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);
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 (((size_t)in | (size_t)out | (size_t)ecount_buf) % sizeof(size_t) != 0) {
104     size_t l = 0;
105     while (l < len) {
106       if (n == 0) {
107         (*block)(ivec, ecount_buf, key);
108         ctr128_inc(ivec);
109       }
110       out[l] = in[l] ^ ecount_buf[n];
111       ++l;
112       n = (n + 1) % 16;
113     }
114 
115     *num = n;
116     return;
117   }
118 #endif
119 
120   while (len >= 16) {
121     (*block)(ivec, ecount_buf, key);
122     ctr128_inc(ivec);
123     for (n = 0; n < 16; n += sizeof(size_t)) {
124       *(size_t *)(out + n) = *(const size_t *)(in + n) ^
125                              *(const size_t *)(ecount_buf + n);
126     }
127     len -= 16;
128     out += 16;
129     in += 16;
130     n = 0;
131   }
132   if (len) {
133     (*block)(ivec, ecount_buf, key);
134     ctr128_inc(ivec);
135     while (len--) {
136       out[n] = in[n] ^ ecount_buf[n];
137       ++n;
138     }
139   }
140   *num = n;
141 }
142 
143 /* increment upper 96 bits of 128-bit counter by 1 */
ctr96_inc(uint8_t * counter)144 static void ctr96_inc(uint8_t *counter) {
145   uint32_t n = 12, c = 1;
146 
147   do {
148     --n;
149     c += counter[n];
150     counter[n] = (uint8_t) c;
151     c >>= 8;
152   } while (n);
153 }
154 
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)155 void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out,
156                                  size_t len, const void *key,
157                                  uint8_t ivec[16],
158                                  uint8_t ecount_buf[16],
159                                  unsigned int *num, ctr128_f func) {
160   unsigned int n, ctr32;
161 
162   assert(key && ecount_buf && num);
163   assert(len == 0 || (in && out));
164   assert(*num < 16);
165 
166   n = *num;
167 
168   while (n && len) {
169     *(out++) = *(in++) ^ ecount_buf[n];
170     --len;
171     n = (n + 1) % 16;
172   }
173 
174   ctr32 = GETU32(ivec + 12);
175   while (len >= 16) {
176     size_t blocks = len / 16;
177     /* 1<<28 is just a not-so-small yet not-so-large number...
178      * Below condition is practically never met, but it has to
179      * be checked for code correctness. */
180     if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) {
181       blocks = (1U << 28);
182     }
183     /* As (*func) operates on 32-bit counter, caller
184      * has to handle overflow. 'if' below detects the
185      * overflow, which is then handled by limiting the
186      * amount of blocks to the exact overflow point... */
187     ctr32 += (uint32_t)blocks;
188     if (ctr32 < blocks) {
189       blocks -= ctr32;
190       ctr32 = 0;
191     }
192     (*func)(in, out, blocks, key, ivec);
193     /* (*func) does not update ivec, caller does: */
194     PUTU32(ivec + 12, ctr32);
195     /* ... overflow was detected, propogate carry. */
196     if (ctr32 == 0) {
197       ctr96_inc(ivec);
198     }
199     blocks *= 16;
200     len -= blocks;
201     out += blocks;
202     in += blocks;
203   }
204   if (len) {
205     OPENSSL_memset(ecount_buf, 0, 16);
206     (*func)(ecount_buf, ecount_buf, 1, key, ivec);
207     ++ctr32;
208     PUTU32(ivec + 12, ctr32);
209     if (ctr32 == 0) {
210       ctr96_inc(ivec);
211     }
212     while (len--) {
213       out[n] = in[n] ^ ecount_buf[n];
214       ++n;
215     }
216   }
217 
218   *num = n;
219 }
220