mirror of
https://github.com/Laupetin/OpenAssetTools.git
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143 lines
3.6 KiB
C
143 lines
3.6 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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/**
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@file eax_init.c
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EAX implementation, initialized EAX state, by Tom St Denis
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*/
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#include "tomcrypt.h"
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#ifdef LTC_EAX_MODE
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/**
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Initialized an EAX state
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@param eax [out] The EAX state to initialize
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@param cipher The index of the desired cipher
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@param key The secret key
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@param keylen The length of the secret key (octets)
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@param nonce The use-once nonce for the session
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@param noncelen The length of the nonce (octets)
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@param header The header for the EAX state
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@param headerlen The header length (octets)
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@return CRYPT_OK if successful
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*/
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int eax_init(eax_state *eax, int cipher,
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const unsigned char *key, unsigned long keylen,
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const unsigned char *nonce, unsigned long noncelen,
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const unsigned char *header, unsigned long headerlen)
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{
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unsigned char *buf;
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int err, blklen;
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omac_state *omac;
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unsigned long len;
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LTC_ARGCHK(eax != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(nonce != NULL);
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if (headerlen > 0) {
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LTC_ARGCHK(header != NULL);
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}
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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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blklen = cipher_descriptor[cipher].block_length;
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/* allocate ram */
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buf = XMALLOC(MAXBLOCKSIZE);
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omac = XMALLOC(sizeof(*omac));
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if (buf == NULL || omac == NULL) {
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if (buf != NULL) {
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XFREE(buf);
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}
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if (omac != NULL) {
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XFREE(omac);
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}
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return CRYPT_MEM;
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}
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/* N = LTC_OMAC_0K(nonce) */
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zeromem(buf, MAXBLOCKSIZE);
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if ((err = omac_init(omac, cipher, key, keylen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* omac the [0]_n */
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if ((err = omac_process(omac, buf, blklen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* omac the nonce */
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if ((err = omac_process(omac, nonce, noncelen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* store result */
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len = sizeof(eax->N);
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if ((err = omac_done(omac, eax->N, &len)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* H = LTC_OMAC_1K(header) */
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zeromem(buf, MAXBLOCKSIZE);
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buf[blklen - 1] = 1;
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if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* omac the [1]_n */
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if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* omac the header */
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if (headerlen != 0) {
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if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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}
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/* note we don't finish the headeromac, this allows us to add more header later */
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/* setup the CTR mode */
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if ((err = ctr_start(cipher, eax->N, key, keylen, 0, CTR_COUNTER_BIG_ENDIAN, &eax->ctr)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* setup the LTC_OMAC for the ciphertext */
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if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* omac [2]_n */
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zeromem(buf, MAXBLOCKSIZE);
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buf[blklen-1] = 2;
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if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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err = CRYPT_OK;
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LBL_ERR:
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#ifdef LTC_CLEAN_STACK
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zeromem(buf, MAXBLOCKSIZE);
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zeromem(omac, sizeof(*omac));
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#endif
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XFREE(omac);
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XFREE(buf);
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return err;
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}
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#endif
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/* ref: HEAD -> master, tag: v1.18.2 */
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/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
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/* commit time: 2018-07-01 22:49:01 +0200 */
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