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93 lines
2.1 KiB
C
93 lines
2.1 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 gcm_add_iv.c
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GCM implementation, add IV data to the state, by Tom St Denis
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*/
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#include "tomcrypt.h"
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#ifdef LTC_GCM_MODE
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/**
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Add IV data to the GCM state
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@param gcm The GCM state
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@param IV The initial value data to add
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@param IVlen The length of the IV
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@return CRYPT_OK on success
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*/
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int gcm_add_iv(gcm_state *gcm,
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const unsigned char *IV, unsigned long IVlen)
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{
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unsigned long x, y;
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int err;
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LTC_ARGCHK(gcm != NULL);
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if (IVlen > 0) {
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LTC_ARGCHK(IV != NULL);
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}
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/* must be in IV mode */
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if (gcm->mode != LTC_GCM_MODE_IV) {
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return CRYPT_INVALID_ARG;
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}
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if (gcm->buflen >= 16 || gcm->buflen < 0) {
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return CRYPT_INVALID_ARG;
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}
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if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
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return err;
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}
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/* trip the ivmode flag */
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if (IVlen + gcm->buflen > 12) {
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gcm->ivmode |= 1;
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}
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x = 0;
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#ifdef LTC_FAST
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if (gcm->buflen == 0) {
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for (x = 0; x < (IVlen & ~15); x += 16) {
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for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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*(LTC_FAST_TYPE_PTR_CAST(&gcm->X[y])) ^= *(LTC_FAST_TYPE_PTR_CAST(&IV[x + y]));
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}
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gcm_mult_h(gcm, gcm->X);
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gcm->totlen += 128;
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}
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IV += x;
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}
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#endif
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/* start adding IV data to the state */
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for (; x < IVlen; x++) {
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gcm->buf[gcm->buflen++] = *IV++;
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if (gcm->buflen == 16) {
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/* GF mult it */
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for (y = 0; y < 16; y++) {
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gcm->X[y] ^= gcm->buf[y];
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}
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gcm_mult_h(gcm, gcm->X);
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gcm->buflen = 0;
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gcm->totlen += 128;
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}
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}
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return CRYPT_OK;
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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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