60 lines
1.4 KiB
C
60 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 xcbc_done.c
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XCBC Support, terminate the state
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*/
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#ifdef LTC_XCBC
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/** Terminate the XCBC-MAC state
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@param xcbc XCBC state to terminate
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@param out [out] Destination for the MAC tag
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@param outlen [in/out] Destination size and final tag size
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Return CRYPT_OK on success
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*/
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int xcbc_done(xcbc_state *xcbc, unsigned char *out, unsigned long *outlen)
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{
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int x;
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LTC_ARGCHK(xcbc != NULL);
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LTC_ARGCHK(out != NULL);
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if ((xcbc->blocksize < 0) || (xcbc->buflen > xcbc->blocksize) || (xcbc->buflen < 0)) {
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return CRYPT_INVALID_ARG;
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}
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/* which key do we use? */
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if (xcbc->buflen == xcbc->blocksize) {
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/* k2 */
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for (x = 0; x < xcbc->blocksize; x++) {
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xcbc->IV[x] ^= xcbc->K[1][x];
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}
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} else {
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xcbc->IV[xcbc->buflen] ^= 0x80;
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/* k3 */
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for (x = 0; x < xcbc->blocksize; x++) {
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xcbc->IV[x] ^= xcbc->K[2][x];
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}
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}
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/* encrypt */
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ecb_encrypt_block(xcbc->IV, xcbc->IV, &xcbc->key);
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ecb_done(&xcbc->key);
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/* extract tag */
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for (x = 0; x < xcbc->blocksize && (unsigned long)x < *outlen; x++) {
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out[x] = xcbc->IV[x];
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}
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*outlen = x;
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#ifdef LTC_CLEAN_STACK
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zeromem(xcbc, sizeof(*xcbc));
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#endif
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return CRYPT_OK;
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}
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#endif
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