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 <openssl/crypto.h>
52#include "modes_lcl.h"
53#include <string.h>
54
55#ifndef MODES_DEBUG
56# ifndef NDEBUG
57#  define NDEBUG
58# endif
59#endif
60#include <assert.h>
61
62/* NOTE: the IV/counter CTR mode is big-endian.  The code itself
63 * is endian-neutral. */
64
65/* increment counter (128-bit int) by 1 */
66static void ctr128_inc(unsigned char *counter) {
67	u32 n=16;
68	u8  c;
69
70	do {
71		--n;
72		c = counter[n];
73		++c;
74		counter[n] = c;
75		if (c) return;
76	} while (n);
77}
78
79#if !defined(OPENSSL_SMALL_FOOTPRINT)
80static void ctr128_inc_aligned(unsigned char *counter) {
81	size_t *data,c,n;
82	const union { long one; char little; } is_endian = {1};
83
84	if (is_endian.little) {
85		ctr128_inc(counter);
86		return;
87	}
88
89	data = (size_t *)counter;
90	n = 16/sizeof(size_t);
91	do {
92		--n;
93		c = data[n];
94		++c;
95		data[n] = c;
96		if (c) return;
97	} while (n);
98}
99#endif
100
101/* The input encrypted as though 128bit counter mode is being
102 * used.  The extra state information to record how much of the
103 * 128bit block we have used is contained in *num, and the
104 * encrypted counter is kept in ecount_buf.  Both *num and
105 * ecount_buf must be initialised with zeros before the first
106 * call to CRYPTO_ctr128_encrypt().
107 *
108 * This algorithm assumes that the counter is in the x lower bits
109 * of the IV (ivec), and that the application has full control over
110 * overflow and the rest of the IV.  This implementation takes NO
111 * responsability for checking that the counter doesn't overflow
112 * into the rest of the IV when incremented.
113 */
114void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
115			size_t len, const void *key,
116			unsigned char ivec[16], unsigned char ecount_buf[16],
117			unsigned int *num, block128_f block)
118{
119	unsigned int n;
120	size_t l=0;
121
122	assert(in && out && key && ecount_buf && num);
123	assert(*num < 16);
124
125	n = *num;
126
127#if !defined(OPENSSL_SMALL_FOOTPRINT)
128	if (16%sizeof(size_t) == 0) do { /* always true actually */
129		while (n && len) {
130			*(out++) = *(in++) ^ ecount_buf[n];
131			--len;
132			n = (n+1) % 16;
133		}
134
135#if defined(STRICT_ALIGNMENT)
136		if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
137			break;
138#endif
139		while (len>=16) {
140			(*block)(ivec, ecount_buf, key);
141			ctr128_inc_aligned(ivec);
142			for (; n<16; n+=sizeof(size_t))
143				*(size_t *)(out+n) =
144				*(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n);
145			len -= 16;
146			out += 16;
147			in  += 16;
148			n = 0;
149		}
150		if (len) {
151			(*block)(ivec, ecount_buf, key);
152 			ctr128_inc_aligned(ivec);
153			while (len--) {
154				out[n] = in[n] ^ ecount_buf[n];
155				++n;
156			}
157		}
158		*num = n;
159		return;
160	} while(0);
161	/* the rest would be commonly eliminated by x86* compiler */
162#endif
163	while (l<len) {
164		if (n==0) {
165			(*block)(ivec, ecount_buf, key);
166 			ctr128_inc(ivec);
167		}
168		out[l] = in[l] ^ ecount_buf[n];
169		++l;
170		n = (n+1) % 16;
171	}
172
173	*num=n;
174}
175
176/* increment upper 96 bits of 128-bit counter by 1 */
177static void ctr96_inc(unsigned char *counter) {
178	u32 n=12;
179	u8  c;
180
181	do {
182		--n;
183		c = counter[n];
184		++c;
185		counter[n] = c;
186		if (c) return;
187	} while (n);
188}
189
190void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
191			size_t len, const void *key,
192			unsigned char ivec[16], unsigned char ecount_buf[16],
193			unsigned int *num, ctr128_f func)
194{
195	unsigned int n,ctr32;
196
197	assert(in && out && key && ecount_buf && num);
198	assert(*num < 16);
199
200	n = *num;
201
202	while (n && len) {
203		*(out++) = *(in++) ^ ecount_buf[n];
204		--len;
205		n = (n+1) % 16;
206	}
207
208	ctr32 = GETU32(ivec+12);
209	while (len>=16) {
210		size_t blocks = len/16;
211		/*
212		 * 1<<28 is just a not-so-small yet not-so-large number...
213		 * Below condition is practically never met, but it has to
214		 * be checked for code correctness.
215		 */
216		if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
217			blocks = (1U<<28);
218		/*
219		 * As (*func) operates on 32-bit counter, caller
220		 * has to handle overflow. 'if' below detects the
221		 * overflow, which is then handled by limiting the
222		 * amount of blocks to the exact overflow point...
223		 */
224		ctr32 += (u32)blocks;
225		if (ctr32 < blocks) {
226			blocks -= ctr32;
227			ctr32   = 0;
228		}
229		(*func)(in,out,blocks,key,ivec);
230		/* (*ctr) does not update ivec, caller does: */
231		PUTU32(ivec+12,ctr32);
232		/* ... overflow was detected, propogate carry. */
233		if (ctr32 == 0)	ctr96_inc(ivec);
234		blocks *= 16;
235		len -= blocks;
236		out += blocks;
237		in  += blocks;
238	}
239	if (len) {
240		memset(ecount_buf,0,16);
241		(*func)(ecount_buf,ecount_buf,1,key,ivec);
242		++ctr32;
243		PUTU32(ivec+12,ctr32);
244		if (ctr32 == 0)	ctr96_inc(ivec);
245		while (len--) {
246			out[n] = in[n] ^ ecount_buf[n];
247			++n;
248		}
249	}
250
251	*num=n;
252}
253