/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org *//**   @file gcm_add_aad.c   GCM implementation, Add AAD data to the stream, by Tom St Denis*/#include "tomcrypt.h"#ifdef GCM_MODE/**  Add AAD to the GCM state  @param gcm       The GCM state  @param adata     The additional authentication data to add to the GCM state  @param adatalen  The length of the AAD data.  @return CRYPT_OK on success */int gcm_add_aad(gcm_state *gcm,               const unsigned char *adata,  unsigned long adatalen){   unsigned long x;   int           err;#ifdef LTC_FAST   unsigned long y;#endif   LTC_ARGCHK(gcm    != NULL);   if (adatalen > 0) {      LTC_ARGCHK(adata  != NULL);   }   if (gcm->buflen > 16 || gcm->buflen < 0) {      return CRYPT_INVALID_ARG;   }   if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {      return err;   }   /* in IV mode? */   if (gcm->mode == GCM_MODE_IV) {      /* let's process the IV */      if (gcm->ivmode || gcm->buflen != 12) {         for (x = 0; x < (unsigned long)gcm->buflen; x++) {             gcm->X[x] ^= gcm->buf[x];         }         if (gcm->buflen) {            gcm->totlen += gcm->buflen * CONST64(8);            gcm_mult_h(gcm, gcm->X);         }          /* mix in the length */         zeromem(gcm->buf, 8);         STORE64H(gcm->totlen, gcm->buf+8);         for (x = 0; x < 16; x++) {             gcm->X[x] ^= gcm->buf[x];         }         gcm_mult_h(gcm, gcm->X);         /* copy counter out */          XMEMCPY(gcm->Y, gcm->X, 16);         zeromem(gcm->X, 16);      } else {         XMEMCPY(gcm->Y, gcm->buf, 12);         gcm->Y[12] = 0;         gcm->Y[13] = 0;         gcm->Y[14] = 0;         gcm->Y[15] = 1;      }      XMEMCPY(gcm->Y_0, gcm->Y, 16);      zeromem(gcm->buf, 16);      gcm->buflen = 0;      gcm->totlen = 0;      gcm->mode   = GCM_MODE_AAD;   }   if (gcm->mode != GCM_MODE_AAD || gcm->buflen >= 16) {      return CRYPT_INVALID_ARG;   }   x = 0;#ifdef LTC_FAST   if (gcm->buflen == 0) {      for (x = 0; x < (adatalen & ~15); x += 16) {          for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {              *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&adata[x + y]));          }          gcm_mult_h(gcm, gcm->X);          gcm->totlen += 128;      }      adata += x;   }#endif   /* start adding AAD data to the state */   for (; x < adatalen; x++) {       gcm->X[gcm->buflen++] ^= *adata++;       if (gcm->buflen == 16) {         /* GF mult it */         gcm_mult_h(gcm, gcm->X);         gcm->buflen = 0;         gcm->totlen += 128;      }   }   return CRYPT_OK;}#endif   /* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_add_aad.c,v $ *//* $Revision: 1.14 $ *//* $Date: 2005/05/05 14:35:58 $ */