1 /*
2 * Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 #include <openssl/crypto.h>
11 #include "modes_local.h"
12 #include <string.h>
13
14 #if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
15 typedef size_t size_t_aX __attribute((__aligned__(1)));
16 #else
17 typedef size_t size_t_aX;
18 #endif
19
20 /*
21 * NOTE: the IV/counter CTR mode is big-endian. The code itself is
22 * endian-neutral.
23 */
24
25 /* increment counter (128-bit int) by 1 */
ctr128_inc(unsigned char * counter)26 static void ctr128_inc(unsigned char *counter)
27 {
28 u32 n = 16, c = 1;
29
30 do {
31 --n;
32 c += counter[n];
33 counter[n] = (u8)c;
34 c >>= 8;
35 } while (n);
36 }
37
38 #if !defined(OPENSSL_SMALL_FOOTPRINT)
ctr128_inc_aligned(unsigned char * counter)39 static void ctr128_inc_aligned(unsigned char *counter)
40 {
41 size_t *data, c, d, n;
42 const union {
43 long one;
44 char little;
45 } is_endian = {
46 1
47 };
48
49 if (is_endian.little || ((size_t)counter % sizeof(size_t)) != 0) {
50 ctr128_inc(counter);
51 return;
52 }
53
54 data = (size_t *)counter;
55 c = 1;
56 n = 16 / sizeof(size_t);
57 do {
58 --n;
59 d = data[n] += c;
60 /* did addition carry? */
61 c = ((d - c) & ~d) >> (sizeof(size_t) * 8 - 1);
62 } while (n);
63 }
64 #endif
65
66 /*
67 * The input encrypted as though 128bit counter mode is being used. The
68 * extra state information to record how much of the 128bit block we have
69 * used is contained in *num, and the encrypted counter is kept in
70 * ecount_buf. Both *num and ecount_buf must be initialised with zeros
71 * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
72 * that the counter is in the x lower bits of the IV (ivec), and that the
73 * application has full control over overflow and the rest of the IV. This
74 * implementation takes NO responsibility for checking that the counter
75 * doesn't overflow into the rest of the IV when incremented.
76 */
CRYPTO_ctr128_encrypt(const unsigned char * in,unsigned char * out,size_t len,const void * key,unsigned char ivec[16],unsigned char ecount_buf[16],unsigned int * num,block128_f block)77 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
78 size_t len, const void *key,
79 unsigned char ivec[16],
80 unsigned char ecount_buf[16], unsigned int *num,
81 block128_f block)
82 {
83 unsigned int n;
84 size_t l = 0;
85
86 n = *num;
87
88 #if !defined(OPENSSL_SMALL_FOOTPRINT)
89 if (16 % sizeof(size_t) == 0) { /* always true actually */
90 do {
91 while (n && len) {
92 *(out++) = *(in++) ^ ecount_buf[n];
93 --len;
94 n = (n + 1) % 16;
95 }
96
97 # if defined(STRICT_ALIGNMENT)
98 if (((size_t)in | (size_t)out | (size_t)ecount_buf)
99 % sizeof(size_t) != 0)
100 break;
101 # endif
102 while (len >= 16) {
103 (*block) (ivec, ecount_buf, key);
104 ctr128_inc_aligned(ivec);
105 for (n = 0; n < 16; n += sizeof(size_t))
106 *(size_t_aX *)(out + n) =
107 *(size_t_aX *)(in + n)
108 ^ *(size_t_aX *)(ecount_buf + n);
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_aligned(ivec);
117 while (len--) {
118 out[n] = in[n] ^ ecount_buf[n];
119 ++n;
120 }
121 }
122 *num = n;
123 return;
124 } while (0);
125 }
126 /* the rest would be commonly eliminated by x86* compiler */
127 #endif
128 while (l < len) {
129 if (n == 0) {
130 (*block) (ivec, ecount_buf, key);
131 ctr128_inc(ivec);
132 }
133 out[l] = in[l] ^ ecount_buf[n];
134 ++l;
135 n = (n + 1) % 16;
136 }
137
138 *num = n;
139 }
140
141 /* increment upper 96 bits of 128-bit counter by 1 */
ctr96_inc(unsigned char * counter)142 static void ctr96_inc(unsigned char *counter)
143 {
144 u32 n = 12, c = 1;
145
146 do {
147 --n;
148 c += counter[n];
149 counter[n] = (u8)c;
150 c >>= 8;
151 } while (n);
152 }
153
CRYPTO_ctr128_encrypt_ctr32(const unsigned char * in,unsigned char * out,size_t len,const void * key,unsigned char ivec[16],unsigned char ecount_buf[16],unsigned int * num,ctr128_f func)154 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
155 size_t len, const void *key,
156 unsigned char ivec[16],
157 unsigned char ecount_buf[16],
158 unsigned int *num, ctr128_f func)
159 {
160 unsigned int n, ctr32;
161
162 n = *num;
163
164 while (n && len) {
165 *(out++) = *(in++) ^ ecount_buf[n];
166 --len;
167 n = (n + 1) % 16;
168 }
169
170 ctr32 = GETU32(ivec + 12);
171 while (len >= 16) {
172 size_t blocks = len / 16;
173 /*
174 * 1<<28 is just a not-so-small yet not-so-large number...
175 * Below condition is practically never met, but it has to
176 * be checked for code correctness.
177 */
178 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
179 blocks = (1U << 28);
180 /*
181 * As (*func) operates on 32-bit counter, caller
182 * has to handle overflow. 'if' below detects the
183 * overflow, which is then handled by limiting the
184 * amount of blocks to the exact overflow point...
185 */
186 ctr32 += (u32)blocks;
187 if (ctr32 < blocks) {
188 blocks -= ctr32;
189 ctr32 = 0;
190 }
191 (*func) (in, out, blocks, key, ivec);
192 /* (*ctr) does not update ivec, caller does: */
193 PUTU32(ivec + 12, ctr32);
194 /* ... overflow was detected, propagate 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 while (len--) {
210 out[n] = in[n] ^ ecount_buf[n];
211 ++n;
212 }
213 }
214
215 *num = n;
216 }
217