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#include <openssl/modes.h>
49
50#include <assert.h>
51
52#include "internal.h"
53
54
55/* NOTE: the IV/counter CTR mode is big-endian.  The code itself
56 * is endian-neutral. */
57
58/* increment counter (128-bit int) by 1 */
59static void ctr128_inc(uint8_t *counter) {
60  uint32_t n = 16;
61  uint8_t c;
62
63  do {
64    --n;
65    c = counter[n];
66    ++c;
67    counter[n] = c;
68    if (c) {
69      return;
70    }
71  } while (n);
72}
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. */
84void 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  size_t l=0;
90
91  assert(in && out && key && ecount_buf && num);
92  assert(*num < 16);
93  assert((16 % sizeof(size_t)) == 0);
94
95  n = *num;
96
97  while (n && len) {
98    *(out++) = *(in++) ^ ecount_buf[n];
99    --len;
100    n = (n + 1) % 16;
101  }
102
103  if (STRICT_ALIGNMENT &&
104      ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 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
119  while (len >= 16) {
120    (*block)(ivec, ecount_buf, key);
121    ctr128_inc(ivec);
122    for (; n < 16; n += sizeof(size_t))
123      *(size_t *)(out + n) = *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
124    len -= 16;
125    out += 16;
126    in += 16;
127    n = 0;
128  }
129  if (len) {
130    (*block)(ivec, ecount_buf, key);
131    ctr128_inc(ivec);
132    while (len--) {
133      out[n] = in[n] ^ ecount_buf[n];
134      ++n;
135    }
136  }
137  *num = n;
138}
139
140/* increment upper 96 bits of 128-bit counter by 1 */
141static void ctr96_inc(uint8_t *counter) {
142  uint32_t n = 12;
143  uint8_t c;
144
145  do {
146    --n;
147    c = counter[n];
148    ++c;
149    counter[n] = c;
150    if (c) {
151      return;
152    }
153  } while (n);
154}
155
156void 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(in && out && key && ecount_buf && num);
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    /* As (*func) operates on 32-bit counter, caller
183     * has to handle overflow. 'if' below detects the
184     * overflow, which is then handled by limiting the
185     * amount of blocks to the exact overflow point... */
186    ctr32 += (uint32_t)blocks;
187    if (ctr32 < blocks) {
188      blocks -= ctr32;
189      ctr32 = 0;
190    }
191    (*func)(in, out, blocks, key, ivec);
192    /* (*func) does not update ivec, caller does: */
193    PUTU32(ivec + 12, ctr32);
194    /* ... overflow was detected, propogate carry. */
195    if (ctr32 == 0)
196      ctr96_inc(ivec);
197    blocks *= 16;
198    len -= blocks;
199    out += blocks;
200    in += blocks;
201  }
202  if (len) {
203    memset(ecount_buf, 0, 16);
204    (*func)(ecount_buf, ecount_buf, 1, key, ivec);
205    ++ctr32;
206    PUTU32(ivec + 12, ctr32);
207    if (ctr32 == 0) {
208      ctr96_inc(ivec);
209    }
210    while (len--) {
211      out[n] = in[n] ^ ecount_buf[n];
212      ++n;
213    }
214  }
215
216  *num = n;
217}
218