aboutsummaryrefslogtreecommitdiffstats
path: root/gpxe/src/crypto/axtls_aes.c
blob: 51e1924ed0ab2259668a0e3c2034a123f3f17a2e (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
/*
 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * 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 Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <string.h>
#include <errno.h>
#include <byteswap.h>
#include <gpxe/crypto.h>
#include <gpxe/cbc.h>
#include <gpxe/aes.h>
#include "crypto/axtls/crypto.h"

/** @file
 *
 * AES algorithm
 *
 */

/** Basic AES blocksize */
#define AES_BLOCKSIZE 16

/** AES context */
struct aes_context {
	/** AES context for AXTLS */
	AES_CTX axtls_ctx;
	/** Cipher is being used for decrypting */
	int decrypting;
};

/**
 * Set key
 *
 * @v ctx		Context
 * @v key		Key
 * @v keylen		Key length
 * @ret rc		Return status code
 */
static int aes_setkey ( void *ctx, const void *key, size_t keylen ) {
	struct aes_context *aes_ctx = ctx;
	AES_MODE mode;
	void *iv;

	switch ( keylen ) {
	case ( 128 / 8 ):
		mode = AES_MODE_128;
		break;
	case ( 256 / 8 ):
		mode = AES_MODE_256;
		break;
	default:
		return -EINVAL;
	}

	/* IV is not a relevant concept at this stage; use a dummy
	 * value that will have no side-effects.
	 */
	iv = &aes_ctx->axtls_ctx.iv;

	AES_set_key ( &aes_ctx->axtls_ctx, key, iv, mode );

	aes_ctx->decrypting = 0;

	return 0;
}

/**
 * Set initialisation vector
 *
 * @v ctx		Context
 * @v iv		Initialisation vector
 */
static void aes_setiv ( void *ctx __unused, const void *iv __unused ) {
	/* Nothing to do */
}

/**
 * Call AXTLS' AES_encrypt() or AES_decrypt() functions
 *
 * @v axtls_ctx		AXTLS AES context
 * @v src		Data to process
 * @v dst		Buffer for output
 * @v func		AXTLS AES function to call
 */
static void aes_call_axtls ( AES_CTX *axtls_ctx, const void *src, void *dst,
			     void ( * func ) ( const AES_CTX *axtls_ctx,
					       uint32_t *data ) ){
	const uint32_t *srcl = src;
	uint32_t *dstl = dst;
	unsigned int i;

	/* AXTLS' AES_encrypt() and AES_decrypt() functions both
	 * expect to deal with an array of four dwords in host-endian
	 * order.
	 */
	for ( i = 0 ; i < 4 ; i++ )
		dstl[i] = ntohl ( srcl[i] );
	func ( axtls_ctx, dstl );
	for ( i = 0 ; i < 4 ; i++ )
		dstl[i] = htonl ( dstl[i] );
}

/**
 * Encrypt data
 *
 * @v ctx		Context
 * @v src		Data to encrypt
 * @v dst		Buffer for encrypted data
 * @v len		Length of data
 */
static void aes_encrypt ( void *ctx, const void *src, void *dst,
			  size_t len ) {
	struct aes_context *aes_ctx = ctx;

	assert ( len == AES_BLOCKSIZE );
	if ( aes_ctx->decrypting )
		assert ( 0 );
	aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_encrypt );
}

/**
 * Decrypt data
 *
 * @v ctx		Context
 * @v src		Data to decrypt
 * @v dst		Buffer for decrypted data
 * @v len		Length of data
 */
static void aes_decrypt ( void *ctx, const void *src, void *dst,
			  size_t len ) {
	struct aes_context *aes_ctx = ctx;

	assert ( len == AES_BLOCKSIZE );
	if ( ! aes_ctx->decrypting ) {
		AES_convert_key ( &aes_ctx->axtls_ctx );
		aes_ctx->decrypting = 1;
	}
	aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_decrypt );
}

/** Basic AES algorithm */
static struct cipher_algorithm aes_algorithm = {
	.name = "aes",
	.ctxsize = sizeof ( struct aes_context ),
	.blocksize = AES_BLOCKSIZE,
	.setkey = aes_setkey,
	.setiv = aes_setiv,
	.encrypt = aes_encrypt,
	.decrypt = aes_decrypt,
};

/* AES with cipher-block chaining */
CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
	     aes_algorithm, struct aes_context, AES_BLOCKSIZE );