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 */
50
51#include <openssl/crypto.h>
52#include "modes_lcl.h"
53#include <string.h>
54
55#ifndef MODES_DEBUG
56# ifndef NDEBUG
57#  define NDEBUG
58# endif
59#endif
60#include <assert.h>
61
62/*
63 * NOTE: the IV/counter CTR mode is big-endian.  The code itself is
64 * endian-neutral.
65 */
66
67/* increment counter (128-bit int) by 1 */
68static void ctr128_inc(unsigned char *counter)
69{
70    u32 n = 16, c = 1;
71
72    do {
73        --n;
74        c += counter[n];
75        counter[n] = (u8)c;
76        c >>= 8;
77    } while (n);
78}
79
80#if !defined(OPENSSL_SMALL_FOOTPRINT)
81static void ctr128_inc_aligned(unsigned char *counter)
82{
83    size_t *data, c, d, n;
84    const union {
85        long one;
86        char little;
87    } is_endian = {
88        1
89    };
90
91    if (is_endian.little || ((size_t)counter % sizeof(size_t)) != 0) {
92        ctr128_inc(counter);
93        return;
94    }
95
96    data = (size_t *)counter;
97    c = 1;
98    n = 16 / sizeof(size_t);
99    do {
100        --n;
101        d = data[n] += c;
102        /* did addition carry? */
103        c = ((d - c) & ~d) >> (sizeof(size_t) * 8 - 1);
104    } while (n);
105}
106#endif
107
108/*
109 * The input encrypted as though 128bit counter mode is being used.  The
110 * extra state information to record how much of the 128bit block we have
111 * used is contained in *num, and the encrypted counter is kept in
112 * ecount_buf.  Both *num and ecount_buf must be initialised with zeros
113 * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
114 * that the counter is in the x lower bits of the IV (ivec), and that the
115 * application has full control over overflow and the rest of the IV.  This
116 * implementation takes NO responsability for checking that the counter
117 * doesn't overflow into the rest of the IV when incremented.
118 */
119void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
120                           size_t len, const void *key,
121                           unsigned char ivec[16],
122                           unsigned char ecount_buf[16], unsigned int *num,
123                           block128_f block)
124{
125    unsigned int n;
126    size_t l = 0;
127
128    assert(in && out && key && ecount_buf && num);
129    assert(*num < 16);
130
131    n = *num;
132
133#if !defined(OPENSSL_SMALL_FOOTPRINT)
134    if (16 % sizeof(size_t) == 0) { /* always true actually */
135        do {
136            while (n && len) {
137                *(out++) = *(in++) ^ ecount_buf[n];
138                --len;
139                n = (n + 1) % 16;
140            }
141
142# if defined(STRICT_ALIGNMENT)
143            if (((size_t)in | (size_t)out | (size_t)ecount_buf)
144                % sizeof(size_t) != 0)
145                break;
146# endif
147            while (len >= 16) {
148                (*block) (ivec, ecount_buf, key);
149                ctr128_inc_aligned(ivec);
150                for (n = 0; n < 16; n += sizeof(size_t))
151                    *(size_t *)(out + n) =
152                        *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
153                len -= 16;
154                out += 16;
155                in += 16;
156                n = 0;
157            }
158            if (len) {
159                (*block) (ivec, ecount_buf, key);
160                ctr128_inc_aligned(ivec);
161                while (len--) {
162                    out[n] = in[n] ^ ecount_buf[n];
163                    ++n;
164                }
165            }
166            *num = n;
167            return;
168        } while (0);
169    }
170    /* the rest would be commonly eliminated by x86* compiler */
171#endif
172    while (l < len) {
173        if (n == 0) {
174            (*block) (ivec, ecount_buf, key);
175            ctr128_inc(ivec);
176        }
177        out[l] = in[l] ^ ecount_buf[n];
178        ++l;
179        n = (n + 1) % 16;
180    }
181
182    *num = n;
183}
184
185/* increment upper 96 bits of 128-bit counter by 1 */
186static void ctr96_inc(unsigned char *counter)
187{
188    u32 n = 12, c = 1;
189
190    do {
191        --n;
192        c += counter[n];
193        counter[n] = (u8)c;
194        c >>= 8;
195    } while (n);
196}
197
198void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
199                                 size_t len, const void *key,
200                                 unsigned char ivec[16],
201                                 unsigned char ecount_buf[16],
202                                 unsigned int *num, ctr128_f func)
203{
204    unsigned int n, ctr32;
205
206    assert(in && out && key && ecount_buf && num);
207    assert(*num < 16);
208
209    n = *num;
210
211    while (n && len) {
212        *(out++) = *(in++) ^ ecount_buf[n];
213        --len;
214        n = (n + 1) % 16;
215    }
216
217    ctr32 = GETU32(ivec + 12);
218    while (len >= 16) {
219        size_t blocks = len / 16;
220        /*
221         * 1<<28 is just a not-so-small yet not-so-large number...
222         * Below condition is practically never met, but it has to
223         * be checked for code correctness.
224         */
225        if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
226            blocks = (1U << 28);
227        /*
228         * As (*func) operates on 32-bit counter, caller
229         * has to handle overflow. 'if' below detects the
230         * overflow, which is then handled by limiting the
231         * amount of blocks to the exact overflow point...
232         */
233        ctr32 += (u32)blocks;
234        if (ctr32 < blocks) {
235            blocks -= ctr32;
236            ctr32 = 0;
237        }
238        (*func) (in, out, blocks, key, ivec);
239        /* (*ctr) does not update ivec, caller does: */
240        PUTU32(ivec + 12, ctr32);
241        /* ... overflow was detected, propogate carry. */
242        if (ctr32 == 0)
243            ctr96_inc(ivec);
244        blocks *= 16;
245        len -= blocks;
246        out += blocks;
247        in += blocks;
248    }
249    if (len) {
250        memset(ecount_buf, 0, 16);
251        (*func) (ecount_buf, ecount_buf, 1, key, ivec);
252        ++ctr32;
253        PUTU32(ivec + 12, ctr32);
254        if (ctr32 == 0)
255            ctr96_inc(ivec);
256        while (len--) {
257            out[n] = in[n] ^ ecount_buf[n];
258            ++n;
259        }
260    }
261
262    *num = n;
263}
264