[331] | 1 | /*
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| 2 | * Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <openssl/crypto.h>
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| 11 | #include "modes_lcl.h"
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| 12 | #include <string.h>
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| 13 |
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| 14 | /*
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| 15 | * NOTE: the IV/counter CTR mode is big-endian. The code itself is
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| 16 | * endian-neutral.
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| 17 | */
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| 18 |
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| 19 | /* increment counter (128-bit int) by 1 */
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| 20 | static void ctr128_inc(unsigned char *counter)
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| 21 | {
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| 22 | u32 n = 16, c = 1;
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| 23 |
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| 24 | do {
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| 25 | --n;
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| 26 | c += counter[n];
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| 27 | counter[n] = (u8)c;
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| 28 | c >>= 8;
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| 29 | } while (n);
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| 30 | }
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| 31 |
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| 32 | #if !defined(OPENSSL_SMALL_FOOTPRINT)
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| 33 | static void ctr128_inc_aligned(unsigned char *counter)
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| 34 | {
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| 35 | size_t *data, c, d, n;
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| 36 | const union {
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| 37 | long one;
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| 38 | char little;
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| 39 | } is_endian = {
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| 40 | 1
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| 41 | };
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| 42 |
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| 43 | if (is_endian.little || ((size_t)counter % sizeof(size_t)) != 0) {
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| 44 | ctr128_inc(counter);
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| 45 | return;
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| 46 | }
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| 47 |
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| 48 | data = (size_t *)counter;
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| 49 | c = 1;
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| 50 | n = 16 / sizeof(size_t);
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| 51 | do {
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| 52 | --n;
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| 53 | d = data[n] += c;
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| 54 | /* did addition carry? */
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| 55 | c = ((d - c) & ~d) >> (sizeof(size_t) * 8 - 1);
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| 56 | } while (n);
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| 57 | }
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| 58 | #endif
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| 59 |
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| 60 | /*
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| 61 | * The input encrypted as though 128bit counter mode is being used. The
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| 62 | * extra state information to record how much of the 128bit block we have
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| 63 | * used is contained in *num, and the encrypted counter is kept in
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| 64 | * ecount_buf. Both *num and ecount_buf must be initialised with zeros
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| 65 | * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
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| 66 | * that the counter is in the x lower bits of the IV (ivec), and that the
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| 67 | * application has full control over overflow and the rest of the IV. This
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| 68 | * implementation takes NO responsibility for checking that the counter
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| 69 | * doesn't overflow into the rest of the IV when incremented.
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| 70 | */
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| 71 | void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
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| 72 | size_t len, const void *key,
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| 73 | unsigned char ivec[16],
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| 74 | unsigned char ecount_buf[16], unsigned int *num,
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| 75 | block128_f block)
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| 76 | {
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| 77 | unsigned int n;
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| 78 | size_t l = 0;
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| 79 |
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| 80 | n = *num;
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| 81 |
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| 82 | #if !defined(OPENSSL_SMALL_FOOTPRINT)
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| 83 | if (16 % sizeof(size_t) == 0) { /* always true actually */
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| 84 | do {
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| 85 | while (n && len) {
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| 86 | *(out++) = *(in++) ^ ecount_buf[n];
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| 87 | --len;
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| 88 | n = (n + 1) % 16;
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| 89 | }
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| 90 |
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| 91 | # if defined(STRICT_ALIGNMENT)
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| 92 | if (((size_t)in | (size_t)out | (size_t)ecount_buf)
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| 93 | % sizeof(size_t) != 0)
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| 94 | break;
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| 95 | # endif
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| 96 | while (len >= 16) {
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| 97 | (*block) (ivec, ecount_buf, key);
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| 98 | ctr128_inc_aligned(ivec);
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| 99 | for (n = 0; n < 16; n += sizeof(size_t))
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| 100 | *(size_t *)(out + n) =
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| 101 | *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
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| 102 | len -= 16;
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| 103 | out += 16;
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| 104 | in += 16;
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| 105 | n = 0;
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| 106 | }
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| 107 | if (len) {
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| 108 | (*block) (ivec, ecount_buf, key);
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| 109 | ctr128_inc_aligned(ivec);
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| 110 | while (len--) {
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| 111 | out[n] = in[n] ^ ecount_buf[n];
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| 112 | ++n;
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| 113 | }
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| 114 | }
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| 115 | *num = n;
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| 116 | return;
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| 117 | } while (0);
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| 118 | }
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| 119 | /* the rest would be commonly eliminated by x86* compiler */
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| 120 | #endif
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| 121 | while (l < len) {
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| 122 | if (n == 0) {
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| 123 | (*block) (ivec, ecount_buf, key);
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| 124 | ctr128_inc(ivec);
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| 125 | }
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| 126 | out[l] = in[l] ^ ecount_buf[n];
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| 127 | ++l;
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| 128 | n = (n + 1) % 16;
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| 129 | }
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| 130 |
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| 131 | *num = n;
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| 132 | }
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| 133 |
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| 134 | /* increment upper 96 bits of 128-bit counter by 1 */
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| 135 | static void ctr96_inc(unsigned char *counter)
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| 136 | {
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| 137 | u32 n = 12, c = 1;
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| 138 |
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| 139 | do {
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| 140 | --n;
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| 141 | c += counter[n];
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| 142 | counter[n] = (u8)c;
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| 143 | c >>= 8;
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| 144 | } while (n);
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| 145 | }
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| 146 |
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| 147 | void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
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| 148 | size_t len, const void *key,
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| 149 | unsigned char ivec[16],
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| 150 | unsigned char ecount_buf[16],
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| 151 | unsigned int *num, ctr128_f func)
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| 152 | {
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| 153 | unsigned int n, ctr32;
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| 154 |
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| 155 | n = *num;
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| 156 |
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| 157 | while (n && len) {
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| 158 | *(out++) = *(in++) ^ ecount_buf[n];
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| 159 | --len;
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| 160 | n = (n + 1) % 16;
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| 161 | }
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| 162 |
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| 163 | ctr32 = GETU32(ivec + 12);
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| 164 | while (len >= 16) {
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| 165 | size_t blocks = len / 16;
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| 166 | /*
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| 167 | * 1<<28 is just a not-so-small yet not-so-large number...
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| 168 | * Below condition is practically never met, but it has to
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| 169 | * be checked for code correctness.
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| 170 | */
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| 171 | if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
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| 172 | blocks = (1U << 28);
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| 173 | /*
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| 174 | * As (*func) operates on 32-bit counter, caller
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| 175 | * has to handle overflow. 'if' below detects the
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| 176 | * overflow, which is then handled by limiting the
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| 177 | * amount of blocks to the exact overflow point...
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| 178 | */
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| 179 | ctr32 += (u32)blocks;
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| 180 | if (ctr32 < blocks) {
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| 181 | blocks -= ctr32;
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| 182 | ctr32 = 0;
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| 183 | }
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| 184 | (*func) (in, out, blocks, key, ivec);
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| 185 | /* (*ctr) does not update ivec, caller does: */
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| 186 | PUTU32(ivec + 12, ctr32);
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| 187 | /* ... overflow was detected, propagate carry. */
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| 188 | if (ctr32 == 0)
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| 189 | ctr96_inc(ivec);
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| 190 | blocks *= 16;
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| 191 | len -= blocks;
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| 192 | out += blocks;
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| 193 | in += blocks;
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| 194 | }
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| 195 | if (len) {
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| 196 | memset(ecount_buf, 0, 16);
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| 197 | (*func) (ecount_buf, ecount_buf, 1, key, ivec);
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| 198 | ++ctr32;
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| 199 | PUTU32(ivec + 12, ctr32);
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| 200 | if (ctr32 == 0)
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| 201 | ctr96_inc(ivec);
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| 202 | while (len--) {
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| 203 | out[n] = in[n] ^ ecount_buf[n];
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| 204 | ++n;
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| 205 | }
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| 206 | }
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| 207 |
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| 208 | *num = n;
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| 209 | }
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