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_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.
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
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
145static 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
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(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