summaryrefslogtreecommitdiff
path: root/src/libstrongswan/crypto/hmac.c
blob: df4f90bc8cb3cc92b15d0b841db1aba85909b073 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
/**
 * @file hmac.c
 * 
 * @brief Implementation of hmac_t.
 */

/*
 * Copyright (C) 2005-2006 Martin Willi
 * Copyright (C) 2005 Jan Hutter
 * Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General hmac License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General hmac License
 * for more details.
 */

#include <string.h>

#include "hmac.h"


typedef struct private_hmac_t private_hmac_t;

/**
 * Private data of a hmac_t object.
 * 
 * The variable names are the same as in the RFC.
 */
struct private_hmac_t {
	/**
	 * Public hmac_t interface.
	 */
	hmac_t hmac;
	
	/**
	 * Block size, as in RFC.
	 */
	u_int8_t b;
	
	/**
	 * Hash function.
	 */
	hasher_t *h;
	
	/**
	 * Previously xor'ed key using opad.
	 */
	chunk_t opaded_key;
	
	/**
	 * Previously xor'ed key using ipad.
	 */
	chunk_t ipaded_key;
};

/**
 * Implementation of hmac_t.get_mac.
 */
static void get_mac(private_hmac_t *this, chunk_t data, u_int8_t *out)
{
	/* H(K XOR opad, H(K XOR ipad, text)) 
	 * 
	 * if out is NULL, we append text to the inner hash.
	 * else, we complete the inner and do the outer.
	 * 
	 */
	
	u_int8_t buffer[this->h->get_hash_size(this->h)];
	chunk_t inner;
	
	if (out == NULL)
	{
		/* append data to inner */
		this->h->get_hash(this->h, data, NULL);
	}
	else
	{
		/* append and do outer hash */
		inner.ptr = buffer;
		inner.len = this->h->get_hash_size(this->h);
		
		/* complete inner */
		this->h->get_hash(this->h, data, buffer);
		
		/* do outer */
		this->h->get_hash(this->h, this->opaded_key, NULL);
		this->h->get_hash(this->h, inner, out);
		
		/* reinit for next call */
		this->h->get_hash(this->h, this->ipaded_key, NULL);
	}
}

/**
 * Implementation of hmac_t.allocate_mac.
 */
static void allocate_mac(private_hmac_t *this, chunk_t data, chunk_t *out)
{
	/* allocate space and use get_mac */
	if (out == NULL)
	{
		/* append mode */
		this->hmac.get_mac(&(this->hmac), data, NULL);
	}
	else
	{
		out->len = this->h->get_hash_size(this->h);
		out->ptr = malloc(out->len);
		this->hmac.get_mac(&(this->hmac), data, out->ptr);
	}
}
	
/**
 * Implementation of hmac_t.get_block_size.
 */
static size_t get_block_size(private_hmac_t *this)
{
	return this->h->get_hash_size(this->h);
}

/**
 * Implementation of hmac_t.set_key.
 */
static void set_key(private_hmac_t *this, chunk_t key)
{
	int i;
	u_int8_t buffer[this->b];
	
	memset(buffer, 0, this->b);
	
	if (key.len > this->b)
	{	
		/* if key is too long, it will be hashed */
		this->h->get_hash(this->h, key, buffer);
	}
	else
	{	
		/* if not, just copy it in our pre-padded k */
		memcpy(buffer, key.ptr, key.len);	
	}
			
	/* apply ipad and opad to key */
	for (i = 0; i < this->b; i++)
	{
		this->ipaded_key.ptr[i] = buffer[i] ^ 0x36;
		this->opaded_key.ptr[i] = buffer[i] ^ 0x5C;
	}
	
	/* begin hashing of inner pad */
	this->h->reset(this->h);
	this->h->get_hash(this->h, this->ipaded_key, NULL);
}

/**
 * Implementation of hmac_t.destroy.
 */
static void destroy(private_hmac_t *this)
{
	this->h->destroy(this->h);
	free(this->opaded_key.ptr);
	free(this->ipaded_key.ptr);
	free(this);
}

/*
 * Described in header
 */
hmac_t *hmac_create(hash_algorithm_t hash_algorithm)
{
	private_hmac_t *this;
	
	this = malloc_thing(private_hmac_t);

	/* set hmac_t methods */
	this->hmac.get_mac = (void (*)(hmac_t *,chunk_t,u_int8_t*))get_mac;
	this->hmac.allocate_mac = (void (*)(hmac_t *,chunk_t,chunk_t*))allocate_mac;
	this->hmac.get_block_size = (size_t (*)(hmac_t *))get_block_size;
	this->hmac.set_key = (void (*)(hmac_t *,chunk_t))set_key;
	this->hmac.destroy = (void (*)(hmac_t *))destroy;
	
	/* set b, according to hasher */
	switch (hash_algorithm)
	{
		case HASH_SHA1:
		case HASH_MD5:
		case HASH_SHA256:
			this->b = 64;
			break;
		case HASH_SHA384:
		case HASH_SHA512:
			this->b = 128;
			break;
		default:
			free(this);
			return NULL;	
	}
		
	/* build the hasher */
	this->h = hasher_create(hash_algorithm);

	/* build ipad and opad */
	this->opaded_key.ptr = malloc(this->b);
	this->opaded_key.len = this->b;

	this->ipaded_key.ptr = malloc(this->b);
	this->ipaded_key.len = this->b;

	return &(this->hmac);
}