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 #include <openssl/type_check.h>
50
51 #include <assert.h>
52 #include <string.h>
53
54 #include "internal.h"
55
56
57 /* NOTE: the IV/counter CTR mode is big-endian. The code itself
58 * is endian-neutral. */
59
60 /* increment counter (128-bit int) by 1 */
ctr128_inc(uint8_t * counter)61 static void ctr128_inc(uint8_t *counter) {
62 uint32_t n = 16;
63 uint8_t c;
64
65 do {
66 --n;
67 c = counter[n];
68 ++c;
69 counter[n] = c;
70 if (c) {
71 return;
72 }
73 } while (n);
74 }
75
76 OPENSSL_COMPILE_ASSERT((16 % sizeof(size_t)) == 0, bad_size_t_size);
77
78 /* The input encrypted as though 128bit counter mode is being used. The extra
79 * state information to record how much of the 128bit block we have used is
80 * contained in *num, and the encrypted counter is kept in ecount_buf. Both
81 * *num and ecount_buf must be initialised with zeros before the first call to
82 * CRYPTO_ctr128_encrypt().
83 *
84 * This algorithm assumes that the counter is in the x lower bits of the IV
85 * (ivec), and that the application has full control over overflow and the rest
86 * of the IV. This implementation takes NO responsibility for checking that
87 * the counter doesn't overflow into the rest of the IV when incremented. */
CRYPTO_ctr128_encrypt(const uint8_t * in,uint8_t * out,size_t len,const void * key,uint8_t ivec[16],uint8_t ecount_buf[16],unsigned int * num,block128_f block)88 void CRYPTO_ctr128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
89 const void *key, uint8_t ivec[16],
90 uint8_t ecount_buf[16], unsigned int *num,
91 block128_f block) {
92 unsigned int n;
93
94 assert(key && ecount_buf && num);
95 assert(len == 0 || (in && out));
96 assert(*num < 16);
97
98 n = *num;
99
100 while (n && len) {
101 *(out++) = *(in++) ^ ecount_buf[n];
102 --len;
103 n = (n + 1) % 16;
104 }
105
106 #if STRICT_ALIGNMENT
107 if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
108 size_t l = 0;
109 while (l < len) {
110 if (n == 0) {
111 (*block)(ivec, ecount_buf, key);
112 ctr128_inc(ivec);
113 }
114 out[l] = in[l] ^ ecount_buf[n];
115 ++l;
116 n = (n + 1) % 16;
117 }
118
119 *num = n;
120 return;
121 }
122 #endif
123
124 while (len >= 16) {
125 (*block)(ivec, ecount_buf, key);
126 ctr128_inc(ivec);
127 for (; n < 16; n += sizeof(size_t)) {
128 *(size_t *)(out + n) = *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
129 }
130 len -= 16;
131 out += 16;
132 in += 16;
133 n = 0;
134 }
135 if (len) {
136 (*block)(ivec, ecount_buf, key);
137 ctr128_inc(ivec);
138 while (len--) {
139 out[n] = in[n] ^ ecount_buf[n];
140 ++n;
141 }
142 }
143 *num = n;
144 }
145
146 /* increment upper 96 bits of 128-bit counter by 1 */
ctr96_inc(uint8_t * counter)147 static void ctr96_inc(uint8_t *counter) {
148 uint32_t n = 12;
149 uint8_t c;
150
151 do {
152 --n;
153 c = counter[n];
154 ++c;
155 counter[n] = c;
156 if (c) {
157 return;
158 }
159 } while (n);
160 }
161
CRYPTO_ctr128_encrypt_ctr32(const uint8_t * in,uint8_t * out,size_t len,const void * key,uint8_t ivec[16],uint8_t ecount_buf[16],unsigned int * num,ctr128_f func)162 void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out,
163 size_t len, const void *key,
164 uint8_t ivec[16],
165 uint8_t ecount_buf[16],
166 unsigned int *num, ctr128_f func) {
167 unsigned int n, ctr32;
168
169 assert(key && ecount_buf && num);
170 assert(len == 0 || (in && out));
171 assert(*num < 16);
172
173 n = *num;
174
175 while (n && len) {
176 *(out++) = *(in++) ^ ecount_buf[n];
177 --len;
178 n = (n + 1) % 16;
179 }
180
181 ctr32 = GETU32(ivec + 12);
182 while (len >= 16) {
183 size_t blocks = len / 16;
184 /* 1<<28 is just a not-so-small yet not-so-large number...
185 * Below condition is practically never met, but it has to
186 * be checked for code correctness. */
187 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) {
188 blocks = (1U << 28);
189 }
190 /* As (*func) operates on 32-bit counter, caller
191 * has to handle overflow. 'if' below detects the
192 * overflow, which is then handled by limiting the
193 * amount of blocks to the exact overflow point... */
194 ctr32 += (uint32_t)blocks;
195 if (ctr32 < blocks) {
196 blocks -= ctr32;
197 ctr32 = 0;
198 }
199 (*func)(in, out, blocks, key, ivec);
200 /* (*func) does not update ivec, caller does: */
201 PUTU32(ivec + 12, ctr32);
202 /* ... overflow was detected, propogate carry. */
203 if (ctr32 == 0) {
204 ctr96_inc(ivec);
205 }
206 blocks *= 16;
207 len -= blocks;
208 out += blocks;
209 in += blocks;
210 }
211 if (len) {
212 memset(ecount_buf, 0, 16);
213 (*func)(ecount_buf, ecount_buf, 1, key, ivec);
214 ++ctr32;
215 PUTU32(ivec + 12, ctr32);
216 if (ctr32 == 0) {
217 ctr96_inc(ivec);
218 }
219 while (len--) {
220 out[n] = in[n] ^ ecount_buf[n];
221 ++n;
222 }
223 }
224
225 *num = n;
226 }
227