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, 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
72 OPENSSL_COMPILE_ASSERT((16 % sizeof(size_t)) == 0, bad_size_t_size_ctr);
73
74 // The input encrypted as though 128bit counter mode is being used. The extra
75 // state information to record how much of the 128bit block we have used is
76 // contained in *num, and the encrypted counter is kept in ecount_buf. Both
77 // *num and ecount_buf must be initialised with zeros before the first call to
78 // CRYPTO_ctr128_encrypt().
79 //
80 // This algorithm assumes that the counter is in the x lower bits of the IV
81 // (ivec), and that the application has full control over overflow and the rest
82 // of the IV. This implementation takes NO responsibility for checking that
83 // 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)84 void CRYPTO_ctr128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
85 const void *key, uint8_t ivec[16],
86 uint8_t ecount_buf[16], unsigned int *num,
87 block128_f block) {
88 unsigned int n;
89
90 assert(key && ecount_buf && num);
91 assert(len == 0 || (in && out));
92 assert(*num < 16);
93
94 n = *num;
95
96 while (n && len) {
97 *(out++) = *(in++) ^ ecount_buf[n];
98 --len;
99 n = (n + 1) % 16;
100 }
101
102 #if STRICT_ALIGNMENT
103 if (((uintptr_t)in | (uintptr_t)out |
104 (uintptr_t)ecount_buf) % sizeof(size_t) != 0) {
105 size_t l = 0;
106 while (l < len) {
107 if (n == 0) {
108 (*block)(ivec, ecount_buf, key);
109 ctr128_inc(ivec);
110 }
111 out[l] = in[l] ^ ecount_buf[n];
112 ++l;
113 n = (n + 1) % 16;
114 }
115
116 *num = n;
117 return;
118 }
119 #endif
120
121 while (len >= 16) {
122 (*block)(ivec, ecount_buf, key);
123 ctr128_inc(ivec);
124 for (n = 0; n < 16; n += sizeof(size_t)) {
125 store_word_le(out + n,
126 load_word_le(in + n) ^ load_word_le(ecount_buf + n));
127 }
128 len -= 16;
129 out += 16;
130 in += 16;
131 n = 0;
132 }
133 if (len) {
134 (*block)(ivec, ecount_buf, key);
135 ctr128_inc(ivec);
136 while (len--) {
137 out[n] = in[n] ^ ecount_buf[n];
138 ++n;
139 }
140 }
141 *num = n;
142 }
143
144 // increment upper 96 bits of 128-bit counter by 1
ctr96_inc(uint8_t * counter)145 static void ctr96_inc(uint8_t *counter) {
146 uint32_t n = 12, c = 1;
147
148 do {
149 --n;
150 c += counter[n];
151 counter[n] = (uint8_t) c;
152 c >>= 8;
153 } while (n);
154 }
155
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)156 void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out,
157 size_t len, const void *key,
158 uint8_t ivec[16],
159 uint8_t ecount_buf[16],
160 unsigned int *num, ctr128_f func) {
161 unsigned int n, ctr32;
162
163 assert(key && ecount_buf && num);
164 assert(len == 0 || (in && out));
165 assert(*num < 16);
166
167 n = *num;
168
169 while (n && len) {
170 *(out++) = *(in++) ^ ecount_buf[n];
171 --len;
172 n = (n + 1) % 16;
173 }
174
175 ctr32 = GETU32(ivec + 12);
176 while (len >= 16) {
177 size_t blocks = len / 16;
178 // 1<<28 is just a not-so-small yet not-so-large number...
179 // Below condition is practically never met, but it has to
180 // be checked for code correctness.
181 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) {
182 blocks = (1U << 28);
183 }
184 // As (*func) operates on 32-bit counter, caller
185 // has to handle overflow. 'if' below detects the
186 // overflow, which is then handled by limiting the
187 // amount of blocks to the exact overflow point...
188 ctr32 += (uint32_t)blocks;
189 if (ctr32 < blocks) {
190 blocks -= ctr32;
191 ctr32 = 0;
192 }
193 (*func)(in, out, blocks, key, ivec);
194 // (*func) does not update ivec, caller does:
195 PUTU32(ivec + 12, ctr32);
196 // ... overflow was detected, propogate carry.
197 if (ctr32 == 0) {
198 ctr96_inc(ivec);
199 }
200 blocks *= 16;
201 len -= blocks;
202 out += blocks;
203 in += blocks;
204 }
205 if (len) {
206 OPENSSL_memset(ecount_buf, 0, 16);
207 (*func)(ecount_buf, ecount_buf, 1, key, ivec);
208 ++ctr32;
209 PUTU32(ivec + 12, ctr32);
210 if (ctr32 == 0) {
211 ctr96_inc(ivec);
212 }
213 while (len--) {
214 out[n] = in[n] ^ ecount_buf[n];
215 ++n;
216 }
217 }
218
219 *num = n;
220 }
221