1 /* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 tedu 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 #include "includes.h"
19
20 #ifndef HAVE_BCRYPT_PBKDF
21
22 #include <sys/types.h>
23 #include <sys/param.h>
24
25 #ifdef HAVE_STDLIB_H
26 # include <stdlib.h>
27 #endif
28 #include <string.h>
29
30 #ifdef HAVE_BLF_H
31 # include <blf.h>
32 #endif
33
34 #include "crypto_api.h"
35 #ifdef SHA512_DIGEST_LENGTH
36 # undef SHA512_DIGEST_LENGTH
37 #endif
38 #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES
39
40 #define MINIMUM(a,b) (((a) < (b)) ? (a) : (b))
41
42 /*
43 * pkcs #5 pbkdf2 implementation using the "bcrypt" hash
44 *
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 modified
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.)
53 *
54 * Note that this implementation pulls the SHA512 operations into the caller
55 * as a performance optimization.
56 *
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.
64 */
65
66 #define BCRYPT_WORDS 8
67 #define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4)
68
69 static void
bcrypt_hash(u_int8_t * sha2pass,u_int8_t * sha2salt,u_int8_t * out)70 bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out)
71 {
72 blf_ctx state;
73 u_int8_t ciphertext[BCRYPT_HASHSIZE] =
74 "OxychromaticBlowfishSwatDynamite";
75 uint32_t cdata[BCRYPT_WORDS];
76 int i;
77 uint16_t j;
78 size_t shalen = SHA512_DIGEST_LENGTH;
79
80 /* key expansion */
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);
86 }
87
88 /* encryption */
89 j = 0;
90 for (i = 0; i < BCRYPT_WORDS; i++)
91 cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext),
92 &j);
93 for (i = 0; i < 64; i++)
94 blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t));
95
96 /* copy out */
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;
102 }
103
104 /* zap */
105 explicit_bzero(ciphertext, sizeof(ciphertext));
106 explicit_bzero(cdata, sizeof(cdata));
107 explicit_bzero(&state, sizeof(state));
108 }
109
110 int
bcrypt_pbkdf(const char * pass,size_t passlen,const u_int8_t * salt,size_t saltlen,u_int8_t * key,size_t keylen,unsigned int rounds)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)
113 {
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];
118 u_int8_t *countsalt;
119 size_t i, j, amt, stride;
120 uint32_t count;
121 size_t origkeylen = keylen;
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, 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: output the key material non-linearly.
162 */
163 amt = MINIMUM(amt, keylen);
164 for (i = 0; i < amt; i++) {
165 size_t dest = i * stride + (count - 1);
166 if (dest >= origkeylen)
167 break;
168 key[dest] = out[i];
169 }
170 keylen -= i;
171 }
172
173 /* zap */
174 explicit_bzero(out, sizeof(out));
175 free(countsalt);
176
177 return 0;
178 }
179 #endif /* HAVE_BCRYPT_PBKDF */
180