aes_ctr.c revision bdfb8ad83da0647e9b9a32792598e8ce7ba3ef4d 
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: the IV/counter 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	c = GETU32(counter + 12);
71	c++;	c &= 0xFFFFFFFF;
72	PUTU32(counter + 12, c);
73
74	/* if no overflow, we're done */
75	if (c)
76		return;
77
78	/* Grab 1st dword of counter and increment */
79	c = GETU32(counter +  8);
80	c++;	c &= 0xFFFFFFFF;
81	PUTU32(counter +  8, c);
82
83	/* if no overflow, we're done */
84	if (c)
85		return;
86
87	/* Grab 2nd dword of counter and increment */
88	c = GETU32(counter +  4);
89	c++;	c &= 0xFFFFFFFF;
90	PUTU32(counter +  4, c);
91
92	/* if no overflow, we're done */
93	if (c)
94		return;
95
96	/* Grab top dword of counter and increment */
97	c = GETU32(counter +  0);
98	c++;	c &= 0xFFFFFFFF;
99	PUTU32(counter +  0, c);
100}
101
102/* The input encrypted as though 128bit counter mode is being
103 * used.  The extra state information to record how much of the
104 * 128bit block we have used is contained in *num, and the
105 * encrypted counter is kept in ecount_buf.  Both *num and
106 * ecount_buf must be initialised with zeros before the first
107 * call to AES_ctr128_encrypt().
108 *
109 * This algorithm assumes that the counter is in the x lower bits
110 * of the IV (ivec), and that the application has full control over
111 * overflow and the rest of the IV.  This implementation takes NO
112 * responsability for checking that the counter doesn't overflow
113 * into the rest of the IV when incremented.
114 */
115void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
116	const unsigned long length, const AES_KEY *key,
117	unsigned char ivec[AES_BLOCK_SIZE],
118	unsigned char ecount_buf[AES_BLOCK_SIZE],
119	unsigned int *num) {
120
121	unsigned int n;
122	unsigned long l=length;
123
124	assert(in && out && key && counter && num);
125	assert(*num < AES_BLOCK_SIZE);
126
127	n = *num;
128
129	while (l--) {
130		if (n == 0) {
131			AES_encrypt(ivec, ecount_buf, key);
132 			AES_ctr128_inc(ivec);
133		}
134		*(out++) = *(in++) ^ ecount_buf[n];
135		n = (n+1) % AES_BLOCK_SIZE;
136	}
137
138	*num=n;
139}
140