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
61static void ctr128_inc(uint8_t *counter) {
62 uint32_t n = 16, c = 1;
63
64 do {
65 --n;
66 c += counter[n];
67 counter[n] = (uint8_t) c;
68 c >>= 8;
69 } while (n);
70}
71
72OPENSSL_STATIC_ASSERT(16 % sizeof(size_t) == 0,
73 "block cannot be divided into size_t");
74
75// The input encrypted as though 128bit counter mode is being used. The extra
76// state information to record how much of the 128bit block we have used is
77// contained in *num, and the encrypted counter is kept in ecount_buf. Both
78// *num and ecount_buf must be initialised with zeros before the first call to
79// CRYPTO_ctr128_encrypt().
80//
81// This algorithm assumes that the counter is in the x lower bits of the IV
82// (ivec), and that the application has full control over overflow and the rest
83// of the IV. This implementation takes NO responsibility for checking that
84// the counter doesn't overflow into the rest of the IV when incremented.
85void CRYPTO_ctr128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
86 const AES_KEY *key, uint8_t ivec[16],
87 uint8_t ecount_buf[16], unsigned int *num,
88 block128_f block) {
89 unsigned int n;
90
91 assert(key && ecount_buf && num);
92 assert(len == 0 || (in && out));
93 assert(*num < 16);
94
95 n = *num;
96
97 while (n && len) {
98 *(out++) = *(in++) ^ ecount_buf[n];
99 --len;
100 n = (n + 1) % 16;
101 }
102 while (len >= 16) {
103 (*block)(ivec, ecount_buf, key);
104 ctr128_inc(ivec);
105 for (n = 0; n < 16; n += sizeof(size_t)) {
106 store_word_le(out + n,
107 load_word_le(in + n) ^ load_word_le(ecount_buf + n));
108 }
109 len -= 16;
110 out += 16;
111 in += 16;
112 n = 0;
113 }
114 if (len) {
115 (*block)(ivec, ecount_buf, key);
116 ctr128_inc(ivec);
117 while (len--) {
118 out[n] = in[n] ^ ecount_buf[n];
119 ++n;
120 }
121 }
122 *num = n;
123}
124
125// increment upper 96 bits of 128-bit counter by 1
126static void ctr96_inc(uint8_t *counter) {
127 uint32_t n = 12, c = 1;
128
129 do {
130 --n;
131 c += counter[n];
132 counter[n] = (uint8_t) c;
133 c >>= 8;
134 } while (n);
135}
136
137void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out, size_t len,
138 const AES_KEY *key, uint8_t ivec[16],
139 uint8_t ecount_buf[16], unsigned int *num,
140 ctr128_f func) {
141 unsigned int n, ctr32;
142
143 assert(key && ecount_buf && num);
144 assert(len == 0 || (in && out));
145 assert(*num < 16);
146
147 n = *num;
148
149 while (n && len) {
150 *(out++) = *(in++) ^ ecount_buf[n];
151 --len;
152 n = (n + 1) % 16;
153 }
154
155 ctr32 = GETU32(ivec + 12);
156 while (len >= 16) {
157 size_t blocks = len / 16;
158 // 1<<28 is just a not-so-small yet not-so-large number...
159 // Below condition is practically never met, but it has to
160 // be checked for code correctness.
161 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) {
162 blocks = (1U << 28);
163 }
164 // As (*func) operates on 32-bit counter, caller
165 // has to handle overflow. 'if' below detects the
166 // overflow, which is then handled by limiting the
167 // amount of blocks to the exact overflow point...
168 ctr32 += (uint32_t)blocks;
169 if (ctr32 < blocks) {
170 blocks -= ctr32;
171 ctr32 = 0;
172 }
173 (*func)(in, out, blocks, key, ivec);
174 // (*func) does not update ivec, caller does:
175 PUTU32(ivec + 12, ctr32);
176 // ... overflow was detected, propogate carry.
177 if (ctr32 == 0) {
178 ctr96_inc(ivec);
179 }
180 blocks *= 16;
181 len -= blocks;
182 out += blocks;
183 in += blocks;
184 }
185 if (len) {
186 OPENSSL_memset(ecount_buf, 0, 16);
187 (*func)(ecount_buf, ecount_buf, 1, key, ivec);
188 ++ctr32;
189 PUTU32(ivec + 12, ctr32);
190 if (ctr32 == 0) {
191 ctr96_inc(ivec);
192 }
193 while (len--) {
194 out[n] = in[n] ^ ecount_buf[n];
195 ++n;
196 }
197 }
198
199 *num = n;
200}
201