1 /*
2 * Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (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 <string.h>
11 #include <openssl/crypto.h>
12 #include "internal/endian.h"
13 #include "crypto/modes.h"
14
15 #if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
16 typedef size_t size_t_aX __attribute((__aligned__(1)));
17 #else
18 typedef size_t size_t_aX;
19 #endif
20
21 /*
22 * NOTE: the IV/counter CTR mode is big-endian. The code itself is
23 * endian-neutral.
24 */
25
26 /* increment counter (128-bit int) by 1 */
ctr128_inc(unsigned char * counter)27 static void ctr128_inc(unsigned char *counter)
28 {
29 u32 n = 16, c = 1;
30
31 do {
32 --n;
33 c += counter[n];
34 counter[n] = (u8)c;
35 c >>= 8;
36 } while (n);
37 }
38
39 #if !defined(OPENSSL_SMALL_FOOTPRINT)
ctr128_inc_aligned(unsigned char * counter)40 static void ctr128_inc_aligned(unsigned char *counter)
41 {
42 size_t *data, c, d, n;
43 DECLARE_IS_ENDIAN;
44
45 if (IS_LITTLE_ENDIAN || ((size_t)counter % sizeof(size_t)) != 0) {
46 ctr128_inc(counter);
47 return;
48 }
49
50 data = (size_t *)counter;
51 c = 1;
52 n = 16 / sizeof(size_t);
53 do {
54 --n;
55 d = data[n] += c;
56 /* did addition carry? */
57 c = ((d - c) & ~d) >> (sizeof(size_t) * 8 - 1);
58 } while (n);
59 }
60 #endif
61
62 /*
63 * The input encrypted as though 128bit counter mode is being used. The
64 * extra state information to record how much of the 128bit block we have
65 * used is contained in *num, and the encrypted counter is kept in
66 * ecount_buf. Both *num and ecount_buf must be initialised with zeros
67 * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
68 * that the counter is in the x lower bits of the IV (ivec), and that the
69 * application has full control over overflow and the rest of the IV. This
70 * implementation takes NO responsibility for checking that the counter
71 * doesn't overflow into the rest of the IV when incremented.
72 */
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)73 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
74 size_t len, const void *key,
75 unsigned char ivec[16],
76 unsigned char ecount_buf[16], unsigned int *num,
77 block128_f block)
78 {
79 unsigned int n;
80 size_t l = 0;
81
82 n = *num;
83
84 #if !defined(OPENSSL_SMALL_FOOTPRINT)
85 if (16 % sizeof(size_t) == 0) { /* always true actually */
86 do {
87 while (n && len) {
88 *(out++) = *(in++) ^ ecount_buf[n];
89 --len;
90 n = (n + 1) % 16;
91 }
92
93 # if defined(STRICT_ALIGNMENT)
94 if (((size_t)in | (size_t)out | (size_t)ecount_buf)
95 % sizeof(size_t) != 0)
96 break;
97 # endif
98 while (len >= 16) {
99 (*block) (ivec, ecount_buf, key);
100 ctr128_inc_aligned(ivec);
101 for (n = 0; n < 16; n += sizeof(size_t))
102 *(size_t_aX *)(out + n) =
103 *(size_t_aX *)(in + n)
104 ^ *(size_t_aX *)(ecount_buf + n);
105 len -= 16;
106 out += 16;
107 in += 16;
108 n = 0;
109 }
110 if (len) {
111 (*block) (ivec, ecount_buf, key);
112 ctr128_inc_aligned(ivec);
113 while (len--) {
114 out[n] = in[n] ^ ecount_buf[n];
115 ++n;
116 }
117 }
118 *num = n;
119 return;
120 } while (0);
121 }
122 /* the rest would be commonly eliminated by x86* compiler */
123 #endif
124 while (l < len) {
125 if (n == 0) {
126 (*block) (ivec, ecount_buf, key);
127 ctr128_inc(ivec);
128 }
129 out[l] = in[l] ^ ecount_buf[n];
130 ++l;
131 n = (n + 1) % 16;
132 }
133
134 *num = n;
135 }
136
137 /* increment upper 96 bits of 128-bit counter by 1 */
ctr96_inc(unsigned char * counter)138 static void ctr96_inc(unsigned char *counter)
139 {
140 u32 n = 12, c = 1;
141
142 do {
143 --n;
144 c += counter[n];
145 counter[n] = (u8)c;
146 c >>= 8;
147 } while (n);
148 }
149
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)150 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
151 size_t len, const void *key,
152 unsigned char ivec[16],
153 unsigned char ecount_buf[16],
154 unsigned int *num, ctr128_f func)
155 {
156 unsigned int n, ctr32;
157
158 n = *num;
159
160 while (n && len) {
161 *(out++) = *(in++) ^ ecount_buf[n];
162 --len;
163 n = (n + 1) % 16;
164 }
165
166 ctr32 = GETU32(ivec + 12);
167 while (len >= 16) {
168 size_t blocks = len / 16;
169 /*
170 * 1<<28 is just a not-so-small yet not-so-large number...
171 * Below condition is practically never met, but it has to
172 * be checked for code correctness.
173 */
174 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
175 blocks = (1U << 28);
176 /*
177 * As (*func) operates on 32-bit counter, caller
178 * has to handle overflow. 'if' below detects the
179 * overflow, which is then handled by limiting the
180 * amount of blocks to the exact overflow point...
181 */
182 ctr32 += (u32)blocks;
183 if (ctr32 < blocks) {
184 blocks -= ctr32;
185 ctr32 = 0;
186 }
187 (*func) (in, out, blocks, key, ivec);
188 /* (*ctr) does not update ivec, caller does: */
189 PUTU32(ivec + 12, ctr32);
190 /* ... overflow was detected, propagate carry. */
191 if (ctr32 == 0)
192 ctr96_inc(ivec);
193 blocks *= 16;
194 len -= blocks;
195 out += blocks;
196 in += blocks;
197 }
198 if (len) {
199 memset(ecount_buf, 0, 16);
200 (*func) (ecount_buf, ecount_buf, 1, key, ivec);
201 ++ctr32;
202 PUTU32(ivec + 12, ctr32);
203 if (ctr32 == 0)
204 ctr96_inc(ivec);
205 while (len--) {
206 out[n] = in[n] ^ ecount_buf[n];
207 ++n;
208 }
209 }
210
211 *num = n;
212 }
213
