(QCryptographicHash::Sha512);
QByteArray sha2pass;
QByteArray sha2salt;
quint8 out[BCRYPT_HASHSIZE];
quint8 tmpout[BCRYPT_HASHSIZE];
quint8 countsalt[4];
/* nothing crazy */
if (rounds < 1) {
return -1;
}
if (pass.isEmpty() || salt.isEmpty() || key.isEmpty() ||
static_cast<quint32>(key.length()) > sizeof(out) * sizeof(out)) {
return -1;
}
quint32 stride = (key.length() + sizeof(out) - 1) / sizeof(out);
quint32 amt = (key.length() + stride - 1) / stride;
/* collapse password */
ctx.reset();
ctx.addData(pass);
sha2pass = ctx.result();
/* generate key, sizeof(out) at a time */
for (quint32 count = 1, keylen = key.length(); keylen > 0; count++) {
countsalt[0] = (count >> 24) & 0xff;
countsalt[1] = (count >> 16) & 0xff;
countsalt[2] = (count >> 8) & 0xff;
countsalt[3] = count & 0xff;
/* first round, salt is salt */
ctx.reset();
ctx.addData(salt);
ctx.addData(reinterpret_cast<char *>(countsalt), sizeof(countsalt));
sha2salt = ctx.result();
bcrypt_hash(reinterpret_cast<quint8 *>(sha2pass.data()), reinterpret_cast<quint8 *>(sha2salt.data()), tmpout);
memcpy(out, tmpout, sizeof(out));
for (quint32 i = 1; i < rounds; i++) {
/* subsequent rounds, salt is previous output */
ctx.reset();
ctx.addData(reinterpret_cast<char *>(tmpout), sizeof(tmpout));
sha2salt = ctx.result();
bcrypt_hash(reinterpret_cast<quint8 *>(sha2pass.data()), reinterpret_cast<quint8 *>(sha2salt.data()), tmpout);
for (quint32 j = 0; j < sizeof(out); j++)
out[j] ^= tmpout[j];
}
/*
* pbkdf2 deviation: output the key material non-linearly.
*/
amt = MINIMUM(amt, keylen);
quint32 i;
for (i = 0; i < amt; i++) {
int dest = i * stride + (count - 1);
if (dest >= key.length())
break;
key.data()[dest] = out[i];
}
keylen -= i;
}
/* zap */
explicit_bzero(out, sizeof(out));
return 0;
}
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