aes_ctr.c revision 120631 
1/* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
2/* ====================================================================
3 * Copyright (c) 1998-2002 The OpenSSL Project.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in
14 *    the documentation and/or other materials provided with the
15 *    distribution.
16 *
17 * 3. All advertising materials mentioning features or use of this
18 *    software must display the following acknowledgment:
19 *    "This product includes software developed by the OpenSSL Project
20 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
21 *
22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
23 *    endorse or promote products derived from this software without
24 *    prior written permission. For written permission, please contact
25 *    openssl-core@openssl.org.
26 *
27 * 5. Products derived from this software may not be called "OpenSSL"
28 *    nor may "OpenSSL" appear in their names without prior written
29 *    permission of the OpenSSL Project.
30 *
31 * 6. Redistributions of any form whatsoever must retain the following
32 *    acknowledgment:
33 *    "This product includes software developed by the OpenSSL Project
34 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
39 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 */
51
52#ifndef AES_DEBUG
53# ifndef NDEBUG
54#  define NDEBUG
55# endif
56#endif
57#include <assert.h>
58
59#include <openssl/aes.h>
60#include "aes_locl.h"
61
62/* NOTE: CTR mode is big-endian.  The rest of the AES code
63 * is endian-neutral. */
64
65/* increment counter (128-bit int) by 1 */
66static void AES_ctr128_inc(unsigned char *counter) {
67	unsigned long c;
68
69	/* Grab bottom dword of counter and increment */
70#ifdef L_ENDIAN
71	c = GETU32(counter +  0);
72	c++;
73	PUTU32(counter +  0, c);
74#else
75	c = GETU32(counter + 12);
76	c++;
77	PUTU32(counter + 12, c);
78#endif
79
80	/* if no overflow, we're done */
81	if (c)
82		return;
83
84	/* Grab 1st dword of counter and increment */
85#ifdef L_ENDIAN
86	c = GETU32(counter +  4);
87	c++;
88	PUTU32(counter +  4, c);
89#else
90	c = GETU32(counter +  8);
91	c++;
92	PUTU32(counter +  8, c);
93#endif
94
95	/* if no overflow, we're done */
96	if (c)
97		return;
98
99	/* Grab 2nd dword of counter and increment */
100#ifdef L_ENDIAN
101	c = GETU32(counter +  8);
102	c++;
103	PUTU32(counter +  8, c);
104#else
105	c = GETU32(counter +  4);
106	c++;
107	PUTU32(counter +  4, c);
108#endif
109
110	/* if no overflow, we're done */
111	if (c)
112		return;
113
114	/* Grab top dword of counter and increment */
115#ifdef L_ENDIAN
116	c = GETU32(counter + 12);
117	c++;
118	PUTU32(counter + 12, c);
119#else
120	c = GETU32(counter +  0);
121	c++;
122	PUTU32(counter +  0, c);
123#endif
124
125}
126
127/* The input encrypted as though 128bit counter mode is being
128 * used.  The extra state information to record how much of the
129 * 128bit block we have used is contained in *num, and the
130 * encrypted counter is kept in ecount_buf.  Both *num and
131 * ecount_buf must be initialised with zeros before the first
132 * call to AES_ctr128_encrypt().
133 *
134 * This algorithm assumes that the counter is in the x lower bits
135 * of the IV (ivec), and that the application has full control over
136 * overflow and the rest of the IV.  This implementation takes NO
137 * responsability for checking that the counter doesn't overflow
138 * into the rest of the IV when incremented.
139 */
140void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
141	const unsigned long length, const AES_KEY *key,
142	unsigned char ivec[AES_BLOCK_SIZE],
143	unsigned char ecount_buf[AES_BLOCK_SIZE],
144	unsigned int *num) {
145
146	unsigned int n;
147	unsigned long l=length;
148
149	assert(in && out && key && counter && num);
150	assert(*num < AES_BLOCK_SIZE);
151
152	n = *num;
153
154	while (l--) {
155		if (n == 0) {
156			AES_encrypt(ivec, ecount_buf, key);
157 			AES_ctr128_inc(ivec);
158		}
159		*(out++) = *(in++) ^ ecount_buf[n];
160		n = (n+1) % AES_BLOCK_SIZE;
161	}
162
163	*num=n;
164}
165