52 lines
1.4 KiB
C
52 lines
1.4 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#include "tomcrypt_private.h"
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/**
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@file copy_or_zeromem.c
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Either copy or zero a block of memory in constant time, Steffen Jaeckel
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*/
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/**
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Either copy or zero a block of memory in constant time
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@param src The source where to read from
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@param dest The destination where to write to
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@param len The length of the area to process (octets)
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@param coz Copy (on 0) Or Zero (> 0)
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*/
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void copy_or_zeromem(const unsigned char* src, unsigned char* dest, unsigned long len, int coz)
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{
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unsigned long y;
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#ifdef LTC_FAST
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unsigned long z;
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LTC_FAST_TYPE fastMask = ~(LTC_FAST_TYPE)0; /* initialize fastMask at all ones */
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#endif
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unsigned char mask = 0xff; /* initialize mask at all ones */
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LTC_ARGCHKVD(src != NULL);
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LTC_ARGCHKVD(dest != NULL);
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if (coz != 0) coz = 1;
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y = 0;
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mask *= 1 - coz; /* mask = ( coz ? 0 : 0xff ) */
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#ifdef LTC_FAST
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fastMask *= 1 - coz;
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if (len & ~15) {
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for (; y < (len & ~15); y += 16) {
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for (z = 0; z < 16; z += sizeof(LTC_FAST_TYPE)) {
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*(LTC_FAST_TYPE_PTR_CAST(&dest[y+z])) = *(LTC_FAST_TYPE_PTR_CAST(&src[y+z])) & fastMask;
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}
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}
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}
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#endif
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for (; y < len; y++) {
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dest[y] = src[y] & mask;
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}
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#ifdef LTC_CLEAN_STACK
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#ifdef LTC_FAST
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fastMask = 0;
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#endif
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mask = 0;
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#endif
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}
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