1/* This file is distributed under the following terms:
2
3 * Copyright 2005-2014 Colin Percival.  All rights reserved.
4 * Copyright 2014 Sean Kelly.  All rights reserved.
5
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28#include <assert.h>
29#include <stdint.h>
30#include <string.h>
31#include <ByteOrder.h>
32
33#include "pbkdf2.h"
34
35/* Function which does the zeroing. */
36static void
37insecure_memzero_func(volatile void * buf, size_t len)
38{
39	volatile uint8_t * _buf = (volatile uint8_t *)buf;
40	size_t i;
41
42	for (i = 0; i < len; i++)
43		_buf[i] = 0;
44}
45
46/* Pointer to memory-zeroing function. */
47void (* volatile insecure_memzero_ptr)(volatile void *, size_t) =
48    insecure_memzero_func;
49
50/**
51 * HMAC_SHA256_Init(ctx, K, Klen):
52 * Initialize the HMAC-SHA256 context ${ctx} with ${Klen} bytes of key from
53 * ${K}.
54 */
55void
56HMAC_SHA256_Init(HMAC_SHA256_CTX * ctx, const void * _K, size_t Klen)
57{
58	uint8_t pad[64];
59	uint8_t khash[32];
60	const uint8_t * K = (const uint8_t *)_K;
61	size_t i;
62
63	/* If Klen > 64, the key is really SHA256(K). */
64	if (Klen > 64) {
65		ctx->ictx.Init();
66		ctx->ictx.Update(K, Klen);
67		memcpy(khash, ctx->ictx.Digest(), 32);
68		K = khash;
69		Klen = 32;
70	}
71
72	/* Inner SHA256 operation is SHA256(K xor [block of 0x36] || data). */
73	ctx->ictx.Init();
74	memset(pad, 0x36, 64);
75	for (i = 0; i < Klen; i++)
76		pad[i] ^= K[i];
77	ctx->ictx.Update(pad, 64);
78
79	/* Outer SHA256 operation is SHA256(K xor [block of 0x5c] || hash). */
80	ctx->octx.Init();
81	memset(pad, 0x5c, 64);
82	for (i = 0; i < Klen; i++)
83		pad[i] ^= K[i];
84	ctx->octx.Update(pad, 64);
85
86	/* Clean the stack. */
87	insecure_memzero(khash, 32);
88	insecure_memzero(pad, 64);
89}
90
91/**
92 * HMAC_SHA256_Update(ctx, in, len):
93 * Input ${len} bytes from ${in} into the HMAC-SHA256 context ${ctx}.
94 */
95void
96HMAC_SHA256_Update(HMAC_SHA256_CTX * ctx, const void * in, size_t len)
97{
98
99	/* Feed data to the inner SHA256 operation. */
100	ctx->ictx.Update(in, len);
101}
102
103/**
104 * HMAC_SHA256_Final(digest, ctx):
105 * Output the HMAC-SHA256 of the data input to the context ${ctx} into the
106 * buffer ${digest}.
107 */
108void
109HMAC_SHA256_Final(uint8_t digest[32], HMAC_SHA256_CTX * ctx)
110{
111	uint8_t ihash[32];
112
113	/* Finish the inner SHA256 operation. */
114	memcpy(ihash, ctx->ictx.Digest(), 32);
115
116	/* Feed the inner hash to the outer SHA256 operation. */
117	ctx->octx.Update(ihash, 32);
118
119	/* Finish the outer SHA256 operation. */
120	memcpy(digest, ctx->octx.Digest(), 32);
121
122	/* Clean the stack. */
123	insecure_memzero(ihash, 32);
124}
125
126/**
127 * PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, c, buf, dkLen):
128 * Compute PBKDF2(passwd, salt, c, dkLen) using HMAC-SHA256 as the PRF, and
129 * write the output to buf.  The value dkLen must be at most 32 * (2^32 - 1).
130 */
131void
132PBKDF2_SHA256(const uint8_t * passwd, size_t passwdlen, const uint8_t * salt,
133    size_t saltlen, uint64_t c, uint8_t * buf, size_t dkLen)
134{
135	HMAC_SHA256_CTX PShctx, hctx;
136	size_t i;
137	uint32_t ivec;
138	uint8_t U[32];
139	uint8_t T[32];
140	uint64_t j;
141	int k;
142	size_t clen;
143
144	/* Sanity-check. */
145	assert(dkLen <= 32 * (size_t)(UINT32_MAX));
146
147	/* Compute HMAC state after processing P and S. */
148	HMAC_SHA256_Init(&PShctx, passwd, passwdlen);
149	HMAC_SHA256_Update(&PShctx, salt, saltlen);
150
151	/* Iterate through the blocks. */
152	for (i = 0; i * 32 < dkLen; i++) {
153		/* Generate INT(i + 1). */
154		ivec = B_HOST_TO_BENDIAN_INT32((uint32_t)(i + 1));
155
156		/* Compute U_1 = PRF(P, S || INT(i)). */
157		memcpy(&hctx, &PShctx, sizeof(HMAC_SHA256_CTX));
158		HMAC_SHA256_Update(&hctx, &ivec, 4);
159		HMAC_SHA256_Final(U, &hctx);
160
161		/* T_i = U_1 ... */
162		memcpy(T, U, 32);
163
164		for (j = 2; j <= c; j++) {
165			/* Compute U_j. */
166			HMAC_SHA256_Init(&hctx, passwd, passwdlen);
167			HMAC_SHA256_Update(&hctx, U, 32);
168			HMAC_SHA256_Final(U, &hctx);
169
170			/* ... xor U_j ... */
171			for (k = 0; k < 32; k++)
172				T[k] ^= U[k];
173		}
174
175		/* Copy as many bytes as necessary into buf. */
176		clen = dkLen - i * 32;
177		if (clen > 32)
178			clen = 32;
179		memcpy(&buf[i * 32], T, clen);
180	}
181
182	/* Clean PShctx, since we never called _Final on it. */
183	insecure_memzero(&PShctx, sizeof(HMAC_SHA256_CTX));
184}
185