1 /* $OpenBSD: ctr128.c,v 1.7 2017/08/13 17:46:24 bcook Exp $ */
2 /* ====================================================================
3  * Copyright (c) 2008 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 #include <openssl/crypto.h>
53 #include "modes_lcl.h"
54 #include <string.h>
55 
56 #ifndef MODES_DEBUG
57 # ifndef NDEBUG
58 #  define NDEBUG
59 # endif
60 #endif
61 #include <assert.h>
62 
63 /* NOTE: the IV/counter CTR mode is big-endian.  The code itself
64  * is endian-neutral. */
65 
66 /* increment counter (128-bit int) by 1 */
67 static void ctr128_inc(unsigned char *counter) {
68 	u32 n=16;
69 	u8  c;
70 
71 	do {
72 		--n;
73 		c = counter[n];
74 		++c;
75 		counter[n] = c;
76 		if (c) return;
77 	} while (n);
78 }
79 
80 #if !defined(OPENSSL_SMALL_FOOTPRINT)
81 static void
82 ctr128_inc_aligned(unsigned char *counter)
83 {
84 #if BYTE_ORDER == LITTLE_ENDIAN
85 	ctr128_inc(counter);
86 #else
87 	size_t *data, c, n;
88 	data = (size_t *)counter;
89 	n = 16 / sizeof(size_t);
90 	do {
91 		--n;
92 		c = data[n];
93 		++c;
94 		data[n] = c;
95 		if (c)
96 			return;
97 	} while (n);
98 #endif
99 }
100 #endif
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 CRYPTO_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  */
115 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
116 			size_t len, const void *key,
117 			unsigned char ivec[16], unsigned char ecount_buf[16],
118 			unsigned int *num, block128_f block)
119 {
120 	unsigned int n;
121 	size_t l=0;
122 
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 #ifdef __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 */
177 static 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 
190 void 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(*num < 16);
198 
199 	n = *num;
200 
201 	while (n && len) {
202 		*(out++) = *(in++) ^ ecount_buf[n];
203 		--len;
204 		n = (n+1) % 16;
205 	}
206 
207 	ctr32 = GETU32(ivec+12);
208 	while (len>=16) {
209 		size_t blocks = len/16;
210 		/*
211 		 * 1<<28 is just a not-so-small yet not-so-large number...
212 		 * Below condition is practically never met, but it has to
213 		 * be checked for code correctness.
214 		 */
215 		if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
216 			blocks = (1U<<28);
217 		/*
218 		 * As (*func) operates on 32-bit counter, caller
219 		 * has to handle overflow. 'if' below detects the
220 		 * overflow, which is then handled by limiting the
221 		 * amount of blocks to the exact overflow point...
222 		 */
223 		ctr32 += (u32)blocks;
224 		if (ctr32 < blocks) {
225 			blocks -= ctr32;
226 			ctr32   = 0;
227 		}
228 		(*func)(in,out,blocks,key,ivec);
229 		/* (*ctr) does not update ivec, caller does: */
230 		PUTU32(ivec+12,ctr32);
231 		/* ... overflow was detected, propogate carry. */
232 		if (ctr32 == 0)	ctr96_inc(ivec);
233 		blocks *= 16;
234 		len -= blocks;
235 		out += blocks;
236 		in  += blocks;
237 	}
238 	if (len) {
239 		memset(ecount_buf,0,16);
240 		(*func)(ecount_buf,ecount_buf,1,key,ivec);
241 		++ctr32;
242 		PUTU32(ivec+12,ctr32);
243 		if (ctr32 == 0)	ctr96_inc(ivec);
244 		while (len--) {
245 			out[n] = in[n] ^ ecount_buf[n];
246 			++n;
247 		}
248 	}
249 
250 	*num=n;
251 }
252