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git.ipfire.org Git - thirdparty/openssl.git/blob - crypto/modes/ctr128.c
2 * Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
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
11 #include <openssl/crypto.h>
12 #include "internal/modes_int.h"
15 * NOTE: the IV/counter CTR mode is big-endian. The code itself is
19 /* increment counter (128-bit int) by 1 */
20 static void ctr128_inc(unsigned char *counter
)
32 #if !defined(OPENSSL_SMALL_FOOTPRINT)
33 static void ctr128_inc_aligned(unsigned char *counter
)
35 size_t *data
, c
, d
, n
;
43 if (is_endian
.little
|| ((size_t)counter
% sizeof(size_t)) != 0) {
48 data
= (size_t *)counter
;
50 n
= 16 / sizeof(size_t);
54 /* did addition carry? */
55 c
= ((d
- c
) & ~d
) >> (sizeof(size_t) * 8 - 1);
61 * The input encrypted as though 128bit counter mode is being used. The
62 * extra state information to record how much of the 128bit block we have
63 * used is contained in *num, and the encrypted counter is kept in
64 * ecount_buf. Both *num and ecount_buf must be initialised with zeros
65 * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
66 * that the counter is in the x lower bits of the IV (ivec), and that the
67 * application has full control over overflow and the rest of the IV. This
68 * implementation takes NO responsibility for checking that the counter
69 * doesn't overflow into the rest of the IV when incremented.
71 void CRYPTO_ctr128_encrypt(const unsigned char *in
, unsigned char *out
,
72 size_t len
, const void *key
,
73 unsigned char ivec
[16],
74 unsigned char ecount_buf
[16], unsigned int *num
,
82 #if !defined(OPENSSL_SMALL_FOOTPRINT)
83 if (16 % sizeof(size_t) == 0) { /* always true actually */
86 *(out
++) = *(in
++) ^ ecount_buf
[n
];
91 # if defined(STRICT_ALIGNMENT)
92 if (((size_t)in
| (size_t)out
| (size_t)ecount_buf
)
93 % sizeof(size_t) != 0)
97 (*block
) (ivec
, ecount_buf
, key
);
98 ctr128_inc_aligned(ivec
);
99 for (n
= 0; n
< 16; n
+= sizeof(size_t))
100 *(size_t *)(out
+ n
) =
101 *(size_t *)(in
+ n
) ^ *(size_t *)(ecount_buf
+ n
);
108 (*block
) (ivec
, ecount_buf
, key
);
109 ctr128_inc_aligned(ivec
);
111 out
[n
] = in
[n
] ^ ecount_buf
[n
];
119 /* the rest would be commonly eliminated by x86* compiler */
123 (*block
) (ivec
, ecount_buf
, key
);
126 out
[l
] = in
[l
] ^ ecount_buf
[n
];
134 /* increment upper 96 bits of 128-bit counter by 1 */
135 static void ctr96_inc(unsigned char *counter
)
147 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in
, unsigned char *out
,
148 size_t len
, const void *key
,
149 unsigned char ivec
[16],
150 unsigned char ecount_buf
[16],
151 unsigned int *num
, ctr128_f func
)
153 unsigned int n
, ctr32
;
158 *(out
++) = *(in
++) ^ ecount_buf
[n
];
163 ctr32
= GETU32(ivec
+ 12);
165 size_t blocks
= len
/ 16;
167 * 1<<28 is just a not-so-small yet not-so-large number...
168 * Below condition is practically never met, but it has to
169 * be checked for code correctness.
171 if (sizeof(size_t) > sizeof(unsigned int) && blocks
> (1U << 28))
174 * As (*func) operates on 32-bit counter, caller
175 * has to handle overflow. 'if' below detects the
176 * overflow, which is then handled by limiting the
177 * amount of blocks to the exact overflow point...
179 ctr32
+= (u32
)blocks
;
180 if (ctr32
< blocks
) {
184 (*func
) (in
, out
, blocks
, key
, ivec
);
185 /* (*ctr) does not update ivec, caller does: */
186 PUTU32(ivec
+ 12, ctr32
);
187 /* ... overflow was detected, propagate carry. */
196 memset(ecount_buf
, 0, 16);
197 (*func
) (ecount_buf
, ecount_buf
, 1, key
, ivec
);
199 PUTU32(ivec
+ 12, ctr32
);
203 out
[n
] = in
[n
] ^ ecount_buf
[n
];