1/* ====================================================================
2 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in
13 *    the documentation and/or other materials provided with the
14 *    distribution.
15 *
16 * 3. All advertising materials mentioning features or use of this
17 *    software must display the following acknowledgment:
18 *    "This product includes software developed by the OpenSSL Project
19 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
20 *
21 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
22 *    endorse or promote products derived from this software without
23 *    prior written permission. For written permission, please contact
24 *    openssl-core@openssl.org.
25 *
26 * 5. Products derived from this software may not be called "OpenSSL"
27 *    nor may "OpenSSL" appear in their names without prior written
28 *    permission of the OpenSSL Project.
29 *
30 * 6. Redistributions of any form whatsoever must retain the following
31 *    acknowledgment:
32 *    "This product includes software developed by the OpenSSL Project
33 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
34 *
35 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
36 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
38 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
39 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
41 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
42 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
44 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
45 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
46 * OF THE POSSIBILITY OF SUCH DAMAGE.
47 * ====================================================================
48 *
49 */
50
51#include "modes.h"
52#include <string.h>
53
54#ifndef MODES_DEBUG
55# ifndef NDEBUG
56#  define NDEBUG
57# endif
58#endif
59#include <assert.h>
60
61typedef unsigned int u32;
62typedef unsigned char u8;
63
64#define STRICT_ALIGNMENT
65#if defined(__i386)	|| defined(__i386__)	|| \
66    defined(__x86_64)	|| defined(__x86_64__)	|| \
67    defined(_M_IX86)	|| defined(_M_AMD64)	|| defined(_M_X64) || \
68    defined(__s390__)	|| defined(__s390x__)
69#  undef STRICT_ALIGNMENT
70#endif
71
72/* NOTE: the IV/counter CTR mode is big-endian.  The code itself
73 * is endian-neutral. */
74
75/* increment counter (128-bit int) by 1 */
76static void ctr128_inc(unsigned char *counter) {
77	u32 n=16;
78	u8  c;
79
80	do {
81		--n;
82		c = counter[n];
83		++c;
84		counter[n] = c;
85		if (c) return;
86	} while (n);
87}
88
89#if !defined(OPENSSL_SMALL_FOOTPRINT)
90static void ctr128_inc_aligned(unsigned char *counter) {
91	size_t *data,c,n;
92	const union { long one; char little; } is_endian = {1};
93
94	if (is_endian.little) {
95		ctr128_inc(counter);
96		return;
97	}
98
99	data = (size_t *)counter;
100	n = 16/sizeof(size_t);
101	do {
102		--n;
103		c = data[n];
104		++c;
105		data[n] = c;
106		if (c) return;
107	} while (n);
108}
109#endif
110
111/* The input encrypted as though 128bit counter mode is being
112 * used.  The extra state information to record how much of the
113 * 128bit block we have used is contained in *num, and the
114 * encrypted counter is kept in ecount_buf.  Both *num and
115 * ecount_buf must be initialised with zeros before the first
116 * call to CRYPTO_ctr128_encrypt().
117 *
118 * This algorithm assumes that the counter is in the x lower bits
119 * of the IV (ivec), and that the application has full control over
120 * overflow and the rest of the IV.  This implementation takes NO
121 * responsability for checking that the counter doesn't overflow
122 * into the rest of the IV when incremented.
123 */
124void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
125			size_t len, const void *key,
126			unsigned char ivec[16], unsigned char ecount_buf[16],
127			unsigned int *num, block128_f block)
128{
129	unsigned int n;
130	size_t l=0;
131
132	assert(in && out && key && ecount_buf && num);
133	assert(*num < 16);
134
135	n = *num;
136
137#if !defined(OPENSSL_SMALL_FOOTPRINT)
138	if (16%sizeof(size_t) == 0) do { /* always true actually */
139		while (n && len) {
140			*(out++) = *(in++) ^ ecount_buf[n];
141			--len;
142			n = (n+1) % 16;
143		}
144
145#if defined(STRICT_ALIGNMENT)
146		if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
147			break;
148#endif
149		while (len>=16) {
150			(*block)(ivec, ecount_buf, key);
151			ctr128_inc_aligned(ivec);
152			for (; n<16; n+=sizeof(size_t))
153				*(size_t *)(out+n) =
154				*(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n);
155			len -= 16;
156			out += 16;
157			in  += 16;
158			n = 0;
159		}
160		if (len) {
161			(*block)(ivec, ecount_buf, key);
162 			ctr128_inc_aligned(ivec);
163			while (len--) {
164				out[n] = in[n] ^ ecount_buf[n];
165				++n;
166			}
167		}
168		*num = n;
169		return;
170	} while(0);
171	/* the rest would be commonly eliminated by x86* compiler */
172#endif
173	while (l<len) {
174		if (n==0) {
175			(*block)(ivec, ecount_buf, key);
176 			ctr128_inc(ivec);
177		}
178		out[l] = in[l] ^ ecount_buf[n];
179		++l;
180		n = (n+1) % 16;
181	}
182
183	*num=n;
184}
185