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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_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.
CRYPTO_ctr128_encrypt(const uint8_t * in,uint8_t * out,size_t len,const AES_KEY * key,uint8_t ivec[16],uint8_t ecount_buf[16],unsigned int * num,block128_f block)85 void 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
ctr96_inc(uint8_t * counter)126 static 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 
CRYPTO_ctr128_encrypt_ctr32(const uint8_t * in,uint8_t * out,size_t len,const AES_KEY * key,uint8_t ivec[16],uint8_t ecount_buf[16],unsigned int * num,ctr128_f func)137 void 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