1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 tedu Exp $ */
3 * Copyright (c) 2013 Ted Unangst <tedu@openbsd.org>
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.
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.
20 #ifndef HAVE_BCRYPT_PBKDF
22 #include <sys/types.h>
23 #include <sys/param.h>
34 #include "crypto_api.h"
35 #ifdef SHA512_DIGEST_LENGTH
36 # undef SHA512_DIGEST_LENGTH
38 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES
40 #define MINIMUM(a,b) (((a) < (b)) ? (a) : (b))
43 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash
45 * The bcrypt hash function is derived from the bcrypt password hashing
46 * function with the following modifications:
47 * 1. The input password and salt are preprocessed with SHA512.
48 * 2. The output length is expanded to 256 bits.
49 * 3. Subsequently the magic string to be encrypted is lengthened and modifed
50 * to "OxychromaticBlowfishSwatDynamite"
51 * 4. The hash function is defined to perform 64 rounds of initial state
52 * expansion. (More rounds are performed by iterating the hash.)
54 * Note that this implementation pulls the SHA512 operations into the caller
55 * as a performance optimization.
57 * One modification from official pbkdf2. Instead of outputting key material
58 * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to
59 * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an
60 * attacker can merely run once through the outer loop, but the user
61 * always runs it twice. Shuffling output bytes requires computing the
62 * entirety of the key material to assemble any subkey. This is something a
63 * wise caller could do; we just do it for you.
66 #define BCRYPT_WORDS 8
67 #define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4)
70 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out)
73 u_int8_t ciphertext[BCRYPT_HASHSIZE] =
74 "OxychromaticBlowfishSwatDynamite";
75 uint32_t cdata[BCRYPT_WORDS];
78 size_t shalen = SHA512_DIGEST_LENGTH;
81 Blowfish_initstate(&state);
82 Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen);
83 for (i = 0; i < 64; i++) {
84 Blowfish_expand0state(&state, sha2salt, shalen);
85 Blowfish_expand0state(&state, sha2pass, shalen);
90 for (i = 0; i < BCRYPT_WORDS; i++)
91 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext),
93 for (i = 0; i < 64; i++)
94 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t));
97 for (i = 0; i < BCRYPT_WORDS; i++) {
98 out[4 * i + 3] = (cdata[i] >> 24) & 0xff;
99 out[4 * i + 2] = (cdata[i] >> 16) & 0xff;
100 out[4 * i + 1] = (cdata[i] >> 8) & 0xff;
101 out[4 * i + 0] = cdata[i] & 0xff;
105 explicit_bzero(ciphertext, sizeof(ciphertext));
106 explicit_bzero(cdata, sizeof(cdata));
107 explicit_bzero(&state, sizeof(state));
111 bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen,
112 u_int8_t *key, size_t keylen, unsigned int rounds)
114 u_int8_t sha2pass[SHA512_DIGEST_LENGTH];
115 u_int8_t sha2salt[SHA512_DIGEST_LENGTH];
116 u_int8_t out[BCRYPT_HASHSIZE];
117 u_int8_t tmpout[BCRYPT_HASHSIZE];
119 size_t i, j, amt, stride;
121 size_t origkeylen = keylen;
126 if (passlen == 0 || saltlen == 0 || keylen == 0 ||
127 keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20)
129 if ((countsalt = calloc(1, saltlen + 4)) == NULL)
131 stride = (keylen + sizeof(out) - 1) / sizeof(out);
132 amt = (keylen + stride - 1) / stride;
134 memcpy(countsalt, salt, saltlen);
136 /* collapse password */
137 crypto_hash_sha512(sha2pass, pass, passlen);
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;
146 /* first round, salt is salt */
147 crypto_hash_sha512(sha2salt, countsalt, saltlen + 4);
149 bcrypt_hash(sha2pass, sha2salt, tmpout);
150 memcpy(out, tmpout, sizeof(out));
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++)
161 * pbkdf2 deviation: output the key material non-linearly.
163 amt = MINIMUM(amt, keylen);
164 for (i = 0; i < amt; i++) {
165 size_t dest = i * stride + (count - 1);
166 if (dest >= origkeylen)
174 explicit_bzero(out, sizeof(out));
179 #endif /* HAVE_BCRYPT_PBKDF */