64 lines
1.5 KiB
C
64 lines
1.5 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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#ifdef LTC_CCM_MODE
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/**
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Initialize a CCM state
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@param ccm The CCM state to initialize
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@param cipher The index of the cipher to use
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@param key The secret key
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@param keylen The length of the secret key
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@param ptlen The length of the plain/cipher text that will be processed
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@param taglen The max length of the MAC tag
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@param aadlen The length of the AAD
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@return CRYPT_OK on success
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*/
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int ccm_init(ccm_state *ccm, int cipher,
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const unsigned char *key, int keylen, int ptlen, int taglen, int aadlen)
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{
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int err;
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LTC_ARGCHK(ccm != NULL);
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LTC_ARGCHK(key != NULL);
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XMEMSET(ccm, 0, sizeof(ccm_state));
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/* check cipher input */
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if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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return err;
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}
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if (cipher_descriptor[cipher].block_length != 16) {
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return CRYPT_INVALID_CIPHER;
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}
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/* make sure the taglen is valid */
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if (taglen < 4 || taglen > 16 || (taglen % 2) == 1 || aadlen < 0 || ptlen < 0) {
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return CRYPT_INVALID_ARG;
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}
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ccm->taglen = taglen;
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/* schedule key */
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if ((err = ecb_start(cipher, key, keylen, 0, &ccm->K)) != CRYPT_OK) {
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return err;
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}
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/* let's get the L value */
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ccm->ptlen = ptlen;
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ccm->L = 0;
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while (ptlen) {
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++ccm->L;
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ptlen >>= 8;
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}
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if (ccm->L <= 1) {
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ccm->L = 2;
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}
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ccm->aadlen = aadlen;
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return CRYPT_OK;
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}
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#endif
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