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1 : : /* $OpenBSD: bcrypt_pbkdf.c,v 1.4 2013/07/29 00:55:53 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 : : #define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES
36 : :
37 : : /*
38 : : * pkcs #5 pbkdf2 implementation using the "bcrypt" hash
39 : : *
40 : : * The bcrypt hash function is derived from the bcrypt password hashing
41 : : * function with the following modifications:
42 : : * 1. The input password and salt are preprocessed with SHA512.
43 : : * 2. The output length is expanded to 256 bits.
44 : : * 3. Subsequently the magic string to be encrypted is lengthened and modifed
45 : : * to "OxychromaticBlowfishSwatDynamite"
46 : : * 4. The hash function is defined to perform 64 rounds of initial state
47 : : * expansion. (More rounds are performed by iterating the hash.)
48 : : *
49 : : * Note that this implementation pulls the SHA512 operations into the caller
50 : : * as a performance optimization.
51 : : *
52 : : * One modification from official pbkdf2. Instead of outputting key material
53 : : * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to
54 : : * generate (i.e.) 512 bits of key material for use as two 256 bit keys, an
55 : : * attacker can merely run once through the outer loop below, but the user
56 : : * always runs it twice. Shuffling output bytes requires computing the
57 : : * entirety of the key material to assemble any subkey. This is something a
58 : : * wise caller could do; we just do it for you.
59 : : */
60 : :
61 : : #define BCRYPT_BLOCKS 8
62 : : #define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4)
63 : :
64 : : static void
65 : 0 : bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out)
66 : : {
67 : : blf_ctx state;
68 : 0 : u_int8_t ciphertext[BCRYPT_HASHSIZE] =
69 : : "OxychromaticBlowfishSwatDynamite";
70 : : uint32_t cdata[BCRYPT_BLOCKS];
71 : : int i;
72 : : uint16_t j;
73 : 0 : size_t shalen = SHA512_DIGEST_LENGTH;
74 : :
75 : : /* key expansion */
76 : 0 : Blowfish_initstate(&state);
77 : 0 : Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen);
78 [ # # ]: 0 : for (i = 0; i < 64; i++) {
79 : 0 : Blowfish_expand0state(&state, sha2salt, shalen);
80 : 0 : Blowfish_expand0state(&state, sha2pass, shalen);
81 : : }
82 : :
83 : : /* encryption */
84 : 0 : j = 0;
85 [ # # ]: 0 : for (i = 0; i < BCRYPT_BLOCKS; i++)
86 : 0 : cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext),
87 : : &j);
88 [ # # ]: 0 : for (i = 0; i < 64; i++)
89 : 0 : blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t));
90 : :
91 : : /* copy out */
92 [ # # ]: 0 : for (i = 0; i < BCRYPT_BLOCKS; i++) {
93 : 0 : out[4 * i + 3] = (cdata[i] >> 24) & 0xff;
94 : 0 : out[4 * i + 2] = (cdata[i] >> 16) & 0xff;
95 : 0 : out[4 * i + 1] = (cdata[i] >> 8) & 0xff;
96 : 0 : out[4 * i + 0] = cdata[i] & 0xff;
97 : : }
98 : :
99 : : /* zap */
100 : : memset(ciphertext, 0, sizeof(ciphertext));
101 : : memset(cdata, 0, sizeof(cdata));
102 : : memset(&state, 0, sizeof(state));
103 : 0 : }
104 : :
105 : : int
106 : 0 : bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen,
107 : : u_int8_t *key, size_t keylen, unsigned int rounds)
108 : : {
109 : : u_int8_t sha2pass[SHA512_DIGEST_LENGTH];
110 : : u_int8_t sha2salt[SHA512_DIGEST_LENGTH];
111 : : u_int8_t out[BCRYPT_HASHSIZE];
112 : : u_int8_t tmpout[BCRYPT_HASHSIZE];
113 : : u_int8_t *countsalt;
114 : : size_t i, j, amt, stride;
115 : : uint32_t count;
116 : :
117 : : /* nothing crazy */
118 [ # # ]: 0 : if (rounds < 1)
119 : : return -1;
120 [ # # ][ # # ]: 0 : if (passlen == 0 || saltlen == 0 || keylen == 0 ||
121 [ # # ]: 0 : keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20)
122 : : return -1;
123 [ # # ]: 0 : if ((countsalt = calloc(1, saltlen + 4)) == NULL)
124 : : return -1;
125 : 0 : stride = (keylen + sizeof(out) - 1) / sizeof(out);
126 : 0 : amt = (keylen + stride - 1) / stride;
127 : :
128 : : memcpy(countsalt, salt, saltlen);
129 : :
130 : : /* collapse password */
131 : 0 : crypto_hash_sha512(sha2pass, pass, passlen);
132 : :
133 : : /* generate key, sizeof(out) at a time */
134 [ # # ]: 0 : for (count = 1; keylen > 0; count++) {
135 : 0 : countsalt[saltlen + 0] = (count >> 24) & 0xff;
136 : 0 : countsalt[saltlen + 1] = (count >> 16) & 0xff;
137 : 0 : countsalt[saltlen + 2] = (count >> 8) & 0xff;
138 : 0 : countsalt[saltlen + 3] = count & 0xff;
139 : :
140 : : /* first round, salt is salt */
141 : 0 : crypto_hash_sha512(sha2salt, countsalt, saltlen + 4);
142 : :
143 : 0 : bcrypt_hash(sha2pass, sha2salt, tmpout);
144 : : memcpy(out, tmpout, sizeof(out));
145 : :
146 [ # # ]: 0 : for (i = 1; i < rounds; i++) {
147 : : /* subsequent rounds, salt is previous output */
148 : 0 : crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout));
149 : 0 : bcrypt_hash(sha2pass, sha2salt, tmpout);
150 [ # # ]: 0 : for (j = 0; j < sizeof(out); j++)
151 : 0 : out[j] ^= tmpout[j];
152 : : }
153 : :
154 : : /*
155 : : * pbkdf2 deviation: ouput the key material non-linearly.
156 : : */
157 : 0 : amt = MIN(amt, keylen);
158 [ # # ]: 0 : for (i = 0; i < amt; i++)
159 : 0 : key[i * stride + (count - 1)] = out[i];
160 : 0 : keylen -= amt;
161 : : }
162 : :
163 : : /* zap */
164 : : memset(out, 0, sizeof(out));
165 : 0 : memset(countsalt, 0, saltlen + 4);
166 : 0 : free(countsalt);
167 : :
168 : 0 : return 0;
169 : : }
170 : : #endif /* HAVE_BCRYPT_PBKDF */
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